Update version

Update changelog and version
Restore symbol from 10.1
2024-01-03 11:17:28 -08:00 · 2024-01-03 10:11:10 -08:00 · 2024-01-03 10:09:01 -08:00 · 2024-01-01 11:10:16 -08:00 · 2024-01-01 11:06:44 -08:00 · 2024-01-01 10:06:52 -08:00
85 changed files with 14362 additions and 11936 deletions
@@ -0,0 +1,8 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # Necessary to update action hashs	
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    # Allow up to 3 opened pull requests for github-actions versions
+    open-pull-requests-limit: 3
@@ -1,6 +1,7 @@
 <!--
 Please read the contribution guidelines before submitting a pull request:
 https://github.com/fmtlib/fmt/blob/master/CONTRIBUTING.md.
-By submitting this pull request, you agree that your contributions are licensed
-under the {fmt} license, and agree to future changes to the licensing.
+By submitting this pull request, you agree to license your contribution(s)
+under the terms outlined in LICENSE.rst and represent that you have the right
+to do so.
 -->
@@ -0,0 +1,30 @@
+name: CIFuzz
+on: [pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Build Fuzzers
+      id: build
+      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@061583ebb5a96653e42feb3a97ee513eedc18078 # master
+      with:
+        oss-fuzz-project-name: 'fmt'
+        dry-run: false
+        language: c++
+    - name: Run Fuzzers
+      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@061583ebb5a96653e42feb3a97ee513eedc18078 # master
+      with:
+        oss-fuzz-project-name: 'fmt'
+        fuzz-seconds: 300
+        dry-run: false
+        language: c++
+    - name: Upload Crash
+      uses: actions/upload-artifact@c7d193f32edcb7bfad88892161225aeda64e9392 # v4.0.0
+      if: failure() && steps.build.outcome == 'success'
+      with:
+        name: artifacts
+        path: ./out/artifacts
@@ -11,7 +11,15 @@ jobs:
    runs-on: ubuntu-20.04

    steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+
+    - name: Add ubuntu mirrors
+      run: |
+        # Github Actions caching proxy is at times unreliable
+        # see https://github.com/actions/runner-images/issues/7048
+        printf 'http://azure.archive.ubuntu.com/ubuntu\tpriority:1\n' | sudo tee /etc/apt/mirrors.txt
+        curl http://mirrors.ubuntu.com/mirrors.txt | sudo tee --append /etc/apt/mirrors.txt
+        sudo sed -i 's~http://azure.archive.ubuntu.com/ubuntu/~mirror+file:/etc/apt/mirrors.txt~' /etc/apt/sources.list

    - name: Create Build Environment
      run: |
@@ -0,0 +1,26 @@
+name: lint
+
+on:
+  pull_request:
+    paths:
+      - '**.h'
+      - '**.cc'
+
+permissions:
+  contents: read
+
+jobs:
+  format_code:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install clang-format
+      uses: aminya/setup-cpp@v1
+      with:
+        clangformat: 17.0.5
+
+    - name: Run clang-format
+      run: |
+        find include src -name '*.h' -o -name '*.cc' |  xargs clang-format -i -style=file -fallback-style=none
+        git diff --exit-code
@@ -7,66 +7,83 @@ permissions:

 jobs:
  build:
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-20.04
    strategy:
      matrix:
        cxx: [g++-4.8, g++-10, clang++-9]
        build_type: [Debug, Release]
        std: [11]
-        os: [ubuntu-18.04]
        include:
          - cxx: g++-4.8
            install: sudo apt install g++-4.8
-            os: ubuntu-18.04
          - cxx: g++-8
            build_type: Debug
            std: 14
            install: sudo apt install g++-8
-            os: ubuntu-18.04
          - cxx: g++-8
            build_type: Debug
            std: 17
            install: sudo apt install g++-8
-            os: ubuntu-18.04
+          - cxx: g++-9
+            build_type: Debug
+            std: 17
          - cxx: g++-10
            build_type: Debug
            std: 17
-            os: ubuntu-18.04
          - cxx: g++-11
            build_type: Debug
            std: 20
-            os: ubuntu-20.04
            install: sudo apt install g++-11
          - cxx: clang++-8
            build_type: Debug
            std: 17
            cxxflags: -stdlib=libc++
-            os: ubuntu-18.04
            install: sudo apt install clang-8 libc++-8-dev libc++abi-8-dev
+          - cxx: clang++-9
+            install: sudo apt install clang-9
          - cxx: clang++-9
            build_type: Debug
            fuzz: -DFMT_FUZZ=ON -DFMT_FUZZ_LINKMAIN=ON
            std: 17
-            os: ubuntu-18.04
+            install: sudo apt install clang-9
          - cxx: clang++-11
            build_type: Debug
            std: 20
-            os: ubuntu-20.04
          - cxx: clang++-11
            build_type: Debug
            std: 20
            cxxflags: -stdlib=libc++
-            os: ubuntu-20.04
            install: sudo apt install libc++-11-dev libc++abi-11-dev
          - shared: -DBUILD_SHARED_LIBS=ON

    steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+
+    - name: Set timezone
+      run: sudo timedatectl set-timezone 'Asia/Yekaterinburg'
+
+    - name: Add repositories for older GCC
+      run: |
+        # Below two repos provide GCC 4.8, 5.5 and 6.4
+        sudo apt-add-repository 'deb http://azure.archive.ubuntu.com/ubuntu/ bionic main'
+        sudo apt-add-repository 'deb http://azure.archive.ubuntu.com/ubuntu/ bionic universe'
+        # Below two repos additionally update GCC 6 to 6.5
+        # sudo apt-add-repository 'deb http://azure.archive.ubuntu.com/ubuntu/ bionic-updates main'
+        # sudo apt-add-repository 'deb http://azure.archive.ubuntu.com/ubuntu/ bionic-updates universe'
+      if: ${{ matrix.cxx == 'g++-4.8' }}
+
+    - name: Add ubuntu mirrors
+      run: |
+        # Github Actions caching proxy is at times unreliable
+        # see https://github.com/actions/runner-images/issues/7048
+        printf 'http://azure.archive.ubuntu.com/ubuntu\tpriority:1\n' | sudo tee /etc/apt/mirrors.txt
+        curl http://mirrors.ubuntu.com/mirrors.txt | sudo tee --append /etc/apt/mirrors.txt
+        sudo sed -i 's~http://azure.archive.ubuntu.com/ubuntu/~mirror+file:/etc/apt/mirrors.txt~' /etc/apt/sources.list

    - name: Create Build Environment
      run: |
-        ${{matrix.install}}
        sudo apt update
+        ${{matrix.install}}
        sudo apt install locales-all
        cmake -E make_directory ${{runner.workspace}}/build

@@ -7,15 +7,29 @@ permissions:

 jobs:
  build:
-    runs-on: macos-10.15
    strategy:
      matrix:
+        os: [macos-11, macos-13]
        build_type: [Debug, Release]
+        std: [11, 17, 20]
+        exclude:
+          - { os: macos-11, std: 20 }
+          - { os: macos-13, std: 11 }
+          - { os: macos-13, std: 17 }
        include:
          - shared: -DBUILD_SHARED_LIBS=ON

+    runs-on: '${{ matrix.os }}'
+
    steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+
+    - name: Set timezone
+      run: sudo systemsetup -settimezone 'Asia/Yekaterinburg'
+
+    - name: Select Xcode 14.3 (macOS 13)
+      run: sudo xcode-select -s "/Applications/Xcode_14.3.app"
+      if: ${{ matrix.os == 'macos-13' }}

    - name: Create Build Environment
      run: cmake -E make_directory ${{runner.workspace}}/build
@@ -24,6 +38,7 @@ jobs:
      working-directory: ${{runner.workspace}}/build
      run: |
        cmake -DCMAKE_BUILD_TYPE=${{matrix.build_type}} ${{matrix.shared}} \
+              -DCMAKE_CXX_STANDARD=${{matrix.std}} \
              -DCMAKE_CXX_VISIBILITY_PRESET=hidden -DCMAKE_VISIBILITY_INLINES_HIDDEN=ON \
              -DFMT_DOC=OFF -DFMT_PEDANTIC=ON -DFMT_WERROR=ON $GITHUB_WORKSPACE

@@ -0,0 +1,65 @@
+# This workflow uses actions that are not certified by GitHub. They are provided
+# by a third-party and are governed by separate terms of service, privacy
+# policy, and support documentation.
+
+name: Scorecard supply-chain security
+on:
+  # For Branch-Protection check. Only the default branch is supported. See
+  # https://github.com/ossf/scorecard/blob/main/docs/checks.md#branch-protection
+  branch_protection_rule:
+  # To guarantee Maintained check is occasionally updated. See
+  # https://github.com/ossf/scorecard/blob/main/docs/checks.md#maintained
+  schedule:
+    - cron: '26 14 * * 5'
+  push:
+    branches: [ "master" ]
+
+# Declare default permissions as read only.
+permissions: read-all
+
+jobs:
+  analysis:
+    name: Scorecard analysis
+    runs-on: ubuntu-latest
+    permissions:
+      # Needed to upload the results to code-scanning dashboard.
+      security-events: write
+      # Needed to publish results and get a badge (see publish_results below).
+      id-token: write
+
+    steps:
+      - name: "Checkout code"
+        uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+        with:
+          persist-credentials: false
+
+      - name: "Run analysis"
+        uses: ossf/scorecard-action@0864cf19026789058feabb7e87baa5f140aac736 # v2.3.1
+        with:
+          results_file: results.sarif
+          results_format: sarif
+          # (Optional) "write" PAT token. Uncomment the `repo_token` line below if:
+          # - you want to enable the Branch-Protection check on a *public* repository, or
+          # To create the PAT, follow the steps in https://github.com/ossf/scorecard-action#authentication-with-pat.
+          # repo_token: ${{ secrets.SCORECARD_TOKEN }}
+
+          # Public repositories:
+          #   - Publish results to OpenSSF REST API for easy access by consumers
+          #   - Allows the repository to include the Scorecard badge.
+          #   - See https://github.com/ossf/scorecard-action#publishing-results.
+          publish_results: true
+
+      # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF
+      # format to the repository Actions tab.
+      - name: "Upload artifact"
+        uses: actions/upload-artifact@c7d193f32edcb7bfad88892161225aeda64e9392 # v4.0.0
+        with:
+          name: SARIF file
+          path: results.sarif
+          retention-days: 5
+
+      # Upload the results to GitHub's code scanning dashboard.
+      - name: "Upload to code-scanning"
+        uses: github/codeql-action/upload-sarif@74483a38d39275f33fcff5f35b679b5ca4a26a99 # v2.22.5
+        with:
+          sarif_file: results.sarif
@@ -15,27 +15,36 @@ jobs:
        # https://github.com/actions/virtual-environments.
        os: [windows-2019]
        platform: [Win32, x64]
+        toolset: [v140, v141, v142]
+        standard: [14, 17, 20]
+        shared: ["", -DBUILD_SHARED_LIBS=ON]
        build_type: [Debug, Release]
-        standard: [11, 17, 20]
+        exclude:
+          - { toolset: v140, standard: 17 }
+          - { toolset: v140, standard: 20 }
+          - { toolset: v141, standard: 14 }
+          - { toolset: v141, standard: 20 }
+          - { toolset: v142, standard: 14 }
+          - { platform: Win32, toolset: v140 }
+          - { platform: Win32, toolset: v141 }
+          - { platform: Win32, standard: 14 }
+          - { platform: Win32, standard: 20 }
+          - { platform: x64, toolset: v140, shared: -DBUILD_SHARED_LIBS=ON }
+          - { platform: x64, toolset: v141, shared: -DBUILD_SHARED_LIBS=ON }
+          - { platform: x64, standard: 14, shared: -DBUILD_SHARED_LIBS=ON }
+          - { platform: x64, standard: 20, shared: -DBUILD_SHARED_LIBS=ON }
        include:
-          - os: windows-2019
-            platform: Win32
-            build_type: Debug
-            shared: -DBUILD_SHARED_LIBS=ON
          - os: windows-2022
            platform: x64
+            toolset: v143
            build_type: Debug
            standard: 20
-        exclude:
-          - os: windows-2019
-            standard: 11
-            platform: Win32
-          - os: windows-2019
-            standard: 20
-            platform: Win32

    steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+
+    - name: Set timezone
+      run: tzutil /s "Ekaterinburg Standard Time"

    - name: Create Build Environment
      run: cmake -E make_directory ${{runner.workspace}}/build
@@ -45,9 +54,9 @@ jobs:
      shell: bash
      working-directory: ${{runner.workspace}}/build
      run: |
-        cmake -DCMAKE_BUILD_TYPE=${{matrix.build_type}} ${{matrix.shared}} \
-              -A ${{matrix.platform}} \
+        cmake -A ${{matrix.platform}} -T ${{matrix.toolset}} \
              -DCMAKE_CXX_STANDARD=${{matrix.standard}} \
+              ${{matrix.shared}} -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
              $GITHUB_WORKSPACE

    - name: Build
@@ -61,3 +70,31 @@ jobs:
      run: ctest -C ${{matrix.build_type}} -V
      env:
        CTEST_OUTPUT_ON_FAILURE: True
+
+  mingw:
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
+    strategy:
+      matrix:
+        sys: [ mingw64, ucrt64 ]
+    steps:
+    - name: Set timezone
+      run: tzutil /s "Ekaterinburg Standard Time"
+      shell: cmd
+    - uses: msys2/setup-msys2@7efe20baefed56359985e327d329042cde2434ff # v2
+      with:
+        release: false
+        msystem: ${{matrix.sys}}
+        pacboy: cc:p cmake:p ninja:p lld:p
+    - uses: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608 # v4.1.0
+    - name: Configure
+      run: cmake -B ../build -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Debug
+      env: { LDFLAGS: -fuse-ld=lld }
+    - name: Build
+      run: cmake --build ../build
+    - name: Test
+      run: ctest -j `nproc` --test-dir ../build
+      env:
+        CTEST_OUTPUT_ON_FAILURE: True
@@ -1,37 +1,24 @@
-.vscode/
-.vs/
-
-*.iml
-.idea/
-.externalNativeBuild/
-.gradle/
-gradle/
-gradlew*
-local.properties
-build/
-support/.cxx
-
-bin/
-/_CPack_Packages
-/CMakeScripts
-/doc/doxyxml
-/doc/html
-/doc/node_modules
-virtualenv
-/Testing
-/install_manifest.txt
-*~
 *.a
 *.so*
 *.xcodeproj
-*.zip
-cmake_install.cmake
-CPack*.cmake
-fmt-*.cmake
-CTestTestfile.cmake
+*~
+.vscode/
+/CMakeScripts
+/Testing
+/_CPack_Packages
+/doc/doxyxml
+/doc/html
+/doc/node_modules
+/install_manifest.txt
 CMakeCache.txt
 CMakeFiles
+CPack*.cmake
+CTestTestfile.cmake
 FMT.build
 Makefile
-run-msbuild.bat
+bin/
+build/
+cmake_install.cmake
+fmt-*.cmake
 fmt.pc
+virtualenv
@@ -1,9 +1,9 @@
-cmake_minimum_required(VERSION 3.1...3.18)
+cmake_minimum_required(VERSION 3.8...3.26)

 # Fallback for using newer policies on CMake <3.12.
-if(${CMAKE_VERSION} VERSION_LESS 3.12)
+if (${CMAKE_VERSION} VERSION_LESS 3.12)
  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-endif()
+endif ()

 # Determine if fmt is built as a subproject (using add_subdirectory)
 # or if it is the master project.
@@ -24,15 +24,86 @@ function(join result_var)
  set(${result_var} "${result}" PARENT_SCOPE)
 endfunction()

+# DEPRECATED! Should be merged into add_module_library.
 function(enable_module target)
  if (MSVC)
    set(BMI ${CMAKE_CURRENT_BINARY_DIR}/${target}.ifc)
    target_compile_options(${target}
      PRIVATE /interface /ifcOutput ${BMI}
      INTERFACE /reference fmt=${BMI})
+    set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
+    set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
  endif ()
-  set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
-  set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
+endfunction()
+
+# Adds a library compiled with C++20 module support.
+# `enabled` is a CMake variables that specifies if modules are enabled.
+# If modules are disabled `add_module_library` falls back to creating a
+# non-modular library.
+#
+# Usage:
+#   add_module_library(<name> [sources...] FALLBACK [sources...] [IF enabled])
+function(add_module_library name)
+  cmake_parse_arguments(AML "" "IF" "FALLBACK" ${ARGN})
+  set(sources ${AML_UNPARSED_ARGUMENTS})
+
+  add_library(${name})
+  set_target_properties(${name} PROPERTIES LINKER_LANGUAGE CXX)
+
+  if (NOT ${${AML_IF}})
+    # Create a non-modular library.
+    target_sources(${name} PRIVATE ${AML_FALLBACK})
+    return()
+  endif ()
+
+  # Modules require C++20.
+  target_compile_features(${name} PUBLIC cxx_std_20)
+  if (CMAKE_COMPILER_IS_GNUCXX)
+    target_compile_options(${name} PUBLIC -fmodules-ts)
+  endif ()
+
+  # `std` is affected by CMake options and may be higher than C++20.
+  get_target_property(std ${name} CXX_STANDARD)
+
+  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(pcms)
+    foreach (src ${sources})
+      get_filename_component(pcm ${src} NAME_WE)
+      set(pcm ${pcm}.pcm)
+
+      # Propagate -fmodule-file=*.pcm to targets that link with this library.
+      target_compile_options(
+        ${name} PUBLIC -fmodule-file=${CMAKE_CURRENT_BINARY_DIR}/${pcm})
+
+      # Use an absolute path to prevent target_link_libraries prepending -l
+      # to it.
+      set(pcms ${pcms} ${CMAKE_CURRENT_BINARY_DIR}/${pcm})
+      add_custom_command(
+        OUTPUT ${pcm}
+        COMMAND ${CMAKE_CXX_COMPILER}
+                -std=c++${std} -x c++-module --precompile -c
+                -o ${pcm} ${CMAKE_CURRENT_SOURCE_DIR}/${src}
+                "-I$<JOIN:$<TARGET_PROPERTY:${name},INCLUDE_DIRECTORIES>,;-I>"
+        # Required by the -I generator expression above.
+        COMMAND_EXPAND_LISTS
+        DEPENDS ${src})
+    endforeach ()
+
+    # Add .pcm files as sources to make sure they are built before the library.
+    set(sources)
+    foreach (pcm ${pcms})
+      get_filename_component(pcm_we ${pcm} NAME_WE)
+      set(obj ${pcm_we}.o)
+      # Use an absolute path to prevent target_link_libraries prepending -l.
+      set(sources ${sources} ${pcm} ${CMAKE_CURRENT_BINARY_DIR}/${obj})
+      add_custom_command(
+        OUTPUT ${obj}
+        COMMAND ${CMAKE_CXX_COMPILER} $<TARGET_PROPERTY:${name},COMPILE_OPTIONS>
+                -c -o ${obj} ${pcm}
+        DEPENDS ${pcm})
+    endforeach ()
+  endif ()
+  target_sources(${name} PRIVATE ${sources})
 endfunction()

 include(CMakeParseArguments)
@@ -75,7 +146,7 @@ option(FMT_WERROR "Halt the compilation with an error on compiler warnings."

 # Options that control generation of various targets.
 option(FMT_DOC "Generate the doc target." ${FMT_MASTER_PROJECT})
-option(FMT_INSTALL "Generate the install target." ${FMT_MASTER_PROJECT})
+option(FMT_INSTALL "Generate the install target." ON)
 option(FMT_TEST "Generate the test target." ${FMT_MASTER_PROJECT})
 option(FMT_FUZZ "Generate the fuzz target." OFF)
 option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
@@ -83,16 +154,6 @@ option(FMT_OS "Include core requiring OS (Windows/Posix) " ON)
 option(FMT_MODULE "Build a module instead of a traditional library." OFF)
 option(FMT_SYSTEM_HEADERS "Expose headers with marking them as system." OFF)

-set(FMT_CAN_MODULE OFF)
-if (CMAKE_CXX_STANDARD GREATER 17 AND
-    # msvc 16.10-pre4
-    MSVC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 19.29.30035)
-  set(FMT_CAN_MODULE OFF)
-endif ()
-if (NOT FMT_CAN_MODULE)
-  set(FMT_MODULE OFF)
-  message(STATUS "Module support is disabled.")
-endif ()
 if (FMT_TEST AND FMT_MODULE)
  # The tests require {fmt} to be compiled as traditional library
  message(STATUS "Testing is incompatible with build mode 'module'.")
@@ -101,6 +162,10 @@ set(FMT_SYSTEM_HEADERS_ATTRIBUTE "")
 if (FMT_SYSTEM_HEADERS)
  set(FMT_SYSTEM_HEADERS_ATTRIBUTE SYSTEM)
 endif ()
+if (CMAKE_SYSTEM_NAME STREQUAL "MSDOS")
+  set(FMT_TEST OFF)
+  message(STATUS "MSDOS is incompatible with gtest")
+endif ()

 # Get version from core.h
 file(READ include/fmt/core.h core_h)
@@ -118,23 +183,15 @@ message(STATUS "Version: ${FMT_VERSION}")
 message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")

 if (NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
-  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 endif ()

 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
  "${CMAKE_CURRENT_SOURCE_DIR}/support/cmake")

-include(cxx14)
+include(CheckCXXCompilerFlag)
 include(JoinPaths)

-list(FIND CMAKE_CXX_COMPILE_FEATURES "cxx_variadic_templates" index)
-if (${index} GREATER -1)
-  # Use cxx_variadic_templates instead of more appropriate cxx_std_11 for
-  # compatibility with older CMake versions.
-  set(FMT_REQUIRED_FEATURES cxx_variadic_templates)
-endif ()
-message(STATUS "Required features: ${FMT_REQUIRED_FEATURES}")
-
 if (FMT_MASTER_PROJECT AND NOT DEFINED CMAKE_CXX_VISIBILITY_PRESET)
  set_verbose(CMAKE_CXX_VISIBILITY_PRESET hidden CACHE STRING
              "Preset for the export of private symbols")
@@ -220,16 +277,18 @@ endfunction()
 add_headers(FMT_HEADERS args.h chrono.h color.h compile.h core.h format.h
                        format-inl.h os.h ostream.h printf.h ranges.h std.h
                        xchar.h)
-if (FMT_MODULE)
-  set(FMT_SOURCES src/fmt.cc)
-elseif (FMT_OS)
-  set(FMT_SOURCES src/format.cc src/os.cc)
-else()
-  set(FMT_SOURCES src/format.cc)
+set(FMT_SOURCES src/format.cc)
+if (FMT_OS)
+  set(FMT_SOURCES ${FMT_SOURCES} src/os.cc)
 endif ()

-add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS} README.rst ChangeLog.rst)
+add_module_library(fmt src/fmt.cc FALLBACK
+                   ${FMT_SOURCES} ${FMT_HEADERS} README.md ChangeLog.md
+                   IF FMT_MODULE)
 add_library(fmt::fmt ALIAS fmt)
+if (FMT_MODULE)
+  enable_module(fmt)
+endif ()

 if (FMT_WERROR)
  target_compile_options(fmt PRIVATE ${WERROR_FLAG})
@@ -237,11 +296,12 @@ endif ()
 if (FMT_PEDANTIC)
  target_compile_options(fmt PRIVATE ${PEDANTIC_COMPILE_FLAGS})
 endif ()
-if (FMT_MODULE)
-  enable_module(fmt)
-endif ()

-target_compile_features(fmt INTERFACE ${FMT_REQUIRED_FEATURES})
+if (cxx_std_11 IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+  target_compile_features(fmt PUBLIC cxx_std_11)
+else ()
+  message(WARNING "Feature cxx_std_11 is unknown for the CXX compiler")
+endif ()

 target_include_directories(fmt ${FMT_SYSTEM_HEADERS_ATTRIBUTE} PUBLIC
  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
@@ -252,7 +312,15 @@ set(FMT_DEBUG_POSTFIX d CACHE STRING "Debug library postfix.")
 set_target_properties(fmt PROPERTIES
  VERSION ${FMT_VERSION} SOVERSION ${CPACK_PACKAGE_VERSION_MAJOR}
  PUBLIC_HEADER "${FMT_HEADERS}"
-  DEBUG_POSTFIX "${FMT_DEBUG_POSTFIX}")
+  DEBUG_POSTFIX "${FMT_DEBUG_POSTFIX}"
+
+  # Workaround for Visual Studio 2017:
+  # Ensure the .pdb is created with the same name and in the same directory
+  # as the .lib. Newer VS versions already do this by default, but there is no
+  # harm in setting it for those too. Ignored by other generators.
+  COMPILE_PDB_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
+  COMPILE_PDB_NAME "fmt"
+  COMPILE_PDB_NAME_DEBUG "fmt${FMT_DEBUG_POSTFIX}")

 # Set FMT_LIB_NAME for pkg-config fmt.pc. We cannot use the OUTPUT_NAME target
 # property because it's not set by default.
@@ -262,25 +330,20 @@ if (CMAKE_BUILD_TYPE STREQUAL "Debug")
 endif ()

 if (BUILD_SHARED_LIBS)
-  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS" AND
-      NOT EMSCRIPTEN)
-    # Fix rpmlint warning:
-    # unused-direct-shlib-dependency /usr/lib/libformat.so.1.1.0 /lib/libm.so.6.
-    target_link_libraries(fmt -Wl,--as-needed)
-  endif ()
-  target_compile_definitions(fmt PRIVATE FMT_EXPORT INTERFACE FMT_SHARED)
+  target_compile_definitions(fmt PRIVATE FMT_LIB_EXPORT INTERFACE FMT_SHARED)
 endif ()
 if (FMT_SAFE_DURATION_CAST)
  target_compile_definitions(fmt PUBLIC FMT_SAFE_DURATION_CAST)
-endif()
+endif ()

 add_library(fmt-header-only INTERFACE)
 add_library(fmt::fmt-header-only ALIAS fmt-header-only)

 target_compile_definitions(fmt-header-only INTERFACE FMT_HEADER_ONLY=1)
-target_compile_features(fmt-header-only INTERFACE ${FMT_REQUIRED_FEATURES})
+target_compile_features(fmt-header-only INTERFACE cxx_std_11)

-target_include_directories(fmt-header-only ${FMT_SYSTEM_HEADERS_ATTRIBUTE} INTERFACE
+target_include_directories(fmt-header-only
+  ${FMT_SYSTEM_HEADERS_ATTRIBUTE} INTERFACE
  $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)

@@ -300,7 +363,7 @@ if (FMT_INSTALL)
              "Installation directory for libraries, a relative path that "
              "will be joined to ${CMAKE_INSTALL_PREFIX} or an absolute path.")

-  set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE PATH
+  set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE STRING
              "Installation directory for pkgconfig (.pc) files, a relative "
              "path that will be joined with ${CMAKE_INSTALL_PREFIX} or an "
              "absolute path.")
@@ -330,7 +393,6 @@ if (FMT_INSTALL)
          LIBRARY DESTINATION ${FMT_LIB_DIR}
          ARCHIVE DESTINATION ${FMT_LIB_DIR}
          PUBLIC_HEADER DESTINATION "${FMT_INC_DIR}/fmt"
-          FRAMEWORK DESTINATION "."
          RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})

  # Use a namespace because CMake provides better diagnostics for namespaced
@@ -345,8 +407,6 @@ if (FMT_INSTALL)
  install(EXPORT ${targets_export_name} DESTINATION ${FMT_CMAKE_DIR}
          NAMESPACE fmt::)

-  install(FILES $<TARGET_PDB_FILE:${INSTALL_TARGETS}>
-          DESTINATION ${FMT_LIB_DIR} OPTIONAL)
  install(FILES "${pkgconfig}" DESTINATION "${FMT_PKGCONFIG_DIR}")
 endif ()

@@ -388,6 +448,6 @@ if (FMT_MASTER_PROJECT AND EXISTS ${gitignore})
  set(CPACK_SOURCE_IGNORE_FILES ${ignored_files})
  set(CPACK_SOURCE_PACKAGE_FILE_NAME fmt-${FMT_VERSION})
  set(CPACK_PACKAGE_NAME fmt)
-  set(CPACK_RESOURCE_FILE_README ${PROJECT_SOURCE_DIR}/README.rst)
+  set(CPACK_RESOURCE_FILE_README ${PROJECT_SOURCE_DIR}/README.md)
  include(CPack)
 endif ()
@@ -1,4 +1,4 @@
-Copyright (c) 2012 - present, Victor Zverovich
+Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors

 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
@@ -0,0 +1,490 @@
+<img src="https://user-images.githubusercontent.com/576385/156254208-f5b743a9-88cf-439d-b0c0-923d53e8d551.png" alt="{fmt}" width="25%"/>
+
+[![image](https://github.com/fmtlib/fmt/workflows/linux/badge.svg)](https://github.com/fmtlib/fmt/actions?query=workflow%3Alinux)
+[![image](https://github.com/fmtlib/fmt/workflows/macos/badge.svg)](https://github.com/fmtlib/fmt/actions?query=workflow%3Amacos)
+[![image](https://github.com/fmtlib/fmt/workflows/windows/badge.svg)](https://github.com/fmtlib/fmt/actions?query=workflow%3Awindows)
+[![fmt is continuously fuzzed at oss-fuzz](https://oss-fuzz-build-logs.storage.googleapis.com/badges/fmt.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?\%0Acolspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\%0ASummary&q=proj%3Dfmt&can=1)
+[![Ask questions at StackOverflow with the tag fmt](https://img.shields.io/badge/stackoverflow-fmt-blue.svg)](https://stackoverflow.com/questions/tagged/fmt)
+[![image](https://api.securityscorecards.dev/projects/github.com/fmtlib/fmt/badge)](https://securityscorecards.dev/viewer/?uri=github.com/fmtlib/fmt)
+
+**{fmt}** is an open-source formatting library providing a fast and safe
+alternative to C stdio and C++ iostreams.
+
+If you like this project, please consider donating to one of the funds
+that help victims of the war in Ukraine: <https://www.stopputin.net/>.
+
+[Documentation](https://fmt.dev)
+
+[Cheat Sheets](https://hackingcpp.com/cpp/libs/fmt.html)
+
+Q&A: ask questions on [StackOverflow with the tag
+fmt](https://stackoverflow.com/questions/tagged/fmt).
+
+Try {fmt} in [Compiler Explorer](https://godbolt.org/z/Eq5763).
+
+# Features
+
+- Simple [format API](https://fmt.dev/latest/api.html) with positional
+  arguments for localization
+- Implementation of [C++20
+  std::format](https://en.cppreference.com/w/cpp/utility/format) and
+  [C++23 std::print](https://en.cppreference.com/w/cpp/io/print)
+- [Format string syntax](https://fmt.dev/latest/syntax.html) similar
+  to Python\'s
+  [format](https://docs.python.org/3/library/stdtypes.html#str.format)
+- Fast IEEE 754 floating-point formatter with correct rounding,
+  shortness and round-trip guarantees using the
+  [Dragonbox](https://github.com/jk-jeon/dragonbox) algorithm
+- Portable Unicode support
+- Safe [printf
+  implementation](https://fmt.dev/latest/api.html#printf-formatting)
+  including the POSIX extension for positional arguments
+- Extensibility: [support for user-defined
+  types](https://fmt.dev/latest/api.html#formatting-user-defined-types)
+- High performance: faster than common standard library
+  implementations of `(s)printf`, iostreams, `to_string` and
+  `to_chars`, see [Speed tests](#speed-tests) and [Converting a
+  hundred million integers to strings per
+  second](http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html)
+- Small code size both in terms of source code with the minimum
+  configuration consisting of just three files, `core.h`, `format.h`
+  and `format-inl.h`, and compiled code; see [Compile time and code
+  bloat](#compile-time-and-code-bloat)
+- Reliability: the library has an extensive set of
+  [tests](https://github.com/fmtlib/fmt/tree/master/test) and is
+  [continuously fuzzed](https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dfmt&can=1)
+- Safety: the library is fully type-safe, errors in format strings can
+  be reported at compile time, automatic memory management prevents
+  buffer overflow errors
+- Ease of use: small self-contained code base, no external
+  dependencies, permissive MIT
+  [license](https://github.com/fmtlib/fmt/blob/master/LICENSE.rst)
+- [Portability](https://fmt.dev/latest/index.html#portability) with
+  consistent output across platforms and support for older compilers
+- Clean warning-free codebase even on high warning levels such as
+  `-Wall -Wextra -pedantic`
+- Locale independence by default
+- Optional header-only configuration enabled with the
+  `FMT_HEADER_ONLY` macro
+
+See the [documentation](https://fmt.dev) for more details.
+
+# Examples
+
+**Print to stdout** ([run](https://godbolt.org/z/Tevcjh))
+
+``` c++
+#include <fmt/core.h>
+
+int main() {
+  fmt::print("Hello, world!\n");
+}
+```
+
+**Format a string** ([run](https://godbolt.org/z/oK8h33))
+
+``` c++
+std::string s = fmt::format("The answer is {}.", 42);
+// s == "The answer is 42."
+```
+
+**Format a string using positional arguments**
+([run](https://godbolt.org/z/Yn7Txe))
+
+``` c++
+std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
+// s == "I'd rather be happy than right."
+```
+
+**Print dates and times** ([run](https://godbolt.org/z/c31ExdY3W))
+
+``` c++
+#include <fmt/chrono.h>
+
+int main() {
+  auto now = std::chrono::system_clock::now();
+  fmt::print("Date and time: {}\n", now);
+  fmt::print("Time: {:%H:%M}\n", now);
+}
+```
+
+Output:
+
+    Date and time: 2023-12-26 19:10:31.557195597
+    Time: 19:10
+
+**Print a container** ([run](https://godbolt.org/z/MxM1YqjE7))
+
+``` c++
+#include <vector>
+#include <fmt/ranges.h>
+
+int main() {
+  std::vector<int> v = {1, 2, 3};
+  fmt::print("{}\n", v);
+}
+```
+
+Output:
+
+    [1, 2, 3]
+
+**Check a format string at compile time**
+
+``` c++
+std::string s = fmt::format("{:d}", "I am not a number");
+```
+
+This gives a compile-time error in C++20 because `d` is an invalid
+format specifier for a string.
+
+**Write a file from a single thread**
+
+``` c++
+#include <fmt/os.h>
+
+int main() {
+  auto out = fmt::output_file("guide.txt");
+  out.print("Don't {}", "Panic");
+}
+```
+
+This can be [5 to 9 times faster than
+fprintf](http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html).
+
+**Print with colors and text styles**
+
+``` c++
+#include <fmt/color.h>
+
+int main() {
+  fmt::print(fg(fmt::color::crimson) | fmt::emphasis::bold,
+             "Hello, {}!\n", "world");
+  fmt::print(fg(fmt::color::floral_white) | bg(fmt::color::slate_gray) |
+             fmt::emphasis::underline, "Olá, {}!\n", "Mundo");
+  fmt::print(fg(fmt::color::steel_blue) | fmt::emphasis::italic,
+             "你好{}！\n", "世界");
+}
+```
+
+Output on a modern terminal with Unicode support:
+
+![image](https://github.com/fmtlib/fmt/assets/%0A576385/2a93c904-d6fa-4aa6-b453-2618e1c327d7)
+
+# Benchmarks
+
+## Speed tests
+
+| Library           | Method        | Run Time, s |
+|-------------------|---------------|-------------|
+| libc              | printf        |   0.91      |
+| libc++            | std::ostream  |   2.49      |
+| {fmt} 9.1         | fmt::print    |   0.74      |
+| Boost Format 1.80 | boost::format |   6.26      |
+| Folly Format      | folly::format |   1.87      |
+
+{fmt} is the fastest of the benchmarked methods, \~20% faster than
+`printf`.
+
+The above results were generated by building `tinyformat_test.cpp` on
+macOS 12.6.1 with `clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT`, and
+taking the best of three runs. In the test, the format string
+`"%0.10f:%04d:%+g:%s:%p:%c:%%\n"` or equivalent is filled 2,000,000
+times with output sent to `/dev/null`; for further details refer to the
+[source](https://github.com/fmtlib/format-benchmark/blob/master/src/tinyformat-test.cc).
+
+{fmt} is up to 20-30x faster than `std::ostringstream` and `sprintf` on
+IEEE754 `float` and `double` formatting
+([dtoa-benchmark](https://github.com/fmtlib/dtoa-benchmark)) and faster
+than [double-conversion](https://github.com/google/double-conversion)
+and [ryu](https://github.com/ulfjack/ryu):
+
+[![image](https://user-images.githubusercontent.com/576385/95684665-11719600-0ba8-11eb-8e5b-972ff4e49428.png)](https://fmt.dev/unknown_mac64_clang12.0.html)
+
+## Compile time and code bloat
+
+The script
+[bloat-test.py](https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py)
+from [format-benchmark](https://github.com/fmtlib/format-benchmark)
+tests compile time and code bloat for nontrivial projects. It generates
+100 translation units and uses `printf()` or its alternative five times
+in each to simulate a medium-sized project. The resulting executable
+size and compile time (Apple LLVM version 8.1.0 (clang-802.0.42), macOS
+Sierra, best of three) is shown in the following tables.
+
+**Optimized build (-O3)**
+
+| Method        | Compile Time, s | Executable size, KiB | Stripped size, KiB |
+|---------------|-----------------|----------------------|--------------------|
+| printf        |   2.6           |   29                 |   26               |
+| printf+string |   16.4          |   29                 |   26               |
+| iostreams     |   31.1          |   59                 |   55               |
+| {fmt}         |   19.0          |   37                 |   34               |
+| Boost Format  |   91.9          |   226                |   203              |
+| Folly Format  |   115.7         |   101                |   88               |
+
+As you can see, {fmt} has 60% less overhead in terms of resulting binary
+code size compared to iostreams and comes pretty close to `printf`.
+Boost Format and Folly Format have the largest overheads.
+
+`printf+string` is the same as `printf` but with an extra `<string>`
+include to measure the overhead of the latter.
+
+**Non-optimized build**
+
+| Method        | Compile Time, s | Executable size, KiB | Stripped size, KiB |
+|---------------|-----------------|----------------------|--------------------|
+| printf        |   2.2           |   33                 |   30               |
+| printf+string |   16.0          |   33                 |   30               |
+| iostreams     |   28.3          |   56                 |   52               |
+| {fmt}         |   18.2          |   59                 |   50               |
+| Boost Format  |   54.1          |   365                |   303              |
+| Folly Format  |   79.9          |   445                |   430              |
+
+`libc`, `lib(std)c++`, and `libfmt` are all linked as shared libraries
+to compare formatting function overhead only. Boost Format is a
+header-only library so it doesn\'t provide any linkage options.
+
+## Running the tests
+
+Please refer to [Building the
+library](https://fmt.dev/latest/usage.html#building-the-library) for
+instructions on how to build the library and run the unit tests.
+
+Benchmarks reside in a separate repository,
+[format-benchmarks](https://github.com/fmtlib/format-benchmark), so to
+run the benchmarks you first need to clone this repository and generate
+Makefiles with CMake:
+
+    $ git clone --recursive https://github.com/fmtlib/format-benchmark.git
+    $ cd format-benchmark
+    $ cmake .
+
+Then you can run the speed test:
+
+    $ make speed-test
+
+or the bloat test:
+
+    $ make bloat-test
+
+# Migrating code
+
+[clang-tidy](https://clang.llvm.org/extra/clang-tidy/) v17 (not yet
+released) provides the
+[modernize-use-std-print](https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-std-print.html)
+check that is capable of converting occurrences of `printf` and
+`fprintf` to `fmt::print` if configured to do so. (By default it
+converts to `std::print`.)
+
+# Notable projects using this library
+
+- [0 A.D.](https://play0ad.com/): a free, open-source, cross-platform
+  real-time strategy game
+- [AMPL/MP](https://github.com/ampl/mp): an open-source library for
+  mathematical programming
+- [Apple's FoundationDB](https://github.com/apple/foundationdb): an open-source,
+  distributed, transactional key-value store
+- [Aseprite](https://github.com/aseprite/aseprite): animated sprite
+  editor & pixel art tool
+- [AvioBook](https://www.aviobook.aero/en): a comprehensive aircraft
+  operations suite
+- [Blizzard Battle.net](https://battle.net/): an online gaming
+  platform
+- [Celestia](https://celestia.space/): real-time 3D visualization of
+  space
+- [Ceph](https://ceph.com/): a scalable distributed storage system
+- [ccache](https://ccache.dev/): a compiler cache
+- [ClickHouse](https://github.com/ClickHouse/ClickHouse): an
+  analytical database management system
+- [Contour](https://github.com/contour-terminal/contour/): a modern
+  terminal emulator
+- [CUAUV](https://cuauv.org/): Cornell University\'s autonomous
+  underwater vehicle
+- [Drake](https://drake.mit.edu/): a planning, control, and analysis
+  toolbox for nonlinear dynamical systems (MIT)
+- [Envoy](https://lyft.github.io/envoy/): C++ L7 proxy and
+  communication bus (Lyft)
+- [FiveM](https://fivem.net/): a modification framework for GTA V
+- [fmtlog](https://github.com/MengRao/fmtlog): a performant
+  fmtlib-style logging library with latency in nanoseconds
+- [Folly](https://github.com/facebook/folly): Facebook open-source
+  library
+- [GemRB](https://gemrb.org/): a portable open-source implementation
+  of Bioware's Infinity Engine
+- [Grand Mountain
+  Adventure](https://store.steampowered.com/app/1247360/Grand_Mountain_Adventure/):
+  a beautiful open-world ski & snowboarding game
+- [HarpyWar/pvpgn](https://github.com/pvpgn/pvpgn-server): Player vs
+  Player Gaming Network with tweaks
+- [KBEngine](https://github.com/kbengine/kbengine): an open-source
+  MMOG server engine
+- [Keypirinha](https://keypirinha.com/): a semantic launcher for
+  Windows
+- [Kodi](https://kodi.tv/) (formerly xbmc): home theater software
+- [Knuth](https://kth.cash/): high-performance Bitcoin full-node
+- [libunicode](https://github.com/contour-terminal/libunicode/): a
+  modern C++17 Unicode library
+- [MariaDB](https://mariadb.org/): relational database management
+  system
+- [Microsoft Verona](https://github.com/microsoft/verona): research
+  programming language for concurrent ownership
+- [MongoDB](https://mongodb.com/): distributed document database
+- [MongoDB Smasher](https://github.com/duckie/mongo_smasher): a small
+  tool to generate randomized datasets
+- [OpenSpace](https://openspaceproject.com/): an open-source
+  astrovisualization framework
+- [PenUltima Online (POL)](https://www.polserver.com/): an MMO server,
+  compatible with most Ultima Online clients
+- [PyTorch](https://github.com/pytorch/pytorch): an open-source
+  machine learning library
+- [quasardb](https://www.quasardb.net/): a distributed,
+  high-performance, associative database
+- [Quill](https://github.com/odygrd/quill): asynchronous low-latency
+  logging library
+- [QKW](https://github.com/ravijanjam/qkw): generalizing aliasing to
+  simplify navigation, and executing complex multi-line terminal
+  command sequences
+- [redis-cerberus](https://github.com/HunanTV/redis-cerberus): a Redis
+  cluster proxy
+- [redpanda](https://vectorized.io/redpanda): a 10x faster Kafka®
+  replacement for mission-critical systems written in C++
+- [rpclib](http://rpclib.net/): a modern C++ msgpack-RPC server and
+  client library
+- [Salesforce Analytics
+  Cloud](https://www.salesforce.com/analytics-cloud/overview/):
+  business intelligence software
+- [Scylla](https://www.scylladb.com/): a Cassandra-compatible NoSQL
+  data store that can handle 1 million transactions per second on a
+  single server
+- [Seastar](http://www.seastar-project.org/): an advanced, open-source
+  C++ framework for high-performance server applications on modern
+  hardware
+- [spdlog](https://github.com/gabime/spdlog): super fast C++ logging
+  library
+- [Stellar](https://www.stellar.org/): financial platform
+- [Touch Surgery](https://www.touchsurgery.com/): surgery simulator
+- [TrinityCore](https://github.com/TrinityCore/TrinityCore):
+  open-source MMORPG framework
+- [🐙 userver framework](https://userver.tech/): open-source
+  asynchronous framework with a rich set of abstractions and database
+  drivers
+- [Windows Terminal](https://github.com/microsoft/terminal): the new
+  Windows terminal
+
+[More\...](https://github.com/search?q=fmtlib&type=Code)
+
+If you are aware of other projects using this library, please let me
+know by [email](mailto:victor.zverovich@gmail.com) or by submitting an
+[issue](https://github.com/fmtlib/fmt/issues).
+
+# Motivation
+
+So why yet another formatting library?
+
+There are plenty of methods for doing this task, from standard ones like
+the printf family of function and iostreams to Boost Format and
+FastFormat libraries. The reason for creating a new library is that
+every existing solution that I found either had serious issues or
+didn\'t provide all the features I needed.
+
+## printf
+
+The good thing about `printf` is that it is pretty fast and readily
+available being a part of the C standard library. The main drawback is
+that it doesn\'t support user-defined types. `printf` also has safety
+issues although they are somewhat mitigated with [\_\_attribute\_\_
+((format (printf,
+\...))](https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html) in
+GCC. There is a POSIX extension that adds positional arguments required
+for
+[i18n](https://en.wikipedia.org/wiki/Internationalization_and_localization)
+to `printf` but it is not a part of C99 and may not be available on some
+platforms.
+
+## iostreams
+
+The main issue with iostreams is best illustrated with an example:
+
+``` c++
+std::cout << std::setprecision(2) << std::fixed << 1.23456 << "\n";
+```
+
+which is a lot of typing compared to printf:
+
+``` c++
+printf("%.2f\n", 1.23456);
+```
+
+Matthew Wilson, the author of FastFormat, called this \"chevron hell\".
+iostreams don\'t support positional arguments by design.
+
+The good part is that iostreams support user-defined types and are safe
+although error handling is awkward.
+
+## Boost Format
+
+This is a very powerful library that supports both `printf`-like format
+strings and positional arguments. Its main drawback is performance.
+According to various benchmarks, it is much slower than other methods
+considered here. Boost Format also has excessive build times and severe
+code bloat issues (see [Benchmarks](#benchmarks)).
+
+## FastFormat
+
+This is an interesting library that is fast, safe, and has positional
+arguments. However, it has significant limitations, citing its author:
+
+> Three features that have no hope of being accommodated within the
+> current design are:
+>
+> - Leading zeros (or any other non-space padding)
+> - Octal/hexadecimal encoding
+> - Runtime width/alignment specification
+
+It is also quite big and has a heavy dependency, STLSoft, which might be
+too restrictive for using it in some projects.
+
+## Boost Spirit.Karma
+
+This is not a formatting library but I decided to include it here for
+completeness. As iostreams, it suffers from the problem of mixing
+verbatim text with arguments. The library is pretty fast, but slower on
+integer formatting than `fmt::format_to` with format string compilation
+on Karma\'s own benchmark, see [Converting a hundred million integers to
+strings per
+second](http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html).
+
+# License
+
+{fmt} is distributed under the MIT
+[license](https://github.com/fmtlib/fmt/blob/master/LICENSE).
+
+# Documentation License
+
+The [Format String Syntax](https://fmt.dev/latest/syntax.html) section
+in the documentation is based on the one from Python [string module
+documentation](https://docs.python.org/3/library/string.html#module-string).
+For this reason, the documentation is distributed under the Python
+Software Foundation license available in
+[doc/python-license.txt](https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt).
+It only applies if you distribute the documentation of {fmt}.
+
+# Maintainers
+
+The {fmt} library is maintained by Victor Zverovich
+([vitaut](https://github.com/vitaut)) with contributions from many other
+people. See
+[Contributors](https://github.com/fmtlib/fmt/graphs/contributors) and
+[Releases](https://github.com/fmtlib/fmt/releases) for some of the
+names. Let us know if your contribution is not listed or mentioned
+incorrectly and we\'ll make it right.
+
+# Security Policy
+
+To report a security issue, please disclose it at [security
+advisory](https://github.com/fmtlib/fmt/security/advisories/new).
+
+This project is maintained by a team of volunteers on a
+reasonable-effort basis. As such, please give us at least 90 days to
+work on a fix before public exposure.
@@ -1,534 +0,0 @@
-.. image:: https://user-images.githubusercontent.com/
-           576385/156254208-f5b743a9-88cf-439d-b0c0-923d53e8d551.png
-   :width: 25%
-   :alt: {fmt}
-
-.. image:: https://github.com/fmtlib/fmt/workflows/linux/badge.svg
-   :target: https://github.com/fmtlib/fmt/actions?query=workflow%3Alinux
-
-.. image:: https://github.com/fmtlib/fmt/workflows/macos/badge.svg
-   :target: https://github.com/fmtlib/fmt/actions?query=workflow%3Amacos
-
-.. image:: https://github.com/fmtlib/fmt/workflows/windows/badge.svg
-   :target: https://github.com/fmtlib/fmt/actions?query=workflow%3Awindows
-
-.. image:: https://ci.appveyor.com/api/projects/status/ehjkiefde6gucy1v?svg=true
-   :target: https://ci.appveyor.com/project/vitaut/fmt
-
-.. image:: https://oss-fuzz-build-logs.storage.googleapis.com/badges/fmt.svg
-   :alt: fmt is continuously fuzzed at oss-fuzz
-   :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?\
-            colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\
-            Summary&q=proj%3Dfmt&can=1
-
-.. image:: https://img.shields.io/badge/stackoverflow-fmt-blue.svg
-   :alt: Ask questions at StackOverflow with the tag fmt
-   :target: https://stackoverflow.com/questions/tagged/fmt
-
-**{fmt}** is an open-source formatting library providing a fast and safe
-alternative to C stdio and C++ iostreams.
-
-If you like this project, please consider donating to one of the funds that
-help victims of the war in Ukraine: https://www.stopputin.net/.
-
-`Documentation <https://fmt.dev>`__
-
-`Cheat Sheets <https://hackingcpp.com/cpp/libs/fmt.html>`__
-
-Q&A: ask questions on `StackOverflow with the tag fmt
-<https://stackoverflow.com/questions/tagged/fmt>`_.
-
-Try {fmt} in `Compiler Explorer <https://godbolt.org/z/Eq5763>`_.
-
-Features
--------
-
-* Simple `format API <https://fmt.dev/latest/api.html>`_ with positional arguments
-  for localization
-* Implementation of `C++20 std::format
-  <https://en.cppreference.com/w/cpp/utility/format>`__
-* `Format string syntax <https://fmt.dev/latest/syntax.html>`_ similar to Python's
-  `format <https://docs.python.org/3/library/stdtypes.html#str.format>`_
-* Fast IEEE 754 floating-point formatter with correct rounding, shortness and
-  round-trip guarantees
-* Safe `printf implementation
-  <https://fmt.dev/latest/api.html#printf-formatting>`_ including the POSIX
-  extension for positional arguments
-* Extensibility: `support for user-defined types
-  <https://fmt.dev/latest/api.html#formatting-user-defined-types>`_
-* High performance: faster than common standard library implementations of
-  ``(s)printf``, iostreams, ``to_string`` and ``to_chars``, see `Speed tests`_
-  and `Converting a hundred million integers to strings per second
-  <http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_
-* Small code size both in terms of source code with the minimum configuration
-  consisting of just three files, ``core.h``, ``format.h`` and ``format-inl.h``,
-  and compiled code; see `Compile time and code bloat`_
-* Reliability: the library has an extensive set of `tests
-  <https://github.com/fmtlib/fmt/tree/master/test>`_ and is `continuously fuzzed
-  <https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20
-  Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dfmt&can=1>`_
-* Safety: the library is fully type safe, errors in format strings can be
-  reported at compile time, automatic memory management prevents buffer overflow
-  errors
-* Ease of use: small self-contained code base, no external dependencies,
-  permissive MIT `license
-  <https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_
-* `Portability <https://fmt.dev/latest/index.html#portability>`_ with
-  consistent output across platforms and support for older compilers
-* Clean warning-free codebase even on high warning levels such as
-  ``-Wall -Wextra -pedantic``
-* Locale-independence by default
-* Optional header-only configuration enabled with the ``FMT_HEADER_ONLY`` macro
-
-See the `documentation <https://fmt.dev>`_ for more details.
-
-Examples
--------
-
-**Print to stdout** (`run <https://godbolt.org/z/Tevcjh>`_)
-
-.. code:: c++
-
-    #include <fmt/core.h>
-    
-    int main() {
-      fmt::print("Hello, world!\n");
-    }
-
-**Format a string** (`run <https://godbolt.org/z/oK8h33>`_)
-
-.. code:: c++
-
-    std::string s = fmt::format("The answer is {}.", 42);
-    // s == "The answer is 42."
-
-**Format a string using positional arguments** (`run <https://godbolt.org/z/Yn7Txe>`_)
-
-.. code:: c++
-
-    std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
-    // s == "I'd rather be happy than right."
-
-**Print chrono durations** (`run <https://godbolt.org/z/K8s4Mc>`_)
-
-.. code:: c++
-
-    #include <fmt/chrono.h>
-
-    int main() {
-      using namespace std::literals::chrono_literals;
-      fmt::print("Default format: {} {}\n", 42s, 100ms);
-      fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);
-    }
-
-Output::
-
-    Default format: 42s 100ms
-    strftime-like format: 03:15:30
-
-**Print a container** (`run <https://godbolt.org/z/MxM1YqjE7>`_)
-
-.. code:: c++
-
-    #include <vector>
-    #include <fmt/ranges.h>
-
-    int main() {
-      std::vector<int> v = {1, 2, 3};
-      fmt::print("{}\n", v);
-    }
-
-Output::
-
-    [1, 2, 3]
-
-**Check a format string at compile time**
-
-.. code:: c++
-
-    std::string s = fmt::format("{:d}", "I am not a number");
-
-This gives a compile-time error in C++20 because ``d`` is an invalid format
-specifier for a string.
-
-**Write a file from a single thread**
-
-.. code:: c++
-
-    #include <fmt/os.h>
-
-    int main() {
-      auto out = fmt::output_file("guide.txt");
-      out.print("Don't {}", "Panic");
-    }
-
-This can be `5 to 9 times faster than fprintf
-<http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html>`_.
-
-**Print with colors and text styles**
-
-.. code:: c++
-
-    #include <fmt/color.h>
-
-    int main() {
-      fmt::print(fg(fmt::color::crimson) | fmt::emphasis::bold,
-                 "Hello, {}!\n", "world");
-      fmt::print(fg(fmt::color::floral_white) | bg(fmt::color::slate_gray) |
-                 fmt::emphasis::underline, "Hello, {}!\n", "мир");
-      fmt::print(fg(fmt::color::steel_blue) | fmt::emphasis::italic,
-                 "Hello, {}!\n", "世界");
-    }
-
-Output on a modern terminal:
-
-.. image:: https://user-images.githubusercontent.com/
-           576385/88485597-d312f600-cf2b-11ea-9cbe-61f535a86e28.png
-
-Benchmarks
----------
-
-Speed tests
-~~~~~~~~~~~
-
-================= ============= ===========
-Library           Method        Run Time, s
-================= ============= ===========
-libc              printf          1.04
-libc++            std::ostream    3.05
-{fmt} 6.1.1       fmt::print      0.75
-Boost Format 1.67 boost::format   7.24
-Folly Format      folly::format   2.23
-================= ============= ===========
-
-{fmt} is the fastest of the benchmarked methods, ~35% faster than ``printf``.
-
-The above results were generated by building ``tinyformat_test.cpp`` on macOS
-10.14.6 with ``clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT``, and taking the
-best of three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
-or equivalent is filled 2,000,000 times with output sent to ``/dev/null``; for
-further details refer to the `source
-<https://github.com/fmtlib/format-benchmark/blob/master/src/tinyformat-test.cc>`_.
-
-{fmt} is up to 20-30x faster than ``std::ostringstream`` and ``sprintf`` on
-floating-point formatting (`dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_)
-and faster than `double-conversion <https://github.com/google/double-conversion>`_ and
-`ryu <https://github.com/ulfjack/ryu>`_:
-
-.. image:: https://user-images.githubusercontent.com/576385/
-           95684665-11719600-0ba8-11eb-8e5b-972ff4e49428.png
-   :target: https://fmt.dev/unknown_mac64_clang12.0.html
-
-Compile time and code bloat
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The script `bloat-test.py
-<https://github.com/fmtlib/format-benchmark/blob/master/bloat-test.py>`_
-from `format-benchmark <https://github.com/fmtlib/format-benchmark>`_
-tests compile time and code bloat for nontrivial projects.
-It generates 100 translation units and uses ``printf()`` or its alternative
-five times in each to simulate a medium sized project.  The resulting
-executable size and compile time (Apple LLVM version 8.1.0 (clang-802.0.42),
-macOS Sierra, best of three) is shown in the following tables.
-
-**Optimized build (-O3)**
-
-============= =============== ==================== ==================
-Method        Compile Time, s Executable size, KiB Stripped size, KiB
-============= =============== ==================== ==================
-printf                    2.6                   29                 26
-printf+string            16.4                   29                 26
-iostreams                31.1                   59                 55
-{fmt}                    19.0                   37                 34
-Boost Format             91.9                  226                203
-Folly Format            115.7                  101                 88
-============= =============== ==================== ==================
-
-As you can see, {fmt} has 60% less overhead in terms of resulting binary code
-size compared to iostreams and comes pretty close to ``printf``. Boost Format
-and Folly Format have the largest overheads.
-
-``printf+string`` is the same as ``printf`` but with extra ``<string>``
-include to measure the overhead of the latter.
-
-**Non-optimized build**
-
-============= =============== ==================== ==================
-Method        Compile Time, s Executable size, KiB Stripped size, KiB
-============= =============== ==================== ==================
-printf                    2.2                   33                 30
-printf+string            16.0                   33                 30
-iostreams                28.3                   56                 52
-{fmt}                    18.2                   59                 50
-Boost Format             54.1                  365                303
-Folly Format             79.9                  445                430
-============= =============== ==================== ==================
-
-``libc``, ``lib(std)c++`` and ``libfmt`` are all linked as shared libraries to
-compare formatting function overhead only. Boost Format is a
-header-only library so it doesn't provide any linkage options.
-
-Running the tests
-~~~~~~~~~~~~~~~~~
-
-Please refer to `Building the library`__ for the instructions on how to build
-the library and run the unit tests.
-
-__ https://fmt.dev/latest/usage.html#building-the-library
-
-Benchmarks reside in a separate repository,
-`format-benchmarks <https://github.com/fmtlib/format-benchmark>`_,
-so to run the benchmarks you first need to clone this repository and
-generate Makefiles with CMake::
-
-    $ git clone --recursive https://github.com/fmtlib/format-benchmark.git
-    $ cd format-benchmark
-    $ cmake .
-
-Then you can run the speed test::
-
-    $ make speed-test
-
-or the bloat test::
-
-    $ make bloat-test
-    
-Migrating code
--------------
-
-`clang-tidy-fmt <https://github.com/mikecrowe/clang-tidy-fmt>`_ provides clang
-tidy checks for converting occurrences of ``printf`` and ``fprintf`` to
-``fmt::print``.
-
-Projects using this library
---------------------------
-
-* `0 A.D. <https://play0ad.com/>`_: a free, open-source, cross-platform
-  real-time strategy game
-
-* `2GIS <https://2gis.ru/>`_: free business listings with a city map
-
-* `AMPL/MP <https://github.com/ampl/mp>`_:
-  an open-source library for mathematical programming
-
-* `Aseprite <https://github.com/aseprite/aseprite>`_:
-  animated sprite editor & pixel art tool 
-
-* `AvioBook <https://www.aviobook.aero/en>`_: a comprehensive aircraft
-  operations suite
-  
-* `Blizzard Battle.net <https://battle.net/>`_: an online gaming platform
-  
-* `Celestia <https://celestia.space/>`_: real-time 3D visualization of space
-
-* `Ceph <https://ceph.com/>`_: a scalable distributed storage system
-
-* `ccache <https://ccache.dev/>`_: a compiler cache
-
-* `ClickHouse <https://github.com/ClickHouse/ClickHouse>`_: analytical database
-  management system
-
-* `CUAUV <https://cuauv.org/>`_: Cornell University's autonomous underwater
-  vehicle
-
-* `Drake <https://drake.mit.edu/>`_: a planning, control, and analysis toolbox
-  for nonlinear dynamical systems (MIT)
-
-* `Envoy <https://lyft.github.io/envoy/>`_: C++ L7 proxy and communication bus
-  (Lyft)
-
-* `FiveM <https://fivem.net/>`_: a modification framework for GTA V
-
-* `fmtlog <https://github.com/MengRao/fmtlog>`_: a performant fmtlib-style
-  logging library with latency in nanoseconds
-
-* `Folly <https://github.com/facebook/folly>`_: Facebook open-source library
-
-* `GemRB <https://gemrb.org/>`_: a portable open-source implementation of
-  Bioware’s Infinity Engine
-
-* `Grand Mountain Adventure
-  <https://store.steampowered.com/app/1247360/Grand_Mountain_Adventure/>`_:
-  a beautiful open-world ski & snowboarding game
-
-* `HarpyWar/pvpgn <https://github.com/pvpgn/pvpgn-server>`_:
-  Player vs Player Gaming Network with tweaks
-
-* `KBEngine <https://github.com/kbengine/kbengine>`_: an open-source MMOG server
-  engine
-
-* `Keypirinha <https://keypirinha.com/>`_: a semantic launcher for Windows
-
-* `Kodi <https://kodi.tv/>`_ (formerly xbmc): home theater software
-
-* `Knuth <https://kth.cash/>`_: high-performance Bitcoin full-node
-
-* `Microsoft Verona <https://github.com/microsoft/verona>`_:
-  research programming language for concurrent ownership
-
-* `MongoDB <https://mongodb.com/>`_: distributed document database
-
-* `MongoDB Smasher <https://github.com/duckie/mongo_smasher>`_: a small tool to
-  generate randomized datasets
-
-* `OpenSpace <https://openspaceproject.com/>`_: an open-source
-  astrovisualization framework
-
-* `PenUltima Online (POL) <https://www.polserver.com/>`_:
-  an MMO server, compatible with most Ultima Online clients
-
-* `PyTorch <https://github.com/pytorch/pytorch>`_: an open-source machine
-  learning library
-
-* `quasardb <https://www.quasardb.net/>`_: a distributed, high-performance,
-  associative database
-  
-* `Quill <https://github.com/odygrd/quill>`_: asynchronous low-latency logging library
-
-* `QKW <https://github.com/ravijanjam/qkw>`_: generalizing aliasing to simplify
-  navigation, and executing complex multi-line terminal command sequences
-
-* `redis-cerberus <https://github.com/HunanTV/redis-cerberus>`_: a Redis cluster
-  proxy
-
-* `redpanda <https://vectorized.io/redpanda>`_: a 10x faster Kafka® replacement
-  for mission critical systems written in C++
-
-* `rpclib <http://rpclib.net/>`_: a modern C++ msgpack-RPC server and client
-  library
-
-* `Salesforce Analytics Cloud
-  <https://www.salesforce.com/analytics-cloud/overview/>`_:
-  business intelligence software
-
-* `Scylla <https://www.scylladb.com/>`_: a Cassandra-compatible NoSQL data store
-  that can handle 1 million transactions per second on a single server
-
-* `Seastar <http://www.seastar-project.org/>`_: an advanced, open-source C++
-  framework for high-performance server applications on modern hardware
-
-* `spdlog <https://github.com/gabime/spdlog>`_: super fast C++ logging library
-
-* `Stellar <https://www.stellar.org/>`_: financial platform
-
-* `Touch Surgery <https://www.touchsurgery.com/>`_: surgery simulator
-
-* `TrinityCore <https://github.com/TrinityCore/TrinityCore>`_: open-source
-  MMORPG framework
-
-* `Windows Terminal <https://github.com/microsoft/terminal>`_: the new Windows
-  terminal
-
-`More... <https://github.com/search?q=fmtlib&type=Code>`_
-
-If you are aware of other projects using this library, please let me know
-by `email <mailto:victor.zverovich@gmail.com>`_ or by submitting an
-`issue <https://github.com/fmtlib/fmt/issues>`_.
-
-Motivation
----------
-
-So why yet another formatting library?
-
-There are plenty of methods for doing this task, from standard ones like
-the printf family of function and iostreams to Boost Format and FastFormat
-libraries. The reason for creating a new library is that every existing
-solution that I found either had serious issues or didn't provide
-all the features I needed.
-
-printf
-~~~~~~
-
-The good thing about ``printf`` is that it is pretty fast and readily available
-being a part of the C standard library. The main drawback is that it
-doesn't support user-defined types. ``printf`` also has safety issues although
-they are somewhat mitigated with `__attribute__ ((format (printf, ...))
-<https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html>`_ in GCC.
-There is a POSIX extension that adds positional arguments required for
-`i18n <https://en.wikipedia.org/wiki/Internationalization_and_localization>`_
-to ``printf`` but it is not a part of C99 and may not be available on some
-platforms.
-
-iostreams
-~~~~~~~~~
-
-The main issue with iostreams is best illustrated with an example:
-
-.. code:: c++
-
-    std::cout << std::setprecision(2) << std::fixed << 1.23456 << "\n";
-
-which is a lot of typing compared to printf:
-
-.. code:: c++
-
-    printf("%.2f\n", 1.23456);
-
-Matthew Wilson, the author of FastFormat, called this "chevron hell". iostreams
-don't support positional arguments by design.
-
-The good part is that iostreams support user-defined types and are safe although
-error handling is awkward.
-
-Boost Format
-~~~~~~~~~~~~
-
-This is a very powerful library which supports both ``printf``-like format
-strings and positional arguments. Its main drawback is performance. According to
-various benchmarks, it is much slower than other methods considered here. Boost
-Format also has excessive build times and severe code bloat issues (see
-`Benchmarks`_).
-
-FastFormat
-~~~~~~~~~~
-
-This is an interesting library which is fast, safe and has positional arguments.
-However, it has significant limitations, citing its author:
-
-    Three features that have no hope of being accommodated within the
-    current design are:
-
-    * Leading zeros (or any other non-space padding)
-    * Octal/hexadecimal encoding
-    * Runtime width/alignment specification
-
-It is also quite big and has a heavy dependency, STLSoft, which might be too
-restrictive for using it in some projects.
-
-Boost Spirit.Karma
-~~~~~~~~~~~~~~~~~~
-
-This is not really a formatting library but I decided to include it here for
-completeness. As iostreams, it suffers from the problem of mixing verbatim text
-with arguments. The library is pretty fast, but slower on integer formatting
-than ``fmt::format_to`` with format string compilation on Karma's own benchmark,
-see `Converting a hundred million integers to strings per second
-<http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_.
-
-License
-------
-
-{fmt} is distributed under the MIT `license
-<https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_.
-
-Documentation License
---------------------
-
-The `Format String Syntax <https://fmt.dev/latest/syntax.html>`_
-section in the documentation is based on the one from Python `string module
-documentation <https://docs.python.org/3/library/string.html#module-string>`_.
-For this reason the documentation is distributed under the Python Software
-Foundation license available in `doc/python-license.txt
-<https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt>`_.
-It only applies if you distribute the documentation of {fmt}.
-
-Maintainers
-----------
-
-The {fmt} library is maintained by Victor Zverovich (`vitaut
-<https://github.com/vitaut>`_) and Jonathan Müller (`foonathan
-<https://github.com/foonathan>`_) with contributions from many other people.
-See `Contributors <https://github.com/fmtlib/fmt/graphs/contributors>`_ and
-`Releases <https://github.com/fmtlib/fmt/releases>`_ for some of the names.
-Let us know if your contribution is not listed or mentioned incorrectly and
-we'll make it right.
@@ -1,10 +1,19 @@
-find_program(DOXYGEN doxygen)
+find_program(DOXYGEN doxygen
+  PATHS "$ENV{ProgramFiles}/doxygen/bin"
+        "$ENV{ProgramFiles\(x86\)}/doxygen/bin")
 if (NOT DOXYGEN)
  message(STATUS "Target 'doc' disabled (requires doxygen)")
  return ()
 endif ()

-find_package(PythonInterp QUIET REQUIRED)
+# Find the Python interpreter and set the PYTHON_EXECUTABLE variable.
+if (CMAKE_VERSION VERSION_LESS 3.12)
+  # This logic is deprecated in CMake after 3.12.
+  find_package(PythonInterp QUIET REQUIRED)
+else ()
+  find_package(Python QUIET REQUIRED)
+  set(PYTHON_EXECUTABLE ${Python_EXECUTABLE})
+endif ()

 add_custom_target(doc
  COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/build.py
@@ -7,7 +7,7 @@ API Reference
 The {fmt} library API consists of the following parts:

 * :ref:`fmt/core.h <core-api>`: the core API providing main formatting functions
-  for ``char``/UTF-8 with compile-time checks and minimal dependencies
+  for ``char``/UTF-8 with C++20 compile-time checks and minimal dependencies
 * :ref:`fmt/format.h <format-api>`: the full format API providing additional
  formatting functions and locale support
 * :ref:`fmt/ranges.h <ranges-api>`: formatting of ranges and tuples
@@ -17,6 +17,7 @@ The {fmt} library API consists of the following parts:
 * :ref:`fmt/color.h <color-api>`: terminal color and text style
 * :ref:`fmt/os.h <os-api>`: system APIs
 * :ref:`fmt/ostream.h <ostream-api>`: ``std::ostream`` support
+* :ref:`fmt/args.h <args-api>`: dynamic argument lists
 * :ref:`fmt/printf.h <printf-api>`: ``printf`` formatting
 * :ref:`fmt/xchar.h <xchar-api>`: optional ``wchar_t`` support 

@@ -28,10 +29,11 @@ macros have prefix ``FMT_``.
 Core API
 ========

-``fmt/core.h`` defines the core API which provides main formatting functions for
-``char``/UTF-8 with compile-time checks. It has minimal include dependencies for
-better compile times. This header is only beneficial when using {fmt} as a
-library and not in the header-only mode.
+``fmt/core.h`` defines the core API which provides main formatting functions
+for ``char``/UTF-8 with C++20 compile-time checks. It has minimal include
+dependencies for better compile times. This header is only beneficial when
+using {fmt} as a library (the default) and not in the header-only mode.
+It also provides ``formatter`` specializations for built-in and string types.

 The following functions use :ref:`format string syntax <syntax>`
 similar to that of Python's `str.format
@@ -47,6 +49,10 @@ checked at compile time in C++20. To pass a runtime format string wrap it in

 *args* is an argument list representing objects to be formatted.

+I/O errors are reported as `std::system_error
+<https://en.cppreference.com/w/cpp/error/system_error>`_ exceptions unless
+specified otherwise.
+
 .. _format:

 .. doxygenfunction:: format(format_string<T...> fmt, T&&... args) -> std::string
@@ -70,24 +76,190 @@ checked at compile time in C++20. To pass a runtime format string wrap it in
 Compile-Time Format String Checks
 ---------------------------------

-Compile-time checks are enabled when using ``FMT_STRING``. They support built-in
-and string types as well as user-defined types with ``constexpr`` ``parse``
-functions in their ``formatter`` specializations.
-Requires C++14 and is a no-op in C++11.
+Compile-time format string checks are enabled by default on compilers
+that support C++20 ``consteval``. On older compilers you can use the
+:ref:`FMT_STRING <legacy-checks>`: macro defined in ``fmt/format.h`` instead.

-.. doxygendefine:: FMT_STRING
-
-To force the use of compile-time checks, define the preprocessor variable
-``FMT_ENFORCE_COMPILE_STRING``. When set, functions accepting ``FMT_STRING``
-will fail to compile with regular strings. Runtime-checked
-formatting is still possible using ``fmt::vformat``, ``fmt::vprint``, etc.
+Unused arguments are allowed as in Python's `str.format` and ordinary functions.

 .. doxygenclass:: fmt::basic_format_string
   :members:

 .. doxygentypedef:: fmt::format_string

-.. doxygenfunction:: fmt::runtime(const S&)
+.. doxygenfunction:: fmt::runtime(string_view) -> runtime_format_string<>
+
+.. _udt:
+
+Formatting User-Defined Types
+-----------------------------
+
+The {fmt} library provides formatters for many standard C++ types.
+See :ref:`fmt/ranges.h <ranges-api>` for ranges and tuples including standard
+containers such as ``std::vector``, :ref:`fmt/chrono.h <chrono-api>` for date
+and time formatting and :ref:`fmt/std.h <std-api>` for other standard library
+types.
+
+There are two ways to make a user-defined type formattable: providing a
+``format_as`` function or specializing the ``formatter`` struct template.
+
+Use ``format_as`` if you want to make your type formattable as some other type
+with the same format specifiers. The ``format_as`` function should take an
+object of your type and return an object of a formattable type. It should be
+defined in the same namespace as your type.
+
+Example (https://godbolt.org/z/nvME4arz8)::
+
+  #include <fmt/format.h>
+
+  namespace kevin_namespacy {
+  enum class film {
+    house_of_cards, american_beauty, se7en = 7
+  };
+  auto format_as(film f) { return fmt::underlying(f); }
+  }
+
+  int main() {
+    fmt::print("{}\n", kevin_namespacy::film::se7en); // prints "7"
+  }
+
+Using specialization is more complex but gives you full control over parsing and
+formatting. To use this method specialize the ``formatter`` struct template for
+your type and implement ``parse`` and ``format`` methods.
+
+The recommended way of defining a formatter is by reusing an existing one via
+inheritance or composition. This way you can support standard format specifiers
+without implementing them yourself. For example::
+
+  // color.h:
+  #include <fmt/core.h>
+
+  enum class color {red, green, blue};
+
+  template <> struct fmt::formatter<color>: formatter<string_view> {
+    // parse is inherited from formatter<string_view>.
+
+    auto format(color c, format_context& ctx) const;
+  };
+
+  // color.cc:
+  #include "color.h"
+  #include <fmt/format.h>
+
+  auto fmt::formatter<color>::format(color c, format_context& ctx) const {
+    string_view name = "unknown";
+    switch (c) {
+    case color::red:   name = "red"; break;
+    case color::green: name = "green"; break;
+    case color::blue:  name = "blue"; break;
+    }
+    return formatter<string_view>::format(name, ctx);
+  }
+
+Note that ``formatter<string_view>::format`` is defined in ``fmt/format.h`` so
+it has to be included in the source file. Since ``parse`` is inherited from
+``formatter<string_view>`` it will recognize all string format specifications,
+for example
+
+.. code-block:: c++
+
+   fmt::format("{:>10}", color::blue)
+
+will return ``"      blue"``.
+
+The experimental ``nested_formatter`` provides an easy way of applying a
+formatter to one or more subobjects.
+
+For example::
+
+  #include <fmt/format.h>
+
+  struct point {
+    double x, y;
+  };
+
+  template <>
+  struct fmt::formatter<point> : nested_formatter<double> {
+    auto format(point p, format_context& ctx) const {
+      return write_padded(ctx, [=](auto out) {
+        return format_to(out, "({}, {})", nested(p.x), nested(p.y));
+      });
+    }
+  };
+
+  int main() {
+    fmt::print("[{:>20.2f}]", point{1, 2});
+  }
+
+prints::
+
+  [          (1.00, 2.00)]
+
+Notice that fill, align and width are applied to the whole object which is the
+recommended behavior while the remaining specifiers apply to elements.
+
+In general the formatter has the following form::
+
+  template <> struct fmt::formatter<T> {
+    // Parses format specifiers and stores them in the formatter.
+    //
+    // [ctx.begin(), ctx.end()) is a, possibly empty, character range that
+    // contains a part of the format string starting from the format
+    // specifications to be parsed, e.g. in
+    //
+    //   fmt::format("{:f} continued", ...);
+    //
+    // the range will contain "f} continued". The formatter should parse
+    // specifiers until '}' or the end of the range. In this example the
+    // formatter should parse the 'f' specifier and return an iterator
+    // pointing to '}'.
+    constexpr auto parse(format_parse_context& ctx)
+      -> format_parse_context::iterator;
+
+    // Formats value using the parsed format specification stored in this
+    // formatter and writes the output to ctx.out().
+    auto format(const T& value, format_context& ctx) const
+      -> format_context::iterator;
+  };
+
+It is recommended to at least support fill, align and width that apply to the
+whole object and have the same semantics as in standard formatters.
+
+You can also write a formatter for a hierarchy of classes::
+
+  // demo.h:
+  #include <type_traits>
+  #include <fmt/core.h>
+
+  struct A {
+    virtual ~A() {}
+    virtual std::string name() const { return "A"; }
+  };
+
+  struct B : A {
+    virtual std::string name() const { return "B"; }
+  };
+
+  template <typename T>
+  struct fmt::formatter<T, std::enable_if_t<std::is_base_of<A, T>::value, char>> :
+      fmt::formatter<std::string> {
+    auto format(const A& a, format_context& ctx) const {
+      return fmt::formatter<std::string>::format(a.name(), ctx);
+    }
+  };
+
+  // demo.cc:
+  #include "demo.h"
+  #include <fmt/format.h>
+
+  int main() {
+    B b;
+    A& a = b;
+    fmt::print("{}", a); // prints "B"
+  }
+
+Providing both a ``formatter`` specialization and a ``format_as`` overload is
+disallowed.

 Named Arguments
 ---------------
@@ -100,11 +272,11 @@ Argument Lists
 --------------

 You can create your own formatting function with compile-time checks and small
-binary footprint, for example (https://godbolt.org/z/oba4Mc):
+binary footprint, for example (https://godbolt.org/z/vajfWEG4b):

 .. code:: c++

-    #include <fmt/format.h>
+    #include <fmt/core.h>

    void vlog(const char* file, int line, fmt::string_view format,
              fmt::format_args args) {
@@ -112,13 +284,12 @@ binary footprint, for example (https://godbolt.org/z/oba4Mc):
      fmt::vprint(format, args);
    }

-    template <typename S, typename... Args>
-    void log(const char* file, int line, const S& format, Args&&... args) {
+    template <typename... T>
+    void log(const char* file, int line, fmt::format_string<T...> format, T&&... args) {
      vlog(file, line, format, fmt::make_format_args(args...));
    }

-    #define MY_LOG(format, ...) \
-      log(__FILE__, __LINE__, FMT_STRING(format), __VA_ARGS__)
+    #define MY_LOG(format, ...) log(__FILE__, __LINE__, format, __VA_ARGS__)

    MY_LOG("invalid squishiness: {}", 42);

@@ -130,9 +301,6 @@ times and reduces binary code size compared to a fully parameterized version.
 .. doxygenclass:: fmt::format_arg_store
   :members:

-.. doxygenclass:: fmt::dynamic_format_arg_store
-   :members:
-
 .. doxygenclass:: fmt::basic_format_args
   :members:

@@ -149,6 +317,17 @@ times and reduces binary code size compared to a fully parameterized version.

 .. doxygentypedef:: fmt::format_context

+.. _args-api:
+
+Dynamic Argument Lists
+----------------------
+
+The header ``fmt/args.h`` provides ``dynamic_format_arg_store``, a builder-like
+API that can be used to construct format argument lists dynamically.
+
+.. doxygenclass:: fmt::dynamic_format_arg_store
+   :members:
+
 Compatibility
 -------------

@@ -157,19 +336,6 @@ Compatibility

 .. doxygentypedef:: fmt::string_view

-Locale
------
-
-All formatting is locale-independent by default. Use the ``'L'`` format
-specifier to insert the appropriate number separator characters from the
-locale::
-
-  #include <fmt/core.h>
-  #include <locale>
-
-  std::locale::global(std::locale("en_US.UTF-8"));
-  auto s = fmt::format("{:L}", 1000000);  // s == "1,000,000"
-
 .. _format-api:

 Format API
@@ -178,156 +344,6 @@ Format API
 ``fmt/format.h`` defines the full format API providing additional formatting
 functions and locale support.

-.. _udt:
-
-Formatting User-Defined Types
-----------------------------
-
-The {fmt} library provides formatters for many standard C++ types.
-See :ref:`fmt/ranges.h <ranges-api>` for ranges and tuples including standard
-containers such as ``std::vector``, :ref:`fmt/chrono.h <chrono-api>` for date
-and time formatting and :ref:`fmt/std.h <std-api>` for path and variant 
-formatting.
-
-To make a user-defined type formattable, specialize the ``formatter<T>`` struct
-template and implement ``parse`` and ``format`` methods::
-
-  #include <fmt/format.h>
-
-  struct point {
-    double x, y;
-  };
-
-  template <> struct fmt::formatter<point> {
-    // Presentation format: 'f' - fixed, 'e' - exponential.
-    char presentation = 'f';
-
-    // Parses format specifications of the form ['f' | 'e'].
-    constexpr auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
-      // [ctx.begin(), ctx.end()) is a character range that contains a part of
-      // the format string starting from the format specifications to be parsed,
-      // e.g. in
-      //
-      //   fmt::format("{:f} - point of interest", point{1, 2});
-      //
-      // the range will contain "f} - point of interest". The formatter should
-      // parse specifiers until '}' or the end of the range. In this example
-      // the formatter should parse the 'f' specifier and return an iterator
-      // pointing to '}'.
-      
-      // Please also note that this character range may be empty, in case of
-      // the "{}" format string, so therefore you should check ctx.begin()
-      // for equality with ctx.end().
-
-      // Parse the presentation format and store it in the formatter:
-      auto it = ctx.begin(), end = ctx.end();
-      if (it != end && (*it == 'f' || *it == 'e')) presentation = *it++;
-
-      // Check if reached the end of the range:
-      if (it != end && *it != '}') throw format_error("invalid format");
-
-      // Return an iterator past the end of the parsed range:
-      return it;
-    }
-
-    // Formats the point p using the parsed format specification (presentation)
-    // stored in this formatter.
-    template <typename FormatContext>
-    auto format(const point& p, FormatContext& ctx) const -> decltype(ctx.out()) {
-      // ctx.out() is an output iterator to write to.
-      return presentation == 'f'
-                ? fmt::format_to(ctx.out(), "({:.1f}, {:.1f})", p.x, p.y)
-                : fmt::format_to(ctx.out(), "({:.1e}, {:.1e})", p.x, p.y);
-    }
-  };
-
-Then you can pass objects of type ``point`` to any formatting function::
-
-  point p = {1, 2};
-  std::string s = fmt::format("{:f}", p);
-  // s == "(1.0, 2.0)"
-
-You can also reuse existing formatters via inheritance or composition, for
-example::
-
-  enum class color {red, green, blue};
-
-  template <> struct fmt::formatter<color>: formatter<string_view> {
-    // parse is inherited from formatter<string_view>.
-    template <typename FormatContext>
-    auto format(color c, FormatContext& ctx) const {
-      string_view name = "unknown";
-      switch (c) {
-      case color::red:   name = "red"; break;
-      case color::green: name = "green"; break;
-      case color::blue:  name = "blue"; break;
-      }
-      return formatter<string_view>::format(name, ctx);
-    }
-  };
-
-Since ``parse`` is inherited from ``formatter<string_view>`` it will recognize
-all string format specifications, for example
-
-.. code-block:: c++
-
-   fmt::format("{:>10}", color::blue)
-
-will return ``"      blue"``.
-
-You can also write a formatter for a hierarchy of classes::
-
-  #include <type_traits>
-  #include <fmt/format.h>
-
-  struct A {
-    virtual ~A() {}
-    virtual std::string name() const { return "A"; }
-  };
-
-  struct B : A {
-    virtual std::string name() const { return "B"; }
-  };
-
-  template <typename T>
-  struct fmt::formatter<T, std::enable_if_t<std::is_base_of<A, T>::value, char>> :
-      fmt::formatter<std::string> {
-    template <typename FormatCtx>
-    auto format(const A& a, FormatCtx& ctx) const {
-      return fmt::formatter<std::string>::format(a.name(), ctx);
-    }
-  };
-
-  int main() {
-    B b;
-    A& a = b;
-    fmt::print("{}", a); // prints "B"
-  }
-
-If a type provides both a ``formatter`` specialization and an implicit
-conversion to a formattable type, the specialization takes precedence over the
-conversion.
-
-For enums {fmt} also provides the ``format_as`` extension API. To format an enum
-via this API define ``format_as`` that takes this enum and converts it to the
-underlying type. ``format_as`` should be defined in the same namespace as the
-enum.
-
-Example (https://godbolt.org/z/r7vvGE1v7)::
-
-  #include <fmt/format.h>
-
-  namespace kevin_namespacy {
-  enum class film {
-    house_of_cards, american_beauty, se7en = 7
-  };
-  auto format_as(film f) { return fmt::underlying(f); }
-  }
-
-  int main() {
-    fmt::print("{}\n", kevin_namespacy::film::se7en); // prints "7"
-  }
-
 Literal-Based API
 -----------------

@@ -339,7 +355,7 @@ Utilities
 ---------

 .. doxygenfunction:: fmt::ptr(T p) -> const void*
-.. doxygenfunction:: fmt::ptr(const std::unique_ptr<T> &p) -> const void*
+.. doxygenfunction:: fmt::ptr(const std::unique_ptr<T, Deleter> &p) -> const void*
 .. doxygenfunction:: fmt::ptr(const std::shared_ptr<T> &p) -> const void*

 .. doxygenfunction:: fmt::underlying(Enum e) -> typename std::underlying_type<Enum>::type
@@ -405,6 +421,41 @@ normally don't do any allocations for built-in and string types except for
 non-default floating-point formatting that occasionally falls back on
 ``sprintf``.

+Locale
+------
+
+All formatting is locale-independent by default. Use the ``'L'`` format
+specifier to insert the appropriate number separator characters from the
+locale::
+
+  #include <fmt/core.h>
+  #include <locale>
+
+  std::locale::global(std::locale("en_US.UTF-8"));
+  auto s = fmt::format("{:L}", 1000000);  // s == "1,000,000"
+
+``fmt/format.h`` provides the following overloads of formatting functions that
+take ``std::locale`` as a parameter. The locale type is a template parameter to
+avoid the expensive ``<locale>`` include.
+
+.. doxygenfunction:: format(const Locale& loc, format_string<T...> fmt, T&&... args) -> std::string
+.. doxygenfunction:: format_to(OutputIt out, const Locale& loc, format_string<T...> fmt, T&&... args) -> OutputIt
+.. doxygenfunction:: formatted_size(const Locale& loc, format_string<T...> fmt, T&&... args) -> size_t
+
+.. _legacy-checks:
+
+Legacy Compile-Time Format String Checks
+----------------------------------------
+
+``FMT_STRING`` enables compile-time checks on older compilers. It requires C++14
+or later and is a no-op in C++11.
+
+.. doxygendefine:: FMT_STRING
+
+To force the use of legacy compile-time checks, define the preprocessor variable
+``FMT_ENFORCE_COMPILE_STRING``. When set, functions accepting ``FMT_STRING``
+will fail to compile with regular strings.
+
 .. _ranges-api:

 Range and Tuple Formatting
@@ -474,10 +525,11 @@ Standard Library Types Formatting

 ``fmt/std.h`` provides formatters for:

-* `std::filesystem::path <std::filesystem::path>`_
+* `std::filesystem::path <https://en.cppreference.com/w/cpp/filesystem/path>`_
 * `std::thread::id <https://en.cppreference.com/w/cpp/thread/thread/id>`_
 * `std::monostate <https://en.cppreference.com/w/cpp/utility/variant/monostate>`_
 * `std::variant <https://en.cppreference.com/w/cpp/utility/variant/variant>`_
+* `std::optional <https://en.cppreference.com/w/cpp/utility/optional>`_

 Formatting Variants
 -------------------
@@ -505,10 +557,20 @@ Format String Compilation
 ``FMT_COMPILE`` macro or the ``_cf`` user-defined literal. Format strings
 marked with ``FMT_COMPILE`` or ``_cf`` are parsed, checked and converted into
 efficient formatting code at compile-time. This supports arguments of built-in
-and string types as well as user-defined types with ``constexpr`` ``parse``
-functions in their ``formatter`` specializations. Format string compilation can
-generate more binary code compared to the default API and is only recommended in
-places where formatting is a performance bottleneck.
+and string types as well as user-defined types with ``format`` functions taking
+the format context type as a template parameter in their ``formatter``
+specializations. For example::
+
+  template <> struct fmt::formatter<point> {
+    constexpr auto parse(format_parse_context& ctx);
+
+    template <typename FormatContext>
+    auto format(const point& p, FormatContext& ctx) const;
+  };
+
+Format string compilation can generate more binary code compared to the default
+API and is only recommended in places where formatting is a performance
+bottleneck.

 .. doxygendefine:: FMT_COMPILE

@@ -538,7 +600,6 @@ System APIs
   :members:

 .. doxygenfunction:: fmt::windows_error
-   :members:

 .. _ostream-api:

@@ -581,7 +642,7 @@ the POSIX extension for positional arguments. Unlike their standard
 counterparts, the ``fmt`` functions are type-safe and throw an exception if an
 argument type doesn't match its format specification.

-.. doxygenfunction:: printf(const S &format_str, const T&... args)
+.. doxygenfunction:: printf(string_view fmt, const T&... args) -> int

 .. doxygenfunction:: fprintf(std::FILE *f, const S &fmt, const T&... args) -> int

@@ -4,7 +4,12 @@
 import errno, os, re, sys
 from subprocess import check_call, CalledProcessError, Popen, PIPE, STDOUT

-versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0', '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1', '6.1.2', '6.2.0', '6.2.1', '7.0.0', '7.0.1', '7.0.2', '7.0.3', '7.1.0', '7.1.1', '7.1.2', '7.1.3', '8.0.0', '8.0.1', '8.1.0', '8.1.1', '9.0.0']
+versions = [
+  '1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0',
+  '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1', '6.1.2', '6.2.0',
+  '6.2.1', '7.0.0', '7.0.1', '7.0.2', '7.0.3', '7.1.0', '7.1.1', '7.1.2',
+  '7.1.3', '8.0.0', '8.0.1', '8.1.0', '8.1.1', '9.0.0', '9.1.0']
+versions += ['10.0.0', '10.1.0', '10.1.1', '10.1.1', '10.2.0', '10.2.1']

 class Pip:
  def __init__(self, venv_dir):
@@ -31,7 +36,7 @@ def create_build_env(venv_dir='virtualenv'):
  # Jinja2 >= 3.1 incompatible with sphinx 3.3.0
  # See: https://github.com/sphinx-doc/sphinx/issues/10291
  pip.install('Jinja2<3.1')
-  pip.install('sphinx-doc/sphinx', 'v3.3.0')
+  pip.install('sphinx==3.3.0')
  pip.install('michaeljones/breathe', 'v4.25.0')

 def build_docs(version='dev', **kwargs):
@@ -49,9 +54,9 @@ def build_docs(version='dev', **kwargs):
      GENERATE_MAN      = NO
      GENERATE_RTF      = NO
      CASE_SENSE_NAMES  = NO
-      INPUT             = {0}/chrono.h {0}/color.h {0}/core.h {0}/compile.h \
-                          {0}/format.h {0}/os.h {0}/ostream.h {0}/printf.h \
-                          {0}/xchar.h
+      INPUT             = {0}/args.h {0}/chrono.h {0}/color.h {0}/core.h \
+                          {0}/compile.h {0}/format.h {0}/os.h {0}/ostream.h \
+                          {0}/printf.h {0}/xchar.h
      QUIET             = YES
      JAVADOC_AUTOBRIEF = YES
      AUTOLINK_SUPPORT  = NO
@@ -83,8 +88,7 @@ def build_docs(version='dev', **kwargs):
  internal_symbols = [
    'fmt::detail::.*',
    'basic_data<>',
-    'fmt::type_identity',
-    'fmt::dynamic_formatter'
+    'fmt::type_identity'
  ]
  noisy_warnings = [
    'warning: (Compound|Member .* of class) (' + '|'.join(internal_symbols) + \
@@ -39,7 +39,7 @@ The ``fmt::format`` function returns a string "The answer is 42.". You can use
 .. code:: c++

  auto out = fmt::memory_buffer();
-  format_to(std::back_inserter(out),
+  fmt::format_to(std::back_inserter(out),
            "For a moment, {} happened.", "nothing");
  auto data = out.data(); // pointer to the formatted data
  auto size = out.size(); // size of the formatted data
@@ -82,7 +82,7 @@ The general form of a *standard format specifier* is:
   width: `integer` | "{" [`arg_id`] "}"
   precision: `integer` | "{" [`arg_id`] "}"
   type: "a" | "A" | "b" | "B" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" |
-       : "o" | "p" | "s" | "x" | "X"
+       : "o" | "p" | "s" | "x" | "X" | "?"

 The *fill* character can be any Unicode code point other than ``'{'`` or
 ``'}'``. The presence of a fill character is signaled by the character following
@@ -109,8 +109,8 @@ Note that unless a minimum field width is defined, the field width will always
 be the same size as the data to fill it, so that the alignment option has no
 meaning in this case.

-The *sign* option is only valid for number types, and can be one of the
-following:
+The *sign* option is only valid for floating point and signed integer types,
+and can be one of the following:

 +---------+------------------------------------------------------------+
 | Option  | Meaning                                                    |
@@ -177,6 +177,9 @@ The available string presentation types are:
 | ``'s'`` | String format. This is the default type for strings and  |
 |         | may be omitted.                                          |
 +---------+----------------------------------------------------------+
+| ``'?'`` | Debug format. The string is quoted and special           |
+|         | characters escaped.                                      |
+---------+----------------------------------------------------------+
 | none    | The same as ``'s'``.                                     |
 +---------+----------------------------------------------------------+

@@ -188,6 +191,9 @@ The available character presentation types are:
 | ``'c'`` | Character format. This is the default type for           |
 |         | characters and may be omitted.                           |
 +---------+----------------------------------------------------------+
+| ``'?'`` | Debug format. The character is quoted and special        |
+|         | characters escaped.                                      |
+---------+----------------------------------------------------------+
 | none    | The same as ``'c'``.                                     |
 +---------+----------------------------------------------------------+

@@ -223,9 +229,10 @@ The available integer presentation types are:
 | none    | The same as ``'d'``.                                     |
 +---------+----------------------------------------------------------+

-Integer presentation types can also be used with character and Boolean values.
-Boolean values are formatted using textual representation, either ``true`` or
-``false``, if the presentation type is not specified.
+Integer presentation types can also be used with character and Boolean values
+with the only exception that ``'c'`` cannot be used with `bool`. Boolean values
+are formatted using textual representation, either ``true`` or ``false``, if the
+presentation type is not specified.

 The available presentation types for floating-point values are:

@@ -304,8 +311,8 @@ The available presentation types for pointers are:
 Chrono Format Specifications
 ============================

-Format specifications for chrono types and ``std::tm`` have the following
-syntax:
+Format specifications for chrono duration and time point types as well as
+``std::tm`` have the following syntax:

 .. productionlist:: sf
   chrono_format_spec: [[`fill`]`align`][`width`]["." `precision`][`chrono_specs`]
@@ -321,20 +328,89 @@ syntax:
 Literal chars are copied unchanged to the output. Precision is valid only for
 ``std::chrono::duration`` types with a floating-point representation type.

-The available presentation types (*chrono_type*) for chrono durations and time
-points are:
+The available presentation types (*chrono_type*) are:

 +---------+--------------------------------------------------------------------+
 | Type    | Meaning                                                            |
 +=========+====================================================================+
+| ``'a'`` | The abbreviated weekday name, e.g. "Sat". If the value does not    |
+|         | contain a valid weekday, an exception of type ``format_error`` is  |
+|         | thrown.                                                            |
+---------+--------------------------------------------------------------------+
+| ``'A'`` | The full weekday name, e.g. "Saturday". If the value does not      |
+|         | contain a valid weekday, an exception of type ``format_error`` is  |
+|         | thrown.                                                            |
+---------+--------------------------------------------------------------------+
+| ``'b'`` | The abbreviated month name, e.g. "Nov". If the value does not      |
+|         | contain a valid month, an exception of type ``format_error`` is    |
+|         | thrown.                                                            |
+---------+--------------------------------------------------------------------+
+| ``'B'`` | The full month name, e.g. "November". If the value does not        |
+|         | contain a valid month, an exception of type ``format_error`` is    |
+|         | thrown.                                                            |
+---------+--------------------------------------------------------------------+
+| ``'c'`` | The date and time representation, e.g. "Sat Nov 12 22:04:00 1955". |
+|         | The modified command ``%Ec`` produces the locale's alternate date  |
+|         | and time representation.                                           |
+---------+--------------------------------------------------------------------+
+| ``'C'`` | The year divided by 100 using floored division, e.g. "55". If the  |
+|         | result is a single decimal digit, it is prefixed with 0.           |
+|         | The modified command ``%EC`` produces the locale's alternative     |
+|         | representation of the century.                                     |
+---------+--------------------------------------------------------------------+
+| ``'d'`` | The day of month as a decimal number. If the result is a single    |
+|         | decimal digit, it is prefixed with 0. The modified command ``%Od`` |
+|         | produces the locale's alternative representation.                  |
+---------+--------------------------------------------------------------------+
+| ``'D'`` | Equivalent to ``%m/%d/%y``, e.g. "11/12/55".                       |
+---------+--------------------------------------------------------------------+
+| ``'e'`` | The day of month as a decimal number. If the result is a single    |
+|         | decimal digit, it is prefixed with a space. The modified command   |
+|         | ``%Oe`` produces the locale's alternative representation.          |
+---------+--------------------------------------------------------------------+
+| ``'F'`` | Equivalent to ``%Y-%m-%d``, e.g. "1955-11-12".                     |
+---------+--------------------------------------------------------------------+
+| ``'g'`` | The last two decimal digits of the ISO week-based year. If the     |
+|         | result is a single digit it is prefixed by 0.                      |
+---------+--------------------------------------------------------------------+
+| ``'G'`` | The ISO week-based year as a decimal number. If the result is less |
+|         | than four digits it is left-padded with 0 to four digits.          |
+---------+--------------------------------------------------------------------+
+| ``'h'`` | Equivalent to ``%b``, e.g. "Nov".                                  |
+---------+--------------------------------------------------------------------+
 | ``'H'`` | The hour (24-hour clock) as a decimal number. If the result is a   |
 |         | single digit, it is prefixed with 0. The modified command ``%OH``  |
 |         | produces the locale's alternative representation.                  |
 +---------+--------------------------------------------------------------------+
+| ``'I'`` | The hour (12-hour clock) as a decimal number. If the result is a   |
+|         | single digit, it is prefixed with 0. The modified command ``%OI``  |
+|         | produces the locale's alternative representation.                  |
+---------+--------------------------------------------------------------------+
+| ``'j'`` | If the type being formatted is a specialization of duration, the   |
+|         | decimal number of days without padding. Otherwise, the day of the  |
+|         | year as a decimal number. Jan 1 is 001. If the result is less than |
+|         | three digits, it is left-padded with 0 to three digits.            |
+---------+--------------------------------------------------------------------+
+| ``'m'`` | The month as a decimal number. Jan is 01. If the result is a       |
+|         | single digit, it is prefixed with 0. The modified command ``%Om``  |
+|         | produces the locale's alternative representation.                  |
+---------+--------------------------------------------------------------------+
 | ``'M'`` | The minute as a decimal number. If the result is a single digit,   |
 |         | it is prefixed with 0. The modified command ``%OM`` produces the   |
 |         | locale's alternative representation.                               |
 +---------+--------------------------------------------------------------------+
+| ``'n'`` | A new-line character.                                              |
+---------+--------------------------------------------------------------------+
+| ``'p'`` | The AM/PM designations associated with a 12-hour clock.            |
+---------+--------------------------------------------------------------------+
+| ``'q'`` | The duration's unit suffix.                                        |
+---------+--------------------------------------------------------------------+
+| ``'Q'`` | The duration's numeric value (as if extracted via ``.count()``).   |
+---------+--------------------------------------------------------------------+
+| ``'r'`` | The 12-hour clock time, e.g. "10:04:00 PM".                        |
+---------+--------------------------------------------------------------------+
+| ``'R'`` | Equivalent to ``%H:%M``, e.g. "22:04".                             |
+---------+--------------------------------------------------------------------+
 | ``'S'`` | Seconds as a decimal number. If the number of seconds is less than |
 |         | 10, the result is prefixed with 0. If the precision of the input   |
 |         | cannot be exactly represented with seconds, then the format is a   |
@@ -345,9 +421,66 @@ points are:
 |         | decimal point is localized according to the locale. The modified   |
 |         | command ``%OS`` produces the locale's alternative representation.  |
 +---------+--------------------------------------------------------------------+
+| ``'t'`` | A horizontal-tab character.                                        |
+---------+--------------------------------------------------------------------+
+| ``'T'`` | Equivalent to ``%H:%M:%S``.                                        |
+---------+--------------------------------------------------------------------+
+| ``'u'`` | The ISO weekday as a decimal number (1-7), where Monday is 1. The  |
+|         | modified command ``%Ou`` produces the locale's alternative         |
+|         | representation.                                                    |
+---------+--------------------------------------------------------------------+
+| ``'U'`` | The week number of the year as a decimal number. The first Sunday  |
+|         | of the year is the first day of week 01. Days of the same year     |
+|         | prior to that are in week 00. If the result is a single digit, it  |
+|         | is prefixed with 0. The modified command ``%OU`` produces the      |
+|         | locale's alternative representation.                               |
+---------+--------------------------------------------------------------------+
+| ``'V'`` | The ISO week-based week number as a decimal number. If the result  |
+|         | is a single digit, it is prefixed with 0. The modified command     |
+|         | ``%OV`` produces the locale's alternative representation.          |
+---------+--------------------------------------------------------------------+
+| ``'w'`` | The weekday as a decimal number (0-6), where Sunday is 0.          |
+|         | The modified command ``%Ow`` produces the locale's alternative     |
+|         | representation.                                                    |
+---------+--------------------------------------------------------------------+
+| ``'W'`` | The week number of the year as a decimal number. The first Monday  |
+|         | of the year is the first day of week 01. Days of the same year     |
+|         | prior to that are in week 00. If the result is a single digit, it  |
+|         | is prefixed with 0. The modified command ``%OW`` produces the      |
+|         | locale's alternative representation.                               |
+---------+--------------------------------------------------------------------+
+| ``'x'`` | The date representation, e.g. "11/12/55". The modified command     |
+|         | ``%Ex`` produces the locale's alternate date representation.       |
+---------+--------------------------------------------------------------------+
+| ``'X'`` | The time representation, e.g. "10:04:00". The modified command     |
+|         | ``%EX`` produces the locale's alternate time representation.       |
+---------+--------------------------------------------------------------------+
+| ``'y'`` | The last two decimal digits of the year. If the result is a single |
+|         | digit it is prefixed by 0. The modified command ``%Oy`` produces   |
+|         | the locale's alternative representation. The modified command      |
+|         | ``%Ey`` produces the locale's alternative representation of offset |
+|         | from ``%EC`` (year only).                                          |
+---------+--------------------------------------------------------------------+
+| ``'Y'`` | The year as a decimal number. If the result is less than four      |
+|         | digits it is left-padded with 0 to four digits. The modified       |
+|         | command ``%EY`` produces the locale's alternative full year        |
+|         | representation.                                                    |
+---------+--------------------------------------------------------------------+
+| ``'z'`` | The offset from UTC in the ISO 8601:2004 format. For example -0430 |
+|         | refers to 4 hours 30 minutes behind UTC. If the offset is zero,    |
+|         | +0000 is used. The modified commands ``%Ez`` and ``%Oz`` insert a  |
+|         | ``:`` between the hours and minutes: -04:30. If the offset         |
+|         | information is not available, an exception of type                 |
+|         | ``format_error`` is thrown.                                        |
+---------+--------------------------------------------------------------------+
+| ``'Z'`` | The time zone abbreviation. If the time zone abbreviation is not   |
+|         | available, an exception of type ``format_error`` is thrown.        |
+---------+--------------------------------------------------------------------+
+| ``'%'`` | A % character.                                                     |
+---------+--------------------------------------------------------------------+

 Specifiers that have a calendaric component such as ``'d'`` (the day of month)
-are valid only for ``std::tm`` and not durations or time points.
+are valid only for ``std::tm`` and time points but not durations.

 .. range-specs:

@@ -356,8 +489,8 @@ Range Format Specifications

 Format specifications for range types have the following syntax:

-..productionlist:: sf
-  range_format_spec: [":" [`underlying_spec`]]
+.. productionlist:: sf
+   range_format_spec: [":" [`underlying_spec`]]

 The `underlying_spec` is parsed based on the formatter of the range's
 reference type.
@@ -366,12 +499,12 @@ By default, a range of characters or strings is printed escaped and quoted. But
 if any `underlying_spec` is provided (even if it is empty), then the characters
 or strings are printed according to the provided specification.

-Examples:
+Examples::

  fmt::format("{}", std::vector{10, 20, 30});
  // Result: [10, 20, 30]
  fmt::format("{::#x}", std::vector{10, 20, 30});
-  // Result: [0xa, 0x14, 0x13]
+  // Result: [0xa, 0x14, 0x1e]
  fmt::format("{}", vector{'h', 'e', 'l', 'l', 'o'});
  // Result: ['h', 'e', 'l', 'l', 'o']
  fmt::format("{::}", vector{'h', 'e', 'l', 'l', 'o'});
@@ -134,6 +134,44 @@ For ``build2`` newcomers or to get more details and use cases, you can read the
 ``build2``
 `toolchain introduction <https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml>`_.

+Usage with Meson
+================
+
+`Meson's WrapDB <https://mesonbuild.com/Wrapdb-projects.html>` includes a ``fmt``
+package, which repackages fmt to be built by Meson as a subproject.
+
+**Usage:**
+
+- Install the ``fmt`` subproject from the WrapDB by running::
+
+    meson wrap install fmt
+
+  from the root of your project.
+
+- In your project's ``meson.build`` file, add an entry for the new subproject::
+
+    fmt = subproject('fmt')
+    fmt_dep = fmt.get_variable('fmt_dep')
+
+- Include the new dependency object to link with fmt::
+
+    my_build_target = executable('name', 'src/main.cc', dependencies: [fmt_dep])
+
+**Options:**
+
+If desired, ``fmt`` may be built as a static library, or as a header-only
+library.
+
+For a static build, use the following subproject definition::
+
+  fmt = subproject('fmt', default_options: 'default_library=static')
+  fmt_dep = fmt.get_variable('fmt_dep')
+
+For the header-only version, use::
+
+  fmt = subproject('fmt')
+  fmt_dep = fmt.get_variable('fmt_header_only_dep')
+
 Building the Documentation
 ==========================

@@ -1,4 +1,4 @@
-// Formatting library for C++ - dynamic format arguments
+// Formatting library for C++ - dynamic argument lists
 //
 // Copyright (c) 2012 - present, Victor Zverovich
 // All rights reserved.
@@ -22,8 +22,9 @@ template <typename T> struct is_reference_wrapper : std::false_type {};
 template <typename T>
 struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};

-template <typename T> const T& unwrap(const T& v) { return v; }
-template <typename T> const T& unwrap(const std::reference_wrapper<T>& v) {
+template <typename T> auto unwrap(const T& v) -> const T& { return v; }
+template <typename T>
+auto unwrap(const std::reference_wrapper<T>& v) -> const T& {
  return static_cast<const T&>(v);
 }

@@ -50,7 +51,7 @@ class dynamic_arg_list {
  std::unique_ptr<node<>> head_;

 public:
-  template <typename T, typename Arg> const T& push(const Arg& arg) {
+  template <typename T, typename Arg> auto push(const Arg& arg) -> const T& {
    auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
    auto& value = new_node->value;
    new_node->next = std::move(head_);
@@ -110,14 +111,14 @@ class dynamic_format_arg_store

  friend class basic_format_args<Context>;

-  unsigned long long get_types() const {
+  auto get_types() const -> unsigned long long {
    return detail::is_unpacked_bit | data_.size() |
           (named_info_.empty()
                ? 0ULL
                : static_cast<unsigned long long>(detail::has_named_args_bit));
  }

-  const basic_format_arg<Context>* data() const {
+  auto data() const -> const basic_format_arg<Context>* {
    return named_info_.empty() ? data_.data() : data_.data() + 1;
  }

@@ -11,7 +11,7 @@
 #include "format.h"

 FMT_BEGIN_NAMESPACE
-FMT_MODULE_EXPORT_BEGIN
+FMT_BEGIN_EXPORT

 enum class color : uint32_t {
  alice_blue = 0xF0F8FF,               // rgb(240,248,255)
@@ -203,7 +203,7 @@ struct rgb {
  uint8_t b;
 };

-FMT_BEGIN_DETAIL_NAMESPACE
+namespace detail {

 // color is a struct of either a rgb color or a terminal color.
 struct color_type {
@@ -225,8 +225,7 @@ struct color_type {
    uint32_t rgb_color;
  } value;
 };
-
-FMT_END_DETAIL_NAMESPACE
+}  // namespace detail

 /** A text style consisting of foreground and background colors and emphasis. */
 class text_style {
@@ -234,7 +233,7 @@ class text_style {
  FMT_CONSTEXPR text_style(emphasis em = emphasis()) noexcept
      : set_foreground_color(), set_background_color(), ems(em) {}

-  FMT_CONSTEXPR text_style& operator|=(const text_style& rhs) {
+  FMT_CONSTEXPR auto operator|=(const text_style& rhs) -> text_style& {
    if (!set_foreground_color) {
      set_foreground_color = rhs.set_foreground_color;
      foreground_color = rhs.foreground_color;
@@ -258,29 +257,29 @@ class text_style {
    return *this;
  }

-  friend FMT_CONSTEXPR text_style operator|(text_style lhs,
-                                            const text_style& rhs) {
+  friend FMT_CONSTEXPR auto operator|(text_style lhs, const text_style& rhs)
+      -> text_style {
    return lhs |= rhs;
  }

-  FMT_CONSTEXPR bool has_foreground() const noexcept {
+  FMT_CONSTEXPR auto has_foreground() const noexcept -> bool {
    return set_foreground_color;
  }
-  FMT_CONSTEXPR bool has_background() const noexcept {
+  FMT_CONSTEXPR auto has_background() const noexcept -> bool {
    return set_background_color;
  }
-  FMT_CONSTEXPR bool has_emphasis() const noexcept {
+  FMT_CONSTEXPR auto has_emphasis() const noexcept -> bool {
    return static_cast<uint8_t>(ems) != 0;
  }
-  FMT_CONSTEXPR detail::color_type get_foreground() const noexcept {
+  FMT_CONSTEXPR auto get_foreground() const noexcept -> detail::color_type {
    FMT_ASSERT(has_foreground(), "no foreground specified for this style");
    return foreground_color;
  }
-  FMT_CONSTEXPR detail::color_type get_background() const noexcept {
+  FMT_CONSTEXPR auto get_background() const noexcept -> detail::color_type {
    FMT_ASSERT(has_background(), "no background specified for this style");
    return background_color;
  }
-  FMT_CONSTEXPR emphasis get_emphasis() const noexcept {
+  FMT_CONSTEXPR auto get_emphasis() const noexcept -> emphasis {
    FMT_ASSERT(has_emphasis(), "no emphasis specified for this style");
    return ems;
  }
@@ -298,9 +297,11 @@ class text_style {
    }
  }

-  friend FMT_CONSTEXPR text_style fg(detail::color_type foreground) noexcept;
+  friend FMT_CONSTEXPR auto fg(detail::color_type foreground) noexcept
+      -> text_style;

-  friend FMT_CONSTEXPR text_style bg(detail::color_type background) noexcept;
+  friend FMT_CONSTEXPR auto bg(detail::color_type background) noexcept
+      -> text_style;

  detail::color_type foreground_color;
  detail::color_type background_color;
@@ -310,20 +311,23 @@ class text_style {
 };

 /** Creates a text style from the foreground (text) color. */
-FMT_CONSTEXPR inline text_style fg(detail::color_type foreground) noexcept {
+FMT_CONSTEXPR inline auto fg(detail::color_type foreground) noexcept
+    -> text_style {
  return text_style(true, foreground);
 }

 /** Creates a text style from the background color. */
-FMT_CONSTEXPR inline text_style bg(detail::color_type background) noexcept {
+FMT_CONSTEXPR inline auto bg(detail::color_type background) noexcept
+    -> text_style {
  return text_style(false, background);
 }

-FMT_CONSTEXPR inline text_style operator|(emphasis lhs, emphasis rhs) noexcept {
+FMT_CONSTEXPR inline auto operator|(emphasis lhs, emphasis rhs) noexcept
+    -> text_style {
  return text_style(lhs) | rhs;
 }

-FMT_BEGIN_DETAIL_NAMESPACE
+namespace detail {

 template <typename Char> struct ansi_color_escape {
  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
@@ -385,8 +389,8 @@ template <typename Char> struct ansi_color_escape {
  }
  FMT_CONSTEXPR operator const Char*() const noexcept { return buffer; }

-  FMT_CONSTEXPR const Char* begin() const noexcept { return buffer; }
-  FMT_CONSTEXPR_CHAR_TRAITS const Char* end() const noexcept {
+  FMT_CONSTEXPR auto begin() const noexcept -> const Char* { return buffer; }
+  FMT_CONSTEXPR_CHAR_TRAITS auto end() const noexcept -> const Char* {
    return buffer + std::char_traits<Char>::length(buffer);
  }

@@ -401,56 +405,39 @@ template <typename Char> struct ansi_color_escape {
    out[2] = static_cast<Char>('0' + c % 10);
    out[3] = static_cast<Char>(delimiter);
  }
-  static FMT_CONSTEXPR bool has_emphasis(emphasis em, emphasis mask) noexcept {
+  static FMT_CONSTEXPR auto has_emphasis(emphasis em, emphasis mask) noexcept
+      -> bool {
    return static_cast<uint8_t>(em) & static_cast<uint8_t>(mask);
  }
 };

 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_foreground_color(
-    detail::color_type foreground) noexcept {
+FMT_CONSTEXPR auto make_foreground_color(detail::color_type foreground) noexcept
+    -> ansi_color_escape<Char> {
  return ansi_color_escape<Char>(foreground, "\x1b[38;2;");
 }

 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_background_color(
-    detail::color_type background) noexcept {
+FMT_CONSTEXPR auto make_background_color(detail::color_type background) noexcept
+    -> ansi_color_escape<Char> {
  return ansi_color_escape<Char>(background, "\x1b[48;2;");
 }

 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_emphasis(emphasis em) noexcept {
+FMT_CONSTEXPR auto make_emphasis(emphasis em) noexcept
+    -> ansi_color_escape<Char> {
  return ansi_color_escape<Char>(em);
 }

-template <typename Char> inline void fputs(const Char* chars, FILE* stream) {
-  int result = std::fputs(chars, stream);
-  if (result < 0)
-    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
-}
-
-template <> inline void fputs<wchar_t>(const wchar_t* chars, FILE* stream) {
-  int result = std::fputws(chars, stream);
-  if (result < 0)
-    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
-}
-
-template <typename Char> inline void reset_color(FILE* stream) {
-  fputs("\x1b[0m", stream);
-}
-
-template <> inline void reset_color<wchar_t>(FILE* stream) {
-  fputs(L"\x1b[0m", stream);
-}
-
 template <typename Char> inline void reset_color(buffer<Char>& buffer) {
  auto reset_color = string_view("\x1b[0m");
  buffer.append(reset_color.begin(), reset_color.end());
 }

-template <typename T> struct styled_arg {
+template <typename T> struct styled_arg : detail::view {
  const T& value;
  text_style style;
+  styled_arg(const T& v, text_style s) : value(v), style(s) {}
 };

 template <typename Char>
@@ -477,19 +464,21 @@ void vformat_to(buffer<Char>& buf, const text_style& ts,
  if (has_style) detail::reset_color<Char>(buf);
 }

-FMT_END_DETAIL_NAMESPACE
+}  // namespace detail

-template <typename S, typename Char = char_t<S>>
-void vprint(std::FILE* f, const text_style& ts, const S& format,
-            basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buf;
-  detail::vformat_to(buf, ts, detail::to_string_view(format), args);
+inline void vprint(std::FILE* f, const text_style& ts, string_view fmt,
+                   format_args args) {
+  // Legacy wide streams are not supported.
+  auto buf = memory_buffer();
+  detail::vformat_to(buf, ts, fmt, args);
  if (detail::is_utf8()) {
-    detail::print(f, basic_string_view<Char>(buf.begin(), buf.size()));
-  } else {
-    buf.push_back(Char(0));
-    detail::fputs(buf.data(), f);
+    detail::print(f, string_view(buf.begin(), buf.size()));
+    return;
  }
+  buf.push_back('\0');
+  int result = std::fputs(buf.data(), f);
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }

 /**
@@ -529,9 +518,10 @@ void print(const text_style& ts, const S& format_str, const Args&... args) {
 }

 template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
+inline auto vformat(
    const text_style& ts, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+    basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
  basic_memory_buffer<Char> buf;
  detail::vformat_to(buf, ts, detail::to_string_view(format_str), args);
  return fmt::to_string(buf);
@@ -550,8 +540,8 @@ inline std::basic_string<Char> vformat(
  \endrst
 */
 template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
-                                      const Args&... args) {
+inline auto format(const text_style& ts, const S& format_str,
+                   const Args&... args) -> std::basic_string<Char> {
  return fmt::vformat(ts, detail::to_string_view(format_str),
                      fmt::make_format_args<buffer_context<Char>>(args...));
 }
@@ -561,12 +551,13 @@ inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
 */
 template <typename OutputIt, typename Char,
          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
-OutputIt vformat_to(
-    OutputIt out, const text_style& ts, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+auto vformat_to(OutputIt out, const text_style& ts,
+                basic_string_view<Char> format_str,
+                basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> OutputIt {
  auto&& buf = detail::get_buffer<Char>(out);
  detail::vformat_to(buf, ts, format_str, args);
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }

 /**
@@ -581,9 +572,10 @@ OutputIt vformat_to(
                   fmt::emphasis::bold | fg(fmt::color::red), "{}", 42);
  \endrst
 */
-template <typename OutputIt, typename S, typename... Args,
-          bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value&&
-              detail::is_string<S>::value>
+template <
+    typename OutputIt, typename S, typename... Args,
+    bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value &&
+                  detail::is_string<S>::value>
 inline auto format_to(OutputIt out, const text_style& ts, const S& format_str,
                      Args&&... args) ->
    typename std::enable_if<enable, OutputIt>::type {
@@ -634,7 +626,7 @@ struct formatter<detail::styled_arg<T>, Char> : formatter<T, Char> {

  **Example**::

-    fmt::print("Elapsed time: {s:.2f} seconds",
+    fmt::print("Elapsed time: {0:.2f} seconds",
               fmt::styled(1.23, fmt::fg(fmt::color::green) |
                                 fmt::bg(fmt::color::blue)));
  \endrst
@@ -645,7 +637,7 @@ FMT_CONSTEXPR auto styled(const T& value, text_style ts)
  return detail::styled_arg<remove_cvref_t<T>>{value, ts};
 }

-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_COLOR_H_
@@ -14,89 +14,11 @@ FMT_BEGIN_NAMESPACE
 namespace detail {

 template <typename Char, typename InputIt>
-inline counting_iterator copy_str(InputIt begin, InputIt end,
-                                  counting_iterator it) {
+FMT_CONSTEXPR inline auto copy_str(InputIt begin, InputIt end,
+                                   counting_iterator it) -> counting_iterator {
  return it + (end - begin);
 }

-template <typename OutputIt> class truncating_iterator_base {
- protected:
-  OutputIt out_;
-  size_t limit_;
-  size_t count_ = 0;
-
-  truncating_iterator_base() : out_(), limit_(0) {}
-
-  truncating_iterator_base(OutputIt out, size_t limit)
-      : out_(out), limit_(limit) {}
-
- public:
-  using iterator_category = std::output_iterator_tag;
-  using value_type = typename std::iterator_traits<OutputIt>::value_type;
-  using difference_type = std::ptrdiff_t;
-  using pointer = void;
-  using reference = void;
-  FMT_UNCHECKED_ITERATOR(truncating_iterator_base);
-
-  OutputIt base() const { return out_; }
-  size_t count() const { return count_; }
-};
-
-// An output iterator that truncates the output and counts the number of objects
-// written to it.
-template <typename OutputIt,
-          typename Enable = typename std::is_void<
-              typename std::iterator_traits<OutputIt>::value_type>::type>
-class truncating_iterator;
-
-template <typename OutputIt>
-class truncating_iterator<OutputIt, std::false_type>
-    : public truncating_iterator_base<OutputIt> {
-  mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;
-
- public:
-  using value_type = typename truncating_iterator_base<OutputIt>::value_type;
-
-  truncating_iterator() = default;
-
-  truncating_iterator(OutputIt out, size_t limit)
-      : truncating_iterator_base<OutputIt>(out, limit) {}
-
-  truncating_iterator& operator++() {
-    if (this->count_++ < this->limit_) ++this->out_;
-    return *this;
-  }
-
-  truncating_iterator operator++(int) {
-    auto it = *this;
-    ++*this;
-    return it;
-  }
-
-  value_type& operator*() const {
-    return this->count_ < this->limit_ ? *this->out_ : blackhole_;
-  }
-};
-
-template <typename OutputIt>
-class truncating_iterator<OutputIt, std::true_type>
-    : public truncating_iterator_base<OutputIt> {
- public:
-  truncating_iterator() = default;
-
-  truncating_iterator(OutputIt out, size_t limit)
-      : truncating_iterator_base<OutputIt>(out, limit) {}
-
-  template <typename T> truncating_iterator& operator=(T val) {
-    if (this->count_++ < this->limit_) *this->out_++ = val;
-    return *this;
-  }
-
-  truncating_iterator& operator++() { return *this; }
-  truncating_iterator& operator++(int) { return *this; }
-  truncating_iterator& operator*() { return *this; }
-};
-
 // A compile-time string which is compiled into fast formatting code.
 class compiled_string {};

@@ -135,7 +57,7 @@ struct udl_compiled_string : compiled_string {
 #endif

 template <typename T, typename... Tail>
-const T& first(const T& value, const Tail&...) {
+auto first(const T& value, const Tail&...) -> const T& {
  return value;
 }

@@ -196,7 +118,8 @@ template <typename Char> struct code_unit {

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&...) const {
-    return write<Char>(out, value);
+    *out++ = value;
+    return out;
  }
 };

@@ -220,7 +143,12 @@ template <typename Char, typename T, int N> struct field {

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&... args) const {
-    return write<Char>(out, get_arg_checked<T, N>(args...));
+    const T& arg = get_arg_checked<T, N>(args...);
+    if constexpr (std::is_convertible_v<T, basic_string_view<Char>>) {
+      auto s = basic_string_view<Char>(arg);
+      return copy_str<Char>(s.begin(), s.end(), out);
+    }
+    return write<Char>(out, arg);
  }
 };

@@ -331,39 +259,35 @@ template <typename T, typename Char> struct parse_specs_result {
  int next_arg_id;
 };

-constexpr int manual_indexing_id = -1;
+enum { manual_indexing_id = -1 };

 template <typename T, typename Char>
 constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
                                                  size_t pos, int next_arg_id) {
  str.remove_prefix(pos);
-  auto ctx = compile_parse_context<Char>(str, max_value<int>(), nullptr, {},
-                                         next_arg_id);
+  auto ctx =
+      compile_parse_context<Char>(str, max_value<int>(), nullptr, next_arg_id);
  auto f = formatter<T, Char>();
  auto end = f.parse(ctx);
-  return {f, pos + fmt::detail::to_unsigned(end - str.data()) + 1,
+  return {f, pos + fmt::detail::to_unsigned(end - str.data()),
          next_arg_id == 0 ? manual_indexing_id : ctx.next_arg_id()};
 }

 template <typename Char> struct arg_id_handler {
  arg_ref<Char> arg_id;

-  constexpr int operator()() {
+  constexpr int on_auto() {
    FMT_ASSERT(false, "handler cannot be used with automatic indexing");
    return 0;
  }
-  constexpr int operator()(int id) {
+  constexpr int on_index(int id) {
    arg_id = arg_ref<Char>(id);
    return 0;
  }
-  constexpr int operator()(basic_string_view<Char> id) {
+  constexpr int on_name(basic_string_view<Char> id) {
    arg_id = arg_ref<Char>(id);
    return 0;
  }
-
-  constexpr void on_error(const char* message) {
-    FMT_THROW(format_error(message));
-  }
 };

 template <typename Char> struct parse_arg_id_result {
@@ -397,13 +321,20 @@ constexpr auto parse_replacement_field_then_tail(S format_str) {
    return parse_tail<Args, END_POS + 1, NEXT_ID>(
        field<char_type, typename field_type<T>::type, ARG_INDEX>(),
        format_str);
-  } else if constexpr (c == ':') {
+  } else if constexpr (c != ':') {
+    FMT_THROW(format_error("expected ':'"));
+  } else {
    constexpr auto result = parse_specs<typename field_type<T>::type>(
        str, END_POS + 1, NEXT_ID == manual_indexing_id ? 0 : NEXT_ID);
-    return parse_tail<Args, result.end, result.next_arg_id>(
-        spec_field<char_type, typename field_type<T>::type, ARG_INDEX>{
-            result.fmt},
-        format_str);
+    if constexpr (result.end >= str.size() || str[result.end] != '}') {
+      FMT_THROW(format_error("expected '}'"));
+      return 0;
+    } else {
+      return parse_tail<Args, result.end + 1, result.next_arg_id>(
+          spec_field<char_type, typename field_type<T>::type, ARG_INDEX>{
+              result.fmt},
+          format_str);
+    }
  }
 }

@@ -445,20 +376,18 @@ constexpr auto compile_format_string(S format_str) {
      } else if constexpr (arg_id_result.arg_id.kind == arg_id_kind::name) {
        constexpr auto arg_index =
            get_arg_index_by_name(arg_id_result.arg_id.val.name, Args{});
-        if constexpr (arg_index != invalid_arg_index) {
+        if constexpr (arg_index >= 0) {
          constexpr auto next_id =
              ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
          return parse_replacement_field_then_tail<
              decltype(get_type<arg_index, Args>::value), Args, arg_id_end_pos,
              arg_index, next_id>(format_str);
-        } else {
-          if constexpr (c == '}') {
-            return parse_tail<Args, arg_id_end_pos + 1, ID>(
-                runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
-                format_str);
-          } else if constexpr (c == ':') {
-            return unknown_format();  // no type info for specs parsing
-          }
+        } else if constexpr (c == '}') {
+          return parse_tail<Args, arg_id_end_pos + 1, ID>(
+              runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
+              format_str);
+        } else if constexpr (c == ':') {
+          return unknown_format();  // no type info for specs parsing
        }
      }
    }
@@ -494,7 +423,7 @@ constexpr auto compile(S format_str) {
 #endif  // defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 }  // namespace detail

-FMT_MODULE_EXPORT_BEGIN
+FMT_BEGIN_EXPORT

 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)

@@ -559,16 +488,19 @@ FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {

 template <typename OutputIt, typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
-                                         const S& format_str, Args&&... args) {
-  auto it = fmt::format_to(detail::truncating_iterator<OutputIt>(out, n),
-                           format_str, std::forward<Args>(args)...);
-  return {it.base(), it.count()};
+auto format_to_n(OutputIt out, size_t n, const S& format_str, Args&&... args)
+    -> format_to_n_result<OutputIt> {
+  using traits = detail::fixed_buffer_traits;
+  auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
+  fmt::format_to(std::back_inserter(buf), format_str,
+                 std::forward<Args>(args)...);
+  return {buf.out(), buf.count()};
 }

 template <typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
-size_t formatted_size(const S& format_str, const Args&... args) {
+FMT_CONSTEXPR20 auto formatted_size(const S& format_str, const Args&... args)
+    -> size_t {
  return fmt::format_to(detail::counting_iterator(), format_str, args...)
      .count();
 }
@@ -597,7 +529,7 @@ template <detail_exported::fixed_string Str> constexpr auto operator""_cf() {
 }  // namespace literals
 #endif

-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_COMPILE_H_
@@ -9,20 +9,16 @@
 #define FMT_FORMAT_INL_H_

 #include <algorithm>
-#include <cctype>
 #include <cerrno>  // errno
 #include <climits>
 #include <cmath>
-#include <cstdarg>
-#include <cstring>  // std::memmove
-#include <cwchar>
 #include <exception>

 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 #  include <locale>
 #endif

-#ifdef _WIN32
+#if defined(_WIN32) && !defined(FMT_WINDOWS_NO_WCHAR)
 #  include <io.h>  // _isatty
 #endif

@@ -62,8 +58,8 @@ FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
  error_code_size += detail::to_unsigned(detail::count_digits(abs_value));
  auto it = buffer_appender<char>(out);
  if (message.size() <= inline_buffer_size - error_code_size)
-    format_to(it, FMT_STRING("{}{}"), message, SEP);
-  format_to(it, FMT_STRING("{}{}"), ERROR_STR, error_code);
+    fmt::format_to(it, FMT_STRING("{}{}"), message, SEP);
+  fmt::format_to(it, FMT_STRING("{}{}"), ERROR_STR, error_code);
  FMT_ASSERT(out.size() <= inline_buffer_size, "");
 }

@@ -77,9 +73,8 @@ FMT_FUNC void report_error(format_func func, int error_code,
 }

 // A wrapper around fwrite that throws on error.
-inline void fwrite_fully(const void* ptr, size_t size, size_t count,
-                         FILE* stream) {
-  size_t written = std::fwrite(ptr, size, count, stream);
+inline void fwrite_fully(const void* ptr, size_t count, FILE* stream) {
+  size_t written = std::fwrite(ptr, 1, count, stream);
  if (written < count)
    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }
@@ -90,7 +85,7 @@ locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
  static_assert(std::is_same<Locale, std::locale>::value, "");
 }

-template <typename Locale> Locale locale_ref::get() const {
+template <typename Locale> auto locale_ref::get() const -> Locale {
  static_assert(std::is_same<Locale, std::locale>::value, "");
  return locale_ ? *static_cast<const std::locale*>(locale_) : std::locale();
 }
@@ -102,7 +97,8 @@ FMT_FUNC auto thousands_sep_impl(locale_ref loc) -> thousands_sep_result<Char> {
  auto thousands_sep = grouping.empty() ? Char() : facet.thousands_sep();
  return {std::move(grouping), thousands_sep};
 }
-template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref loc) {
+template <typename Char>
+FMT_FUNC auto decimal_point_impl(locale_ref loc) -> Char {
  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
      .decimal_point();
 }
@@ -115,96 +111,74 @@ template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref) {
  return '.';
 }
 #endif
+
+FMT_FUNC auto write_loc(appender out, loc_value value,
+                        const format_specs<>& specs, locale_ref loc) -> bool {
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+  auto locale = loc.get<std::locale>();
+  // We cannot use the num_put<char> facet because it may produce output in
+  // a wrong encoding.
+  using facet = format_facet<std::locale>;
+  if (std::has_facet<facet>(locale))
+    return std::use_facet<facet>(locale).put(out, value, specs);
+  return facet(locale).put(out, value, specs);
+#endif
+  return false;
+}
 }  // namespace detail

-#if !FMT_MSC_VERSION
-FMT_API FMT_FUNC format_error::~format_error() noexcept = default;
+template <typename Locale> typename Locale::id format_facet<Locale>::id;
+
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+template <typename Locale> format_facet<Locale>::format_facet(Locale& loc) {
+  auto& numpunct = std::use_facet<std::numpunct<char>>(loc);
+  grouping_ = numpunct.grouping();
+  if (!grouping_.empty()) separator_ = std::string(1, numpunct.thousands_sep());
+}
+
+template <>
+FMT_API FMT_FUNC auto format_facet<std::locale>::do_put(
+    appender out, loc_value val, const format_specs<>& specs) const -> bool {
+  return val.visit(
+      detail::loc_writer<>{out, specs, separator_, grouping_, decimal_point_});
+}
 #endif

-FMT_FUNC std::system_error vsystem_error(int error_code, string_view format_str,
-                                         format_args args) {
+FMT_FUNC auto vsystem_error(int error_code, string_view fmt, format_args args)
+    -> std::system_error {
  auto ec = std::error_code(error_code, std::generic_category());
-  return std::system_error(ec, vformat(format_str, args));
+  return std::system_error(ec, vformat(fmt, args));
 }

 namespace detail {

-template <typename F> inline bool operator==(basic_fp<F> x, basic_fp<F> y) {
+template <typename F>
+inline auto operator==(basic_fp<F> x, basic_fp<F> y) -> bool {
  return x.f == y.f && x.e == y.e;
 }

 // Compilers should be able to optimize this into the ror instruction.
-FMT_CONSTEXPR inline uint32_t rotr(uint32_t n, uint32_t r) noexcept {
+FMT_CONSTEXPR inline auto rotr(uint32_t n, uint32_t r) noexcept -> uint32_t {
  r &= 31;
  return (n >> r) | (n << (32 - r));
 }
-FMT_CONSTEXPR inline uint64_t rotr(uint64_t n, uint32_t r) noexcept {
+FMT_CONSTEXPR inline auto rotr(uint64_t n, uint32_t r) noexcept -> uint64_t {
  r &= 63;
  return (n >> r) | (n << (64 - r));
 }

-// Computes 128-bit result of multiplication of two 64-bit unsigned integers.
-inline uint128_fallback umul128(uint64_t x, uint64_t y) noexcept {
-#if FMT_USE_INT128
-  auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
-  return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)};
-#elif defined(_MSC_VER) && defined(_M_X64)
-  auto result = uint128_fallback();
-  result.lo_ = _umul128(x, y, &result.hi_);
-  return result;
-#else
-  const uint64_t mask = static_cast<uint64_t>(max_value<uint32_t>());
-
-  uint64_t a = x >> 32;
-  uint64_t b = x & mask;
-  uint64_t c = y >> 32;
-  uint64_t d = y & mask;
-
-  uint64_t ac = a * c;
-  uint64_t bc = b * c;
-  uint64_t ad = a * d;
-  uint64_t bd = b * d;
-
-  uint64_t intermediate = (bd >> 32) + (ad & mask) + (bc & mask);
-
-  return {ac + (intermediate >> 32) + (ad >> 32) + (bc >> 32),
-          (intermediate << 32) + (bd & mask)};
-#endif
-}
-
 // Implementation of Dragonbox algorithm: https://github.com/jk-jeon/dragonbox.
 namespace dragonbox {
-// Computes upper 64 bits of multiplication of two 64-bit unsigned integers.
-inline uint64_t umul128_upper64(uint64_t x, uint64_t y) noexcept {
-#if FMT_USE_INT128
-  auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
-  return static_cast<uint64_t>(p >> 64);
-#elif defined(_MSC_VER) && defined(_M_X64)
-  return __umulh(x, y);
-#else
-  return umul128(x, y).high();
-#endif
-}
-
-// Computes upper 128 bits of multiplication of a 64-bit unsigned integer and a
-// 128-bit unsigned integer.
-inline uint128_fallback umul192_upper128(uint64_t x,
-                                         uint128_fallback y) noexcept {
-  uint128_fallback r = umul128(x, y.high());
-  r += umul128_upper64(x, y.low());
-  return r;
-}
-
 // Computes upper 64 bits of multiplication of a 32-bit unsigned integer and a
 // 64-bit unsigned integer.
-inline uint64_t umul96_upper64(uint32_t x, uint64_t y) noexcept {
+inline auto umul96_upper64(uint32_t x, uint64_t y) noexcept -> uint64_t {
  return umul128_upper64(static_cast<uint64_t>(x) << 32, y);
 }

 // Computes lower 128 bits of multiplication of a 64-bit unsigned integer and a
 // 128-bit unsigned integer.
-inline uint128_fallback umul192_lower128(uint64_t x,
-                                         uint128_fallback y) noexcept {
+inline auto umul192_lower128(uint64_t x, uint128_fallback y) noexcept
+    -> uint128_fallback {
  uint64_t high = x * y.high();
  uint128_fallback high_low = umul128(x, y.low());
  return {high + high_low.high(), high_low.low()};
@@ -212,29 +186,17 @@ inline uint128_fallback umul192_lower128(uint64_t x,

 // Computes lower 64 bits of multiplication of a 32-bit unsigned integer and a
 // 64-bit unsigned integer.
-inline uint64_t umul96_lower64(uint32_t x, uint64_t y) noexcept {
+inline auto umul96_lower64(uint32_t x, uint64_t y) noexcept -> uint64_t {
  return x * y;
 }

-// Computes floor(log10(pow(2, e))) for e in [-2620, 2620] using the method from
-// https://fmt.dev/papers/Dragonbox.pdf#page=28, section 6.1.
-inline int floor_log10_pow2(int e) noexcept {
-  FMT_ASSERT(e <= 2620 && e >= -2620, "too large exponent");
-  static_assert((-1 >> 1) == -1, "right shift is not arithmetic");
-  return (e * 315653) >> 20;
-}
-
 // Various fast log computations.
-inline int floor_log2_pow10(int e) noexcept {
-  FMT_ASSERT(e <= 1233 && e >= -1233, "too large exponent");
-  return (e * 1741647) >> 19;
-}
-inline int floor_log10_pow2_minus_log10_4_over_3(int e) noexcept {
+inline auto floor_log10_pow2_minus_log10_4_over_3(int e) noexcept -> int {
  FMT_ASSERT(e <= 2936 && e >= -2985, "too large exponent");
  return (e * 631305 - 261663) >> 21;
 }

-static constexpr struct {
+FMT_INLINE_VARIABLE constexpr struct {
  uint32_t divisor;
  int shift_amount;
 } div_small_pow10_infos[] = {{10, 16}, {100, 16}};
@@ -243,7 +205,7 @@ static constexpr struct {
 // divisible by pow(10, N).
 // Precondition: n <= pow(10, N + 1).
 template <int N>
-bool check_divisibility_and_divide_by_pow10(uint32_t& n) noexcept {
+auto check_divisibility_and_divide_by_pow10(uint32_t& n) noexcept -> bool {
  // The numbers below are chosen such that:
  //   1. floor(n/d) = floor(nm / 2^k) where d=10 or d=100,
  //   2. nm mod 2^k < m if and only if n is divisible by d,
@@ -268,7 +230,7 @@ bool check_divisibility_and_divide_by_pow10(uint32_t& n) noexcept {

 // Computes floor(n / pow(10, N)) for small n and N.
 // Precondition: n <= pow(10, N + 1).
-template <int N> uint32_t small_division_by_pow10(uint32_t n) noexcept {
+template <int N> auto small_division_by_pow10(uint32_t n) noexcept -> uint32_t {
  constexpr auto info = div_small_pow10_infos[N - 1];
  FMT_ASSERT(n <= info.divisor * 10, "n is too large");
  constexpr uint32_t magic_number =
@@ -277,24 +239,24 @@ template <int N> uint32_t small_division_by_pow10(uint32_t n) noexcept {
 }

 // Computes floor(n / 10^(kappa + 1)) (float)
-inline uint32_t divide_by_10_to_kappa_plus_1(uint32_t n) noexcept {
+inline auto divide_by_10_to_kappa_plus_1(uint32_t n) noexcept -> uint32_t {
  // 1374389535 = ceil(2^37/100)
  return static_cast<uint32_t>((static_cast<uint64_t>(n) * 1374389535) >> 37);
 }
 // Computes floor(n / 10^(kappa + 1)) (double)
-inline uint64_t divide_by_10_to_kappa_plus_1(uint64_t n) noexcept {
+inline auto divide_by_10_to_kappa_plus_1(uint64_t n) noexcept -> uint64_t {
  // 2361183241434822607 = ceil(2^(64+7)/1000)
  return umul128_upper64(n, 2361183241434822607ull) >> 7;
 }

 // Various subroutines using pow10 cache
-template <class T> struct cache_accessor;
+template <typename T> struct cache_accessor;

 template <> struct cache_accessor<float> {
  using carrier_uint = float_info<float>::carrier_uint;
  using cache_entry_type = uint64_t;

-  static uint64_t get_cached_power(int k) noexcept {
+  static auto get_cached_power(int k) noexcept -> uint64_t {
    FMT_ASSERT(k >= float_info<float>::min_k && k <= float_info<float>::max_k,
               "k is out of range");
    static constexpr const uint64_t pow10_significands[] = {
@@ -336,20 +298,23 @@ template <> struct cache_accessor<float> {
    bool is_integer;
  };

-  static compute_mul_result compute_mul(
-      carrier_uint u, const cache_entry_type& cache) noexcept {
+  static auto compute_mul(carrier_uint u,
+                          const cache_entry_type& cache) noexcept
+      -> compute_mul_result {
    auto r = umul96_upper64(u, cache);
    return {static_cast<carrier_uint>(r >> 32),
            static_cast<carrier_uint>(r) == 0};
  }

-  static uint32_t compute_delta(const cache_entry_type& cache,
-                                int beta) noexcept {
+  static auto compute_delta(const cache_entry_type& cache, int beta) noexcept
+      -> uint32_t {
    return static_cast<uint32_t>(cache >> (64 - 1 - beta));
  }

-  static compute_mul_parity_result compute_mul_parity(
-      carrier_uint two_f, const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta) noexcept
+      -> compute_mul_parity_result {
    FMT_ASSERT(beta >= 1, "");
    FMT_ASSERT(beta < 64, "");

@@ -358,22 +323,22 @@ template <> struct cache_accessor<float> {
            static_cast<uint32_t>(r >> (32 - beta)) == 0};
  }

-  static carrier_uint compute_left_endpoint_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return static_cast<carrier_uint>(
        (cache - (cache >> (num_significand_bits<float>() + 2))) >>
        (64 - num_significand_bits<float>() - 1 - beta));
  }

-  static carrier_uint compute_right_endpoint_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return static_cast<carrier_uint>(
        (cache + (cache >> (num_significand_bits<float>() + 1))) >>
        (64 - num_significand_bits<float>() - 1 - beta));
  }

-  static carrier_uint compute_round_up_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return (static_cast<carrier_uint>(
                cache >> (64 - num_significand_bits<float>() - 2 - beta)) +
            1) /
@@ -385,7 +350,7 @@ template <> struct cache_accessor<double> {
  using carrier_uint = float_info<double>::carrier_uint;
  using cache_entry_type = uint128_fallback;

-  static uint128_fallback get_cached_power(int k) noexcept {
+  static auto get_cached_power(int k) noexcept -> uint128_fallback {
    FMT_ASSERT(k >= float_info<double>::min_k && k <= float_info<double>::max_k,
               "k is out of range");

@@ -1009,8 +974,22 @@ template <> struct cache_accessor<double> {
      {0xfcf62c1dee382c42, 0x46729e03dd9ed7b6},
      {0x9e19db92b4e31ba9, 0x6c07a2c26a8346d2},
      {0xc5a05277621be293, 0xc7098b7305241886},
-      { 0xf70867153aa2db38,
-        0xb8cbee4fc66d1ea8 }
+      {0xf70867153aa2db38, 0xb8cbee4fc66d1ea8},
+      {0x9a65406d44a5c903, 0x737f74f1dc043329},
+      {0xc0fe908895cf3b44, 0x505f522e53053ff3},
+      {0xf13e34aabb430a15, 0x647726b9e7c68ff0},
+      {0x96c6e0eab509e64d, 0x5eca783430dc19f6},
+      {0xbc789925624c5fe0, 0xb67d16413d132073},
+      {0xeb96bf6ebadf77d8, 0xe41c5bd18c57e890},
+      {0x933e37a534cbaae7, 0x8e91b962f7b6f15a},
+      {0xb80dc58e81fe95a1, 0x723627bbb5a4adb1},
+      {0xe61136f2227e3b09, 0xcec3b1aaa30dd91d},
+      {0x8fcac257558ee4e6, 0x213a4f0aa5e8a7b2},
+      {0xb3bd72ed2af29e1f, 0xa988e2cd4f62d19e},
+      {0xe0accfa875af45a7, 0x93eb1b80a33b8606},
+      {0x8c6c01c9498d8b88, 0xbc72f130660533c4},
+      {0xaf87023b9bf0ee6a, 0xeb8fad7c7f8680b5},
+      {0xdb68c2ca82ed2a05, 0xa67398db9f6820e2},
 #else
      {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
      {0xce5d73ff402d98e3, 0xfb0a3d212dc81290},
@@ -1034,8 +1013,8 @@ template <> struct cache_accessor<double> {
      {0x8da471a9de737e24, 0x5ceaecfed289e5d3},
      {0xe4d5e82392a40515, 0x0fabaf3feaa5334b},
      {0xb8da1662e7b00a17, 0x3d6a751f3b936244},
-      { 0x95527a5202df0ccb,
-        0x0f37801e0c43ebc9 }
+      {0x95527a5202df0ccb, 0x0f37801e0c43ebc9},
+      {0xf13e34aabb430a15, 0x647726b9e7c68ff0}
 #endif
    };

@@ -1095,19 +1074,22 @@ template <> struct cache_accessor<double> {
    bool is_integer;
  };

-  static compute_mul_result compute_mul(
-      carrier_uint u, const cache_entry_type& cache) noexcept {
+  static auto compute_mul(carrier_uint u,
+                          const cache_entry_type& cache) noexcept
+      -> compute_mul_result {
    auto r = umul192_upper128(u, cache);
    return {r.high(), r.low() == 0};
  }

-  static uint32_t compute_delta(cache_entry_type const& cache,
-                                int beta) noexcept {
+  static auto compute_delta(cache_entry_type const& cache, int beta) noexcept
+      -> uint32_t {
    return static_cast<uint32_t>(cache.high() >> (64 - 1 - beta));
  }

-  static compute_mul_parity_result compute_mul_parity(
-      carrier_uint two_f, const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta) noexcept
+      -> compute_mul_parity_result {
    FMT_ASSERT(beta >= 1, "");
    FMT_ASSERT(beta < 64, "");

@@ -1116,31 +1098,35 @@ template <> struct cache_accessor<double> {
            ((r.high() << beta) | (r.low() >> (64 - beta))) == 0};
  }

-  static carrier_uint compute_left_endpoint_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return (cache.high() -
            (cache.high() >> (num_significand_bits<double>() + 2))) >>
           (64 - num_significand_bits<double>() - 1 - beta);
  }

-  static carrier_uint compute_right_endpoint_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return (cache.high() +
            (cache.high() >> (num_significand_bits<double>() + 1))) >>
           (64 - num_significand_bits<double>() - 1 - beta);
  }

-  static carrier_uint compute_round_up_for_shorter_interval_case(
-      const cache_entry_type& cache, int beta) noexcept {
+  static auto compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
    return ((cache.high() >> (64 - num_significand_bits<double>() - 2 - beta)) +
            1) /
           2;
  }
 };

+FMT_FUNC auto get_cached_power(int k) noexcept -> uint128_fallback {
+  return cache_accessor<double>::get_cached_power(k);
+}
+
 // Various integer checks
-template <class T>
-bool is_left_endpoint_integer_shorter_interval(int exponent) noexcept {
+template <typename T>
+auto is_left_endpoint_integer_shorter_interval(int exponent) noexcept -> bool {
  const int case_shorter_interval_left_endpoint_lower_threshold = 2;
  const int case_shorter_interval_left_endpoint_upper_threshold = 3;
  return exponent >= case_shorter_interval_left_endpoint_lower_threshold &&
@@ -1148,12 +1134,12 @@ bool is_left_endpoint_integer_shorter_interval(int exponent) noexcept {
 }

 // Remove trailing zeros from n and return the number of zeros removed (float)
-FMT_INLINE int remove_trailing_zeros(uint32_t& n) noexcept {
+FMT_INLINE int remove_trailing_zeros(uint32_t& n, int s = 0) noexcept {
  FMT_ASSERT(n != 0, "");
-  const uint32_t mod_inv_5 = 0xcccccccd;
-  const uint32_t mod_inv_25 = mod_inv_5 * mod_inv_5;
+  // Modular inverse of 5 (mod 2^32): (mod_inv_5 * 5) mod 2^32 = 1.
+  constexpr uint32_t mod_inv_5 = 0xcccccccd;
+  constexpr uint32_t mod_inv_25 = 0xc28f5c29;  // = mod_inv_5 * mod_inv_5

-  int s = 0;
  while (true) {
    auto q = rotr(n * mod_inv_25, 2);
    if (q > max_value<uint32_t>() / 100) break;
@@ -1165,7 +1151,6 @@ FMT_INLINE int remove_trailing_zeros(uint32_t& n) noexcept {
    n = q;
    s |= 1;
  }
-
  return s;
 }

@@ -1179,32 +1164,17 @@ FMT_INLINE int remove_trailing_zeros(uint64_t& n) noexcept {

  // Is n is divisible by 10^8?
  if ((nm.high() & ((1ull << (90 - 64)) - 1)) == 0 && nm.low() < magic_number) {
-    // If yes, work with the quotient.
+    // If yes, work with the quotient...
    auto n32 = static_cast<uint32_t>(nm.high() >> (90 - 64));
-
-    const uint32_t mod_inv_5 = 0xcccccccd;
-    const uint32_t mod_inv_25 = mod_inv_5 * mod_inv_5;
-
-    int s = 8;
-    while (true) {
-      auto q = rotr(n32 * mod_inv_25, 2);
-      if (q > max_value<uint32_t>() / 100) break;
-      n32 = q;
-      s += 2;
-    }
-    auto q = rotr(n32 * mod_inv_5, 1);
-    if (q <= max_value<uint32_t>() / 10) {
-      n32 = q;
-      s |= 1;
-    }
-
+    // ... and use the 32 bit variant of the function
+    int s = remove_trailing_zeros(n32, 8);
    n = n32;
    return s;
  }

  // If n is not divisible by 10^8, work with n itself.
-  const uint64_t mod_inv_5 = 0xcccccccccccccccd;
-  const uint64_t mod_inv_25 = mod_inv_5 * mod_inv_5;
+  constexpr uint64_t mod_inv_5 = 0xcccccccccccccccd;
+  constexpr uint64_t mod_inv_25 = 0x8f5c28f5c28f5c29;  // mod_inv_5 * mod_inv_5

  int s = 0;
  while (true) {
@@ -1223,7 +1193,7 @@ FMT_INLINE int remove_trailing_zeros(uint64_t& n) noexcept {
 }

 // The main algorithm for shorter interval case
-template <class T>
+template <typename T>
 FMT_INLINE decimal_fp<T> shorter_interval_case(int exponent) noexcept {
  decimal_fp<T> ret_value;
  // Compute k and beta
@@ -1270,7 +1240,7 @@ FMT_INLINE decimal_fp<T> shorter_interval_case(int exponent) noexcept {
  return ret_value;
 }

-template <typename T> decimal_fp<T> to_decimal(T x) noexcept {
+template <typename T> auto to_decimal(T x) noexcept -> decimal_fp<T> {
  // Step 1: integer promotion & Schubfach multiplier calculation.

  using carrier_uint = typename float_info<T>::carrier_uint;
@@ -1337,7 +1307,7 @@ template <typename T> decimal_fp<T> to_decimal(T x) noexcept {

  if (r < deltai) {
    // Exclude the right endpoint if necessary.
-    if (r == 0 && z_mul.is_integer && !include_right_endpoint) {
+    if (r == 0 && (z_mul.is_integer & !include_right_endpoint)) {
      --ret_value.significand;
      r = float_info<T>::big_divisor;
      goto small_divisor_case_label;
@@ -1346,26 +1316,11 @@ template <typename T> decimal_fp<T> to_decimal(T x) noexcept {
    goto small_divisor_case_label;
  } else {
    // r == deltai; compare fractional parts.
-    const carrier_uint two_fl = two_fc - 1;
+    const typename cache_accessor<T>::compute_mul_parity_result x_mul =
+        cache_accessor<T>::compute_mul_parity(two_fc - 1, cache, beta);

-    if (!include_left_endpoint ||
-        exponent < float_info<T>::case_fc_pm_half_lower_threshold ||
-        exponent > float_info<T>::divisibility_check_by_5_threshold) {
-      // If the left endpoint is not included, the condition for
-      // success is z^(f) < delta^(f) (odd parity).
-      // Otherwise, the inequalities on exponent ensure that
-      // x is not an integer, so if z^(f) >= delta^(f) (even parity), we in fact
-      // have strict inequality.
-      if (!cache_accessor<T>::compute_mul_parity(two_fl, cache, beta).parity) {
-        goto small_divisor_case_label;
-      }
-    } else {
-      const typename cache_accessor<T>::compute_mul_parity_result x_mul =
-          cache_accessor<T>::compute_mul_parity(two_fl, cache, beta);
-      if (!x_mul.parity && !x_mul.is_integer) {
-        goto small_divisor_case_label;
-      }
-    }
+    if (!(x_mul.parity | (x_mul.is_integer & include_left_endpoint)))
+      goto small_divisor_case_label;
  }
  ret_value.exponent = minus_k + float_info<T>::kappa + 1;

@@ -1404,22 +1359,11 @@ small_divisor_case_label:
  // or equivalently, when y is an integer.
  if (y_mul.parity != approx_y_parity)
    --ret_value.significand;
-  else if (y_mul.is_integer && ret_value.significand % 2 != 0)
+  else if (y_mul.is_integer & (ret_value.significand % 2 != 0))
    --ret_value.significand;
  return ret_value;
 }
 }  // namespace dragonbox
-
-#ifdef _MSC_VER
-FMT_FUNC auto fmt_snprintf(char* buf, size_t size, const char* fmt, ...)
-    -> int {
-  auto args = va_list();
-  va_start(args, fmt);
-  int result = vsnprintf_s(buf, size, _TRUNCATE, fmt, args);
-  va_end(args);
-  return result;
-}
-#endif
 }  // namespace detail

 template <> struct formatter<detail::bigint> {
@@ -1428,23 +1372,22 @@ template <> struct formatter<detail::bigint> {
    return ctx.begin();
  }

-  template <typename FormatContext>
-  auto format(const detail::bigint& n, FormatContext& ctx) const ->
-      typename FormatContext::iterator {
+  auto format(const detail::bigint& n, format_context& ctx) const
+      -> format_context::iterator {
    auto out = ctx.out();
    bool first = true;
    for (auto i = n.bigits_.size(); i > 0; --i) {
      auto value = n.bigits_[i - 1u];
      if (first) {
-        out = format_to(out, FMT_STRING("{:x}"), value);
+        out = fmt::format_to(out, FMT_STRING("{:x}"), value);
        first = false;
        continue;
      }
-      out = format_to(out, FMT_STRING("{:08x}"), value);
+      out = fmt::format_to(out, FMT_STRING("{:08x}"), value);
    }
    if (n.exp_ > 0)
-      out = format_to(out, FMT_STRING("p{}"),
-                      n.exp_ * detail::bigint::bigit_bits);
+      out = fmt::format_to(out, FMT_STRING("p{}"),
+                           n.exp_ * detail::bigint::bigit_bits);
    return out;
  }
 };
@@ -1480,7 +1423,7 @@ FMT_FUNC void report_system_error(int error_code,
  report_error(format_system_error, error_code, message);
 }

-FMT_FUNC std::string vformat(string_view fmt, format_args args) {
+FMT_FUNC auto vformat(string_view fmt, format_args args) -> std::string {
  // Don't optimize the "{}" case to keep the binary size small and because it
  // can be better optimized in fmt::format anyway.
  auto buffer = memory_buffer();
@@ -1488,53 +1431,55 @@ FMT_FUNC std::string vformat(string_view fmt, format_args args) {
  return to_string(buffer);
 }

-#ifdef _WIN32
 namespace detail {
+#if !defined(_WIN32) || defined(FMT_WINDOWS_NO_WCHAR)
+FMT_FUNC auto write_console(int, string_view) -> bool { return false; }
+FMT_FUNC auto write_console(std::FILE*, string_view) -> bool { return false; }
+#else
 using dword = conditional_t<sizeof(long) == 4, unsigned long, unsigned>;
 extern "C" __declspec(dllimport) int __stdcall WriteConsoleW(  //
    void*, const void*, dword, dword*, void*);
-}  // namespace detail
-#endif

-namespace detail {
-FMT_FUNC void print(std::FILE* f, string_view text) {
-#ifdef _WIN32
-  auto fd = _fileno(f);
-  if (_isatty(fd)) {
-    detail::utf8_to_utf16 u16(string_view(text.data(), text.size()));
-    auto written = detail::dword();
-    if (detail::WriteConsoleW(reinterpret_cast<void*>(_get_osfhandle(fd)),
-                              u16.c_str(), static_cast<uint32_t>(u16.size()),
-                              &written, nullptr)) {
-      return;
-    }
-    // Fallback to fwrite on failure. It can happen if the output has been
-    // redirected to NUL.
-  }
-#endif
-  detail::fwrite_fully(text.data(), 1, text.size(), f);
+FMT_FUNC bool write_console(int fd, string_view text) {
+  auto u16 = utf8_to_utf16(text);
+  return WriteConsoleW(reinterpret_cast<void*>(_get_osfhandle(fd)), u16.c_str(),
+                       static_cast<dword>(u16.size()), nullptr, nullptr) != 0;
 }
-}  // namespace detail

-FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
-  memory_buffer buffer;
-  detail::vformat_to(buffer, format_str, args);
-  detail::print(f, {buffer.data(), buffer.size()});
+FMT_FUNC auto write_console(std::FILE* f, string_view text) -> bool {
+  return write_console(_fileno(f), text);
 }
+#endif

 #ifdef _WIN32
 // Print assuming legacy (non-Unicode) encoding.
-FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
-                                      format_args args) {
-  memory_buffer buffer;
-  detail::vformat_to(buffer, format_str,
-                     basic_format_args<buffer_context<char>>(args));
-  fwrite_fully(buffer.data(), 1, buffer.size(), f);
+FMT_FUNC void vprint_mojibake(std::FILE* f, string_view fmt, format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt, args);
+  fwrite_fully(buffer.data(), buffer.size(), f);
 }
 #endif

-FMT_FUNC void vprint(string_view format_str, format_args args) {
-  vprint(stdout, format_str, args);
+FMT_FUNC void print(std::FILE* f, string_view text) {
+#ifdef _WIN32
+  int fd = _fileno(f);
+  if (_isatty(fd)) {
+    std::fflush(f);
+    if (write_console(fd, text)) return;
+  }
+#endif
+  fwrite_fully(text.data(), text.size(), f);
+}
+}  // namespace detail
+
+FMT_FUNC void vprint(std::FILE* f, string_view fmt, format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt, args);
+  detail::print(f, {buffer.data(), buffer.size()});
+}
+
+FMT_FUNC void vprint(string_view fmt, format_args args) {
+  vprint(stdout, fmt, args);
 }

 namespace detail {
@@ -13,12 +13,14 @@
 #include <cstdio>
 #include <system_error>  // std::system_error

-#if defined __APPLE__ || defined(__FreeBSD__)
-#  include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
-#endif
-
 #include "format.h"

+#if defined __APPLE__ || defined(__FreeBSD__)
+#  if FMT_HAS_INCLUDE(<xlocale.h>)
+#    include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
+#  endif
+#endif
+
 #ifndef FMT_USE_FCNTL
 // UWP doesn't provide _pipe.
 #  if FMT_HAS_INCLUDE("winapifamily.h")
@@ -46,6 +48,7 @@

 // Calls to system functions are wrapped in FMT_SYSTEM for testability.
 #ifdef FMT_SYSTEM
+#  define FMT_HAS_SYSTEM
 #  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
 #else
 #  define FMT_SYSTEM(call) ::call
@@ -71,7 +74,7 @@
 #define FMT_RETRY(result, expression) FMT_RETRY_VAL(result, expression, -1)

 FMT_BEGIN_NAMESPACE
-FMT_MODULE_EXPORT_BEGIN
+FMT_BEGIN_EXPORT

 /**
  \rst
@@ -114,57 +117,19 @@ template <typename Char> class basic_cstring_view {
  basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}

  /** Returns the pointer to a C string. */
-  const Char* c_str() const { return data_; }
+  auto c_str() const -> const Char* { return data_; }
 };

 using cstring_view = basic_cstring_view<char>;
 using wcstring_view = basic_cstring_view<wchar_t>;

-template <typename Char> struct formatter<std::error_code, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-
-  template <typename FormatContext>
-  FMT_CONSTEXPR auto format(const std::error_code& ec, FormatContext& ctx) const
-      -> decltype(ctx.out()) {
-    auto out = ctx.out();
-    out = detail::write_bytes(out, ec.category().name(),
-                              basic_format_specs<Char>());
-    out = detail::write<Char>(out, Char(':'));
-    out = detail::write<Char>(out, ec.value());
-    return out;
-  }
-};
-
 #ifdef _WIN32
 FMT_API const std::error_category& system_category() noexcept;

-FMT_BEGIN_DETAIL_NAMESPACE
-// A converter from UTF-16 to UTF-8.
-// It is only provided for Windows since other systems support UTF-8 natively.
-class utf16_to_utf8 {
- private:
-  memory_buffer buffer_;
-
- public:
-  utf16_to_utf8() {}
-  FMT_API explicit utf16_to_utf8(basic_string_view<wchar_t> s);
-  operator string_view() const { return string_view(&buffer_[0], size()); }
-  size_t size() const { return buffer_.size() - 1; }
-  const char* c_str() const { return &buffer_[0]; }
-  std::string str() const { return std::string(&buffer_[0], size()); }
-
-  // Performs conversion returning a system error code instead of
-  // throwing exception on conversion error. This method may still throw
-  // in case of memory allocation error.
-  FMT_API int convert(basic_string_view<wchar_t> s);
-};
-
+namespace detail {
 FMT_API void format_windows_error(buffer<char>& out, int error_code,
                                  const char* message) noexcept;
-FMT_END_DETAIL_NAMESPACE
+}

 FMT_API std::system_error vwindows_error(int error_code, string_view format_str,
                                         format_args args);
@@ -207,7 +172,7 @@ std::system_error windows_error(int error_code, string_view message,
 // Can be used to report errors from destructors.
 FMT_API void report_windows_error(int error_code, const char* message) noexcept;
 #else
-inline const std::error_category& system_category() noexcept {
+inline auto system_category() noexcept -> const std::error_category& {
  return std::system_category();
 }
 #endif  // _WIN32
@@ -244,7 +209,7 @@ class buffered_file {
    other.file_ = nullptr;
  }

-  buffered_file& operator=(buffered_file&& other) {
+  auto operator=(buffered_file&& other) -> buffered_file& {
    close();
    file_ = other.file_;
    other.file_ = nullptr;
@@ -258,9 +223,9 @@ class buffered_file {
  FMT_API void close();

  // Returns the pointer to a FILE object representing this file.
-  FILE* get() const noexcept { return file_; }
+  auto get() const noexcept -> FILE* { return file_; }

-  FMT_API int descriptor() const;
+  FMT_API auto descriptor() const -> int;

  void vprint(string_view format_str, format_args args) {
    fmt::vprint(file_, format_str, args);
@@ -310,7 +275,7 @@ class FMT_API file {
  file(file&& other) noexcept : fd_(other.fd_) { other.fd_ = -1; }

  // Move assignment is not noexcept because close may throw.
-  file& operator=(file&& other) {
+  auto operator=(file&& other) -> file& {
    close();
    fd_ = other.fd_;
    other.fd_ = -1;
@@ -321,24 +286,24 @@ class FMT_API file {
  ~file() noexcept;

  // Returns the file descriptor.
-  int descriptor() const noexcept { return fd_; }
+  auto descriptor() const noexcept -> int { return fd_; }

  // Closes the file.
  void close();

  // Returns the file size. The size has signed type for consistency with
  // stat::st_size.
-  long long size() const;
+  auto size() const -> long long;

  // Attempts to read count bytes from the file into the specified buffer.
-  size_t read(void* buffer, size_t count);
+  auto read(void* buffer, size_t count) -> size_t;

  // Attempts to write count bytes from the specified buffer to the file.
-  size_t write(const void* buffer, size_t count);
+  auto write(const void* buffer, size_t count) -> size_t;

  // Duplicates a file descriptor with the dup function and returns
  // the duplicate as a file object.
-  static file dup(int fd);
+  static auto dup(int fd) -> file;

  // Makes fd be the copy of this file descriptor, closing fd first if
  // necessary.
@@ -350,22 +315,29 @@ class FMT_API file {

  // Creates a pipe setting up read_end and write_end file objects for reading
  // and writing respectively.
+  // DEPRECATED! Taking files as out parameters is deprecated.
  static void pipe(file& read_end, file& write_end);

  // Creates a buffered_file object associated with this file and detaches
  // this file object from the file.
-  buffered_file fdopen(const char* mode);
+  auto fdopen(const char* mode) -> buffered_file;
+
+#  if defined(_WIN32) && !defined(__MINGW32__)
+  // Opens a file and constructs a file object representing this file by
+  // wcstring_view filename. Windows only.
+  static file open_windows_file(wcstring_view path, int oflag);
+#  endif
 };

 // Returns the memory page size.
-long getpagesize();
+auto getpagesize() -> long;

-FMT_BEGIN_DETAIL_NAMESPACE
+namespace detail {

 struct buffer_size {
  buffer_size() = default;
  size_t value = 0;
-  buffer_size operator=(size_t val) const {
+  auto operator=(size_t val) const -> buffer_size {
    auto bs = buffer_size();
    bs.value = val;
    return bs;
@@ -397,56 +369,61 @@ struct ostream_params {
 #  endif
 };

-FMT_END_DETAIL_NAMESPACE
+class file_buffer final : public buffer<char> {
+  file file_;
+
+  FMT_API void grow(size_t) override;
+
+ public:
+  FMT_API file_buffer(cstring_view path, const ostream_params& params);
+  FMT_API file_buffer(file_buffer&& other);
+  FMT_API ~file_buffer();
+
+  void flush() {
+    if (size() == 0) return;
+    file_.write(data(), size() * sizeof(data()[0]));
+    clear();
+  }
+
+  void close() {
+    flush();
+    file_.close();
+  }
+};
+
+}  // namespace detail

 // Added {} below to work around default constructor error known to
 // occur in Xcode versions 7.2.1 and 8.2.1.
 constexpr detail::buffer_size buffer_size{};

 /** A fast output stream which is not thread-safe. */
-class FMT_API ostream final : private detail::buffer<char> {
+class FMT_API ostream {
 private:
-  file file_;
-
-  void grow(size_t) override;
+  FMT_MSC_WARNING(suppress : 4251)
+  detail::file_buffer buffer_;

  ostream(cstring_view path, const detail::ostream_params& params)
-      : file_(path, params.oflag) {
-    set(new char[params.buffer_size], params.buffer_size);
-  }
+      : buffer_(path, params) {}

 public:
-  ostream(ostream&& other)
-      : detail::buffer<char>(other.data(), other.size(), other.capacity()),
-        file_(std::move(other.file_)) {
-    other.clear();
-    other.set(nullptr, 0);
-  }
-  ~ostream() {
-    flush();
-    delete[] data();
-  }
+  ostream(ostream&& other) : buffer_(std::move(other.buffer_)) {}

-  void flush() {
-    if (size() == 0) return;
-    file_.write(data(), size());
-    clear();
-  }
+  ~ostream();
+
+  void flush() { buffer_.flush(); }

  template <typename... T>
-  friend ostream output_file(cstring_view path, T... params);
+  friend auto output_file(cstring_view path, T... params) -> ostream;

-  void close() {
-    flush();
-    file_.close();
-  }
+  void close() { buffer_.close(); }

  /**
    Formats ``args`` according to specifications in ``fmt`` and writes the
    output to the file.
   */
  template <typename... T> void print(format_string<T...> fmt, T&&... args) {
-    vformat_to(detail::buffer_appender<char>(*this), fmt,
+    vformat_to(std::back_inserter(buffer_), fmt,
               fmt::make_format_args(args...));
  }
 };
@@ -467,12 +444,12 @@ class FMT_API ostream final : private detail::buffer<char> {
  \endrst
 */
 template <typename... T>
-inline ostream output_file(cstring_view path, T... params) {
+inline auto output_file(cstring_view path, T... params) -> ostream {
  return {path, detail::ostream_params(params...)};
 }
 #endif  // FMT_USE_FCNTL

-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_OS_H_
@@ -8,86 +8,100 @@
 #ifndef FMT_OSTREAM_H_
 #define FMT_OSTREAM_H_

-#include <fstream>
-#include <ostream>
+#include <fstream>  // std::filebuf
+
+#ifdef _WIN32
+#  ifdef __GLIBCXX__
+#    include <ext/stdio_filebuf.h>
+#    include <ext/stdio_sync_filebuf.h>
+#  endif
+#  include <io.h>
+#endif

 #include "format.h"

 FMT_BEGIN_NAMESPACE
-
-template <typename OutputIt, typename Char> class basic_printf_context;
-
 namespace detail {

-// Checks if T has a user-defined operator<<.
-template <typename T, typename Char, typename Enable = void>
-class is_streamable {
+template <typename Streambuf> class formatbuf : public Streambuf {
 private:
-  template <typename U>
-  static auto test(int)
-      -> bool_constant<sizeof(std::declval<std::basic_ostream<Char>&>()
-                              << std::declval<U>()) != 0>;
+  using char_type = typename Streambuf::char_type;
+  using streamsize = decltype(std::declval<Streambuf>().sputn(nullptr, 0));
+  using int_type = typename Streambuf::int_type;
+  using traits_type = typename Streambuf::traits_type;

-  template <typename> static auto test(...) -> std::false_type;
-
-  using result = decltype(test<T>(0));
+  buffer<char_type>& buffer_;

 public:
-  is_streamable() = default;
+  explicit formatbuf(buffer<char_type>& buf) : buffer_(buf) {}

-  static const bool value = result::value;
+ protected:
+  // The put area is always empty. This makes the implementation simpler and has
+  // the advantage that the streambuf and the buffer are always in sync and
+  // sputc never writes into uninitialized memory. A disadvantage is that each
+  // call to sputc always results in a (virtual) call to overflow. There is no
+  // disadvantage here for sputn since this always results in a call to xsputn.
+
+  auto overflow(int_type ch) -> int_type override {
+    if (!traits_type::eq_int_type(ch, traits_type::eof()))
+      buffer_.push_back(static_cast<char_type>(ch));
+    return ch;
+  }
+
+  auto xsputn(const char_type* s, streamsize count) -> streamsize override {
+    buffer_.append(s, s + count);
+    return count;
+  }
 };

-// Formatting of built-in types and arrays is intentionally disabled because
-// it's handled by standard (non-ostream) formatters.
-template <typename T, typename Char>
-struct is_streamable<
-    T, Char,
-    enable_if_t<
-        std::is_arithmetic<T>::value || std::is_array<T>::value ||
-        std::is_pointer<T>::value || std::is_same<T, char8_type>::value ||
-        std::is_convertible<T, fmt::basic_string_view<Char>>::value ||
-        std::is_same<T, std_string_view<Char>>::value ||
-        (std::is_convertible<T, int>::value && !std::is_enum<T>::value)>>
-    : std::false_type {};
-
-template <typename Char> FILE* get_file(std::basic_filebuf<Char>&) {
-  return nullptr;
-}
-
-struct dummy_filebuf {
-  FILE* _Myfile;
-};
-template <typename T, typename U = int> struct ms_filebuf {
-  using type = dummy_filebuf;
-};
-template <typename T> struct ms_filebuf<T, decltype(T::_Myfile, 0)> {
-  using type = T;
-};
-using filebuf_type = ms_filebuf<std::filebuf>::type;
-
-FILE* get_file(filebuf_type& buf);
-
 // Generate a unique explicit instantion in every translation unit using a tag
 // type in an anonymous namespace.
 namespace {
-struct filebuf_access_tag {};
+struct file_access_tag {};
 }  // namespace
-template <typename Tag, typename FileMemberPtr, FileMemberPtr file>
-class filebuf_access {
-  friend FILE* get_file(filebuf_type& buf) { return buf.*file; }
+template <typename Tag, typename BufType, FILE* BufType::*FileMemberPtr>
+class file_access {
+  friend auto get_file(BufType& obj) -> FILE* { return obj.*FileMemberPtr; }
 };
-template class filebuf_access<filebuf_access_tag,
-                              decltype(&filebuf_type::_Myfile),
-                              &filebuf_type::_Myfile>;

-inline bool write(std::filebuf& buf, fmt::string_view data) {
-  FILE* f = get_file(buf);
-  if (!f) return false;
-  print(f, data);
-  return true;
+#if FMT_MSC_VERSION
+template class file_access<file_access_tag, std::filebuf,
+                           &std::filebuf::_Myfile>;
+auto get_file(std::filebuf&) -> FILE*;
+#endif
+
+inline auto write_ostream_unicode(std::ostream& os, fmt::string_view data)
+    -> bool {
+  FILE* f = nullptr;
+#if FMT_MSC_VERSION
+  if (auto* buf = dynamic_cast<std::filebuf*>(os.rdbuf()))
+    f = get_file(*buf);
+  else
+    return false;
+#elif defined(_WIN32) && defined(__GLIBCXX__)
+  auto* rdbuf = os.rdbuf();
+  if (auto* sfbuf = dynamic_cast<__gnu_cxx::stdio_sync_filebuf<char>*>(rdbuf))
+    f = sfbuf->file();
+  else if (auto* fbuf = dynamic_cast<__gnu_cxx::stdio_filebuf<char>*>(rdbuf))
+    f = fbuf->file();
+  else
+    return false;
+#else
+  ignore_unused(os, data, f);
+#endif
+#ifdef _WIN32
+  if (f) {
+    int fd = _fileno(f);
+    if (_isatty(fd)) {
+      os.flush();
+      return write_console(fd, data);
+    }
+  }
+#endif
+  return false;
 }
-inline bool write(std::wfilebuf&, fmt::basic_string_view<wchar_t>) {
+inline auto write_ostream_unicode(std::wostream&,
+                                  fmt::basic_string_view<wchar_t>) -> bool {
  return false;
 }

@@ -95,10 +109,6 @@ inline bool write(std::wfilebuf&, fmt::basic_string_view<wchar_t>) {
 // It is a separate function rather than a part of vprint to simplify testing.
 template <typename Char>
 void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
-  if (const_check(FMT_MSC_VERSION)) {
-    auto filebuf = dynamic_cast<std::basic_filebuf<Char>*>(os.rdbuf());
-    if (filebuf && write(*filebuf, {buf.data(), buf.size()})) return;
-  }
  const Char* buf_data = buf.data();
  using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
  unsigned_streamsize size = buf.size();
@@ -112,29 +122,32 @@ void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
 }

 template <typename Char, typename T>
-void format_value(buffer<Char>& buf, const T& value,
-                  locale_ref loc = locale_ref()) {
+void format_value(buffer<Char>& buf, const T& value) {
  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
  auto&& output = std::basic_ostream<Char>(&format_buf);
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-  if (loc) output.imbue(loc.get<std::locale>());
+  output.imbue(std::locale::classic());  // The default is always unlocalized.
 #endif
  output << value;
  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
 }

-template <typename T> struct streamed_view { const T& value; };
+template <typename T> struct streamed_view {
+  const T& value;
+};

 }  // namespace detail

 // Formats an object of type T that has an overloaded ostream operator<<.
 template <typename Char>
 struct basic_ostream_formatter : formatter<basic_string_view<Char>, Char> {
+  void set_debug_format() = delete;
+
  template <typename T, typename OutputIt>
  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx) const
      -> OutputIt {
    auto buffer = basic_memory_buffer<Char>();
-    format_value(buffer, value, ctx.locale());
+    detail::format_value(buffer, value);
    return formatter<basic_string_view<Char>, Char>::format(
        {buffer.data(), buffer.size()}, ctx);
  }
@@ -142,12 +155,13 @@ struct basic_ostream_formatter : formatter<basic_string_view<Char>, Char> {

 using ostream_formatter = basic_ostream_formatter<char>;

-template <typename T>
-struct formatter<detail::streamed_view<T>> : ostream_formatter {
+template <typename T, typename Char>
+struct formatter<detail::streamed_view<T>, Char>
+    : basic_ostream_formatter<Char> {
  template <typename OutputIt>
  auto format(detail::streamed_view<T> view,
-              basic_format_context<OutputIt, char>& ctx) const -> OutputIt {
-    return ostream_formatter::format(view.value, ctx);
+              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+    return basic_ostream_formatter<Char>::format(view.value, ctx);
  }
 };

@@ -162,27 +176,28 @@ struct formatter<detail::streamed_view<T>> : ostream_formatter {
  \endrst
 */
 template <typename T>
-auto streamed(const T& value) -> detail::streamed_view<T> {
+constexpr auto streamed(const T& value) -> detail::streamed_view<T> {
  return {value};
 }

 namespace detail {

-// Formats an object of type T that has an overloaded ostream operator<<.
-template <typename T, typename Char>
-struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
-    : basic_ostream_formatter<Char> {
-  using basic_ostream_formatter<Char>::format;
-};
+inline void vprint_directly(std::ostream& os, string_view format_str,
+                            format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, format_str, args);
+  detail::write_buffer(os, buffer);
+}

 }  // namespace detail

-FMT_MODULE_EXPORT template <typename Char>
+FMT_EXPORT template <typename Char>
 void vprint(std::basic_ostream<Char>& os,
            basic_string_view<type_identity_t<Char>> format_str,
            basic_format_args<buffer_context<type_identity_t<Char>>> args) {
  auto buffer = basic_memory_buffer<Char>();
  detail::vformat_to(buffer, format_str, args);
+  if (detail::write_ostream_unicode(os, {buffer.data(), buffer.size()})) return;
  detail::write_buffer(os, buffer);
 }

@@ -195,12 +210,16 @@ void vprint(std::basic_ostream<Char>& os,
    fmt::print(cerr, "Don't {}!", "panic");
  \endrst
 */
-FMT_MODULE_EXPORT template <typename... T>
+FMT_EXPORT template <typename... T>
 void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
-  vprint(os, fmt, fmt::make_format_args(args...));
+  const auto& vargs = fmt::make_format_args(args...);
+  if (detail::is_utf8())
+    vprint(os, fmt, vargs);
+  else
+    detail::vprint_directly(os, fmt, vargs);
 }

-FMT_MODULE_EXPORT
+FMT_EXPORT
 template <typename... Args>
 void print(std::wostream& os,
           basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
@@ -208,6 +227,19 @@ void print(std::wostream& os,
  vprint(os, fmt, fmt::make_format_args<buffer_context<wchar_t>>(args...));
 }

+FMT_EXPORT template <typename... T>
+void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
+  fmt::print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+FMT_EXPORT
+template <typename... Args>
+void println(std::wostream& os,
+             basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
+             Args&&... args) {
+  print(os, L"{}\n", fmt::format(fmt, std::forward<Args>(args)...));
+}
+
 FMT_END_NAMESPACE

 #endif  // FMT_OSTREAM_H_
@@ -14,24 +14,24 @@
 #include "format.h"

 FMT_BEGIN_NAMESPACE
-FMT_MODULE_EXPORT_BEGIN
+FMT_BEGIN_EXPORT

-template <typename T> struct printf_formatter { printf_formatter() = delete; };
-
-template <typename Char>
-class basic_printf_parse_context : public basic_format_parse_context<Char> {
-  using basic_format_parse_context<Char>::basic_format_parse_context;
+template <typename T> struct printf_formatter {
+  printf_formatter() = delete;
 };

-template <typename OutputIt, typename Char> class basic_printf_context {
+template <typename Char> class basic_printf_context {
 private:
-  OutputIt out_;
+  detail::buffer_appender<Char> out_;
  basic_format_args<basic_printf_context> args_;

+  static_assert(std::is_same<Char, char>::value ||
+                    std::is_same<Char, wchar_t>::value,
+                "Unsupported code unit type.");
+
 public:
  using char_type = Char;
-  using format_arg = basic_format_arg<basic_printf_context>;
-  using parse_context_type = basic_printf_parse_context<Char>;
+  using parse_context_type = basic_format_parse_context<Char>;
  template <typename T> using formatter_type = printf_formatter<T>;

  /**
@@ -40,75 +40,77 @@ template <typename OutputIt, typename Char> class basic_printf_context {
    stored in the context object so make sure they have appropriate lifetimes.
    \endrst
   */
-  basic_printf_context(OutputIt out,
+  basic_printf_context(detail::buffer_appender<Char> out,
                       basic_format_args<basic_printf_context> args)
      : out_(out), args_(args) {}

-  OutputIt out() { return out_; }
-  void advance_to(OutputIt it) { out_ = it; }
+  auto out() -> detail::buffer_appender<Char> { return out_; }
+  void advance_to(detail::buffer_appender<Char>) {}

-  detail::locale_ref locale() { return {}; }
+  auto locale() -> detail::locale_ref { return {}; }

-  format_arg arg(int id) const { return args_.get(id); }
+  auto arg(int id) const -> basic_format_arg<basic_printf_context> {
+    return args_.get(id);
+  }

  FMT_CONSTEXPR void on_error(const char* message) {
    detail::error_handler().on_error(message);
  }
 };

-FMT_BEGIN_DETAIL_NAMESPACE
+namespace detail {

 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
 template <bool IsSigned> struct int_checker {
-  template <typename T> static bool fits_in_int(T value) {
+  template <typename T> static auto fits_in_int(T value) -> bool {
    unsigned max = max_value<int>();
    return value <= max;
  }
-  static bool fits_in_int(bool) { return true; }
+  static auto fits_in_int(bool) -> bool { return true; }
 };

 template <> struct int_checker<true> {
-  template <typename T> static bool fits_in_int(T value) {
+  template <typename T> static auto fits_in_int(T value) -> bool {
    return value >= (std::numeric_limits<int>::min)() &&
           value <= max_value<int>();
  }
-  static bool fits_in_int(int) { return true; }
+  static auto fits_in_int(int) -> bool { return true; }
 };

-class printf_precision_handler {
- public:
+struct printf_precision_handler {
  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  int operator()(T value) {
+  auto operator()(T value) -> int {
    if (!int_checker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
-      FMT_THROW(format_error("number is too big"));
+      throw_format_error("number is too big");
    return (std::max)(static_cast<int>(value), 0);
  }

  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  int operator()(T) {
-    FMT_THROW(format_error("precision is not integer"));
+  auto operator()(T) -> int {
+    throw_format_error("precision is not integer");
    return 0;
  }
 };

 // An argument visitor that returns true iff arg is a zero integer.
-class is_zero_int {
- public:
+struct is_zero_int {
  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  bool operator()(T value) {
+  auto operator()(T value) -> bool {
    return value == 0;
  }

  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  bool operator()(T) {
+  auto operator()(T) -> bool {
    return false;
  }
 };

 template <typename T> struct make_unsigned_or_bool : std::make_unsigned<T> {};

-template <> struct make_unsigned_or_bool<bool> { using type = bool; };
+template <> struct make_unsigned_or_bool<bool> {
+  using type = bool;
+};

 template <typename T, typename Context> class arg_converter {
 private:
@@ -132,22 +134,23 @@ template <typename T, typename Context> class arg_converter {
    if (const_check(sizeof(target_type) <= sizeof(int))) {
      // Extra casts are used to silence warnings.
      if (is_signed) {
-        arg_ = detail::make_arg<Context>(
-            static_cast<int>(static_cast<target_type>(value)));
+        auto n = static_cast<int>(static_cast<target_type>(value));
+        arg_ = detail::make_arg<Context>(n);
      } else {
        using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
-        arg_ = detail::make_arg<Context>(
-            static_cast<unsigned>(static_cast<unsigned_type>(value)));
+        auto n = static_cast<unsigned>(static_cast<unsigned_type>(value));
+        arg_ = detail::make_arg<Context>(n);
      }
    } else {
      if (is_signed) {
        // glibc's printf doesn't sign extend arguments of smaller types:
        //   std::printf("%lld", -42);  // prints "4294967254"
        // but we don't have to do the same because it's a UB.
-        arg_ = detail::make_arg<Context>(static_cast<long long>(value));
+        auto n = static_cast<long long>(value);
+        arg_ = detail::make_arg<Context>(n);
      } else {
-        arg_ = detail::make_arg<Context>(
-            static_cast<typename make_unsigned_or_bool<U>::type>(value));
+        auto n = static_cast<typename make_unsigned_or_bool<U>::type>(value);
+        arg_ = detail::make_arg<Context>(n);
      }
    }
  }
@@ -175,8 +178,8 @@ template <typename Context> class char_converter {

  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
  void operator()(T value) {
-    arg_ = detail::make_arg<Context>(
-        static_cast<typename Context::char_type>(value));
+    auto c = static_cast<typename Context::char_type>(value);
+    arg_ = detail::make_arg<Context>(c);
  }

  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
@@ -186,122 +189,131 @@ template <typename Context> class char_converter {
 // An argument visitor that return a pointer to a C string if argument is a
 // string or null otherwise.
 template <typename Char> struct get_cstring {
-  template <typename T> const Char* operator()(T) { return nullptr; }
-  const Char* operator()(const Char* s) { return s; }
+  template <typename T> auto operator()(T) -> const Char* { return nullptr; }
+  auto operator()(const Char* s) -> const Char* { return s; }
 };

 // Checks if an argument is a valid printf width specifier and sets
 // left alignment if it is negative.
 template <typename Char> class printf_width_handler {
 private:
-  using format_specs = basic_format_specs<Char>;
-
-  format_specs& specs_;
+  format_specs<Char>& specs_;

 public:
-  explicit printf_width_handler(format_specs& specs) : specs_(specs) {}
+  explicit printf_width_handler(format_specs<Char>& specs) : specs_(specs) {}

  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  unsigned operator()(T value) {
+  auto operator()(T value) -> unsigned {
    auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
    if (detail::is_negative(value)) {
      specs_.align = align::left;
      width = 0 - width;
    }
    unsigned int_max = max_value<int>();
-    if (width > int_max) FMT_THROW(format_error("number is too big"));
+    if (width > int_max) throw_format_error("number is too big");
    return static_cast<unsigned>(width);
  }

  template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  unsigned operator()(T) {
-    FMT_THROW(format_error("width is not integer"));
+  auto operator()(T) -> unsigned {
+    throw_format_error("width is not integer");
    return 0;
  }
 };

+// Workaround for a bug with the XL compiler when initializing
+// printf_arg_formatter's base class.
+template <typename Char>
+auto make_arg_formatter(buffer_appender<Char> iter, format_specs<Char>& s)
+    -> arg_formatter<Char> {
+  return {iter, s, locale_ref()};
+}
+
 // The ``printf`` argument formatter.
-template <typename OutputIt, typename Char>
+template <typename Char>
 class printf_arg_formatter : public arg_formatter<Char> {
 private:
  using base = arg_formatter<Char>;
-  using context_type = basic_printf_context<OutputIt, Char>;
-  using format_specs = basic_format_specs<Char>;
+  using context_type = basic_printf_context<Char>;

  context_type& context_;

-  OutputIt write_null_pointer(bool is_string = false) {
+  void write_null_pointer(bool is_string = false) {
    auto s = this->specs;
    s.type = presentation_type::none;
-    return write_bytes(this->out, is_string ? "(null)" : "(nil)", s);
+    write_bytes(this->out, is_string ? "(null)" : "(nil)", s);
  }

 public:
-  printf_arg_formatter(OutputIt iter, format_specs& s, context_type& ctx)
-      : base{iter, s, locale_ref()}, context_(ctx) {}
+  printf_arg_formatter(buffer_appender<Char> iter, format_specs<Char>& s,
+                       context_type& ctx)
+      : base(make_arg_formatter(iter, s)), context_(ctx) {}

-  OutputIt operator()(monostate value) { return base::operator()(value); }
+  void operator()(monostate value) { base::operator()(value); }

  template <typename T, FMT_ENABLE_IF(detail::is_integral<T>::value)>
-  OutputIt operator()(T value) {
+  void operator()(T value) {
    // MSVC2013 fails to compile separate overloads for bool and Char so use
    // std::is_same instead.
-    if (std::is_same<T, Char>::value) {
-      format_specs fmt_specs = this->specs;
-      if (fmt_specs.type != presentation_type::none &&
-          fmt_specs.type != presentation_type::chr) {
-        return (*this)(static_cast<int>(value));
-      }
-      fmt_specs.sign = sign::none;
-      fmt_specs.alt = false;
-      fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
-      // align::numeric needs to be overwritten here since the '0' flag is
-      // ignored for non-numeric types
-      if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
-        fmt_specs.align = align::right;
-      return write<Char>(this->out, static_cast<Char>(value), fmt_specs);
+    if (!std::is_same<T, Char>::value) {
+      base::operator()(value);
+      return;
    }
-    return base::operator()(value);
+    format_specs<Char> fmt_specs = this->specs;
+    if (fmt_specs.type != presentation_type::none &&
+        fmt_specs.type != presentation_type::chr) {
+      return (*this)(static_cast<int>(value));
+    }
+    fmt_specs.sign = sign::none;
+    fmt_specs.alt = false;
+    fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
+    // align::numeric needs to be overwritten here since the '0' flag is
+    // ignored for non-numeric types
+    if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
+      fmt_specs.align = align::right;
+    write<Char>(this->out, static_cast<Char>(value), fmt_specs);
  }

  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  OutputIt operator()(T value) {
-    return base::operator()(value);
+  void operator()(T value) {
+    base::operator()(value);
  }

  /** Formats a null-terminated C string. */
-  OutputIt operator()(const char* value) {
-    if (value) return base::operator()(value);
-    return write_null_pointer(this->specs.type != presentation_type::pointer);
+  void operator()(const char* value) {
+    if (value)
+      base::operator()(value);
+    else
+      write_null_pointer(this->specs.type != presentation_type::pointer);
  }

  /** Formats a null-terminated wide C string. */
-  OutputIt operator()(const wchar_t* value) {
-    if (value) return base::operator()(value);
-    return write_null_pointer(this->specs.type != presentation_type::pointer);
+  void operator()(const wchar_t* value) {
+    if (value)
+      base::operator()(value);
+    else
+      write_null_pointer(this->specs.type != presentation_type::pointer);
  }

-  OutputIt operator()(basic_string_view<Char> value) {
-    return base::operator()(value);
-  }
+  void operator()(basic_string_view<Char> value) { base::operator()(value); }

  /** Formats a pointer. */
-  OutputIt operator()(const void* value) {
-    return value ? base::operator()(value) : write_null_pointer();
+  void operator()(const void* value) {
+    if (value)
+      base::operator()(value);
+    else
+      write_null_pointer();
  }

  /** Formats an argument of a custom (user-defined) type. */
-  OutputIt operator()(typename basic_format_arg<context_type>::handle handle) {
-    auto parse_ctx =
-        basic_printf_parse_context<Char>(basic_string_view<Char>());
+  void operator()(typename basic_format_arg<context_type>::handle handle) {
+    auto parse_ctx = basic_format_parse_context<Char>({});
    handle.format(parse_ctx, context_);
-    return this->out;
  }
 };

 template <typename Char>
-void parse_flags(basic_format_specs<Char>& specs, const Char*& it,
-                 const Char* end) {
+void parse_flags(format_specs<Char>& specs, const Char*& it, const Char* end) {
  for (; it != end; ++it) {
    switch (*it) {
    case '-':
@@ -314,9 +326,7 @@ void parse_flags(basic_format_specs<Char>& specs, const Char*& it,
      specs.fill[0] = '0';
      break;
    case ' ':
-      if (specs.sign != sign::plus) {
-        specs.sign = sign::space;
-      }
+      if (specs.sign != sign::plus) specs.sign = sign::space;
      break;
    case '#':
      specs.alt = true;
@@ -328,8 +338,8 @@ void parse_flags(basic_format_specs<Char>& specs, const Char*& it,
 }

 template <typename Char, typename GetArg>
-int parse_header(const Char*& it, const Char* end,
-                 basic_format_specs<Char>& specs, GetArg get_arg) {
+auto parse_header(const Char*& it, const Char* end, format_specs<Char>& specs,
+                  GetArg get_arg) -> int {
  int arg_index = -1;
  Char c = *it;
  if (c >= '0' && c <= '9') {
@@ -344,7 +354,7 @@ int parse_header(const Char*& it, const Char* end,
      if (value != 0) {
        // Nonzero value means that we parsed width and don't need to
        // parse it or flags again, so return now.
-        if (value == -1) FMT_THROW(format_error("number is too big"));
+        if (value == -1) throw_format_error("number is too big");
        specs.width = value;
        return arg_index;
      }
@@ -355,7 +365,7 @@ int parse_header(const Char*& it, const Char* end,
  if (it != end) {
    if (*it >= '0' && *it <= '9') {
      specs.width = parse_nonnegative_int(it, end, -1);
-      if (specs.width == -1) FMT_THROW(format_error("number is too big"));
+      if (specs.width == -1) throw_format_error("number is too big");
    } else if (*it == '*') {
      ++it;
      specs.width = static_cast<int>(visit_format_arg(
@@ -365,13 +375,53 @@ int parse_header(const Char*& it, const Char* end,
  return arg_index;
 }

+inline auto parse_printf_presentation_type(char c, type t)
+    -> presentation_type {
+  using pt = presentation_type;
+  constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
+  switch (c) {
+  case 'd':
+    return in(t, integral_set) ? pt::dec : pt::none;
+  case 'o':
+    return in(t, integral_set) ? pt::oct : pt::none;
+  case 'x':
+    return in(t, integral_set) ? pt::hex_lower : pt::none;
+  case 'X':
+    return in(t, integral_set) ? pt::hex_upper : pt::none;
+  case 'a':
+    return in(t, float_set) ? pt::hexfloat_lower : pt::none;
+  case 'A':
+    return in(t, float_set) ? pt::hexfloat_upper : pt::none;
+  case 'e':
+    return in(t, float_set) ? pt::exp_lower : pt::none;
+  case 'E':
+    return in(t, float_set) ? pt::exp_upper : pt::none;
+  case 'f':
+    return in(t, float_set) ? pt::fixed_lower : pt::none;
+  case 'F':
+    return in(t, float_set) ? pt::fixed_upper : pt::none;
+  case 'g':
+    return in(t, float_set) ? pt::general_lower : pt::none;
+  case 'G':
+    return in(t, float_set) ? pt::general_upper : pt::none;
+  case 'c':
+    return in(t, integral_set) ? pt::chr : pt::none;
+  case 's':
+    return in(t, string_set | cstring_set) ? pt::string : pt::none;
+  case 'p':
+    return in(t, pointer_set | cstring_set) ? pt::pointer : pt::none;
+  default:
+    return pt::none;
+  }
+}
+
 template <typename Char, typename Context>
 void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
             basic_format_args<Context> args) {
-  using OutputIt = buffer_appender<Char>;
-  auto out = OutputIt(buf);
-  auto context = basic_printf_context<OutputIt, Char>(out, args);
-  auto parse_ctx = basic_printf_parse_context<Char>(format);
+  using iterator = buffer_appender<Char>;
+  auto out = iterator(buf);
+  auto context = basic_printf_context<Char>(out, args);
+  auto parse_ctx = basic_format_parse_context<Char>(format);

  // Returns the argument with specified index or, if arg_index is -1, the next
  // argument.
@@ -387,26 +437,24 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
  const Char* end = parse_ctx.end();
  auto it = start;
  while (it != end) {
-    if (!detail::find<false, Char>(it, end, '%', it)) {
-      it = end;  // detail::find leaves it == nullptr if it doesn't find '%'
+    if (!find<false, Char>(it, end, '%', it)) {
+      it = end;  // find leaves it == nullptr if it doesn't find '%'.
      break;
    }
    Char c = *it++;
    if (it != end && *it == c) {
-      out = detail::write(
-          out, basic_string_view<Char>(start, detail::to_unsigned(it - start)));
+      write(out, basic_string_view<Char>(start, to_unsigned(it - start)));
      start = ++it;
      continue;
    }
-    out = detail::write(out, basic_string_view<Char>(
-                                 start, detail::to_unsigned(it - 1 - start)));
+    write(out, basic_string_view<Char>(start, to_unsigned(it - 1 - start)));

-    basic_format_specs<Char> specs;
+    auto specs = format_specs<Char>();
    specs.align = align::right;

    // Parse argument index, flags and width.
    int arg_index = parse_header(it, end, specs, get_arg);
-    if (arg_index == 0) parse_ctx.on_error("argument not found");
+    if (arg_index == 0) throw_format_error("argument not found");

    // Parse precision.
    if (it != end && *it == '.') {
@@ -417,7 +465,7 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
      } else if (c == '*') {
        ++it;
        specs.precision = static_cast<int>(
-            visit_format_arg(detail::printf_precision_handler(), get_arg(-1)));
+            visit_format_arg(printf_precision_handler(), get_arg(-1)));
      } else {
        specs.precision = 0;
      }
@@ -426,20 +474,19 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
    auto arg = get_arg(arg_index);
    // For d, i, o, u, x, and X conversion specifiers, if a precision is
    // specified, the '0' flag is ignored
-    if (specs.precision >= 0 && arg.is_integral())
-      specs.fill[0] =
-          ' ';  // Ignore '0' flag for non-numeric types or if '-' present.
-    if (specs.precision >= 0 && arg.type() == detail::type::cstring_type) {
-      auto str = visit_format_arg(detail::get_cstring<Char>(), arg);
+    if (specs.precision >= 0 && arg.is_integral()) {
+      // Ignore '0' for non-numeric types or if '-' present.
+      specs.fill[0] = ' ';
+    }
+    if (specs.precision >= 0 && arg.type() == type::cstring_type) {
+      auto str = visit_format_arg(get_cstring<Char>(), arg);
      auto str_end = str + specs.precision;
      auto nul = std::find(str, str_end, Char());
-      arg = detail::make_arg<basic_printf_context<OutputIt, Char>>(
-          basic_string_view<Char>(
-              str, detail::to_unsigned(nul != str_end ? nul - str
-                                                      : specs.precision)));
+      auto sv = basic_string_view<Char>(
+          str, to_unsigned(nul != str_end ? nul - str : specs.precision));
+      arg = make_arg<basic_printf_context<Char>>(sv);
    }
-    if (specs.alt && visit_format_arg(detail::is_zero_int(), arg))
-      specs.alt = false;
+    if (specs.alt && visit_format_arg(is_zero_int(), arg)) specs.alt = false;
    if (specs.fill[0] == '0') {
      if (arg.is_arithmetic() && specs.align != align::left)
        specs.align = align::numeric;
@@ -451,7 +498,6 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
    // Parse length and convert the argument to the required type.
    c = it != end ? *it++ : 0;
    Char t = it != end ? *it : 0;
-    using detail::convert_arg;
    switch (c) {
    case 'h':
      if (t == 'h') {
@@ -490,7 +536,7 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
    }

    // Parse type.
-    if (it == end) FMT_THROW(format_error("invalid format string"));
+    if (it == end) throw_format_error("invalid format string");
    char type = static_cast<char>(*it++);
    if (arg.is_integral()) {
      // Normalize type.
@@ -500,32 +546,25 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
        type = 'd';
        break;
      case 'c':
-        visit_format_arg(
-            detail::char_converter<basic_printf_context<OutputIt, Char>>(arg),
-            arg);
+        visit_format_arg(char_converter<basic_printf_context<Char>>(arg), arg);
        break;
      }
    }
-    specs.type = parse_presentation_type(type);
+    specs.type = parse_printf_presentation_type(type, arg.type());
    if (specs.type == presentation_type::none)
-      parse_ctx.on_error("invalid type specifier");
+      throw_format_error("invalid format specifier");

    start = it;

    // Format argument.
-    out = visit_format_arg(
-        detail::printf_arg_formatter<OutputIt, Char>(out, specs, context), arg);
+    visit_format_arg(printf_arg_formatter<Char>(out, specs, context), arg);
  }
-  detail::write(out, basic_string_view<Char>(start, to_unsigned(it - start)));
+  write(out, basic_string_view<Char>(start, to_unsigned(it - start)));
 }
-FMT_END_DETAIL_NAMESPACE
+}  // namespace detail

-template <typename Char>
-using basic_printf_context_t =
-    basic_printf_context<detail::buffer_appender<Char>, Char>;
-
-using printf_context = basic_printf_context_t<char>;
-using wprintf_context = basic_printf_context_t<wchar_t>;
+using printf_context = basic_printf_context<char>;
+using wprintf_context = basic_printf_context<wchar_t>;

 using printf_args = basic_format_args<printf_context>;
 using wprintf_args = basic_format_args<wprintf_context>;
@@ -542,26 +581,21 @@ inline auto make_printf_args(const T&... args)
  return {args...};
 }

-/**
-  \rst
-  Constructs an `~fmt::format_arg_store` object that contains references to
-  arguments and can be implicitly converted to `~fmt::wprintf_args`.
-  \endrst
- */
+// DEPRECATED!
 template <typename... T>
 inline auto make_wprintf_args(const T&... args)
    -> format_arg_store<wprintf_context, T...> {
  return {args...};
 }

-template <typename S, typename Char = char_t<S>>
+template <typename Char>
 inline auto vsprintf(
-    const S& fmt,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args)
+    basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
    -> std::basic_string<Char> {
-  basic_memory_buffer<Char> buffer;
-  vprintf(buffer, detail::to_string_view(fmt), args);
-  return to_string(buffer);
+  auto buf = basic_memory_buffer<Char>();
+  detail::vprintf(buf, fmt, args);
+  return to_string(buf);
 }

 /**
@@ -576,20 +610,19 @@ inline auto vsprintf(
 template <typename S, typename... T,
          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline auto sprintf(const S& fmt, const T&... args) -> std::basic_string<Char> {
-  using context = basic_printf_context_t<Char>;
  return vsprintf(detail::to_string_view(fmt),
-                  fmt::make_format_args<context>(args...));
+                  fmt::make_format_args<basic_printf_context<Char>>(args...));
 }

-template <typename S, typename Char = char_t<S>>
+template <typename Char>
 inline auto vfprintf(
-    std::FILE* f, const S& fmt,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args)
+    std::FILE* f, basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
    -> int {
-  basic_memory_buffer<Char> buffer;
-  vprintf(buffer, detail::to_string_view(fmt), args);
-  size_t size = buffer.size();
-  return std::fwrite(buffer.data(), sizeof(Char), size, f) < size
+  auto buf = basic_memory_buffer<Char>();
+  detail::vprintf(buf, fmt, args);
+  size_t size = buf.size();
+  return std::fwrite(buf.data(), sizeof(Char), size, f) < size
             ? -1
             : static_cast<int>(size);
 }
@@ -605,17 +638,16 @@ inline auto vfprintf(
 */
 template <typename S, typename... T, typename Char = char_t<S>>
 inline auto fprintf(std::FILE* f, const S& fmt, const T&... args) -> int {
-  using context = basic_printf_context_t<Char>;
  return vfprintf(f, detail::to_string_view(fmt),
-                  fmt::make_format_args<context>(args...));
+                  fmt::make_format_args<basic_printf_context<Char>>(args...));
 }

-template <typename S, typename Char = char_t<S>>
-inline auto vprintf(
-    const S& fmt,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args)
+template <typename Char>
+FMT_DEPRECATED inline auto vprintf(
+    basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
    -> int {
-  return vfprintf(stdout, detail::to_string_view(fmt), args);
+  return vfprintf(stdout, fmt, args);
 }

 /**
@@ -627,14 +659,17 @@ inline auto vprintf(
    fmt::printf("Elapsed time: %.2f seconds", 1.23);
  \endrst
 */
-template <typename S, typename... T, FMT_ENABLE_IF(detail::is_string<S>::value)>
-inline auto printf(const S& fmt, const T&... args) -> int {
-  return vprintf(
-      detail::to_string_view(fmt),
-      fmt::make_format_args<basic_printf_context_t<char_t<S>>>(args...));
+template <typename... T>
+inline auto printf(string_view fmt, const T&... args) -> int {
+  return vfprintf(stdout, fmt, make_printf_args(args...));
+}
+template <typename... T>
+FMT_DEPRECATED inline auto printf(basic_string_view<wchar_t> fmt,
+                                  const T&... args) -> int {
+  return vfprintf(stdout, fmt, make_wprintf_args(args...));
 }

-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_PRINTF_H_
@@ -1,13 +1,9 @@
-// Formatting library for C++ - experimental range support
+// Formatting library for C++ - range and tuple support
 //
-// Copyright (c) 2012 - present, Victor Zverovich
+// Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors
 // All rights reserved.
 //
 // For the license information refer to format.h.
-//
-// Copyright (c) 2018 - present, Remotion (Igor Schulz)
-// All Rights Reserved
-// {fmt} support for ranges, containers and types tuple interface.

 #ifndef FMT_RANGES_H_
 #define FMT_RANGES_H_
@@ -22,27 +18,25 @@ FMT_BEGIN_NAMESPACE

 namespace detail {

-template <typename RangeT, typename OutputIterator>
-OutputIterator copy(const RangeT& range, OutputIterator out) {
+template <typename Range, typename OutputIt>
+auto copy(const Range& range, OutputIt out) -> OutputIt {
  for (auto it = range.begin(), end = range.end(); it != end; ++it)
    *out++ = *it;
  return out;
 }

-template <typename OutputIterator>
-OutputIterator copy(const char* str, OutputIterator out) {
+template <typename OutputIt>
+auto copy(const char* str, OutputIt out) -> OutputIt {
  while (*str) *out++ = *str++;
  return out;
 }

-template <typename OutputIterator>
-OutputIterator copy(char ch, OutputIterator out) {
+template <typename OutputIt> auto copy(char ch, OutputIt out) -> OutputIt {
  *out++ = ch;
  return out;
 }

-template <typename OutputIterator>
-OutputIterator copy(wchar_t ch, OutputIterator out) {
+template <typename OutputIt> auto copy(wchar_t ch, OutputIt out) -> OutputIt {
  *out++ = ch;
  return out;
 }
@@ -69,7 +63,7 @@ template <typename T> class is_map {
  template <typename> static void check(...);

 public:
-#ifdef FMT_FORMAT_MAP_AS_LIST
+#ifdef FMT_FORMAT_MAP_AS_LIST  // DEPRECATED!
  static constexpr const bool value = false;
 #else
  static constexpr const bool value =
@@ -82,7 +76,7 @@ template <typename T> class is_set {
  template <typename> static void check(...);

 public:
-#ifdef FMT_FORMAT_SET_AS_LIST
+#ifdef FMT_FORMAT_SET_AS_LIST  // DEPRECATED!
  static constexpr const bool value = false;
 #else
  static constexpr const bool value =
@@ -157,8 +151,9 @@ template <typename T>
 struct has_mutable_begin_end<
    T, void_t<decltype(detail::range_begin(std::declval<T>())),
              decltype(detail::range_end(std::declval<T>())),
-              enable_if_t<std::is_copy_constructible<T>::value>>>
-    : std::true_type {};
+              // the extra int here is because older versions of MSVC don't
+              // SFINAE properly unless there are distinct types
+              int>> : std::true_type {};

 template <typename T>
 struct is_range_<T, void>
@@ -188,7 +183,7 @@ template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 template <typename T, T... N> struct integer_sequence {
  using value_type = T;

-  static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
+  static FMT_CONSTEXPR auto size() -> size_t { return sizeof...(N); }
 };

 template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
@@ -211,41 +206,61 @@ class is_tuple_formattable_ {
  static constexpr const bool value = false;
 };
 template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
-  template <std::size_t... I>
-  static std::true_type check2(index_sequence<I...>,
-                               integer_sequence<bool, (I == I)...>);
-  static std::false_type check2(...);
-  template <std::size_t... I>
-  static decltype(check2(
-      index_sequence<I...>{},
-      integer_sequence<
-          bool, (is_formattable<typename std::tuple_element<I, T>::type,
-                                C>::value)...>{})) check(index_sequence<I...>);
+  template <std::size_t... Is>
+  static auto check2(index_sequence<Is...>,
+                     integer_sequence<bool, (Is == Is)...>) -> std::true_type;
+  static auto check2(...) -> std::false_type;
+  template <std::size_t... Is>
+  static auto check(index_sequence<Is...>) -> decltype(check2(
+      index_sequence<Is...>{},
+      integer_sequence<bool,
+                       (is_formattable<typename std::tuple_element<Is, T>::type,
+                                       C>::value)...>{}));

 public:
  static constexpr const bool value =
      decltype(check(tuple_index_sequence<T>{}))::value;
 };

-template <class Tuple, class F, size_t... Is>
-void for_each(index_sequence<Is...>, Tuple&& tup, F&& f) noexcept {
+template <typename Tuple, typename F, size_t... Is>
+FMT_CONSTEXPR void for_each(index_sequence<Is...>, Tuple&& t, F&& f) {
  using std::get;
-  // using free function get<I>(T) now.
-  const int _[] = {0, ((void)f(get<Is>(tup)), 0)...};
-  (void)_;  // blocks warnings
+  // Using a free function get<Is>(Tuple) now.
+  const int unused[] = {0, ((void)f(get<Is>(t)), 0)...};
+  ignore_unused(unused);
 }

-template <class T>
-FMT_CONSTEXPR make_index_sequence<std::tuple_size<T>::value> get_indexes(
-    T const&) {
-  return {};
+template <typename Tuple, typename F>
+FMT_CONSTEXPR void for_each(Tuple&& t, F&& f) {
+  for_each(tuple_index_sequence<remove_cvref_t<Tuple>>(),
+           std::forward<Tuple>(t), std::forward<F>(f));
 }

-template <class Tuple, class F> void for_each(Tuple&& tup, F&& f) {
-  const auto indexes = get_indexes(tup);
-  for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
+template <typename Tuple1, typename Tuple2, typename F, size_t... Is>
+void for_each2(index_sequence<Is...>, Tuple1&& t1, Tuple2&& t2, F&& f) {
+  using std::get;
+  const int unused[] = {0, ((void)f(get<Is>(t1), get<Is>(t2)), 0)...};
+  ignore_unused(unused);
 }

+template <typename Tuple1, typename Tuple2, typename F>
+void for_each2(Tuple1&& t1, Tuple2&& t2, F&& f) {
+  for_each2(tuple_index_sequence<remove_cvref_t<Tuple1>>(),
+            std::forward<Tuple1>(t1), std::forward<Tuple2>(t2),
+            std::forward<F>(f));
+}
+
+namespace tuple {
+// Workaround a bug in MSVC 2019 (v140).
+template <typename Char, typename... T>
+using result_t = std::tuple<formatter<remove_cvref_t<T>, Char>...>;
+
+using std::get;
+template <typename Tuple, typename Char, std::size_t... Is>
+auto get_formatters(index_sequence<Is...>)
+    -> result_t<Char, decltype(get<Is>(std::declval<Tuple>()))...>;
+}  // namespace tuple
+
 #if FMT_MSC_VERSION && FMT_MSC_VERSION < 1920
 // Older MSVC doesn't get the reference type correctly for arrays.
 template <typename R> struct range_reference_type_impl {
@@ -269,45 +284,37 @@ using range_reference_type =
 template <typename Range>
 using uncvref_type = remove_cvref_t<range_reference_type<Range>>;

-template <typename Range>
-using uncvref_first_type = remove_cvref_t<
-    decltype(std::declval<range_reference_type<Range>>().first)>;
-
-template <typename Range>
-using uncvref_second_type = remove_cvref_t<
-    decltype(std::declval<range_reference_type<Range>>().second)>;
-
-template <typename OutputIt> OutputIt write_delimiter(OutputIt out) {
-  *out++ = ',';
-  *out++ = ' ';
-  return out;
+template <typename Formatter>
+FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
+    -> decltype(f.set_debug_format(set)) {
+  f.set_debug_format(set);
 }
+template <typename Formatter>
+FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}

-template <typename Char, typename OutputIt>
-auto write_range_entry(OutputIt out, basic_string_view<Char> str) -> OutputIt {
-  return write_escaped_string(out, str);
-}
+// These are not generic lambdas for compatibility with C++11.
+template <typename ParseContext> struct parse_empty_specs {
+  template <typename Formatter> FMT_CONSTEXPR void operator()(Formatter& f) {
+    f.parse(ctx);
+    detail::maybe_set_debug_format(f, true);
+  }
+  ParseContext& ctx;
+};
+template <typename FormatContext> struct format_tuple_element {
+  using char_type = typename FormatContext::char_type;

-template <typename Char, typename OutputIt, typename T,
-          FMT_ENABLE_IF(std::is_convertible<T, std_string_view<char>>::value)>
-inline auto write_range_entry(OutputIt out, const T& str) -> OutputIt {
-  auto sv = std_string_view<Char>(str);
-  return write_range_entry<Char>(out, basic_string_view<Char>(sv));
-}
+  template <typename T>
+  void operator()(const formatter<T, char_type>& f, const T& v) {
+    if (i > 0)
+      ctx.advance_to(detail::copy_str<char_type>(separator, ctx.out()));
+    ctx.advance_to(f.format(v, ctx));
+    ++i;
+  }

-template <typename Char, typename OutputIt, typename Arg,
-          FMT_ENABLE_IF(std::is_same<Arg, Char>::value)>
-OutputIt write_range_entry(OutputIt out, const Arg v) {
-  return write_escaped_char(out, v);
-}
-
-template <
-    typename Char, typename OutputIt, typename Arg,
-    FMT_ENABLE_IF(!is_std_string_like<typename std::decay<Arg>::type>::value &&
-                  !std::is_same<Arg, Char>::value)>
-OutputIt write_range_entry(OutputIt out, const Arg& v) {
-  return write<Char>(out, v);
-}
+  int i;
+  FormatContext& ctx;
+  basic_string_view<char_type> separator;
+};

 }  // namespace detail

@@ -321,45 +328,58 @@ template <typename T, typename C> struct is_tuple_formattable {
      detail::is_tuple_formattable_<T, C>::value;
 };

-template <typename TupleT, typename Char>
-struct formatter<TupleT, Char,
-                 enable_if_t<fmt::is_tuple_like<TupleT>::value &&
-                             fmt::is_tuple_formattable<TupleT, Char>::value>> {
+template <typename Tuple, typename Char>
+struct formatter<Tuple, Char,
+                 enable_if_t<fmt::is_tuple_like<Tuple>::value &&
+                             fmt::is_tuple_formattable<Tuple, Char>::value>> {
 private:
-  // C++11 generic lambda for format().
-  template <typename FormatContext> struct format_each {
-    template <typename T> void operator()(const T& v) {
-      if (i > 0) out = detail::write_delimiter(out);
-      out = detail::write_range_entry<Char>(out, v);
-      ++i;
-    }
-    int i;
-    typename FormatContext::iterator& out;
-  };
+  decltype(detail::tuple::get_formatters<Tuple, Char>(
+      detail::tuple_index_sequence<Tuple>())) formatters_;
+
+  basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
+  basic_string_view<Char> opening_bracket_ =
+      detail::string_literal<Char, '('>{};
+  basic_string_view<Char> closing_bracket_ =
+      detail::string_literal<Char, ')'>{};

 public:
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
+  FMT_CONSTEXPR formatter() {}
+
+  FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
+    separator_ = sep;
  }

-  template <typename FormatContext = format_context>
-  auto format(const TupleT& values, FormatContext& ctx) const
+  FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
+                                  basic_string_view<Char> close) {
+    opening_bracket_ = open;
+    closing_bracket_ = close;
+  }
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    auto it = ctx.begin();
+    if (it != ctx.end() && *it != '}')
+      FMT_THROW(format_error("invalid format specifier"));
+    detail::for_each(formatters_, detail::parse_empty_specs<ParseContext>{ctx});
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(const Tuple& value, FormatContext& ctx) const
      -> decltype(ctx.out()) {
-    auto out = ctx.out();
-    *out++ = '(';
-    detail::for_each(values, format_each<FormatContext>{0, out});
-    *out++ = ')';
-    return out;
+    ctx.advance_to(detail::copy_str<Char>(opening_bracket_, ctx.out()));
+    detail::for_each2(
+        formatters_, value,
+        detail::format_tuple_element<FormatContext>{0, ctx, separator_});
+    return detail::copy_str<Char>(closing_bracket_, ctx.out());
  }
 };

 template <typename T, typename Char> struct is_range {
  static constexpr const bool value =
      detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
-      !detail::is_map<T>::value &&
      !std::is_convertible<T, std::basic_string<Char>>::value &&
-      !std::is_constructible<detail::std_string_view<Char>, T>::value;
+      !std::is_convertible<T, detail::std_string_view<Char>>::value;
 };

 namespace detail {
@@ -380,126 +400,178 @@ template <typename Context> struct range_mapper {
 };

 template <typename Char, typename Element>
-using range_formatter_type = conditional_t<
-    is_formattable<Element, Char>::value,
+using range_formatter_type =
    formatter<remove_cvref_t<decltype(range_mapper<buffer_context<Char>>{}.map(
                  std::declval<Element>()))>,
-              Char>,
-    fallback_formatter<Element, Char>>;
+              Char>;

 template <typename R>
 using maybe_const_range =
    conditional_t<has_const_begin_end<R>::value, const R, R>;
+
+// Workaround a bug in MSVC 2015 and earlier.
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
+template <typename R, typename Char>
+struct is_formattable_delayed
+    : is_formattable<uncvref_type<maybe_const_range<R>>, Char> {};
+#endif
 }  // namespace detail

-template <typename R, typename Char>
-struct formatter<
-    R, Char,
-    enable_if_t<
-        conjunction<fmt::is_range<R, Char>
-// Workaround a bug in MSVC 2017 and earlier.
-#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920
-        ,
-        disjunction<
-          is_formattable<detail::uncvref_type<detail::maybe_const_range<R>>,
-                         Char>,
-          detail::has_fallback_formatter<
-             detail::uncvref_type<detail::maybe_const_range<R>>, Char>
-        >
-#endif
-        >::value
-        >> {
+template <typename...> struct conjunction : std::true_type {};
+template <typename P> struct conjunction<P> : P {};
+template <typename P1, typename... Pn>
+struct conjunction<P1, Pn...>
+    : conditional_t<bool(P1::value), conjunction<Pn...>, P1> {};

-  using range_type = detail::maybe_const_range<R>;
-  using formatter_type =
-      detail::range_formatter_type<Char, detail::uncvref_type<range_type>>;
-  formatter_type underlying_;
-  bool custom_specs_ = false;
+template <typename T, typename Char, typename Enable = void>
+struct range_formatter;
+
+template <typename T, typename Char>
+struct range_formatter<
+    T, Char,
+    enable_if_t<conjunction<std::is_same<T, remove_cvref_t<T>>,
+                            is_formattable<T, Char>>::value>> {
+ private:
+  detail::range_formatter_type<Char, T> underlying_;
+  basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
+  basic_string_view<Char> opening_bracket_ =
+      detail::string_literal<Char, '['>{};
+  basic_string_view<Char> closing_bracket_ =
+      detail::string_literal<Char, ']'>{};
+
+ public:
+  FMT_CONSTEXPR range_formatter() {}
+
+  FMT_CONSTEXPR auto underlying() -> detail::range_formatter_type<Char, T>& {
+    return underlying_;
+  }
+
+  FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
+    separator_ = sep;
+  }
+
+  FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
+                                  basic_string_view<Char> close) {
+    opening_bracket_ = open;
+    closing_bracket_ = close;
+  }

  template <typename ParseContext>
  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
    auto it = ctx.begin();
    auto end = ctx.end();
-    if (it == end || *it == '}') return it;

-    if (*it != ':')
-      FMT_THROW(format_error("no top-level range formatters supported"));
+    if (it != end && *it == 'n') {
+      set_brackets({}, {});
+      ++it;
+    }
+
+    if (it != end && *it != '}') {
+      if (*it != ':') FMT_THROW(format_error("invalid format specifier"));
+      ++it;
+    } else {
+      detail::maybe_set_debug_format(underlying_, true);
+    }

-    custom_specs_ = true;
-    ++it;
    ctx.advance_to(it);
    return underlying_.parse(ctx);
  }

+  template <typename R, typename FormatContext>
+  auto format(R&& range, FormatContext& ctx) const -> decltype(ctx.out()) {
+    detail::range_mapper<buffer_context<Char>> mapper;
+    auto out = ctx.out();
+    out = detail::copy_str<Char>(opening_bracket_, out);
+    int i = 0;
+    auto it = detail::range_begin(range);
+    auto end = detail::range_end(range);
+    for (; it != end; ++it) {
+      if (i > 0) out = detail::copy_str<Char>(separator_, out);
+      ctx.advance_to(out);
+      auto&& item = *it;
+      out = underlying_.format(mapper.map(item), ctx);
+      ++i;
+    }
+    out = detail::copy_str<Char>(closing_bracket_, out);
+    return out;
+  }
+};
+
+enum class range_format { disabled, map, set, sequence, string, debug_string };
+
+namespace detail {
+template <typename T>
+struct range_format_kind_
+    : std::integral_constant<range_format,
+                             std::is_same<uncvref_type<T>, T>::value
+                                 ? range_format::disabled
+                             : is_map<T>::value ? range_format::map
+                             : is_set<T>::value ? range_format::set
+                                                : range_format::sequence> {};
+
+template <range_format K, typename R, typename Char, typename Enable = void>
+struct range_default_formatter;
+
+template <range_format K>
+using range_format_constant = std::integral_constant<range_format, K>;
+
+template <range_format K, typename R, typename Char>
+struct range_default_formatter<
+    K, R, Char,
+    enable_if_t<(K == range_format::sequence || K == range_format::map ||
+                 K == range_format::set)>> {
+  using range_type = detail::maybe_const_range<R>;
+  range_formatter<detail::uncvref_type<range_type>, Char> underlying_;
+
+  FMT_CONSTEXPR range_default_formatter() { init(range_format_constant<K>()); }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::set>) {
+    underlying_.set_brackets(detail::string_literal<Char, '{'>{},
+                             detail::string_literal<Char, '}'>{});
+  }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::map>) {
+    underlying_.set_brackets(detail::string_literal<Char, '{'>{},
+                             detail::string_literal<Char, '}'>{});
+    underlying_.underlying().set_brackets({}, {});
+    underlying_.underlying().set_separator(
+        detail::string_literal<Char, ':', ' '>{});
+  }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::sequence>) {}
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return underlying_.parse(ctx);
+  }
+
  template <typename FormatContext>
  auto format(range_type& range, FormatContext& ctx) const
      -> decltype(ctx.out()) {
-    Char prefix = detail::is_set<R>::value ? '{' : '[';
-    Char postfix = detail::is_set<R>::value ? '}' : ']';
-    detail::range_mapper<buffer_context<Char>> mapper;
-    auto out = ctx.out();
-    *out++ = prefix;
-    int i = 0;
-    auto it = detail::range_begin(range);
-    auto end = detail::range_end(range);
-    for (; it != end; ++it) {
-      if (i > 0) out = detail::write_delimiter(out);
-      if (custom_specs_) {
-        ctx.advance_to(out);
-        out = underlying_.format(mapper.map(*it), ctx);
-      } else {
-        out = detail::write_range_entry<Char>(out, *it);
-      }
-      ++i;
-    }
-    *out++ = postfix;
-    return out;
+    return underlying_.format(range, ctx);
  }
 };
+}  // namespace detail

-template <typename T, typename Char>
+template <typename T, typename Char, typename Enable = void>
+struct range_format_kind
+    : conditional_t<
+          is_range<T, Char>::value, detail::range_format_kind_<T>,
+          std::integral_constant<range_format, range_format::disabled>> {};
+
+template <typename R, typename Char>
 struct formatter<
-    T, Char,
-    enable_if_t<conjunction<detail::is_map<T>
-// Workaround a bug in MSVC 2017 and earlier.
-#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920
-        ,
-        disjunction<
-          is_formattable<detail::uncvref_first_type<T>, Char>,
-          detail::has_fallback_formatter<detail::uncvref_first_type<T>, Char>
-        >,
-        disjunction<
-          is_formattable<detail::uncvref_second_type<T>, Char>,
-          detail::has_fallback_formatter<detail::uncvref_second_type<T>, Char>
-        >
+    R, Char,
+    enable_if_t<conjunction<bool_constant<range_format_kind<R, Char>::value !=
+                                          range_format::disabled>
+// Workaround a bug in MSVC 2015 and earlier.
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
+                            ,
+                            detail::is_formattable_delayed<R, Char>
 #endif
-    >::value
-    >> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-
-  template <
-      typename FormatContext, typename U,
-      FMT_ENABLE_IF(
-          std::is_same<U, conditional_t<detail::has_const_begin_end<T>::value,
-                                        const T, T>>::value)>
-  auto format(U& map, FormatContext& ctx) const -> decltype(ctx.out()) {
-    auto out = ctx.out();
-    *out++ = '{';
-    int i = 0;
-    for (const auto& item : map) {
-      if (i > 0) out = detail::write_delimiter(out);
-      out = detail::write_range_entry<Char>(out, item.first);
-      *out++ = ':';
-      *out++ = ' ';
-      out = detail::write_range_entry<Char>(out, item.second);
-      ++i;
-    }
-    *out++ = '}';
-    return out;
-  }
+                            >::value>>
+    : detail::range_default_formatter<range_format_kind<R, Char>::value, R,
+                                      Char> {
 };

 template <typename Char, typename... T> struct tuple_join_view : detail::view {
@@ -510,9 +582,6 @@ template <typename Char, typename... T> struct tuple_join_view : detail::view {
      : tuple(t), sep{s} {}
 };

-template <typename Char, typename... T>
-using tuple_arg_join = tuple_join_view<Char, T...>;
-
 // Define FMT_TUPLE_JOIN_SPECIFIERS to enable experimental format specifiers
 // support in tuple_join. It is disabled by default because of issues with
 // the dynamic width and precision.
@@ -582,7 +651,45 @@ struct formatter<tuple_join_view<Char, T...>, Char> {
  }
 };

-FMT_MODULE_EXPORT_BEGIN
+namespace detail {
+// Check if T has an interface like a container adaptor (e.g. std::stack,
+// std::queue, std::priority_queue).
+template <typename T> class is_container_adaptor_like {
+  template <typename U> static auto check(U* p) -> typename U::container_type;
+  template <typename> static void check(...);
+
+ public:
+  static constexpr const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+};
+
+template <typename Container> struct all {
+  const Container& c;
+  auto begin() const -> typename Container::const_iterator { return c.begin(); }
+  auto end() const -> typename Container::const_iterator { return c.end(); }
+};
+}  // namespace detail
+
+template <typename T, typename Char>
+struct formatter<
+    T, Char,
+    enable_if_t<conjunction<detail::is_container_adaptor_like<T>,
+                            bool_constant<range_format_kind<T, Char>::value ==
+                                          range_format::disabled>>::value>>
+    : formatter<detail::all<typename T::container_type>, Char> {
+  using all = detail::all<typename T::container_type>;
+  template <typename FormatContext>
+  auto format(const T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
+    struct getter : T {
+      static auto get(const T& t) -> all {
+        return {t.*(&getter::c)};  // Access c through the derived class.
+      }
+    };
+    return formatter<all>::format(getter::get(t), ctx);
+  }
+};
+
+FMT_BEGIN_EXPORT

 /**
  \rst
@@ -625,7 +732,7 @@ auto join(std::initializer_list<T> list, string_view sep)
  return join(std::begin(list), std::end(list), sep);
 }

-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_RANGES_H_
@@ -8,10 +8,18 @@
 #ifndef FMT_STD_H_
 #define FMT_STD_H_

+#include <atomic>
+#include <bitset>
+#include <cstdlib>
+#include <exception>
+#include <memory>
 #include <thread>
 #include <type_traits>
+#include <typeinfo>
 #include <utility>
+#include <vector>

+#include "format.h"
 #include "ostream.h"

 #if FMT_HAS_INCLUDE(<version>)
@@ -25,99 +33,258 @@
 #  if FMT_HAS_INCLUDE(<variant>)
 #    include <variant>
 #  endif
+#  if FMT_HAS_INCLUDE(<optional>)
+#    include <optional>
+#  endif
 #endif

-#ifdef __cpp_lib_filesystem
+#if FMT_CPLUSPLUS > 201703L && FMT_HAS_INCLUDE(<source_location>)
+#  include <source_location>
+#endif
+
+// GCC 4 does not support FMT_HAS_INCLUDE.
+#if FMT_HAS_INCLUDE(<cxxabi.h>) || defined(__GLIBCXX__)
+#  include <cxxabi.h>
+// Android NDK with gabi++ library on some architectures does not implement
+// abi::__cxa_demangle().
+#  ifndef __GABIXX_CXXABI_H__
+#    define FMT_HAS_ABI_CXA_DEMANGLE
+#  endif
+#endif
+
+// Check if typeid is available.
+#ifndef FMT_USE_TYPEID
+// __RTTI is for EDG compilers. In MSVC typeid is available without RTTI.
+#  if defined(__GXX_RTTI) || FMT_HAS_FEATURE(cxx_rtti) || FMT_MSC_VERSION || \
+      defined(__INTEL_RTTI__) || defined(__RTTI)
+#    define FMT_USE_TYPEID 1
+#  else
+#    define FMT_USE_TYPEID 0
+#  endif
+#endif
+
+// For older Xcode versions, __cpp_lib_xxx flags are inaccurately defined.
+#ifndef FMT_CPP_LIB_FILESYSTEM
+#  ifdef __cpp_lib_filesystem
+#    define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
+#  else
+#    define FMT_CPP_LIB_FILESYSTEM 0
+#  endif
+#endif
+
+#ifndef FMT_CPP_LIB_VARIANT
+#  ifdef __cpp_lib_variant
+#    define FMT_CPP_LIB_VARIANT __cpp_lib_variant
+#  else
+#    define FMT_CPP_LIB_VARIANT 0
+#  endif
+#endif
+
+#if FMT_CPP_LIB_FILESYSTEM
 FMT_BEGIN_NAMESPACE

 namespace detail {

-template <typename Char>
+template <typename Char, typename PathChar>
+auto get_path_string(const std::filesystem::path& p,
+                     const std::basic_string<PathChar>& native) {
+  if constexpr (std::is_same_v<Char, char> && std::is_same_v<PathChar, wchar_t>)
+    return to_utf8<wchar_t>(native, to_utf8_error_policy::replace);
+  else
+    return p.string<Char>();
+}
+
+template <typename Char, typename PathChar>
 void write_escaped_path(basic_memory_buffer<Char>& quoted,
-                        const std::filesystem::path& p) {
-  write_escaped_string<Char>(std::back_inserter(quoted), p.string<Char>());
-}
-#  ifdef _WIN32
-template <>
-inline void write_escaped_path<char>(basic_memory_buffer<char>& quoted,
-                                     const std::filesystem::path& p) {
-  auto s = p.u8string();
-  write_escaped_string<char>(
-      std::back_inserter(quoted),
-      string_view(reinterpret_cast<const char*>(s.c_str()), s.size()));
-}
-#  endif
-template <>
-inline void write_escaped_path<std::filesystem::path::value_type>(
-    basic_memory_buffer<std::filesystem::path::value_type>& quoted,
-    const std::filesystem::path& p) {
-  write_escaped_string<std::filesystem::path::value_type>(
-      std::back_inserter(quoted), p.native());
+                        const std::filesystem::path& p,
+                        const std::basic_string<PathChar>& native) {
+  if constexpr (std::is_same_v<Char, char> &&
+                std::is_same_v<PathChar, wchar_t>) {
+    auto buf = basic_memory_buffer<wchar_t>();
+    write_escaped_string<wchar_t>(std::back_inserter(buf), native);
+    bool valid = to_utf8<wchar_t>::convert(quoted, {buf.data(), buf.size()});
+    FMT_ASSERT(valid, "invalid utf16");
+  } else if constexpr (std::is_same_v<Char, PathChar>) {
+    write_escaped_string<std::filesystem::path::value_type>(
+        std::back_inserter(quoted), native);
+  } else {
+    write_escaped_string<Char>(std::back_inserter(quoted), p.string<Char>());
+  }
 }

 }  // namespace detail

-#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920
-// For MSVC 2017 and earlier using the partial specialization
-// would cause an ambiguity error, therefore we provide it only
-// conditionally.
-template <typename Char>
-struct formatter<std::filesystem::path, Char>
-    : formatter<basic_string_view<Char>> {
+FMT_EXPORT
+template <typename Char> struct formatter<std::filesystem::path, Char> {
+ private:
+  format_specs<Char> specs_;
+  detail::arg_ref<Char> width_ref_;
+  bool debug_ = false;
+  char path_type_ = 0;
+
+ public:
+  FMT_CONSTEXPR void set_debug_format(bool set = true) { debug_ = set; }
+
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end) return it;
+
+    it = detail::parse_align(it, end, specs_);
+    if (it == end) return it;
+
+    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
+    if (it != end && *it == '?') {
+      debug_ = true;
+      ++it;
+    }
+    if (it != end && (*it == 'g')) path_type_ = *it++;
+    return it;
+  }
+
  template <typename FormatContext>
-  auto format(const std::filesystem::path& p, FormatContext& ctx) const ->
-      typename FormatContext::iterator {
-    basic_memory_buffer<Char> quoted;
-    detail::write_escaped_path(quoted, p);
-    return formatter<basic_string_view<Char>>::format(
-        basic_string_view<Char>(quoted.data(), quoted.size()), ctx);
+  auto format(const std::filesystem::path& p, FormatContext& ctx) const {
+    auto specs = specs_;
+#  ifdef _WIN32
+    auto path_string = !path_type_ ? p.native() : p.generic_wstring();
+#  else
+    auto path_string = !path_type_ ? p.native() : p.generic_string();
+#  endif
+
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
+                                                       ctx);
+    if (!debug_) {
+      auto s = detail::get_path_string<Char>(p, path_string);
+      return detail::write(ctx.out(), basic_string_view<Char>(s), specs);
+    }
+    auto quoted = basic_memory_buffer<Char>();
+    detail::write_escaped_path(quoted, p, path_string);
+    return detail::write(ctx.out(),
+                         basic_string_view<Char>(quoted.data(), quoted.size()),
+                         specs);
  }
 };
-#endif
 FMT_END_NAMESPACE
-#endif
+#endif  // FMT_CPP_LIB_FILESYSTEM

 FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <std::size_t N, typename Char>
+struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
+ private:
+  // Functor because C++11 doesn't support generic lambdas.
+  struct writer {
+    const std::bitset<N>& bs;
+
+    template <typename OutputIt>
+    FMT_CONSTEXPR auto operator()(OutputIt out) -> OutputIt {
+      for (auto pos = N; pos > 0; --pos) {
+        out = detail::write<Char>(out, bs[pos - 1] ? Char('1') : Char('0'));
+      }
+
+      return out;
+    }
+  };
+
+ public:
+  template <typename FormatContext>
+  auto format(const std::bitset<N>& bs, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return write_padded(ctx, writer{bs});
+  }
+};
+
+FMT_EXPORT
 template <typename Char>
 struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
 FMT_END_NAMESPACE

-#ifdef __cpp_lib_variant
+#ifdef __cpp_lib_optional
 FMT_BEGIN_NAMESPACE
-template <typename Char> struct formatter<std::monostate, Char> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<std::optional<T>, Char,
+                 std::enable_if_t<is_formattable<T, Char>::value>> {
+ private:
+  formatter<T, Char> underlying_;
+  static constexpr basic_string_view<Char> optional =
+      detail::string_literal<Char, 'o', 'p', 't', 'i', 'o', 'n', 'a', 'l',
+                             '('>{};
+  static constexpr basic_string_view<Char> none =
+      detail::string_literal<Char, 'n', 'o', 'n', 'e'>{};
+
+  template <class U>
+  FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, bool set)
+      -> decltype(u.set_debug_format(set)) {
+    u.set_debug_format(set);
+  }
+
+  template <class U>
+  FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
+
+ public:
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+    maybe_set_debug_format(underlying_, true);
+    return underlying_.parse(ctx);
+  }
+
+  template <typename FormatContext>
+  auto format(const std::optional<T>& opt, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    if (!opt) return detail::write<Char>(ctx.out(), none);
+
+    auto out = ctx.out();
+    out = detail::write<Char>(out, optional);
+    ctx.advance_to(out);
+    out = underlying_.format(*opt, ctx);
+    return detail::write(out, ')');
+  }
+};
+FMT_END_NAMESPACE
+#endif  // __cpp_lib_optional
+
+#ifdef __cpp_lib_source_location
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <> struct formatter<std::source_location> {
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
    return ctx.begin();
  }

  template <typename FormatContext>
-  auto format(const std::monostate&, FormatContext& ctx) const
+  auto format(const std::source_location& loc, FormatContext& ctx) const
      -> decltype(ctx.out()) {
    auto out = ctx.out();
-    out = detail::write<Char>(out, "monostate");
+    out = detail::write(out, loc.file_name());
+    out = detail::write(out, ':');
+    out = detail::write<char>(out, loc.line());
+    out = detail::write(out, ':');
+    out = detail::write<char>(out, loc.column());
+    out = detail::write(out, ": ");
+    out = detail::write(out, loc.function_name());
    return out;
  }
 };
+FMT_END_NAMESPACE
+#endif

+#if FMT_CPP_LIB_VARIANT
+FMT_BEGIN_NAMESPACE
 namespace detail {

 template <typename T>
 using variant_index_sequence =
    std::make_index_sequence<std::variant_size<T>::value>;

-// variant_size and variant_alternative check.
-template <typename T, typename U = void>
-struct is_variant_like_ : std::false_type {};
-template <typename T>
-struct is_variant_like_<T, std::void_t<decltype(std::variant_size<T>::value)>>
-    : std::true_type {};
+template <typename> struct is_variant_like_ : std::false_type {};
+template <typename... Types>
+struct is_variant_like_<std::variant<Types...>> : std::true_type {};

-// formattable element check
+// formattable element check.
 template <typename T, typename C> class is_variant_formattable_ {
-  template <std::size_t... I>
+  template <std::size_t... Is>
  static std::conjunction<
-      is_formattable<std::variant_alternative_t<I, T>, C>...>
-      check(std::index_sequence<I...>);
+      is_formattable<std::variant_alternative_t<Is, T>, C>...>
+      check(std::index_sequence<Is...>);

 public:
  static constexpr const bool value =
@@ -145,6 +312,21 @@ template <typename T, typename C> struct is_variant_formattable {
      detail::is_variant_formattable_<T, C>::value;
 };

+FMT_EXPORT
+template <typename Char> struct formatter<std::monostate, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const std::monostate&, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return detail::write<Char>(ctx.out(), "monostate");
+  }
+};
+
+FMT_EXPORT
 template <typename Variant, typename Char>
 struct formatter<
    Variant, Char,
@@ -161,16 +343,195 @@ struct formatter<
    auto out = ctx.out();

    out = detail::write<Char>(out, "variant(");
-    std::visit(
-        [&](const auto& v) {
-          out = detail::write_variant_alternative<Char>(out, v);
-        },
-        value);
+    FMT_TRY {
+      std::visit(
+          [&](const auto& v) {
+            out = detail::write_variant_alternative<Char>(out, v);
+          },
+          value);
+    }
+    FMT_CATCH(const std::bad_variant_access&) {
+      detail::write<Char>(out, "valueless by exception");
+    }
    *out++ = ')';
    return out;
  }
 };
 FMT_END_NAMESPACE
+#endif  // FMT_CPP_LIB_VARIANT
+
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <typename Char> struct formatter<std::error_code, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const std::error_code& ec, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    out = detail::write_bytes(out, ec.category().name(), format_specs<Char>());
+    out = detail::write<Char>(out, Char(':'));
+    out = detail::write<Char>(out, ec.value());
+    return out;
+  }
+};
+
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<
+    T, Char,  // DEPRECATED! Mixing code unit types.
+    typename std::enable_if<std::is_base_of<std::exception, T>::value>::type> {
+ private:
+  bool with_typename_ = false;
+
+ public:
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    auto it = ctx.begin();
+    auto end = ctx.end();
+    if (it == end || *it == '}') return it;
+    if (*it == 't') {
+      ++it;
+      with_typename_ = FMT_USE_TYPEID != 0;
+    }
+    return it;
+  }
+
+  template <typename OutputIt>
+  auto format(const std::exception& ex,
+              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+    format_specs<Char> spec;
+    auto out = ctx.out();
+    if (!with_typename_)
+      return detail::write_bytes(out, string_view(ex.what()), spec);
+
+#if FMT_USE_TYPEID
+    const std::type_info& ti = typeid(ex);
+#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
+    int status = 0;
+    std::size_t size = 0;
+    std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
+        abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &std::free);
+
+    string_view demangled_name_view;
+    if (demangled_name_ptr) {
+      demangled_name_view = demangled_name_ptr.get();
+
+      // Normalization of stdlib inline namespace names.
+      // libc++ inline namespaces.
+      //  std::__1::*       -> std::*
+      //  std::__1::__fs::* -> std::*
+      // libstdc++ inline namespaces.
+      //  std::__cxx11::*             -> std::*
+      //  std::filesystem::__cxx11::* -> std::filesystem::*
+      if (demangled_name_view.starts_with("std::")) {
+        char* begin = demangled_name_ptr.get();
+        char* to = begin + 5;  // std::
+        for (char *from = to, *end = begin + demangled_name_view.size();
+             from < end;) {
+          // This is safe, because demangled_name is NUL-terminated.
+          if (from[0] == '_' && from[1] == '_') {
+            char* next = from + 1;
+            while (next < end && *next != ':') next++;
+            if (next[0] == ':' && next[1] == ':') {
+              from = next + 2;
+              continue;
+            }
+          }
+          *to++ = *from++;
+        }
+        demangled_name_view = {begin, detail::to_unsigned(to - begin)};
+      }
+    } else {
+      demangled_name_view = string_view(ti.name());
+    }
+    out = detail::write_bytes(out, demangled_name_view, spec);
+#  elif FMT_MSC_VERSION
+    string_view demangled_name_view(ti.name());
+    if (demangled_name_view.starts_with("class "))
+      demangled_name_view.remove_prefix(6);
+    else if (demangled_name_view.starts_with("struct "))
+      demangled_name_view.remove_prefix(7);
+    out = detail::write_bytes(out, demangled_name_view, spec);
+#  else
+    out = detail::write_bytes(out, string_view(ti.name()), spec);
+#  endif
+    *out++ = ':';
+    *out++ = ' ';
+    return detail::write_bytes(out, string_view(ex.what()), spec);
+#endif
+  }
+};
+
+namespace detail {
+
+template <typename T, typename Enable = void>
+struct has_flip : std::false_type {};
+
+template <typename T>
+struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
+    : std::true_type {};
+
+template <typename T> struct is_bit_reference_like {
+  static constexpr const bool value =
+      std::is_convertible<T, bool>::value &&
+      std::is_nothrow_assignable<T, bool>::value && has_flip<T>::value;
+};
+
+#ifdef _LIBCPP_VERSION
+
+// Workaround for libc++ incompatibility with C++ standard.
+// According to the Standard, `bitset::operator[] const` returns bool.
+template <typename C>
+struct is_bit_reference_like<std::__bit_const_reference<C>> {
+  static constexpr const bool value = true;
+};
+
 #endif

+}  // namespace detail
+
+// We can't use std::vector<bool, Allocator>::reference and
+// std::bitset<N>::reference because the compiler can't deduce Allocator and N
+// in partial specialization.
+FMT_EXPORT
+template <typename BitRef, typename Char>
+struct formatter<BitRef, Char,
+                 enable_if_t<detail::is_bit_reference_like<BitRef>::value>>
+    : formatter<bool, Char> {
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const BitRef& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<bool, Char>::format(v, ctx);
+  }
+};
+
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<std::atomic<T>, Char,
+                 enable_if_t<is_formattable<T, Char>::value>>
+    : formatter<T, Char> {
+  template <typename FormatContext>
+  auto format(const std::atomic<T>& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<T, Char>::format(v.load(), ctx);
+  }
+};
+
+#ifdef __cpp_lib_atomic_flag_test
+FMT_EXPORT
+template <typename Char>
+struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
+  template <typename FormatContext>
+  auto format(const std::atomic_flag& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<bool, Char>::format(v.test(), ctx);
+  }
+};
+#endif  // __cpp_lib_atomic_flag_test
+
+FMT_END_NAMESPACE
 #endif  // FMT_STD_H_
@@ -9,17 +9,35 @@
 #define FMT_XCHAR_H_

 #include <cwchar>
-#include <tuple>

 #include "format.h"

+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+#  include <locale>
+#endif
+
 FMT_BEGIN_NAMESPACE
 namespace detail {
+
 template <typename T>
 using is_exotic_char = bool_constant<!std::is_same<T, char>::value>;
-}

-FMT_MODULE_EXPORT_BEGIN
+inline auto write_loc(std::back_insert_iterator<detail::buffer<wchar_t>> out,
+                      loc_value value, const format_specs<wchar_t>& specs,
+                      locale_ref loc) -> bool {
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+  auto& numpunct =
+      std::use_facet<std::numpunct<wchar_t>>(loc.get<std::locale>());
+  auto separator = std::wstring();
+  auto grouping = numpunct.grouping();
+  if (!grouping.empty()) separator = std::wstring(1, numpunct.thousands_sep());
+  return value.visit(loc_writer<wchar_t>{out, specs, separator, grouping, {}});
+#endif
+  return false;
+}
+}  // namespace detail
+
+FMT_BEGIN_EXPORT

 using wstring_view = basic_string_view<wchar_t>;
 using wformat_parse_context = basic_format_parse_context<wchar_t>;
@@ -30,9 +48,13 @@ using wmemory_buffer = basic_memory_buffer<wchar_t>;
 #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
 // Workaround broken conversion on older gcc.
 template <typename... Args> using wformat_string = wstring_view;
+inline auto runtime(wstring_view s) -> wstring_view { return s; }
 #else
 template <typename... Args>
 using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
+inline auto runtime(wstring_view s) -> runtime_format_string<wchar_t> {
+  return {{s}};
+}
 #endif

 template <> struct is_char<wchar_t> : std::true_type {};
@@ -40,15 +62,16 @@ template <> struct is_char<detail::char8_type> : std::true_type {};
 template <> struct is_char<char16_t> : std::true_type {};
 template <> struct is_char<char32_t> : std::true_type {};

-template <typename... Args>
-constexpr format_arg_store<wformat_context, Args...> make_wformat_args(
-    const Args&... args) {
+template <typename... T>
+constexpr auto make_wformat_args(const T&... args)
+    -> format_arg_store<wformat_context, T...> {
  return {args...};
 }

 inline namespace literals {
 #if FMT_USE_USER_DEFINED_LITERALS && !FMT_USE_NONTYPE_TEMPLATE_ARGS
-constexpr detail::udl_arg<wchar_t> operator"" _a(const wchar_t* s, size_t) {
+constexpr auto operator""_a(const wchar_t* s, size_t)
+    -> detail::udl_arg<wchar_t> {
  return {s};
 }
 #endif
@@ -77,26 +100,22 @@ template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
 auto vformat(basic_string_view<Char> format_str,
             basic_format_args<buffer_context<type_identity_t<Char>>> args)
    -> std::basic_string<Char> {
-  basic_memory_buffer<Char> buffer;
-  detail::vformat_to(buffer, format_str, args);
-  return to_string(buffer);
+  auto buf = basic_memory_buffer<Char>();
+  detail::vformat_to(buf, format_str, args);
+  return to_string(buf);
 }

-#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 409
-template <typename... Args>
-using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
-#endif
-
 template <typename... T>
 auto format(wformat_string<T...> fmt, T&&... args) -> std::wstring {
-  return vformat(fmt, fmt::make_wformat_args(args...));
+  return vformat(fmt::wstring_view(fmt), fmt::make_wformat_args(args...));
 }

 // Pass char_t as a default template parameter instead of using
 // std::basic_string<char_t<S>> to reduce the symbol size.
-template <typename S, typename... Args, typename Char = char_t<S>,
-          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
-auto format(const S& format_str, Args&&... args) -> std::basic_string<Char> {
+template <typename S, typename... T, typename Char = char_t<S>,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value &&
+                        !std::is_same<Char, wchar_t>::value)>
+auto format(const S& format_str, T&&... args) -> std::basic_string<Char> {
  return vformat(detail::to_string_view(format_str),
                 fmt::make_format_args<buffer_context<Char>>(args...));
 }
@@ -111,11 +130,10 @@ inline auto vformat(
  return detail::vformat(loc, detail::to_string_view(format_str), args);
 }

-template <typename Locale, typename S, typename... Args,
-          typename Char = char_t<S>,
+template <typename Locale, typename S, typename... T, typename Char = char_t<S>,
          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
                            detail::is_exotic_char<Char>::value)>
-inline auto format(const Locale& loc, const S& format_str, Args&&... args)
+inline auto format(const Locale& loc, const S& format_str, T&&... args)
    -> std::basic_string<Char> {
  return detail::vformat(loc, detail::to_string_view(format_str),
                         fmt::make_format_args<buffer_context<Char>>(args...));
@@ -129,14 +147,14 @@ auto vformat_to(OutputIt out, const S& format_str,
    -> OutputIt {
  auto&& buf = detail::get_buffer<Char>(out);
  detail::vformat_to(buf, detail::to_string_view(format_str), args);
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }

-template <typename OutputIt, typename S, typename... Args,
+template <typename OutputIt, typename S, typename... T,
          typename Char = char_t<S>,
          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                            detail::is_exotic_char<Char>::value)>
-inline auto format_to(OutputIt out, const S& fmt, Args&&... args) -> OutputIt {
+inline auto format_to(OutputIt out, const S& fmt, T&&... args) -> OutputIt {
  return vformat_to(out, detail::to_string_view(fmt),
                    fmt::make_format_args<buffer_context<Char>>(args...));
 }
@@ -152,18 +170,18 @@ inline auto vformat_to(
  auto&& buf = detail::get_buffer<Char>(out);
  vformat_to(buf, detail::to_string_view(format_str), args,
             detail::locale_ref(loc));
-  return detail::get_iterator(buf);
+  return detail::get_iterator(buf, out);
 }

-template <
-    typename OutputIt, typename Locale, typename S, typename... Args,
-    typename Char = char_t<S>,
-    bool enable = detail::is_output_iterator<OutputIt, Char>::value&&
-        detail::is_locale<Locale>::value&& detail::is_exotic_char<Char>::value>
+template <typename OutputIt, typename Locale, typename S, typename... T,
+          typename Char = char_t<S>,
+          bool enable = detail::is_output_iterator<OutputIt, Char>::value &&
+                        detail::is_locale<Locale>::value &&
+                        detail::is_exotic_char<Char>::value>
 inline auto format_to(OutputIt out, const Locale& loc, const S& format_str,
-                      Args&&... args) ->
+                      T&&... args) ->
    typename std::enable_if<enable, OutputIt>::type {
-  return vformat_to(out, loc, to_string_view(format_str),
+  return vformat_to(out, loc, detail::to_string_view(format_str),
                    fmt::make_format_args<buffer_context<Char>>(args...));
 }

@@ -174,36 +192,36 @@ inline auto vformat_to_n(
    OutputIt out, size_t n, basic_string_view<Char> format_str,
    basic_format_args<buffer_context<type_identity_t<Char>>> args)
    -> format_to_n_result<OutputIt> {
-  detail::iterator_buffer<OutputIt, Char, detail::fixed_buffer_traits> buf(out,
-                                                                           n);
+  using traits = detail::fixed_buffer_traits;
+  auto buf = detail::iterator_buffer<OutputIt, Char, traits>(out, n);
  detail::vformat_to(buf, format_str, args);
  return {buf.out(), buf.count()};
 }

-template <typename OutputIt, typename S, typename... Args,
+template <typename OutputIt, typename S, typename... T,
          typename Char = char_t<S>,
          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                            detail::is_exotic_char<Char>::value)>
-inline auto format_to_n(OutputIt out, size_t n, const S& fmt,
-                        const Args&... args) -> format_to_n_result<OutputIt> {
+inline auto format_to_n(OutputIt out, size_t n, const S& fmt, T&&... args)
+    -> format_to_n_result<OutputIt> {
  return vformat_to_n(out, n, detail::to_string_view(fmt),
                      fmt::make_format_args<buffer_context<Char>>(args...));
 }

-template <typename S, typename... Args, typename Char = char_t<S>,
+template <typename S, typename... T, typename Char = char_t<S>,
          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
-inline auto formatted_size(const S& fmt, Args&&... args) -> size_t {
-  detail::counting_buffer<Char> buf;
+inline auto formatted_size(const S& fmt, T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<Char>();
  detail::vformat_to(buf, detail::to_string_view(fmt),
                     fmt::make_format_args<buffer_context<Char>>(args...));
  return buf.count();
 }

 inline void vprint(std::FILE* f, wstring_view fmt, wformat_args args) {
-  wmemory_buffer buffer;
-  detail::vformat_to(buffer, fmt, args);
-  buffer.push_back(L'\0');
-  if (std::fputws(buffer.data(), f) == -1)
+  auto buf = wmemory_buffer();
+  detail::vformat_to(buf, fmt, args);
+  buf.push_back(L'\0');
+  if (std::fputws(buf.data(), f) == -1)
    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }

@@ -220,13 +238,22 @@ template <typename... T> void print(wformat_string<T...> fmt, T&&... args) {
  return vprint(wstring_view(fmt), fmt::make_wformat_args(args...));
 }

+template <typename... T>
+void println(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
+  return print(f, L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+template <typename... T> void println(wformat_string<T...> fmt, T&&... args) {
+  return print(L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
 /**
  Converts *value* to ``std::wstring`` using the default format for type *T*.
 */
 template <typename T> inline auto to_wstring(const T& value) -> std::wstring {
  return format(FMT_STRING(L"{}"), value);
 }
-FMT_MODULE_EXPORT_END
+FMT_END_EXPORT
 FMT_END_NAMESPACE

 #endif  // FMT_XCHAR_H_
@@ -1,49 +1,44 @@
 module;
-#ifndef __cpp_modules
-#  error Module not supported.
-#endif
-
-// put all implementation-provided headers into the global module fragment
-// to prevent attachment to this module
-#if !defined(_CRT_SECURE_NO_WARNINGS) && defined(_MSC_VER)
-#  define _CRT_SECURE_NO_WARNINGS
-#endif
-#if !defined(WIN32_LEAN_AND_MEAN) && defined(_WIN32)
-#  define WIN32_LEAN_AND_MEAN
-#endif

+// Put all implementation-provided headers into the global module fragment
+// to prevent attachment to this module.
 #include <algorithm>
-#include <cctype>
 #include <cerrno>
 #include <chrono>
 #include <climits>
-#include <clocale>
 #include <cmath>
-#include <cstdarg>
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <ctime>
-#include <cwchar>
 #include <exception>
+#include <filesystem>
+#include <fstream>
 #include <functional>
 #include <iterator>
 #include <limits>
 #include <locale>
 #include <memory>
+#include <optional>
 #include <ostream>
-#include <sstream>
 #include <stdexcept>
 #include <string>
 #include <string_view>
 #include <system_error>
+#include <thread>
 #include <type_traits>
+#include <typeinfo>
 #include <utility>
+#include <variant>
 #include <vector>
+#include <version>

-#if _MSC_VER
+#if __has_include(<cxxabi.h>)
+#  include <cxxabi.h>
+#endif
+#if defined(_MSC_VER) || defined(__MINGW32__)
 #  include <intrin.h>
 #endif
 #if defined __APPLE__ || defined(__FreeBSD__)
@@ -65,22 +60,31 @@ module;
 #  endif
 #endif
 #ifdef _WIN32
+#  if defined(__GLIBCXX__)
+#    include <ext/stdio_filebuf.h>
+#    include <ext/stdio_sync_filebuf.h>
+#  endif
+#  define WIN32_LEAN_AND_MEAN
 #  include <windows.h>
 #endif

 export module fmt;

-#define FMT_MODULE_EXPORT export
-#define FMT_MODULE_EXPORT_BEGIN export {
-#define FMT_MODULE_EXPORT_END }
-#define FMT_BEGIN_DETAIL_NAMESPACE \
-  }                                \
-  namespace detail {
-#define FMT_END_DETAIL_NAMESPACE \
-  }                              \
-  export {
-// all library-provided declarations and definitions
-// must be in the module purview to be exported
+#define FMT_EXPORT export
+#define FMT_BEGIN_EXPORT export {
+#define FMT_END_EXPORT }
+
+// If you define FMT_ATTACH_TO_GLOBAL_MODULE
+//  - all declarations are detached from module 'fmt'
+//  - the module behaves like a traditional static library, too
+//  - all library symbols are mangled traditionally
+//  - you can mix TUs with either importing or #including the {fmt} API
+#ifdef FMT_ATTACH_TO_GLOBAL_MODULE
+extern "C++" {
+#endif
+
+// All library-provided declarations and definitions must be in the module
+// purview to be exported.
 #include "fmt/args.h"
 #include "fmt/chrono.h"
 #include "fmt/color.h"
@@ -88,11 +92,16 @@ export module fmt;
 #include "fmt/format.h"
 #include "fmt/os.h"
 #include "fmt/printf.h"
+#include "fmt/std.h"
 #include "fmt/xchar.h"

+#ifdef FMT_ATTACH_TO_GLOBAL_MODULE
+}
+#endif
+
 // gcc doesn't yet implement private module fragments
 #if !FMT_GCC_VERSION
-module : private;
+module :private;
 #endif

 #include "format.cc"
@@ -28,12 +28,8 @@ template FMT_API auto decimal_point_impl(locale_ref) -> char;

 template FMT_API void buffer<char>::append(const char*, const char*);

-// DEPRECATED!
-// There is no correspondent extern template in format.h because of
-// incompatibility between clang and gcc (#2377).
 template FMT_API void vformat_to(buffer<char>&, string_view,
-                                 basic_format_args<FMT_BUFFER_CONTEXT(char)>,
-                                 locale_ref);
+                                 typename vformat_args<>::type, locale_ref);

 // Explicit instantiations for wchar_t.

@@ -18,6 +18,10 @@
 #  include <sys/stat.h>
 #  include <sys/types.h>

+#  ifdef _WRS_KERNEL    // VxWorks7 kernel
+#    include <ioLib.h>  // getpagesize
+#  endif
+
 #  ifndef _WIN32
 #    include <unistd.h>
 #  else
@@ -72,34 +76,6 @@ inline std::size_t convert_rwcount(std::size_t count) { return count; }
 FMT_BEGIN_NAMESPACE

 #ifdef _WIN32
-detail::utf16_to_utf8::utf16_to_utf8(basic_string_view<wchar_t> s) {
-  if (int error_code = convert(s)) {
-    FMT_THROW(windows_error(error_code,
-                            "cannot convert string from UTF-16 to UTF-8"));
-  }
-}
-
-int detail::utf16_to_utf8::convert(basic_string_view<wchar_t> s) {
-  if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
-  int s_size = static_cast<int>(s.size());
-  if (s_size == 0) {
-    // WideCharToMultiByte does not support zero length, handle separately.
-    buffer_.resize(1);
-    buffer_[0] = 0;
-    return 0;
-  }
-
-  int length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, nullptr, 0,
-                                   nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_.resize(length + 1);
-  length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, &buffer_[0],
-                               length, nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_[length] = 0;
-  return 0;
-}
-
 namespace detail {

 class system_message {
@@ -138,10 +114,10 @@ class utf8_system_category final : public std::error_category {
 public:
  const char* name() const noexcept override { return "system"; }
  std::string message(int error_code) const override {
-    system_message msg(error_code);
+    auto&& msg = system_message(error_code);
    if (msg) {
-      utf16_to_utf8 utf8_message;
-      if (utf8_message.convert(msg) == ERROR_SUCCESS) {
+      auto utf8_message = to_utf8<wchar_t>();
+      if (utf8_message.convert(msg)) {
        return utf8_message.str();
      }
    }
@@ -165,11 +141,12 @@ std::system_error vwindows_error(int err_code, string_view format_str,
 void detail::format_windows_error(detail::buffer<char>& out, int error_code,
                                  const char* message) noexcept {
  FMT_TRY {
-    system_message msg(error_code);
+    auto&& msg = system_message(error_code);
    if (msg) {
-      utf16_to_utf8 utf8_message;
-      if (utf8_message.convert(msg) == ERROR_SUCCESS) {
-        fmt::format_to(buffer_appender<char>(out), "{}: {}", message, utf8_message);
+      auto utf8_message = to_utf8<wchar_t>();
+      if (utf8_message.convert(msg)) {
+        fmt::format_to(appender(out), FMT_STRING("{}: {}"), message,
+                       string_view(utf8_message));
        return;
      }
    }
@@ -192,37 +169,51 @@ buffered_file::buffered_file(cstring_view filename, cstring_view mode) {
  FMT_RETRY_VAL(file_, FMT_SYSTEM(fopen(filename.c_str(), mode.c_str())),
                nullptr);
  if (!file_)
-    FMT_THROW(system_error(errno, "cannot open file {}", filename.c_str()));
+    FMT_THROW(system_error(errno, FMT_STRING("cannot open file {}"),
+                           filename.c_str()));
 }

 void buffered_file::close() {
  if (!file_) return;
  int result = FMT_SYSTEM(fclose(file_));
  file_ = nullptr;
-  if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }

 int buffered_file::descriptor() const {
+#if !defined(fileno)
  int fd = FMT_POSIX_CALL(fileno(file_));
-  if (fd == -1) FMT_THROW(system_error(errno, "cannot get file descriptor"));
+#elif defined(FMT_HAS_SYSTEM)
+  // fileno is a macro on OpenBSD so we cannot use FMT_POSIX_CALL.
+#  define FMT_DISABLE_MACRO
+  int fd = FMT_SYSTEM(fileno FMT_DISABLE_MACRO(file_));
+#else
+  int fd = fileno(file_);
+#endif
+  if (fd == -1)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get file descriptor")));
  return fd;
 }

 #if FMT_USE_FCNTL
-file::file(cstring_view path, int oflag) {
 #  ifdef _WIN32
-  using mode_t = int;
+using mode_t = int;
 #  endif
-  constexpr mode_t mode =
-      S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
+constexpr mode_t default_open_mode =
+    S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
+
+file::file(cstring_view path, int oflag) {
 #  if defined(_WIN32) && !defined(__MINGW32__)
  fd_ = -1;
-  FMT_POSIX_CALL(sopen_s(&fd_, path.c_str(), oflag, _SH_DENYNO, mode));
+  auto converted = detail::utf8_to_utf16(string_view(path.c_str()));
+  *this = file::open_windows_file(converted.c_str(), oflag);
 #  else
-  FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, mode)));
-#  endif
+  FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, default_open_mode)));
  if (fd_ == -1)
-    FMT_THROW(system_error(errno, "cannot open file {}", path.c_str()));
+    FMT_THROW(
+        system_error(errno, FMT_STRING("cannot open file {}"), path.c_str()));
+#  endif
 }

 file::~file() noexcept {
@@ -238,7 +229,8 @@ void file::close() {
  // See http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
  int result = FMT_POSIX_CALL(close(fd_));
  fd_ = -1;
-  if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }

 long long file::size() const {
@@ -260,7 +252,7 @@ long long file::size() const {
  using Stat = struct stat;
  Stat file_stat = Stat();
  if (FMT_POSIX_CALL(fstat(fd_, &file_stat)) == -1)
-    FMT_THROW(system_error(errno, "cannot get file attributes"));
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get file attributes")));
  static_assert(sizeof(long long) >= sizeof(file_stat.st_size),
                "return type of file::size is not large enough");
  return file_stat.st_size;
@@ -270,14 +262,16 @@ long long file::size() const {
 std::size_t file::read(void* buffer, std::size_t count) {
  rwresult result = 0;
  FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
-  if (result < 0) FMT_THROW(system_error(errno, "cannot read from file"));
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot read from file")));
  return detail::to_unsigned(result);
 }

 std::size_t file::write(const void* buffer, std::size_t count) {
  rwresult result = 0;
  FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
-  if (result < 0) FMT_THROW(system_error(errno, "cannot write to file"));
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
  return detail::to_unsigned(result);
 }

@@ -286,7 +280,8 @@ file file::dup(int fd) {
  // http://pubs.opengroup.org/onlinepubs/009695399/functions/dup.html
  int new_fd = FMT_POSIX_CALL(dup(fd));
  if (new_fd == -1)
-    FMT_THROW(system_error(errno, "cannot duplicate file descriptor {}", fd));
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot duplicate file descriptor {}"), fd));
  return file(new_fd);
 }

@@ -294,8 +289,9 @@ void file::dup2(int fd) {
  int result = 0;
  FMT_RETRY(result, FMT_POSIX_CALL(dup2(fd_, fd)));
  if (result == -1) {
-    FMT_THROW(system_error(errno, "cannot duplicate file descriptor {} to {}",
-                           fd_, fd));
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot duplicate file descriptor {} to {}"), fd_,
+        fd));
  }
 }

@@ -320,7 +316,8 @@ void file::pipe(file& read_end, file& write_end) {
  // http://pubs.opengroup.org/onlinepubs/009696799/functions/pipe.html
  int result = FMT_POSIX_CALL(pipe(fds));
 #  endif
-  if (result != 0) FMT_THROW(system_error(errno, "cannot create pipe"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot create pipe")));
  // The following assignments don't throw because read_fd and write_fd
  // are closed.
  read_end = file(fds[0]);
@@ -334,28 +331,72 @@ buffered_file file::fdopen(const char* mode) {
 #  else
  FILE* f = FMT_POSIX_CALL(fdopen(fd_, mode));
 #  endif
-  if (!f)
-    FMT_THROW(
-        system_error(errno, "cannot associate stream with file descriptor"));
+  if (!f) {
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot associate stream with file descriptor")));
+  }
  buffered_file bf(f);
  fd_ = -1;
  return bf;
 }

+#  if defined(_WIN32) && !defined(__MINGW32__)
+file file::open_windows_file(wcstring_view path, int oflag) {
+  int fd = -1;
+  auto err = _wsopen_s(&fd, path.c_str(), oflag, _SH_DENYNO, default_open_mode);
+  if (fd == -1) {
+    FMT_THROW(system_error(err, FMT_STRING("cannot open file {}"),
+                           detail::to_utf8<wchar_t>(path.c_str()).c_str()));
+  }
+  return file(fd);
+}
+#  endif
+
+#  if !defined(__MSDOS__)
 long getpagesize() {
-#  ifdef _WIN32
+#    ifdef _WIN32
  SYSTEM_INFO si;
  GetSystemInfo(&si);
  return si.dwPageSize;
-#  else
+#    else
+#      ifdef _WRS_KERNEL
+  long size = FMT_POSIX_CALL(getpagesize());
+#      else
  long size = FMT_POSIX_CALL(sysconf(_SC_PAGESIZE));
-  if (size < 0) FMT_THROW(system_error(errno, "cannot get memory page size"));
-  return size;
-#  endif
-}
+#      endif

-FMT_API void ostream::grow(size_t) {
+  if (size < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get memory page size")));
+  return size;
+#    endif
+}
+#  endif
+
+namespace detail {
+
+void file_buffer::grow(size_t) {
  if (this->size() == this->capacity()) flush();
 }
+
+file_buffer::file_buffer(cstring_view path,
+                         const detail::ostream_params& params)
+    : file_(path, params.oflag) {
+  set(new char[params.buffer_size], params.buffer_size);
+}
+
+file_buffer::file_buffer(file_buffer&& other)
+    : detail::buffer<char>(other.data(), other.size(), other.capacity()),
+      file_(std::move(other.file_)) {
+  other.clear();
+  other.set(nullptr, 0);
+}
+
+file_buffer::~file_buffer() {
+  flush();
+  delete[] data();
+}
+}  // namespace detail
+
+ostream::~ostream() = default;
 #endif  // FMT_USE_FCNTL
 FMT_END_NAMESPACE
@@ -1 +1 @@
-<manifest package="net.fmtlib" />
+<manifest package="dev.fmt" />
@@ -13,8 +13,8 @@ Vagrant.configure("2") do |config|
  config.vm.provision "shell", inline: <<-SHELL
    apt-get update
    apt-get install -y g++ make wget git
-    wget -q https://github.com/Kitware/CMake/releases/download/v3.14.4/cmake-3.14.4-Linux-x86_64.tar.gz
-    tar xzf cmake-3.14.4-Linux-x86_64.tar.gz
-    ln -s `pwd`/cmake-3.14.4-Linux-x86_64/bin/cmake /usr/local/bin
+    wget -q https://github.com/Kitware/CMake/releases/download/v3.26.0/cmake-3.26.0-Linux-x86_64.tar.gz
+    tar xzf cmake-3.26.0-Linux-x86_64.tar.gz
+    ln -s `pwd`/cmake-3.26.0-Linux-x86_64/bin/cmake /usr/local/bin
  SHELL
 end
@@ -1,43 +0,0 @@
-#!/usr/bin/env python
-# Build the project on AppVeyor.
-
-import os
-from subprocess import check_call
-
-build = os.environ['BUILD']
-config = os.environ['CONFIGURATION']
-platform = os.environ['PLATFORM']
-path = os.environ['PATH']
-image = os.environ['APPVEYOR_BUILD_WORKER_IMAGE']
-jobid = os.environ['APPVEYOR_JOB_ID']
-cmake_command = ['cmake', '-DFMT_PEDANTIC=ON', '-DCMAKE_BUILD_TYPE=' + config, '..']
-if build == 'mingw':
-    cmake_command.append('-GMinGW Makefiles')
-    build_command = ['mingw32-make', '-j4']
-    test_command = ['mingw32-make', 'test']
-    # Remove the path to Git bin directory from $PATH because it breaks
-    # MinGW config.
-    path = path.replace(r'C:\Program Files (x86)\Git\bin', '')
-    os.environ['PATH'] = r'C:\MinGW\bin;' + path
-else:
-    # Add MSBuild 14.0 to PATH as described in
-    # http://help.appveyor.com/discussions/problems/2229-v140-not-found-on-vs2105rc.
-    os.environ['PATH'] = r'C:\Program Files (x86)\MSBuild\15.0\Bin;' + path
-    if image == 'Visual Studio 2019':
-        generator = 'Visual Studio 16 2019'
-        if platform == 'x64':
-            cmake_command.extend(['-A', 'x64'])
-    else:
-        if image == 'Visual Studio 2015':
-            generator = 'Visual Studio 14 2015'
-        elif image == 'Visual Studio 2017':
-            generator = 'Visual Studio 15 2017'
-        if platform == 'x64':
-            generator += ' Win64'
-    cmake_command.append('-G' + generator)
-    build_command = ['cmake', '--build', '.', '--config', config, '--', '/m:4']
-    test_command = ['ctest', '-C', config]
-
-check_call(cmake_command)
-check_call(build_command)
-check_call(test_command)
@@ -1,31 +0,0 @@
-configuration:
-  - Debug
-  - Release
-
-clone_depth: 1
-
-image:
-  - Visual Studio 2015
-
-platform:
-  - x64
-
-environment:
-  CTEST_OUTPUT_ON_FAILURE: 1
-  MSVC_DEFAULT_OPTIONS: ON
-  BUILD: msvc
-
-before_build:
- - mkdir build
- - cd build
-
-build_script:
-  - python ../support/appveyor-build.py
-
-on_failure:
-  - appveyor PushArtifact Testing/Temporary/LastTest.log
-  - appveyor AddTest test
-
-# Uncomment this to debug AppVeyor failures.
-#on_finish:
-#  - ps: $blockRdp = $true; iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
@@ -1 +0,0 @@
-build --symlink_prefix=/ # Out of source build
@@ -1 +1 @@
-5.1.1
+6.1.2
@@ -11,8 +11,8 @@ cc_library(
        "include/fmt/color.h",
        "include/fmt/compile.h",
        "include/fmt/core.h",
-        "include/fmt/format-inl.h",
        "include/fmt/format.h",
+        "include/fmt/format-inl.h",
        "include/fmt/os.h",
        "include/fmt/ostream.h",
        "include/fmt/printf.h",
@@ -21,7 +21,7 @@ cc_library(
        "include/fmt/xchar.h",
    ],
    includes = [
-        "include",        
+        "include",
    ],
    strip_include_prefix = "include",
    visibility = ["//visibility:public"],
@@ -1,6 +1,6 @@
 # Bazel support

-To get [Bazel](https://bazel.build/) working with {fmt} you can copy the files `BUILD.bazel`, `WORKSPACE.bazel`, `.bazelrc`, and `.bazelversion` from this folder (`support/bazel`) to the root folder of this project. This way {fmt} gets bazelized and can be used with Bazel (e.g. doing a `bazel build //...` on {fmt}). 
+To get [Bazel](https://bazel.build/) working with {fmt} you can copy the files `BUILD.bazel`, `WORKSPACE.bazel`, and `.bazelversion` from this folder (`support/bazel`) to the root folder of this project. This way {fmt} gets bazelized and can be used with Bazel (e.g. doing a `bazel build //...` on {fmt}). 

 ## Using {fmt} as a dependency

@@ -37,7 +37,6 @@ git_repository(
    branch = "master",
    remote = "https://github.com/fmtlib/fmt",
    patch_cmds = [
-        "mv support/bazel/.bazelrc .bazelrc",
        "mv support/bazel/.bazelversion .bazelversion",
        "mv support/bazel/BUILD.bazel BUILD.bazel",
        "mv support/bazel/WORKSPACE.bazel WORKSPACE.bazel",
@@ -47,7 +46,6 @@ git_repository(
    # https://docs.bazel.build/versions/main/install-windows.html#installing-compilers-and-language-runtimes
    # Even if MSYS2 is installed the Windows related patch commands can still be used.
    patch_cmds_win = [
-        "Move-Item -Path support/bazel/.bazelrc -Destination .bazelrc",
        "Move-Item -Path support/bazel/.bazelversion -Destination .bazelversion",
        "Move-Item -Path support/bazel/BUILD.bazel -Destination BUILD.bazel",
        "Move-Item -Path support/bazel/WORKSPACE.bazel -Destination WORKSPACE.bazel",
@@ -55,7 +53,7 @@ git_repository(
 )
 ```

-In the *WORKSPACE* file, the {fmt} GitHub repository is fetched. Using the attribute `patch_cmds` the  files `BUILD.bazel`, `WORKSPACE.bazel`, `.bazelrc`, and `.bazelversion` are moved to the root of the {fmt} repository. This way the {fmt} repository is recognized as a bazelized workspace. 
+In the *WORKSPACE* file, the {fmt} GitHub repository is fetched. Using the attribute `patch_cmds` the  files `BUILD.bazel`, `WORKSPACE.bazel`, and `.bazelversion` are moved to the root of the {fmt} repository. This way the {fmt} repository is recognized as a bazelized workspace. 

 *BUILD.bazel*:

@@ -71,3 +69,6 @@ The *BUILD* file defines a binary named `Demo` that has a dependency to {fmt}.

 To execute the binary you can run `bazel run //:Demo`.

+# Using Bzlmod
+
+The [Bazel Central Registry](https://github.com/bazelbuild/bazel-central-registry/tree/main/modules/fmt) also provides support for {fmt}.
@@ -11,7 +11,7 @@ buildscript {
        // https://developer.android.com/studio/releases/gradle-plugin#updating-gradle
        //
        // Notice that 4.0.0 here is the version of [Android Gradle Plugin]
-        // Accroding to URL above you will need Gradle 6.1 or higher
+        // According to URL above you will need Gradle 6.1 or higher
        //
        classpath "com.android.tools.build:gradle:4.1.1"
    }
@@ -1,54 +0,0 @@
-# C++14 feature support detection
-
-include(CheckCXXCompilerFlag)
-function (fmt_check_cxx_compiler_flag flag result)
-  if (NOT MSVC)
-    check_cxx_compiler_flag("${flag}" ${result})
-  endif ()
-endfunction ()
-
-if (NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 11)
-endif()
-message(STATUS "CXX_STANDARD: ${CMAKE_CXX_STANDARD}")
-
-if (CMAKE_CXX_STANDARD EQUAL 20)
-  fmt_check_cxx_compiler_flag(-std=c++20 has_std_20_flag)
-  fmt_check_cxx_compiler_flag(-std=c++2a has_std_2a_flag)
-
-  if (has_std_20_flag)
-    set(CXX_STANDARD_FLAG -std=c++20)
-  elseif (has_std_2a_flag)
-    set(CXX_STANDARD_FLAG -std=c++2a)
-  endif ()
-
-elseif (CMAKE_CXX_STANDARD EQUAL 17)
-  fmt_check_cxx_compiler_flag(-std=c++17 has_std_17_flag)
-  fmt_check_cxx_compiler_flag(-std=c++1z has_std_1z_flag)
-
-  if (has_std_17_flag)
-    set(CXX_STANDARD_FLAG -std=c++17)
-  elseif (has_std_1z_flag)
-    set(CXX_STANDARD_FLAG -std=c++1z)
-  endif ()
-
-elseif (CMAKE_CXX_STANDARD EQUAL 14)
-  fmt_check_cxx_compiler_flag(-std=c++14 has_std_14_flag)
-  fmt_check_cxx_compiler_flag(-std=c++1y has_std_1y_flag)
-
-  if (has_std_14_flag)
-    set(CXX_STANDARD_FLAG -std=c++14)
-  elseif (has_std_1y_flag)
-    set(CXX_STANDARD_FLAG -std=c++1y)
-  endif ()
-
-elseif (CMAKE_CXX_STANDARD EQUAL 11)
-  fmt_check_cxx_compiler_flag(-std=c++11 has_std_11_flag)
-  fmt_check_cxx_compiler_flag(-std=c++0x has_std_0x_flag)
-
-  if (has_std_11_flag)
-    set(CXX_STANDARD_FLAG -std=c++11)
-  elseif (has_std_0x_flag)
-    set(CXX_STANDARD_FLAG -std=c++0x)
-  endif ()
-endif ()
@@ -12,7 +12,7 @@ obtained from https://github.com/settings/tokens.

 from __future__ import print_function
 import datetime, docopt, errno, fileinput, json, os
-import re, requests, shutil, sys, tempfile
+import re, requests, shutil, sys
 from contextlib import contextmanager
 from distutils.version import LooseVersion
 from subprocess import check_call
@@ -183,6 +183,12 @@ def update_site(env):
        with rewrite(index) as b:
            b.data = b.data.replace(
                'doc/latest/index.html#format-string-syntax', 'syntax.html')
+        # Fix issues in syntax.rst.
+        index = os.path.join(target_doc_dir, 'syntax.rst')
+        with rewrite(index) as b:
+            b.data = b.data.replace(
+                '..productionlist:: sf\n', '.. productionlist:: sf\n ')
+            b.data = b.data.replace('Examples:\n', 'Examples::\n')
        # Build the docs.
        html_dir = os.path.join(env.build_dir, 'html')
        if os.path.exists(html_dir):
@@ -223,12 +229,50 @@ def release(args):
    if not fmt_repo.update('-b', branch, fmt_repo_url):
        clean_checkout(fmt_repo, branch)

-    # Convert changelog from RST to GitHub-flavored Markdown and get the
-    # version.
-    changelog = 'ChangeLog.rst'
+    # Update the date in the changelog and extract the version and the first
+    # section content.
+    changelog = 'ChangeLog.md'
    changelog_path = os.path.join(fmt_repo.dir, changelog)
-    import rst2md
-    changes, version = rst2md.convert(changelog_path)
+    is_first_section = True
+    first_section = []
+    for i, line in enumerate(fileinput.input(changelog_path, inplace=True)):
+        if i == 0:
+            version = re.match(r'# (.*) - TBD', line).group(1)
+            line = '# {} - {}\n'.format(
+                version, datetime.date.today().isoformat())
+        elif not is_first_section:
+            pass
+        elif line.startswith('#'):
+            is_first_section = False
+        else:
+            first_section.append(line)
+        sys.stdout.write(line)
+    if first_section[0] == '\n':
+        first_section.pop(0)
+
+    changes = ''
+    code_block = False
+    stripped = False
+    for line in first_section:
+        if re.match(r'^\s*```', line):
+            code_block = not code_block
+            changes += line
+            stripped = False
+            continue
+        if code_block:
+            changes += line
+            continue
+        if line == '\n':
+            changes += line
+            if stripped:
+                changes += line
+                stripped = False
+            continue
+        if stripped:
+            line = ' ' + line.lstrip()
+        changes += line.rstrip()
+        stripped = True
+
    cmakelists = 'CMakeLists.txt'
    for line in fileinput.input(os.path.join(fmt_repo.dir, cmakelists),
                                inplace=True):
@@ -237,23 +281,11 @@ def release(args):
            line = prefix + version + ')\n'
        sys.stdout.write(line)

-    # Update the version in the changelog.
-    title_len = 0
-    for line in fileinput.input(changelog_path, inplace=True):
-        if line.startswith(version + ' - TBD'):
-            line = version + ' - ' + datetime.date.today().isoformat()
-            title_len = len(line)
-            line += '\n'
-        elif title_len:
-            line = '-' * title_len + '\n'
-            title_len = 0
-        sys.stdout.write(line)
-
    # Add the version to the build script.
    script = os.path.join('doc', 'build.py')
    script_path = os.path.join(fmt_repo.dir, script)
    for line in fileinput.input(script_path, inplace=True):
-      m = re.match(r'( *versions = )\[(.+)\]', line)
+      m = re.match(r'( *versions \+= )\[(.+)\]', line)
      if m:
        line = '{}[{}, \'{}\']\n'.format(m.group(1), m.group(2), version)
      sys.stdout.write(line)
@@ -1,159 +0,0 @@
-#!/usr/bin/env python
-# reStructuredText (RST) to GitHub-flavored Markdown converter
-
-import re, sys
-from docutils import core, nodes, writers
-
-
-def is_github_ref(node):
-    return re.match('https://github.com/.*/(issues|pull)/.*', node['refuri'])
-
-
-class Translator(nodes.NodeVisitor):
-    def __init__(self, document):
-        nodes.NodeVisitor.__init__(self, document)
-        self.output = ''
-        self.indent = 0
-        self.preserve_newlines = False
-
-    def write(self, text):
-        self.output += text.replace('\n', '\n' + ' ' * self.indent)
-
-    def visit_document(self, node):
-        pass
-
-    def depart_document(self, node):
-        pass
-
-    def visit_section(self, node):
-        pass
-
-    def depart_section(self, node):
-        # Skip all sections except the first one.
-        raise nodes.StopTraversal
-
-    def visit_title(self, node):
-        self.version = re.match(r'(\d+\.\d+\.\d+).*', node.children[0]).group(1)
-        raise nodes.SkipChildren
-
-    def visit_title_reference(self, node):
-        raise Exception(node)
-
-    def depart_title(self, node):
-        pass
-
-    def visit_Text(self, node):
-        if not self.preserve_newlines:
-            node = node.replace('\n', ' ')
-        self.write(node)
-
-    def depart_Text(self, node):
-        pass
-
-    def visit_bullet_list(self, node):
-        pass
-
-    def depart_bullet_list(self, node):
-        pass
-
-    def visit_list_item(self, node):
-        self.write('* ')
-        self.indent += 2
-
-    def depart_list_item(self, node):
-        self.indent -= 2
-        self.write('\n\n')
-
-    def visit_paragraph(self, node):
-        self.write('\n\n')
-
-    def depart_paragraph(self, node):
-        pass
-
-    def visit_reference(self, node):
-        if not is_github_ref(node):
-            self.write('[')
-
-    def depart_reference(self, node):
-        if not is_github_ref(node):
-            self.write('](' + node['refuri'] + ')')
-
-    def visit_target(self, node):
-        pass
-
-    def depart_target(self, node):
-        pass
-
-    def visit_literal(self, node):
-        self.write('`')
-
-    def depart_literal(self, node):
-        self.write('`')
-
-    def visit_literal_block(self, node):
-        self.write('\n\n```')
-        if 'c++' in node['classes']:
-            self.write('c++')
-        self.write('\n')
-        self.preserve_newlines = True
-
-    def depart_literal_block(self, node):
-        self.write('\n```\n')
-        self.preserve_newlines = False
-
-    def visit_inline(self, node):
-        pass
-
-    def depart_inline(self, node):
-        pass
-
-    def visit_image(self, node):
-        self.write('![](' + node['uri'] + ')')
-
-    def depart_image(self, node):
-        pass
-
-    def write_row(self, row, widths):
-        for i, entry in enumerate(row):
-            text = entry[0][0] if len(entry) > 0 else ''
-            if i != 0:
-                self.write('|')
-            self.write('{:{}}'.format(text, widths[i]))
-        self.write('\n')
-
-    def visit_table(self, node):
-        table = node.children[0]
-        colspecs = table[:-2]
-        thead = table[-2]
-        tbody = table[-1]
-        widths = [int(cs['colwidth']) for cs in colspecs]
-        sep = '|'.join(['-' * w for w in widths]) + '\n'
-        self.write('\n\n')
-        self.write_row(thead[0], widths)
-        self.write(sep)
-        for row in tbody:
-            self.write_row(row, widths)
-        raise nodes.SkipChildren
-
-    def depart_table(self, node):
-        pass
-
-class MDWriter(writers.Writer):
-    """GitHub-flavored markdown writer"""
-
-    supported = ('md',)
-    """Formats this writer supports."""
-
-    def translate(self):
-        translator = Translator(self.document)
-        self.document.walkabout(translator)
-        self.output = (translator.output, translator.version)
-
-
-def convert(rst_path):
-    """Converts RST file to Markdown."""
-    return core.publish_file(source_path=rst_path, writer=MDWriter())
-
-
-if __name__ == '__main__':
-    convert(sys.argv[1])
@@ -1,5 +1,7 @@
 add_subdirectory(gtest)

+include(CheckSymbolExists)
+
 set(TEST_MAIN_SRC test-main.cc gtest-extra.cc gtest-extra.h util.cc)
 add_library(test-main STATIC ${TEST_MAIN_SRC})
 target_include_directories(test-main PUBLIC
@@ -8,9 +10,6 @@ target_link_libraries(test-main gtest fmt)

 function(add_fmt_executable name)
  add_executable(${name} ${ARGN})
-  if (MINGW)
-    target_link_libraries(${name} -static-libgcc -static-libstdc++)
-  endif ()
  # (Wstringop-overflow) - [meta-bug] bogus/missing -Wstringop-overflow warnings
  #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88443
  # Bogus -Wstringop-overflow warning
@@ -19,6 +18,8 @@ function(add_fmt_executable name)
  #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95353
  if (CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND
      NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0)
+    target_compile_options(${name} PRIVATE -Wno-stringop-overflow)
+    # The linker flag is needed for LTO.
    target_link_libraries(${name} -Wno-stringop-overflow)
  endif ()
 endfunction()
@@ -36,7 +37,7 @@ function(add_fmt_test name)
      set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS} -Wno-weak-vtables)
    endif ()
  elseif (ADD_FMT_TEST_MODULE)
-    set(libs gtest test-module)
+    set(libs test-main test-module)
    set_source_files_properties(${name}.cc PROPERTIES OBJECT_DEPENDS test-module)
  else ()
    set(libs test-main fmt)
@@ -54,6 +55,10 @@ function(add_fmt_test name)
  add_test(NAME ${name} COMMAND ${name})
 endfunction()

+if (FMT_MODULE)
+  return ()
+endif ()
+
 add_fmt_test(args-test)
 add_fmt_test(assert-test)
 add_fmt_test(chrono-test)
@@ -76,7 +81,13 @@ if (MSVC)
 endif()
 add_fmt_test(printf-test)
 add_fmt_test(ranges-test ranges-odr-test.cc)
+
 add_fmt_test(scan-test)
+check_symbol_exists(strptime "time.h" HAVE_STRPTIME)
+if (HAVE_STRPTIME)
+  target_compile_definitions(scan-test PRIVATE FMT_HAVE_STRPTIME)
+endif ()
+
 add_fmt_test(std-test)
 try_compile(compile_result_unused
            ${CMAKE_CURRENT_BINARY_DIR}
@@ -95,13 +106,13 @@ add_fmt_test(enforce-checks-test)
 target_compile_definitions(enforce-checks-test PRIVATE
                           -DFMT_ENFORCE_COMPILE_STRING)

-if (FMT_CAN_MODULE)
+if (FMT_MODULE)
  # The tests need {fmt} to be compiled as traditional library
  # because of visibility of implementation details.
  # If module support is present the module tests require a
  # test-only module to be built from {fmt}
  add_library(test-module OBJECT ${CMAKE_SOURCE_DIR}/src/fmt.cc)
-  target_compile_features(test-module PUBLIC ${FMT_REQUIRED_FEATURES})
+  target_compile_features(test-module PUBLIC cxx_std_11)
  target_include_directories(test-module PUBLIC
    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>)
  enable_module(test-module)
@@ -164,7 +175,12 @@ if (FMT_PEDANTIC)
 endif ()

 # These tests are disabled on Windows because they take too long.
-if (FMT_PEDANTIC AND NOT WIN32)
+# They are disabled on GCC < 4.9 because it can not parse UDLs without
+# a space after `operator""` but that is an incorrect syntax for any more
+# modern compiler.
+if (FMT_PEDANTIC AND NOT WIN32 AND NOT (
+    CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND
+    CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9))
  # Test if incorrect API usages produce compilation error.
  add_test(compile-error-test ${CMAKE_CTEST_COMMAND}
    --build-and-test
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1...3.18)
+cmake_minimum_required(VERSION 3.8...3.25)

 project(fmt-test CXX)

@@ -44,7 +44,7 @@ template <> struct formatter<custom_type> {

  template <typename FormatContext>
  auto format(const custom_type& p, FormatContext& ctx) -> decltype(ctx.out()) {
-    return format_to(ctx.out(), "cust={}", p.i);
+    return fmt::format_to(ctx.out(), "cust={}", p.i);
  }
 };
 FMT_END_NAMESPACE
@@ -7,6 +7,7 @@

 #include "fmt/chrono.h"

+#include <algorithm>
 #include <ctime>
 #include <vector>

@@ -14,9 +15,24 @@
 #include "util.h"         // get_locale

 using fmt::runtime;
-
 using testing::Contains;

+template <typename Duration>
+using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;
+
+#if defined(__MINGW32__) && !defined(_UCRT)
+// Only C89 conversion specifiers when using MSVCRT instead of UCRT
+#  define FMT_HAS_C99_STRFTIME 0
+#else
+#  define FMT_HAS_C99_STRFTIME 1
+#endif
+
+#if defined(__cpp_lib_chrono) && __cpp_lib_chrono >= 201907L
+using days = std::chrono::days;
+#else
+using days = std::chrono::duration<std::chrono::hours::rep, std::ratio<86400>>;
+#endif
+
 auto make_tm() -> std::tm {
  auto time = std::tm();
  time.tm_mday = 1;
@@ -121,6 +137,13 @@ TEST(chrono_test, format_tm) {
      make_tm(2000, 1, 2, 12, 14, 16),    // W52
      make_tm(2000, 1, 3, 12, 14, 16)     // W1
  };
+
+#if !FMT_HAS_C99_STRFTIME
+  GTEST_SKIP() << "Skip the rest of this test because it relies on strftime() "
+                  "conforming to C99, but on this platform, MINGW + MSVCRT, "
+                  "the function conforms only to C89.";
+#endif
+
  const std::string iso_week_spec = "%Y-%m-%d: %G %g %V";
  for (auto ctm : tm_list) {
    // Calculate tm_yday, tm_wday, etc.
@@ -227,32 +250,134 @@ auto equal(const std::tm& lhs, const std::tm& rhs) -> bool {
         lhs.tm_isdst == rhs.tm_isdst;
 }

-TEST(chrono_test, localtime) {
-  auto t = std::time(nullptr);
-  auto tm = *std::localtime(&t);
-  EXPECT_TRUE(equal(tm, fmt::localtime(t)));
-}
-
 TEST(chrono_test, gmtime) {
  auto t = std::time(nullptr);
  auto tm = *std::gmtime(&t);
  EXPECT_TRUE(equal(tm, fmt::gmtime(t)));
 }

-template <typename TimePoint> auto strftime_full(TimePoint tp) -> std::string {
+template <typename TimePoint>
+auto strftime_full_utc(TimePoint tp) -> std::string {
  auto t = std::chrono::system_clock::to_time_t(tp);
+  auto tm = *std::gmtime(&t);
+  return system_strftime("%Y-%m-%d %H:%M:%S", &tm);
+}
+
+TEST(chrono_test, system_clock_time_point) {
+  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
+      std::chrono::system_clock::now());
+  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{:%Y-%m-%d %H:%M:%S}", t1));
+  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{}", t1));
+  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{:}", t1));
+
+  auto t2 = sys_time<std::chrono::seconds>(std::chrono::seconds(42));
+  EXPECT_EQ(strftime_full_utc(t2), fmt::format("{:%Y-%m-%d %H:%M:%S}", t2));
+
+  std::vector<std::string> spec_list = {
+      "%%",  "%n",  "%t",  "%Y",  "%EY", "%y",  "%Oy", "%Ey", "%C",
+      "%EC", "%G",  "%g",  "%b",  "%h",  "%B",  "%m",  "%Om", "%U",
+      "%OU", "%W",  "%OW", "%V",  "%OV", "%j",  "%d",  "%Od", "%e",
+      "%Oe", "%a",  "%A",  "%w",  "%Ow", "%u",  "%Ou", "%H",  "%OH",
+      "%I",  "%OI", "%M",  "%OM", "%S",  "%OS", "%x",  "%Ex", "%X",
+      "%EX", "%D",  "%F",  "%R",  "%T",  "%p"};
+#ifndef _WIN32
+  // Disabled on Windows because these formats are not consistent among
+  // platforms.
+  spec_list.insert(spec_list.end(), {"%c", "%Ec", "%r"});
+#elif !FMT_HAS_C99_STRFTIME
+  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
+  spec_list = {"%%", "%Y", "%y", "%b", "%B", "%m", "%U", "%W", "%j", "%d",
+               "%a", "%A", "%w", "%H", "%I", "%M", "%S", "%x", "%X", "%p"};
+#endif
+  spec_list.push_back("%Y-%m-%d %H:%M:%S");
+
+  for (const auto& spec : spec_list) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    auto sys_output = system_strftime(spec, &tm);
+
+    auto fmt_spec = fmt::format("{{:{}}}", spec);
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
+  }
+
+  // Timezone formatters tests makes sense for localtime.
+#if FMT_HAS_C99_STRFTIME
+  spec_list = {"%z", "%Z"};
+#else
+  spec_list = {"%Z"};
+#endif
+  for (const auto& spec : spec_list) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::localtime(&t);
+
+    auto sys_output = system_strftime(spec, &tm);
+
+    auto fmt_spec = fmt::format("{{:{}}}", spec);
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
+
+    if (spec == "%z") {
+      sys_output.insert(sys_output.end() - 2, 1, ':');
+      EXPECT_EQ(sys_output, fmt::format("{:%Ez}", tm));
+      EXPECT_EQ(sys_output, fmt::format("{:%Oz}", tm));
+    }
+  }
+
+  // Separate tests for UTC, since std::time_put can use local time and ignoring
+  // the timezone in std::tm (if it presents on platform).
+  if (fmt::detail::has_member_data_tm_zone<std::tm>::value) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    std::vector<std::string> tz_names = {"GMT", "UTC"};
+    EXPECT_THAT(tz_names, Contains(fmt::format("{:%Z}", t1)));
+    EXPECT_THAT(tz_names, Contains(fmt::format("{:%Z}", tm)));
+  }
+
+  if (fmt::detail::has_member_data_tm_gmtoff<std::tm>::value) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    EXPECT_EQ(fmt::format("{:%z}", t1), "+0000");
+    EXPECT_EQ(fmt::format("{:%z}", tm), "+0000");
+
+    EXPECT_EQ(fmt::format("{:%Ez}", t1), "+00:00");
+    EXPECT_EQ(fmt::format("{:%Ez}", tm), "+00:00");
+
+    EXPECT_EQ(fmt::format("{:%Oz}", t1), "+00:00");
+    EXPECT_EQ(fmt::format("{:%Oz}", tm), "+00:00");
+  }
+}
+
+#if FMT_USE_LOCAL_TIME
+
+TEST(chrono_test, localtime) {
+  auto t = std::time(nullptr);
+  auto tm = *std::localtime(&t);
+  EXPECT_TRUE(equal(tm, fmt::localtime(t)));
+}
+
+template <typename Duration>
+auto strftime_full_local(std::chrono::local_time<Duration> tp) -> std::string {
+  auto t = std::chrono::system_clock::to_time_t(
+      std::chrono::current_zone()->to_sys(tp));
  auto tm = *std::localtime(&t);
  return system_strftime("%Y-%m-%d %H:%M:%S", &tm);
 }

-TEST(chrono_test, time_point) {
-  auto t1 = std::chrono::system_clock::now();
-  EXPECT_EQ(strftime_full(t1), fmt::format("{:%Y-%m-%d %H:%M:%S}", t1));
-  EXPECT_EQ(strftime_full(t1), fmt::format("{}", t1));
-  using time_point =
-      std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
-  auto t2 = time_point(std::chrono::seconds(42));
-  EXPECT_EQ(strftime_full(t2), fmt::format("{:%Y-%m-%d %H:%M:%S}", t2));
+TEST(chrono_test, local_system_clock_time_point) {
+#  ifdef _WIN32
+  return;  // Not supported on Windows.
+#  endif
+  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
+      std::chrono::current_zone()->to_local(std::chrono::system_clock::now()));
+  EXPECT_EQ(strftime_full_local(t1), fmt::format("{:%Y-%m-%d %H:%M:%S}", t1));
+  EXPECT_EQ(strftime_full_local(t1), fmt::format("{}", t1));
+  EXPECT_EQ(strftime_full_local(t1), fmt::format("{:}", t1));
+  using time_point = std::chrono::local_time<std::chrono::seconds>;
+  auto t2 = time_point(std::chrono::seconds(86400 + 42));
+  EXPECT_EQ(strftime_full_local(t2), fmt::format("{:%Y-%m-%d %H:%M:%S}", t2));

  std::vector<std::string> spec_list = {
      "%%",  "%n",  "%t",  "%Y",  "%EY", "%y",  "%Oy", "%Ey", "%C",
@@ -261,15 +386,20 @@ TEST(chrono_test, time_point) {
      "%Oe", "%a",  "%A",  "%w",  "%Ow", "%u",  "%Ou", "%H",  "%OH",
      "%I",  "%OI", "%M",  "%OM", "%S",  "%OS", "%x",  "%Ex", "%X",
      "%EX", "%D",  "%F",  "%R",  "%T",  "%p",  "%z",  "%Z"};
-  spec_list.push_back("%Y-%m-%d %H:%M:%S");
-#ifndef _WIN32
+#  ifndef _WIN32
  // Disabled on Windows because these formats are not consistent among
  // platforms.
  spec_list.insert(spec_list.end(), {"%c", "%Ec", "%r"});
-#endif
+#  elif !FMT_HAS_C99_STRFTIME
+  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
+  spec_list = {"%%", "%Y", "%y", "%b", "%B", "%m", "%U", "%W", "%j", "%d", "%a",
+               "%A", "%w", "%H", "%I", "%M", "%S", "%x", "%X", "%p", "%Z"};
+#  endif
+  spec_list.push_back("%Y-%m-%d %H:%M:%S");

  for (const auto& spec : spec_list) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto t = std::chrono::system_clock::to_time_t(
+        std::chrono::current_zone()->to_sys(t1));
    auto tm = *std::localtime(&t);

    auto sys_output = system_strftime(spec, &tm);
@@ -278,95 +408,145 @@ TEST(chrono_test, time_point) {
    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
  }
+
+  if (std::find(spec_list.cbegin(), spec_list.cend(), "%z") !=
+      spec_list.cend()) {
+    auto t = std::chrono::system_clock::to_time_t(
+        std::chrono::current_zone()->to_sys(t1));
+    auto tm = *std::localtime(&t);
+
+    auto sys_output = system_strftime("%z", &tm);
+    sys_output.insert(sys_output.end() - 2, 1, ':');
+
+    EXPECT_EQ(sys_output, fmt::format("{:%Ez}", t1));
+    EXPECT_EQ(sys_output, fmt::format("{:%Ez}", tm));
+
+    EXPECT_EQ(sys_output, fmt::format("{:%Oz}", t1));
+    EXPECT_EQ(sys_output, fmt::format("{:%Oz}", tm));
+  }
 }

+#endif  // FMT_USE_LOCAL_TIME
+
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR

 TEST(chrono_test, format_default) {
-  EXPECT_EQ("42s", fmt::format("{}", std::chrono::seconds(42)));
-  EXPECT_EQ("42as",
-            fmt::format("{}", std::chrono::duration<int, std::atto>(42)));
-  EXPECT_EQ("42fs",
-            fmt::format("{}", std::chrono::duration<int, std::femto>(42)));
-  EXPECT_EQ("42ps",
-            fmt::format("{}", std::chrono::duration<int, std::pico>(42)));
-  EXPECT_EQ("42ns", fmt::format("{}", std::chrono::nanoseconds(42)));
-  EXPECT_EQ("42µs", fmt::format("{}", std::chrono::microseconds(42)));
-  EXPECT_EQ("42ms", fmt::format("{}", std::chrono::milliseconds(42)));
-  EXPECT_EQ("42cs",
-            fmt::format("{}", std::chrono::duration<int, std::centi>(42)));
-  EXPECT_EQ("42ds",
-            fmt::format("{}", std::chrono::duration<int, std::deci>(42)));
-  EXPECT_EQ("42s", fmt::format("{}", std::chrono::seconds(42)));
-  EXPECT_EQ("42das",
-            fmt::format("{}", std::chrono::duration<int, std::deca>(42)));
-  EXPECT_EQ("42hs",
-            fmt::format("{}", std::chrono::duration<int, std::hecto>(42)));
-  EXPECT_EQ("42ks",
-            fmt::format("{}", std::chrono::duration<int, std::kilo>(42)));
-  EXPECT_EQ("42Ms",
-            fmt::format("{}", std::chrono::duration<int, std::mega>(42)));
-  EXPECT_EQ("42Gs",
-            fmt::format("{}", std::chrono::duration<int, std::giga>(42)));
-  EXPECT_EQ("42Ts",
-            fmt::format("{}", std::chrono::duration<int, std::tera>(42)));
-  EXPECT_EQ("42Ps",
-            fmt::format("{}", std::chrono::duration<int, std::peta>(42)));
-  EXPECT_EQ("42Es",
-            fmt::format("{}", std::chrono::duration<int, std::exa>(42)));
-  EXPECT_EQ("42m", fmt::format("{}", std::chrono::minutes(42)));
-  EXPECT_EQ("42h", fmt::format("{}", std::chrono::hours(42)));
+  EXPECT_EQ(fmt::format("{}", std::chrono::seconds(42)), "42s");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::atto>(42)),
+            "42as");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::femto>(42)),
+            "42fs");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::pico>(42)),
+            "42ps");
+  EXPECT_EQ(fmt::format("{}", std::chrono::nanoseconds(42)), "42ns");
+  EXPECT_EQ(fmt::format("{}", std::chrono::microseconds(42)), "42µs");
+  EXPECT_EQ(fmt::format("{}", std::chrono::milliseconds(42)), "42ms");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::centi>(42)),
+            "42cs");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::deci>(42)),
+            "42ds");
+  EXPECT_EQ(fmt::format("{}", std::chrono::seconds(42)), "42s");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::deca>(42)),
+            "42das");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::hecto>(42)),
+            "42hs");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::kilo>(42)),
+            "42ks");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::mega>(42)),
+            "42Ms");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::giga>(42)),
+            "42Gs");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::tera>(42)),
+            "42Ts");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::peta>(42)),
+            "42Ps");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::exa>(42)),
+            "42Es");
+  EXPECT_EQ(fmt::format("{}", std::chrono::minutes(42)), "42min");
+  EXPECT_EQ(fmt::format("{}", std::chrono::hours(42)), "42h");
+  EXPECT_EQ(fmt::format("{}", days(42)), "42d");
  EXPECT_EQ(
-      "42[15]s",
-      fmt::format("{}", std::chrono::duration<int, std::ratio<15, 1>>(42)));
+      fmt::format("{}", std::chrono::duration<int, std::ratio<15, 1>>(42)),
+      "42[15]s");
  EXPECT_EQ(
-      "42[15/4]s",
-      fmt::format("{}", std::chrono::duration<int, std::ratio<15, 4>>(42)));
+      fmt::format("{}", std::chrono::duration<int, std::ratio<15, 4>>(42)),
+      "42[15/4]s");
 }

-TEST(chrono_test, align) {
+TEST(chrono_test, duration_align) {
  auto s = std::chrono::seconds(42);
-  EXPECT_EQ("42s  ", fmt::format("{:5}", s));
-  EXPECT_EQ("42s  ", fmt::format("{:{}}", s, 5));
-  EXPECT_EQ("  42s", fmt::format("{:>5}", s));
-  EXPECT_EQ("**42s**", fmt::format("{:*^7}", s));
-  EXPECT_EQ("03:25:45    ",
-            fmt::format("{:12%H:%M:%S}", std::chrono::seconds(12345)));
-  EXPECT_EQ("    03:25:45",
-            fmt::format("{:>12%H:%M:%S}", std::chrono::seconds(12345)));
-  EXPECT_EQ("~~03:25:45~~",
-            fmt::format("{:~^12%H:%M:%S}", std::chrono::seconds(12345)));
-  EXPECT_EQ("03:25:45    ",
-            fmt::format("{:{}%H:%M:%S}", std::chrono::seconds(12345), 12));
+  EXPECT_EQ(fmt::format("{:5}", s), "42s  ");
+  EXPECT_EQ(fmt::format("{:{}}", s, 5), "42s  ");
+  EXPECT_EQ(fmt::format("{:>5}", s), "  42s");
+  EXPECT_EQ(fmt::format("{:*^7}", s), "**42s**");
+  EXPECT_EQ(fmt::format("{:12%H:%M:%S}", std::chrono::seconds(12345)),
+            "03:25:45    ");
+  EXPECT_EQ(fmt::format("{:>12%H:%M:%S}", std::chrono::seconds(12345)),
+            "    03:25:45");
+  EXPECT_EQ(fmt::format("{:~^12%H:%M:%S}", std::chrono::seconds(12345)),
+            "~~03:25:45~~");
+  EXPECT_EQ(fmt::format("{:{}%H:%M:%S}", std::chrono::seconds(12345), 12),
+            "03:25:45    ");
+}
+
+TEST(chrono_test, tm_align) {
+  auto t = make_tm(1975, 12, 29, 12, 14, 16);
+  EXPECT_EQ(fmt::format("{:%F %T}", t), "1975-12-29 12:14:16");
+  EXPECT_EQ(fmt::format("{:30%F %T}", t), "1975-12-29 12:14:16           ");
+  EXPECT_EQ(fmt::format("{:{}%F %T}", t, 30), "1975-12-29 12:14:16           ");
+  EXPECT_EQ(fmt::format("{:<30%F %T}", t), "1975-12-29 12:14:16           ");
+  EXPECT_EQ(fmt::format("{:^30%F %T}", t), "     1975-12-29 12:14:16      ");
+  EXPECT_EQ(fmt::format("{:>30%F %T}", t), "           1975-12-29 12:14:16");
+
+  EXPECT_EQ(fmt::format("{:*<30%F %T}", t), "1975-12-29 12:14:16***********");
+  EXPECT_EQ(fmt::format("{:*^30%F %T}", t), "*****1975-12-29 12:14:16******");
+  EXPECT_EQ(fmt::format("{:*>30%F %T}", t), "***********1975-12-29 12:14:16");
+}
+
+TEST(chrono_test, tp_align) {
+  auto tp = std::chrono::time_point_cast<std::chrono::microseconds>(
+      std::chrono::system_clock::from_time_t(0));
+  EXPECT_EQ(fmt::format("{:%M:%S}", tp), "00:00.000000");
+  EXPECT_EQ(fmt::format("{:15%M:%S}", tp), "00:00.000000   ");
+  EXPECT_EQ(fmt::format("{:{}%M:%S}", tp, 15), "00:00.000000   ");
+  EXPECT_EQ(fmt::format("{:<15%M:%S}", tp), "00:00.000000   ");
+  EXPECT_EQ(fmt::format("{:^15%M:%S}", tp), " 00:00.000000  ");
+  EXPECT_EQ(fmt::format("{:>15%M:%S}", tp), "   00:00.000000");
+
+  EXPECT_EQ(fmt::format("{:*<15%M:%S}", tp), "00:00.000000***");
+  EXPECT_EQ(fmt::format("{:*^15%M:%S}", tp), "*00:00.000000**");
+  EXPECT_EQ(fmt::format("{:*>15%M:%S}", tp), "***00:00.000000");
 }

 TEST(chrono_test, format_specs) {
-  EXPECT_EQ("%", fmt::format("{:%%}", std::chrono::seconds(0)));
-  EXPECT_EQ("\n", fmt::format("{:%n}", std::chrono::seconds(0)));
-  EXPECT_EQ("\t", fmt::format("{:%t}", std::chrono::seconds(0)));
-  EXPECT_EQ("00", fmt::format("{:%S}", std::chrono::seconds(0)));
-  EXPECT_EQ("00", fmt::format("{:%S}", std::chrono::seconds(60)));
-  EXPECT_EQ("42", fmt::format("{:%S}", std::chrono::seconds(42)));
-  EXPECT_EQ("01.234", fmt::format("{:%S}", std::chrono::milliseconds(1234)));
-  EXPECT_EQ("00", fmt::format("{:%M}", std::chrono::minutes(0)));
-  EXPECT_EQ("00", fmt::format("{:%M}", std::chrono::minutes(60)));
-  EXPECT_EQ("42", fmt::format("{:%M}", std::chrono::minutes(42)));
-  EXPECT_EQ("01", fmt::format("{:%M}", std::chrono::seconds(61)));
-  EXPECT_EQ("00", fmt::format("{:%H}", std::chrono::hours(0)));
-  EXPECT_EQ("00", fmt::format("{:%H}", std::chrono::hours(24)));
-  EXPECT_EQ("14", fmt::format("{:%H}", std::chrono::hours(14)));
-  EXPECT_EQ("01", fmt::format("{:%H}", std::chrono::minutes(61)));
-  EXPECT_EQ("12", fmt::format("{:%I}", std::chrono::hours(0)));
-  EXPECT_EQ("12", fmt::format("{:%I}", std::chrono::hours(12)));
-  EXPECT_EQ("12", fmt::format("{:%I}", std::chrono::hours(24)));
-  EXPECT_EQ("04", fmt::format("{:%I}", std::chrono::hours(4)));
-  EXPECT_EQ("02", fmt::format("{:%I}", std::chrono::hours(14)));
-  EXPECT_EQ("03:25:45",
-            fmt::format("{:%H:%M:%S}", std::chrono::seconds(12345)));
-  EXPECT_EQ("03:25", fmt::format("{:%R}", std::chrono::seconds(12345)));
-  EXPECT_EQ("03:25:45", fmt::format("{:%T}", std::chrono::seconds(12345)));
-  EXPECT_EQ("12345", fmt::format("{:%Q}", std::chrono::seconds(12345)));
-  EXPECT_EQ("s", fmt::format("{:%q}", std::chrono::seconds(12345)));
+  EXPECT_EQ(fmt::format("{:%%}", std::chrono::seconds(0)), "%");
+  EXPECT_EQ(fmt::format("{:%n}", std::chrono::seconds(0)), "\n");
+  EXPECT_EQ(fmt::format("{:%t}", std::chrono::seconds(0)), "\t");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::seconds(0)), "00");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::seconds(60)), "00");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::seconds(42)), "42");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::milliseconds(1234)), "01.234");
+  EXPECT_EQ(fmt::format("{:%M}", std::chrono::minutes(0)), "00");
+  EXPECT_EQ(fmt::format("{:%M}", std::chrono::minutes(60)), "00");
+  EXPECT_EQ(fmt::format("{:%M}", std::chrono::minutes(42)), "42");
+  EXPECT_EQ(fmt::format("{:%M}", std::chrono::seconds(61)), "01");
+  EXPECT_EQ(fmt::format("{:%H}", std::chrono::hours(0)), "00");
+  EXPECT_EQ(fmt::format("{:%H}", std::chrono::hours(24)), "00");
+  EXPECT_EQ(fmt::format("{:%H}", std::chrono::hours(14)), "14");
+  EXPECT_EQ(fmt::format("{:%H}", std::chrono::minutes(61)), "01");
+  EXPECT_EQ(fmt::format("{:%I}", std::chrono::hours(0)), "12");
+  EXPECT_EQ(fmt::format("{:%I}", std::chrono::hours(12)), "12");
+  EXPECT_EQ(fmt::format("{:%I}", std::chrono::hours(24)), "12");
+  EXPECT_EQ(fmt::format("{:%I}", std::chrono::hours(4)), "04");
+  EXPECT_EQ(fmt::format("{:%I}", std::chrono::hours(14)), "02");
+  EXPECT_EQ(fmt::format("{:%j}", days(12345)), "12345");
+  EXPECT_EQ(fmt::format("{:%j}", std::chrono::hours(12345 * 24 + 12)), "12345");
+  EXPECT_EQ(fmt::format("{:%H:%M:%S}", std::chrono::seconds(12345)),
+            "03:25:45");
+  EXPECT_EQ(fmt::format("{:%R}", std::chrono::seconds(12345)), "03:25");
+  EXPECT_EQ(fmt::format("{:%T}", std::chrono::seconds(12345)), "03:25:45");
+  EXPECT_EQ(fmt::format("{:%Q}", std::chrono::seconds(12345)), "12345");
+  EXPECT_EQ(fmt::format("{:%q}", std::chrono::seconds(12345)), "s");
 }

 TEST(chrono_test, invalid_specs) {
@@ -407,6 +587,10 @@ TEST(chrono_test, invalid_specs) {
                   "invalid format");
  EXPECT_THROW_MSG((void)fmt::format(runtime("{:%Oq}"), sec), fmt::format_error,
                   "invalid format");
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{:abc}"), sec), fmt::format_error,
+                   "invalid format");
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{:.2f}"), sec), fmt::format_error,
+                   "invalid format");
 }

 auto format_tm(const std::tm& time, fmt::string_view spec,
@@ -443,78 +627,77 @@ TEST(chrono_test, locale) {
 using dms = std::chrono::duration<double, std::milli>;

 TEST(chrono_test, format_default_fp) {
-  typedef std::chrono::duration<float> fs;
-  EXPECT_EQ("1.234s", fmt::format("{}", fs(1.234)));
-  typedef std::chrono::duration<float, std::milli> fms;
-  EXPECT_EQ("1.234ms", fmt::format("{}", fms(1.234)));
-  typedef std::chrono::duration<double> ds;
-  EXPECT_EQ("1.234s", fmt::format("{}", ds(1.234)));
-  EXPECT_EQ("1.234ms", fmt::format("{}", dms(1.234)));
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<float>(1.234)), "1.234s");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<float, std::milli>(1.234)),
+            "1.234ms");
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<double>(1.234)), "1.234s");
+  EXPECT_EQ(fmt::format("{}", dms(1.234)), "1.234ms");
 }

 TEST(chrono_test, format_precision) {
  EXPECT_THROW_MSG(
-      (void)fmt::format(runtime("{:.2}"), std::chrono::seconds(42)),
+      (void)fmt::format(runtime("{:.2%Q}"), std::chrono::seconds(42)),
      fmt::format_error, "precision not allowed for this argument type");
-  EXPECT_EQ("1ms", fmt::format("{:.0}", dms(1.234)));
-  EXPECT_EQ("1.2ms", fmt::format("{:.1}", dms(1.234)));
-  EXPECT_EQ("1.23ms", fmt::format("{:.{}}", dms(1.234), 2));
+  EXPECT_EQ(fmt::format("{:.0}", dms(1.234)), "1ms");
+  EXPECT_EQ(fmt::format("{:.1}", dms(1.234)), "1.2ms");
+  EXPECT_EQ(fmt::format("{:.{}}", dms(1.234), 2), "1.23ms");

-  EXPECT_EQ("13ms", fmt::format("{:.0}", dms(12.56)));
-  EXPECT_EQ("12.6ms", fmt::format("{:.1}", dms(12.56)));
-  EXPECT_EQ("12.56ms", fmt::format("{:.2}", dms(12.56)));
+  EXPECT_EQ(fmt::format("{:.0}", dms(12.56)), "13ms");
+  EXPECT_EQ(fmt::format("{:.1}", dms(12.56)), "12.6ms");
+  EXPECT_EQ(fmt::format("{:.2}", dms(12.56)), "12.56ms");
 }

 TEST(chrono_test, format_full_specs) {
-  EXPECT_EQ("1ms   ", fmt::format("{:6.0}", dms(1.234)));
-  EXPECT_EQ("1.2ms ", fmt::format("{:6.1}", dms(1.234)));
-  EXPECT_EQ("  1.23ms", fmt::format("{:>8.{}}", dms(1.234), 2));
-  EXPECT_EQ(" 1.2ms ", fmt::format("{:^{}.{}}", dms(1.234), 7, 1));
-  EXPECT_EQ(" 1.23ms ", fmt::format("{0:^{2}.{1}}", dms(1.234), 2, 8));
-  EXPECT_EQ("=1.234ms=", fmt::format("{:=^{}.{}}", dms(1.234), 9, 3));
-  EXPECT_EQ("*1.2340ms*", fmt::format("{:*^10.4}", dms(1.234)));
+  EXPECT_EQ(fmt::format("{:6.0}", dms(1.234)), "1ms   ");
+  EXPECT_EQ(fmt::format("{:6.1}", dms(1.234)), "1.2ms ");
+  EXPECT_EQ(fmt::format("{:>8.{}}", dms(1.234), 2), "  1.23ms");
+  EXPECT_EQ(fmt::format("{:^{}.{}}", dms(1.234), 7, 1), " 1.2ms ");
+  EXPECT_EQ(fmt::format("{0:^{2}.{1}}", dms(1.234), 2, 8), " 1.23ms ");
+  EXPECT_EQ(fmt::format("{:=^{}.{}}", dms(1.234), 9, 3), "=1.234ms=");
+  EXPECT_EQ(fmt::format("{:*^10.4}", dms(1.234)), "*1.2340ms*");

-  EXPECT_EQ("13ms  ", fmt::format("{:6.0}", dms(12.56)));
-  EXPECT_EQ("    13ms", fmt::format("{:>8.{}}", dms(12.56), 0));
-  EXPECT_EQ(" 13ms ", fmt::format("{:^{}.{}}", dms(12.56), 6, 0));
-  EXPECT_EQ("  13ms  ", fmt::format("{0:^{2}.{1}}", dms(12.56), 0, 8));
-  EXPECT_EQ("==13ms===", fmt::format("{:=^{}.{}}", dms(12.56), 9, 0));
-  EXPECT_EQ("***13ms***", fmt::format("{:*^10.0}", dms(12.56)));
+  EXPECT_EQ(fmt::format("{:6.0}", dms(12.56)), "13ms  ");
+  EXPECT_EQ(fmt::format("{:>8.{}}", dms(12.56), 0), "    13ms");
+  EXPECT_EQ(fmt::format("{:^{}.{}}", dms(12.56), 6, 0), " 13ms ");
+  EXPECT_EQ(fmt::format("{0:^{2}.{1}}", dms(12.56), 0, 8), "  13ms  ");
+  EXPECT_EQ(fmt::format("{:=^{}.{}}", dms(12.56), 9, 0), "==13ms===");
+  EXPECT_EQ(fmt::format("{:*^10.0}", dms(12.56)), "***13ms***");
 }

 TEST(chrono_test, format_simple_q) {
-  typedef std::chrono::duration<float> fs;
-  EXPECT_EQ("1.234 s", fmt::format("{:%Q %q}", fs(1.234)));
-  typedef std::chrono::duration<float, std::milli> fms;
-  EXPECT_EQ("1.234 ms", fmt::format("{:%Q %q}", fms(1.234)));
-  typedef std::chrono::duration<double> ds;
-  EXPECT_EQ("1.234 s", fmt::format("{:%Q %q}", ds(1.234)));
-  EXPECT_EQ("1.234 ms", fmt::format("{:%Q %q}", dms(1.234)));
+  EXPECT_EQ(fmt::format("{:%Q %q}", std::chrono::duration<float>(1.234)),
+            "1.234 s");
+  EXPECT_EQ(
+      fmt::format("{:%Q %q}", std::chrono::duration<float, std::milli>(1.234)),
+      "1.234 ms");
+  EXPECT_EQ(fmt::format("{:%Q %q}", std::chrono::duration<double>(1.234)),
+            "1.234 s");
+  EXPECT_EQ(fmt::format("{:%Q %q}", dms(1.234)), "1.234 ms");
 }

 TEST(chrono_test, format_precision_q) {
  EXPECT_THROW_MSG(
      (void)fmt::format(runtime("{:.2%Q %q}"), std::chrono::seconds(42)),
      fmt::format_error, "precision not allowed for this argument type");
-  EXPECT_EQ("1.2 ms", fmt::format("{:.1%Q %q}", dms(1.234)));
-  EXPECT_EQ("1.23 ms", fmt::format("{:.{}%Q %q}", dms(1.234), 2));
+  EXPECT_EQ(fmt::format("{:.1%Q %q}", dms(1.234)), "1.2 ms");
+  EXPECT_EQ(fmt::format("{:.{}%Q %q}", dms(1.234), 2), "1.23 ms");
 }

 TEST(chrono_test, format_full_specs_q) {
-  EXPECT_EQ("1 ms   ", fmt::format("{:7.0%Q %q}", dms(1.234)));
-  EXPECT_EQ("1.2 ms ", fmt::format("{:7.1%Q %q}", dms(1.234)));
-  EXPECT_EQ(" 1.23 ms", fmt::format("{:>8.{}%Q %q}", dms(1.234), 2));
-  EXPECT_EQ(" 1.2 ms ", fmt::format("{:^{}.{}%Q %q}", dms(1.234), 8, 1));
-  EXPECT_EQ(" 1.23 ms ", fmt::format("{0:^{2}.{1}%Q %q}", dms(1.234), 2, 9));
-  EXPECT_EQ("=1.234 ms=", fmt::format("{:=^{}.{}%Q %q}", dms(1.234), 10, 3));
-  EXPECT_EQ("*1.2340 ms*", fmt::format("{:*^11.4%Q %q}", dms(1.234)));
+  EXPECT_EQ(fmt::format("{:7.0%Q %q}", dms(1.234)), "1 ms   ");
+  EXPECT_EQ(fmt::format("{:7.1%Q %q}", dms(1.234)), "1.2 ms ");
+  EXPECT_EQ(fmt::format("{:>8.{}%Q %q}", dms(1.234), 2), " 1.23 ms");
+  EXPECT_EQ(fmt::format("{:^{}.{}%Q %q}", dms(1.234), 8, 1), " 1.2 ms ");
+  EXPECT_EQ(fmt::format("{0:^{2}.{1}%Q %q}", dms(1.234), 2, 9), " 1.23 ms ");
+  EXPECT_EQ(fmt::format("{:=^{}.{}%Q %q}", dms(1.234), 10, 3), "=1.234 ms=");
+  EXPECT_EQ(fmt::format("{:*^11.4%Q %q}", dms(1.234)), "*1.2340 ms*");

-  EXPECT_EQ("13 ms  ", fmt::format("{:7.0%Q %q}", dms(12.56)));
-  EXPECT_EQ("   13 ms", fmt::format("{:>8.{}%Q %q}", dms(12.56), 0));
-  EXPECT_EQ(" 13 ms  ", fmt::format("{:^{}.{}%Q %q}", dms(12.56), 8, 0));
-  EXPECT_EQ("  13 ms  ", fmt::format("{0:^{2}.{1}%Q %q}", dms(12.56), 0, 9));
-  EXPECT_EQ("==13 ms==", fmt::format("{:=^{}.{}%Q %q}", dms(12.56), 9, 0));
-  EXPECT_EQ("***13 ms***", fmt::format("{:*^11.0%Q %q}", dms(12.56)));
+  EXPECT_EQ(fmt::format("{:7.0%Q %q}", dms(12.56)), "13 ms  ");
+  EXPECT_EQ(fmt::format("{:>8.{}%Q %q}", dms(12.56), 0), "   13 ms");
+  EXPECT_EQ(fmt::format("{:^{}.{}%Q %q}", dms(12.56), 8, 0), " 13 ms  ");
+  EXPECT_EQ(fmt::format("{0:^{2}.{1}%Q %q}", dms(12.56), 0, 9), "  13 ms  ");
+  EXPECT_EQ(fmt::format("{:=^{}.{}%Q %q}", dms(12.56), 9, 0), "==13 ms==");
+  EXPECT_EQ(fmt::format("{:*^11.0%Q %q}", dms(12.56)), "***13 ms***");
 }

 TEST(chrono_test, invalid_width_id) {
@@ -528,27 +711,26 @@ TEST(chrono_test, invalid_colons) {
 }

 TEST(chrono_test, negative_durations) {
-  EXPECT_EQ("-12345", fmt::format("{:%Q}", std::chrono::seconds(-12345)));
-  EXPECT_EQ("-03:25:45",
-            fmt::format("{:%H:%M:%S}", std::chrono::seconds(-12345)));
-  EXPECT_EQ("-00:01",
-            fmt::format("{:%M:%S}", std::chrono::duration<double>(-1)));
-  EXPECT_EQ("s", fmt::format("{:%q}", std::chrono::seconds(-12345)));
-  EXPECT_EQ("-00.127",
-            fmt::format("{:%S}",
-                        std::chrono::duration<signed char, std::milli>{-127}));
+  EXPECT_EQ(fmt::format("{:%Q}", std::chrono::seconds(-12345)), "-12345");
+  EXPECT_EQ(fmt::format("{:%H:%M:%S}", std::chrono::seconds(-12345)),
+            "-03:25:45");
+  EXPECT_EQ(fmt::format("{:%M:%S}", std::chrono::duration<double>(-1)),
+            "-00:01");
+  EXPECT_EQ(fmt::format("{:%q}", std::chrono::seconds(-12345)), "s");
+  EXPECT_EQ(fmt::format("{:%S}",
+                        std::chrono::duration<signed char, std::milli>(-127)),
+            "-00.127");
  auto min = std::numeric_limits<int>::min();
  EXPECT_EQ(fmt::format("{}", min),
            fmt::format("{:%Q}", std::chrono::duration<int>(min)));
 }

 TEST(chrono_test, special_durations) {
-  auto value = fmt::format("{:%S}", std::chrono::duration<double>(1e20));
-  EXPECT_EQ(value, "40");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<double>(1e20)), "40");
  auto nan = std::numeric_limits<double>::quiet_NaN();
  EXPECT_EQ(
-      "nan nan nan nan nan:nan nan",
-      fmt::format("{:%I %H %M %S %R %r}", std::chrono::duration<double>(nan)));
+      fmt::format("{:%I %H %M %S %R %r}", std::chrono::duration<double>(nan)),
+      "nan nan nan nan nan:nan nan");
  EXPECT_EQ(fmt::format("{}", std::chrono::duration<float, std::exa>(1)),
            "1Es");
  EXPECT_EQ(fmt::format("{}", std::chrono::duration<float, std::atto>(1)),
@@ -557,31 +739,30 @@ TEST(chrono_test, special_durations) {
            "03:33");
  EXPECT_EQ(fmt::format("{:%T}", std::chrono::duration<char, std::mega>{2}),
            "03:33:20");
-  EXPECT_EQ("44.000000000000",
-            fmt::format("{:%S}", std::chrono::duration<float, std::pico>(
-                                     1.54213895E+26)));
+  EXPECT_EQ(
+      fmt::format("{:.3%S}", std::chrono::duration<float, std::pico>(1.234e12)),
+      "01.234");
 }

 TEST(chrono_test, unsigned_duration) {
-  EXPECT_EQ("42s", fmt::format("{}", std::chrono::duration<unsigned>(42)));
+  EXPECT_EQ(fmt::format("{}", std::chrono::duration<unsigned>(42)), "42s");
 }

 TEST(chrono_test, weekday) {
-  auto loc = get_locale("ru_RU.UTF-8");
+  auto loc = get_locale("es_ES.UTF-8");
  std::locale::global(loc);
-  auto mon = fmt::weekday(1);
+  auto sat = fmt::weekday(6);

  auto tm = std::tm();
-  tm.tm_wday = static_cast<int>(mon.c_encoding());
+  tm.tm_wday = static_cast<int>(sat.c_encoding());

-  EXPECT_EQ(fmt::format("{}", mon), "Mon");
-  EXPECT_EQ(fmt::format("{:%a}", tm), "Mon");
+  EXPECT_EQ(fmt::format("{}", sat), "Sat");
+  EXPECT_EQ(fmt::format("{:%a}", tm), "Sat");

  if (loc != std::locale::classic()) {
-    EXPECT_THAT((std::vector<std::string>{"пн", "Пн", "пнд", "Пнд"}),
-                Contains(fmt::format(loc, "{:L}", mon)));
-    EXPECT_THAT((std::vector<std::string>{"пн", "Пн", "пнд", "Пнд"}),
-                Contains(fmt::format(loc, "{:%a}", tm)));
+    auto saturdays = std::vector<std::string>{"sáb", "sá."};
+    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L}", sat)));
+    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:%a}", tm)));
  }
 }

@@ -599,12 +780,28 @@ TEST(chrono_test, cpp20_duration_subsecond_support) {
  EXPECT_EQ(fmt::format("{:%S}", std::chrono::nanoseconds{-13420148734}),
            "-13.420148734");
  EXPECT_EQ(fmt::format("{:%S}", std::chrono::milliseconds{1234}), "01.234");
+  // Check subsecond presision modifier.
+  EXPECT_EQ(fmt::format("{:.6%S}", std::chrono::nanoseconds{1234}),
+            "00.000001");
+  EXPECT_EQ(fmt::format("{:.18%S}", std::chrono::nanoseconds{1234}),
+            "00.000001234000000000");
+  EXPECT_EQ(fmt::format("{:.{}%S}", std::chrono::nanoseconds{1234}, 6),
+            "00.000001");
+  EXPECT_EQ(fmt::format("{:.6%S}", std::chrono::milliseconds{1234}),
+            "01.234000");
+  EXPECT_EQ(fmt::format("{:.6%S}", std::chrono::milliseconds{-1234}),
+            "-01.234000");
+  EXPECT_EQ(fmt::format("{:.3%S}", std::chrono::seconds{1234}), "34.000");
+  EXPECT_EQ(fmt::format("{:.3%S}", std::chrono::hours{1234}), "00.000");
+  EXPECT_EQ(fmt::format("{:.5%S}", dms(1.234)), "00.00123");
+  EXPECT_EQ(fmt::format("{:.8%S}", dms(1.234)), "00.00123400");
  {
    // Check that {:%H:%M:%S} is equivalent to {:%T}.
    auto dur = std::chrono::milliseconds{3601234};
    auto formatted_dur = fmt::format("{:%T}", dur);
    EXPECT_EQ(formatted_dur, "01:00:01.234");
    EXPECT_EQ(fmt::format("{:%H:%M:%S}", dur), formatted_dur);
+    EXPECT_EQ(fmt::format("{:.6%H:%M:%S}", dur), "01:00:01.234000");
  }
  using nanoseconds_dbl = std::chrono::duration<double, std::nano>;
  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{-123456789}), "-00.123456789");
@@ -618,15 +815,185 @@ TEST(chrono_test, cpp20_duration_subsecond_support) {
    auto formatted_dur = fmt::format("{:%T}", dur);
    EXPECT_EQ(formatted_dur, "-00:01:39.123456789");
    EXPECT_EQ(fmt::format("{:%H:%M:%S}", dur), formatted_dur);
+    EXPECT_EQ(fmt::format("{:.3%H:%M:%S}", dur), "-00:01:39.123");
  }
  // Check that durations with precision greater than std::chrono::seconds have
  // fixed precision, and print zeros even if there is no fractional part.
  EXPECT_EQ(fmt::format("{:%S}", std::chrono::microseconds{7000000}),
            "07.000000");
-  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<long long, std::ratio<1, 3>>(1)),
+  EXPECT_EQ(fmt::format("{:%S}",
+                        std::chrono::duration<long long, std::ratio<1, 3>>(1)),
            "00.333333");
-  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<long long, std::ratio<1, 7>>(1)),
+  EXPECT_EQ(fmt::format("{:%S}",
+                        std::chrono::duration<long long, std::ratio<1, 7>>(1)),
            "00.142857");
+
+  EXPECT_EQ(
+      fmt::format("{:%S}",
+                  std::chrono::duration<signed char, std::ratio<1, 100>>(0x80)),
+      "-01.28");
+
+  EXPECT_EQ(
+      fmt::format("{:%M:%S}",
+                  std::chrono::duration<short, std::ratio<1, 100>>(0x8000)),
+      "-05:27.68");
+
+  // Check that floating point seconds with ratio<1,1> are printed.
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<double>{1.5}),
+            "01.500000");
+  EXPECT_EQ(fmt::format("{:%M:%S}", std::chrono::duration<double>{-61.25}),
+            "-01:01.250000");
 }

 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR
+
+// Disable the utc_clock test for windows, as the icu.dll used for tzdb
+// (time zone database) is not shipped with many windows versions.
+#if FMT_USE_UTC_TIME && !defined(_WIN32)
+TEST(chrono_test, utc_clock) {
+  auto t1 = std::chrono::system_clock::now();
+  auto t1_utc = std::chrono::utc_clock::from_sys(t1);
+  EXPECT_EQ(fmt::format("{:%Y-%m-%d %H:%M:%S}", t1),
+            fmt::format("{:%Y-%m-%d %H:%M:%S}", t1_utc));
+}
+#endif
+
+TEST(chrono_test, timestamp_ratios) {
+  auto t1 =
+      sys_time<std::chrono::milliseconds>(std::chrono::milliseconds(67890));
+  EXPECT_EQ(fmt::format("{:%M:%S}", t1), "01:07.890");
+
+  auto t2 = sys_time<std::chrono::minutes>(std::chrono::minutes(7));
+  EXPECT_EQ(fmt::format("{:%M:%S}", t2), "07:00");
+
+  auto t3 = sys_time<std::chrono::duration<int, std::ratio<9>>>(
+      std::chrono::duration<int, std::ratio<9>>(7));
+  EXPECT_EQ(fmt::format("{:%M:%S}", t3), "01:03");
+
+  auto t4 = sys_time<std::chrono::duration<int, std::ratio<63>>>(
+      std::chrono::duration<int, std::ratio<63>>(1));
+  EXPECT_EQ(fmt::format("{:%M:%S}", t4), "01:03");
+
+  if (sizeof(time_t) > 4) {
+    auto tp =
+        sys_time<std::chrono::milliseconds>(std::chrono::seconds(32503680000));
+    EXPECT_EQ(fmt::format("{:%Y-%m-%d}", tp), "3000-01-01");
+  }
+
+  if (FMT_SAFE_DURATION_CAST) {
+    using years = std::chrono::duration<std::int64_t, std::ratio<31556952>>;
+    auto tp = sys_time<years>(years(std::numeric_limits<std::int64_t>::max()));
+    EXPECT_THROW_MSG((void)fmt::format("{:%Y-%m-%d}", tp), fmt::format_error,
+                     "cannot format duration");
+  }
+}
+
+TEST(chrono_test, timestamp_sub_seconds) {
+  auto t1 = sys_time<std::chrono::duration<long long, std::ratio<1, 3>>>(
+      std::chrono::duration<long long, std::ratio<1, 3>>(4));
+  EXPECT_EQ(fmt::format("{:%S}", t1), "01.333333");
+
+  auto t2 = sys_time<std::chrono::duration<double, std::ratio<1, 3>>>(
+      std::chrono::duration<double, std::ratio<1, 3>>(4));
+  EXPECT_EQ(fmt::format("{:%S}", t2), "01.333333");
+
+  auto t3 = sys_time<std::chrono::seconds>(std::chrono::seconds(2));
+  EXPECT_EQ(fmt::format("{:%S}", t3), "02");
+
+  auto t4 = sys_time<std::chrono::duration<double>>(
+      std::chrono::duration<double, std::ratio<1, 1>>(9.5));
+  EXPECT_EQ(fmt::format("{:%S}", t4), "09.500000");
+
+  auto t5 = sys_time<std::chrono::duration<double>>(
+      std::chrono::duration<double, std::ratio<1, 1>>(9));
+  EXPECT_EQ(fmt::format("{:%S}", t5), "09");
+
+  auto t6 = sys_time<std::chrono::milliseconds>(std::chrono::seconds(1) +
+                                                std::chrono::milliseconds(120));
+  EXPECT_EQ(fmt::format("{:%S}", t6), "01.120");
+
+  auto t7 =
+      sys_time<std::chrono::microseconds>(std::chrono::microseconds(1234567));
+  EXPECT_EQ(fmt::format("{:%S}", t7), "01.234567");
+
+  auto t8 =
+      sys_time<std::chrono::nanoseconds>(std::chrono::nanoseconds(123456789));
+  EXPECT_EQ(fmt::format("{:%S}", t8), "00.123456789");
+
+  auto t9 = std::chrono::time_point_cast<std::chrono::nanoseconds>(
+      std::chrono::system_clock::now());
+  auto t9_sec = std::chrono::time_point_cast<std::chrono::seconds>(t9);
+  auto t9_sub_sec_part = fmt::format("{0:09}", (t9 - t9_sec).count());
+  EXPECT_EQ(fmt::format("{}.{}", strftime_full_utc(t9_sec), t9_sub_sec_part),
+            fmt::format("{:%Y-%m-%d %H:%M:%S}", t9));
+  EXPECT_EQ(fmt::format("{}.{}", strftime_full_utc(t9_sec), t9_sub_sec_part),
+            fmt::format("{:%Y-%m-%d %T}", t9));
+
+  auto t10 =
+      sys_time<std::chrono::milliseconds>(std::chrono::milliseconds(2000));
+  EXPECT_EQ(fmt::format("{:%S}", t10), "02.000");
+
+  auto epoch = sys_time<std::chrono::milliseconds>();
+  auto d = std::chrono::milliseconds(250);
+  EXPECT_EQ(fmt::format("{:%S}", epoch - d), "59.750");
+  EXPECT_EQ(fmt::format("{:%S}", epoch), "00.000");
+  EXPECT_EQ(fmt::format("{:%S}", epoch + d), "00.250");
+}
+
+TEST(chrono_test, glibc_extensions) {
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{:%0}"), std::chrono::seconds()),
+                   fmt::format_error, "invalid format");
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{:%_}"), std::chrono::seconds()),
+                   fmt::format_error, "invalid format");
+  EXPECT_THROW_MSG((void)fmt::format(runtime("{:%-}"), std::chrono::seconds()),
+                   fmt::format_error, "invalid format");
+
+  {
+    const auto d = std::chrono::hours(1) + std::chrono::minutes(2) +
+                   std::chrono::seconds(3);
+
+    EXPECT_EQ(fmt::format("{:%I,%H,%M,%S}", d), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%0I,%0H,%0M,%0S}", d), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%_I,%_H,%_M,%_S}", d), " 1, 1, 2, 3");
+    EXPECT_EQ(fmt::format("{:%-I,%-H,%-M,%-S}", d), "1,1,2,3");
+
+    EXPECT_EQ(fmt::format("{:%OI,%OH,%OM,%OS}", d), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%0OI,%0OH,%0OM,%0OS}", d), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%_OI,%_OH,%_OM,%_OS}", d), " 1, 1, 2, 3");
+    EXPECT_EQ(fmt::format("{:%-OI,%-OH,%-OM,%-OS}", d), "1,1,2,3");
+  }
+
+  {
+    const auto tm = make_tm(1970, 1, 1, 1, 2, 3);
+    EXPECT_EQ(fmt::format("{:%I,%H,%M,%S}", tm), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%0I,%0H,%0M,%0S}", tm), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%_I,%_H,%_M,%_S}", tm), " 1, 1, 2, 3");
+    EXPECT_EQ(fmt::format("{:%-I,%-H,%-M,%-S}", tm), "1,1,2,3");
+
+    EXPECT_EQ(fmt::format("{:%OI,%OH,%OM,%OS}", tm), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%0OI,%0OH,%0OM,%0OS}", tm), "01,01,02,03");
+    EXPECT_EQ(fmt::format("{:%_OI,%_OH,%_OM,%_OS}", tm), " 1, 1, 2, 3");
+    EXPECT_EQ(fmt::format("{:%-OI,%-OH,%-OM,%-OS}", tm), "1,1,2,3");
+  }
+
+  {
+    const auto d = std::chrono::seconds(3) + std::chrono::milliseconds(140);
+    EXPECT_EQ(fmt::format("{:%S}", d), "03.140");
+    EXPECT_EQ(fmt::format("{:%0S}", d), "03.140");
+    EXPECT_EQ(fmt::format("{:%_S}", d), " 3.140");
+    EXPECT_EQ(fmt::format("{:%-S}", d), "3.140");
+  }
+
+  {
+    const auto d = std::chrono::duration<double>(3.14);
+    EXPECT_EQ(fmt::format("{:%S}", d), "03.140000");
+    EXPECT_EQ(fmt::format("{:%0S}", d), "03.140000");
+    EXPECT_EQ(fmt::format("{:%_S}", d), " 3.140000");
+    EXPECT_EQ(fmt::format("{:%-S}", d), "3.140000");
+  }
+}
+
+TEST(chrono_test, out_of_range) {
+  auto d = std::chrono::duration<unsigned long, std::giga>(538976288);
+  EXPECT_THROW((void)fmt::format("{:%j}", d), fmt::format_error);
+}
@@ -1,6 +1,6 @@
 # Test if compile errors are produced where necessary.

-cmake_minimum_required(VERSION 3.1...3.18)
+cmake_minimum_required(VERSION 3.8...3.25)
 project(compile-error-test CXX)

 set(fmt_headers "
@@ -64,7 +64,7 @@ function (run_tests)
  ")

  file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test/CMakeLists.txt" "
-    cmake_minimum_required(VERSION 3.1...3.18)
+    cmake_minimum_required(VERSION 3.8...3.25)
    project(tests CXX)
    add_subdirectory(${FMT_DIR} fmt)
    ${cmake_targets}
@@ -12,6 +12,7 @@
    defined(__cpp_constexpr) && __cpp_constexpr >= 201907 &&       \
    defined(__cpp_constexpr_dynamic_alloc) &&                      \
    __cpp_constexpr_dynamic_alloc >= 201907 && FMT_CPLUSPLUS >= 202002L
+
 template <size_t max_string_length, typename Char = char> struct test_string {
  template <typename T> constexpr bool operator==(const T& rhs) const noexcept {
    return fmt::basic_string_view<Char>(rhs).compare(buffer) == 0;
@@ -21,38 +21,6 @@ TEST(iterator_test, counting_iterator) {
  EXPECT_EQ((it + 41).count(), 42);
 }

-TEST(iterator_test, truncating_iterator) {
-  char* p = nullptr;
-  auto it = fmt::detail::truncating_iterator<char*>(p, 3);
-  auto prev = it++;
-  EXPECT_EQ(prev.base(), p);
-  EXPECT_EQ(it.base(), p + 1);
-}
-
-TEST(iterator_test, truncating_iterator_default_construct) {
-  auto it = fmt::detail::truncating_iterator<char*>();
-  EXPECT_EQ(nullptr, it.base());
-  EXPECT_EQ(std::size_t{0}, it.count());
-}
-
-#ifdef __cpp_lib_ranges
-TEST(iterator_test, truncating_iterator_is_output_iterator) {
-  static_assert(
-      std::output_iterator<fmt::detail::truncating_iterator<char*>, char>);
-}
-#endif
-
-TEST(iterator_test, truncating_back_inserter) {
-  auto buffer = std::string();
-  auto bi = std::back_inserter(buffer);
-  auto it = fmt::detail::truncating_iterator<decltype(bi)>(bi, 2);
-  *it++ = '4';
-  *it++ = '2';
-  *it++ = '1';
-  EXPECT_EQ(buffer.size(), 2);
-  EXPECT_EQ(buffer, "42");
-}
-
 TEST(compile_test, compile_fallback) {
  // FMT_COMPILE should fallback on runtime formatting when `if constexpr` is
  // not available.
@@ -227,10 +195,27 @@ TEST(compile_test, format_to_n) {
  EXPECT_STREQ("2a", buffer);
 }

-TEST(compile_test, formatted_size) {
-  EXPECT_EQ(2, fmt::formatted_size(FMT_COMPILE("{0}"), 42));
-  EXPECT_EQ(5, fmt::formatted_size(FMT_COMPILE("{0:<4.2f}"), 42.0));
+#  ifdef __cpp_lib_bit_cast
+TEST(compile_test, constexpr_formatted_size) {
+  FMT_CONSTEXPR20 size_t size = fmt::formatted_size(FMT_COMPILE("{}"), 42);
+  EXPECT_EQ(size, 2);
+  FMT_CONSTEXPR20 size_t hex_size =
+      fmt::formatted_size(FMT_COMPILE("{:x}"), 15);
+  EXPECT_EQ(hex_size, 1);
+  FMT_CONSTEXPR20 size_t binary_size =
+      fmt::formatted_size(FMT_COMPILE("{:b}"), 15);
+  EXPECT_EQ(binary_size, 4);
+  FMT_CONSTEXPR20 size_t padded_size =
+      fmt::formatted_size(FMT_COMPILE("{:*^6}"), 42);
+  EXPECT_EQ(padded_size, 6);
+  FMT_CONSTEXPR20 size_t float_size =
+      fmt::formatted_size(FMT_COMPILE("{:.3}"), 12.345);
+  EXPECT_EQ(float_size, 4);
+  FMT_CONSTEXPR20 size_t str_size =
+      fmt::formatted_size(FMT_COMPILE("{:s}"), "abc");
+  EXPECT_EQ(str_size, 3);
 }
+#  endif

 TEST(compile_test, text_and_arg) {
  EXPECT_EQ(">>>42<<<", fmt::format(FMT_COMPILE(">>>{}<<<"), 42));
@@ -295,14 +280,18 @@ TEST(compile_test, compile_format_string_literal) {
 #endif

 // MSVS 2019 19.29.30145.0 - Support C++20 and OK.
-// MSVS 2022 19.32.31332.0 - compile-test.cc(362,3): fatal error C1001: Internal
-// compiler error.
+// MSVS 2022 19.32.31332.0, 19.37.32826.1 - compile-test.cc(362,3): fatal error
+// C1001: Internal compiler error.
 //  (compiler file
 //  'D:\a\_work\1\s\src\vctools\Compiler\CxxFE\sl\p1\c\constexpr\constexpr.cpp',
 //  line 8635)
-#if ((FMT_CPLUSPLUS >= 202002L) &&                    \
-     (!FMT_MSC_VERSION || FMT_MSC_VERSION < 1930)) || \
-    (FMT_CPLUSPLUS >= 201709L && FMT_GCC_VERSION >= 1002)
+#if (FMT_CPLUSPLUS >= 202002L ||                                \
+     (FMT_CPLUSPLUS >= 201709L && FMT_GCC_VERSION >= 1002)) &&  \
+    ((!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 10) &&  \
+     (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 10000) && \
+     (!FMT_MSC_VERSION ||                                       \
+      (FMT_MSC_VERSION >= 1928 && FMT_MSC_VERSION < 1930))) &&  \
+    defined(__cpp_lib_is_constant_evaluated)
 template <size_t max_string_length, typename Char = char> struct test_string {
  template <typename T> constexpr bool operator==(const T& rhs) const noexcept {
    return fmt::basic_string_view<Char>(rhs).compare(buffer) == 0;
@@ -70,6 +70,16 @@ TEST(string_view_test, compare) {
  EXPECT_LT(string_view("foo").compare(string_view("fop")), 0);
  EXPECT_GT(string_view("foo").compare(string_view("fo")), 0);
  EXPECT_LT(string_view("fo").compare(string_view("foo")), 0);
+
+  EXPECT_TRUE(string_view("foo").starts_with('f'));
+  EXPECT_FALSE(string_view("foo").starts_with('o'));
+  EXPECT_FALSE(string_view().starts_with('o'));
+
+  EXPECT_TRUE(string_view("foo").starts_with("fo"));
+  EXPECT_TRUE(string_view("foo").starts_with("foo"));
+  EXPECT_FALSE(string_view("foo").starts_with("fooo"));
+  EXPECT_FALSE(string_view().starts_with("fooo"));
+
  check_op<std::equal_to>();
  check_op<std::not_equal_to>();
  check_op<std::less>();
@@ -78,24 +88,6 @@ TEST(string_view_test, compare) {
  check_op<std::greater_equal>();
 }

-namespace test_ns {
-template <typename Char> class test_string {
- private:
-  std::basic_string<Char> s_;
-
- public:
-  test_string(const Char* s) : s_(s) {}
-  const Char* data() const { return s_.data(); }
-  size_t length() const { return s_.size(); }
-  operator const Char*() const { return s_.c_str(); }
-};
-
-template <typename Char>
-fmt::basic_string_view<Char> to_string_view(const test_string<Char>& s) {
-  return {s.data(), s.length()};
-}
-}  // namespace test_ns
-
 TEST(core_test, is_output_iterator) {
  EXPECT_TRUE((fmt::detail::is_output_iterator<char*, char>::value));
  EXPECT_FALSE((fmt::detail::is_output_iterator<const char*, char>::value));
@@ -149,7 +141,7 @@ TEST(buffer_test, indestructible) {
 }

 template <typename T> struct mock_buffer final : buffer<T> {
-  MOCK_METHOD1(do_grow, size_t(size_t capacity));
+  MOCK_METHOD(size_t, do_grow, (size_t));

  void grow(size_t capacity) override {
    this->set(this->data(), do_grow(capacity));
@@ -281,7 +273,7 @@ struct custom_context {
  bool called = false;

  template <typename T> struct formatter_type {
-    auto parse(fmt::format_parse_context& ctx) -> decltype(ctx.begin()) {
+    FMT_CONSTEXPR auto parse(fmt::format_parse_context& ctx) -> decltype(ctx.begin()) {
      return ctx.begin();
    }

@@ -298,11 +290,11 @@ struct test_struct {};

 FMT_BEGIN_NAMESPACE
 template <typename Char> struct formatter<test_struct, Char> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }

-  auto format(test_struct, format_context& ctx) -> decltype(ctx.out()) {
+  auto format(test_struct, format_context& ctx) const -> decltype(ctx.out()) {
    auto test = string_view("test");
    return std::copy_n(test.data(), test.size(), ctx.out());
  }
@@ -316,7 +308,7 @@ TEST(arg_test, format_args) {

 TEST(arg_test, make_value_with_custom_context) {
  auto t = test_struct();
-  fmt::detail::value<custom_context> arg(
+  auto arg = fmt::detail::value<custom_context>(
      fmt::detail::arg_mapper<custom_context>().map(t));
  auto ctx = custom_context();
  auto parse_ctx = fmt::format_parse_context("");
@@ -335,12 +327,12 @@ template <typename T> struct mock_visitor {
    ON_CALL(*this, visit(_)).WillByDefault(Return(test_result()));
  }

-  MOCK_METHOD1_T(visit, test_result(T value));
-  MOCK_METHOD0_T(unexpected, void());
+  MOCK_METHOD(test_result, visit, (T));
+  MOCK_METHOD(void, unexpected, ());

-  test_result operator()(T value) { return visit(value); }
+  auto operator()(T value) -> test_result { return visit(value); }

-  template <typename U> test_result operator()(U) {
+  template <typename U> auto operator()(U) -> test_result {
    unexpected();
    return test_result();
  }
@@ -369,10 +361,11 @@ VISIT_TYPE(unsigned long, unsigned long long);
    testing::StrictMock<mock_visitor<decltype(expected)>> visitor;        \
    EXPECT_CALL(visitor, visit(expected));                                \
    using iterator = std::back_insert_iterator<buffer<Char>>;             \
+    auto var = value;                                                     \
    fmt::visit_format_arg(                                                \
        visitor,                                                          \
        fmt::detail::make_arg<fmt::basic_format_context<iterator, Char>>( \
-            value));                                                      \
+            var));                                                        \
  }

 #define CHECK_ARG_SIMPLE(value)                             \
@@ -392,13 +385,13 @@ using test_types =
 TYPED_TEST_SUITE(numeric_arg_test, test_types);

 template <typename T, fmt::enable_if_t<std::is_integral<T>::value, int> = 0>
-T test_value() {
+auto test_value() -> T {
  return static_cast<T>(42);
 }

 template <typename T,
          fmt::enable_if_t<std::is_floating_point<T>::value, int> = 0>
-T test_value() {
+auto test_value() -> T {
  return static_cast<T>(4.2);
 }

@@ -441,8 +434,8 @@ TEST(arg_test, pointer_arg) {
 }

 struct check_custom {
-  test_result operator()(
-      fmt::basic_format_arg<fmt::format_context>::handle h) const {
+  auto operator()(fmt::basic_format_arg<fmt::format_context>::handle h) const
+      -> test_result {
    struct test_buffer final : fmt::detail::buffer<char> {
      char data[10];
      test_buffer() : fmt::detail::buffer<char>(data, 0, 10) {}
@@ -461,13 +454,13 @@ TEST(arg_test, custom_arg) {
  auto test = test_struct();
  using visitor =
      mock_visitor<fmt::basic_format_arg<fmt::format_context>::handle>;
-  testing::StrictMock<visitor> v;
+  auto&& v = testing::StrictMock<visitor>();
  EXPECT_CALL(v, visit(_)).WillOnce(Invoke(check_custom()));
  fmt::visit_format_arg(v, fmt::detail::make_arg<fmt::format_context>(test));
 }

 TEST(arg_test, visit_invalid_arg) {
-  testing::StrictMock<mock_visitor<fmt::monostate>> visitor;
+  auto&& visitor = testing::StrictMock<mock_visitor<fmt::monostate>>();
  EXPECT_CALL(visitor, visit(_));
  auto arg = fmt::basic_format_arg<fmt::format_context>();
  fmt::visit_format_arg(visitor, arg);
@@ -475,185 +468,78 @@ TEST(arg_test, visit_invalid_arg) {

 #if FMT_USE_CONSTEXPR

-enum class arg_id_result { none, empty, index, name, error };
+enum class arg_id_result { none, empty, index, name };
 struct test_arg_id_handler {
  arg_id_result res = arg_id_result::none;
  int index = 0;
  string_view name;

-  constexpr void operator()() { res = arg_id_result::empty; }
+  constexpr void on_auto() { res = arg_id_result::empty; }

-  constexpr void operator()(int i) {
+  constexpr void on_index(int i) {
    res = arg_id_result::index;
    index = i;
  }

-  constexpr void operator()(string_view n) {
+  constexpr void on_name(string_view n) {
    res = arg_id_result::name;
    name = n;
  }
-
-  constexpr void on_error(const char*) { res = arg_id_result::error; }
 };

 template <size_t N>
 constexpr test_arg_id_handler parse_arg_id(const char (&s)[N]) {
-  test_arg_id_handler h;
+  auto h = test_arg_id_handler();
  fmt::detail::parse_arg_id(s, s + N, h);
  return h;
 }

-TEST(format_test, constexpr_parse_arg_id) {
+TEST(core_test, constexpr_parse_arg_id) {
  static_assert(parse_arg_id(":").res == arg_id_result::empty, "");
  static_assert(parse_arg_id("}").res == arg_id_result::empty, "");
  static_assert(parse_arg_id("42:").res == arg_id_result::index, "");
  static_assert(parse_arg_id("42:").index == 42, "");
  static_assert(parse_arg_id("foo:").res == arg_id_result::name, "");
  static_assert(parse_arg_id("foo:").name.size() == 3, "");
-  static_assert(parse_arg_id("!").res == arg_id_result::error, "");
 }

-struct test_format_specs_handler {
-  enum result { none, hash, zero, loc, error };
-  result res = none;
-
-  fmt::align_t alignment = fmt::align::none;
-  fmt::sign_t sign = fmt::sign::none;
-  char fill = 0;
-  int width = 0;
-  fmt::detail::arg_ref<char> width_ref;
-  int precision = 0;
-  fmt::detail::arg_ref<char> precision_ref;
-  fmt::presentation_type type = fmt::presentation_type::none;
-
-  // Workaround for MSVC2017 bug that results in "expression did not evaluate
-  // to a constant" with compiler-generated copy ctor.
-  constexpr test_format_specs_handler() {}
-  constexpr test_format_specs_handler(const test_format_specs_handler& other) =
-      default;
-
-  constexpr void on_align(fmt::align_t a) { alignment = a; }
-  constexpr void on_fill(fmt::string_view f) { fill = f[0]; }
-  constexpr void on_sign(fmt::sign_t s) { sign = s; }
-  constexpr void on_hash() { res = hash; }
-  constexpr void on_zero() { res = zero; }
-  constexpr void on_localized() { res = loc; }
-
-  constexpr void on_width(int w) { width = w; }
-  constexpr void on_dynamic_width(fmt::detail::auto_id) {}
-  constexpr void on_dynamic_width(int index) { width_ref = index; }
-  constexpr void on_dynamic_width(string_view) {}
-
-  constexpr void on_precision(int p) { precision = p; }
-  constexpr void on_dynamic_precision(fmt::detail::auto_id) {}
-  constexpr void on_dynamic_precision(int index) { precision_ref = index; }
-  constexpr void on_dynamic_precision(string_view) {}
-
-  constexpr void end_precision() {}
-  constexpr void on_type(fmt::presentation_type t) { type = t; }
-  constexpr void on_error(const char*) { res = error; }
-};
-
-template <size_t N>
-constexpr test_format_specs_handler parse_test_specs(const char (&s)[N]) {
-  auto h = test_format_specs_handler();
-  fmt::detail::parse_format_specs(s, s + N - 1, h);
-  return h;
+template <size_t N> constexpr auto parse_test_specs(const char (&s)[N]) {
+  auto ctx = fmt::detail::compile_parse_context<char>(fmt::string_view(s, N),
+                                                      43, nullptr);
+  auto specs = fmt::detail::dynamic_format_specs<>();
+  fmt::detail::parse_format_specs(s, s + N - 1, specs, ctx,
+                                  fmt::detail::type::float_type);
+  return specs;
 }

 TEST(core_test, constexpr_parse_format_specs) {
-  using handler = test_format_specs_handler;
-  static_assert(parse_test_specs("<").alignment == fmt::align::left, "");
-  static_assert(parse_test_specs("*^").fill == '*', "");
+  static_assert(parse_test_specs("<").align == fmt::align::left, "");
+  static_assert(parse_test_specs("*^").fill[0] == '*', "");
  static_assert(parse_test_specs("+").sign == fmt::sign::plus, "");
  static_assert(parse_test_specs("-").sign == fmt::sign::minus, "");
  static_assert(parse_test_specs(" ").sign == fmt::sign::space, "");
-  static_assert(parse_test_specs("#").res == handler::hash, "");
-  static_assert(parse_test_specs("0").res == handler::zero, "");
-  static_assert(parse_test_specs("L").res == handler::loc, "");
+  static_assert(parse_test_specs("#").alt, "");
+  static_assert(parse_test_specs("0").align == fmt::align::numeric, "");
+  static_assert(parse_test_specs("L").localized, "");
  static_assert(parse_test_specs("42").width == 42, "");
  static_assert(parse_test_specs("{42}").width_ref.val.index == 42, "");
  static_assert(parse_test_specs(".42").precision == 42, "");
  static_assert(parse_test_specs(".{42}").precision_ref.val.index == 42, "");
-  static_assert(parse_test_specs("d").type == fmt::presentation_type::dec, "");
-  static_assert(parse_test_specs("{<").res == handler::error, "");
-}
-
-struct test_parse_context {
-  using char_type = char;
-
-  constexpr int next_arg_id() { return 11; }
-  template <typename Id> FMT_CONSTEXPR void check_arg_id(Id) {}
-
-  constexpr const char* begin() { return nullptr; }
-  constexpr const char* end() { return nullptr; }
-
-  void on_error(const char*) {}
-};
-
-template <size_t N>
-constexpr fmt::detail::dynamic_format_specs<char> parse_dynamic_specs(
-    const char (&s)[N]) {
-  auto specs = fmt::detail::dynamic_format_specs<char>();
-  auto ctx = test_parse_context();
-  auto h = fmt::detail::dynamic_specs_handler<test_parse_context>(specs, ctx);
-  parse_format_specs(s, s + N - 1, h);
-  return specs;
-}
-
-TEST(format_test, constexpr_dynamic_specs_handler) {
-  static_assert(parse_dynamic_specs("<").align == fmt::align::left, "");
-  static_assert(parse_dynamic_specs("*^").fill[0] == '*', "");
-  static_assert(parse_dynamic_specs("+").sign == fmt::sign::plus, "");
-  static_assert(parse_dynamic_specs("-").sign == fmt::sign::minus, "");
-  static_assert(parse_dynamic_specs(" ").sign == fmt::sign::space, "");
-  static_assert(parse_dynamic_specs("#").alt, "");
-  static_assert(parse_dynamic_specs("0").align == fmt::align::numeric, "");
-  static_assert(parse_dynamic_specs("42").width == 42, "");
-  static_assert(parse_dynamic_specs("{}").width_ref.val.index == 11, "");
-  static_assert(parse_dynamic_specs("{42}").width_ref.val.index == 42, "");
-  static_assert(parse_dynamic_specs(".42").precision == 42, "");
-  static_assert(parse_dynamic_specs(".{}").precision_ref.val.index == 11, "");
-  static_assert(parse_dynamic_specs(".{42}").precision_ref.val.index == 42, "");
-  static_assert(parse_dynamic_specs("d").type == fmt::presentation_type::dec,
-                "");
-}
-
-template <size_t N>
-constexpr test_format_specs_handler check_specs(const char (&s)[N]) {
-  fmt::detail::specs_checker<test_format_specs_handler> checker(
-      test_format_specs_handler(), fmt::detail::type::double_type);
-  parse_format_specs(s, s + N - 1, checker);
-  return checker;
-}
-
-TEST(format_test, constexpr_specs_checker) {
-  using handler = test_format_specs_handler;
-  static_assert(check_specs("<").alignment == fmt::align::left, "");
-  static_assert(check_specs("*^").fill == '*', "");
-  static_assert(check_specs("+").sign == fmt::sign::plus, "");
-  static_assert(check_specs("-").sign == fmt::sign::minus, "");
-  static_assert(check_specs(" ").sign == fmt::sign::space, "");
-  static_assert(check_specs("#").res == handler::hash, "");
-  static_assert(check_specs("0").res == handler::zero, "");
-  static_assert(check_specs("42").width == 42, "");
-  static_assert(check_specs("{42}").width_ref.val.index == 42, "");
-  static_assert(check_specs(".42").precision == 42, "");
-  static_assert(check_specs(".{42}").precision_ref.val.index == 42, "");
-  static_assert(check_specs("d").type == fmt::presentation_type::dec, "");
-  static_assert(check_specs("{<").res == handler::error, "");
+  static_assert(
+      parse_test_specs("f").type == fmt::presentation_type::fixed_lower, "");
 }

 struct test_format_string_handler {
  constexpr void on_text(const char*, const char*) {}

-  constexpr int on_arg_id() { return 0; }
+  constexpr auto on_arg_id() -> int { return 0; }

-  template <typename T> constexpr int on_arg_id(T) { return 0; }
+  template <typename T> constexpr auto on_arg_id(T) -> int { return 0; }

  constexpr void on_replacement_field(int, const char*) {}

-  constexpr const char* on_format_specs(int, const char* begin, const char*) {
+  constexpr auto on_format_specs(int, const char* begin, const char*) -> const
+      char* {
    return begin;
  }

@@ -668,7 +554,7 @@ template <size_t N> constexpr bool parse_string(const char (&s)[N]) {
  return !h.error;
 }

-TEST(format_test, constexpr_parse_format_string) {
+TEST(core_test, constexpr_parse_format_string) {
  static_assert(parse_string("foo"), "");
  static_assert(!parse_string("}"), "");
  static_assert(parse_string("{}"), "");
@@ -687,19 +573,20 @@ struct disabled_formatter_convertible {

 FMT_BEGIN_NAMESPACE
 template <> struct formatter<enabled_formatter> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }
-  auto format(enabled_formatter, format_context& ctx) -> decltype(ctx.out()) {
+  auto format(enabled_formatter, format_context& ctx) const
+      -> decltype(ctx.out()) {
    return ctx.out();
  }
 };

 template <> struct formatter<enabled_ptr_formatter*> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }
-  auto format(enabled_ptr_formatter*, format_context& ctx)
+  auto format(enabled_ptr_formatter*, format_context& ctx) const
      -> decltype(ctx.out()) {
    return ctx.out();
  }
@@ -720,7 +607,7 @@ struct nonconst_formattable {};

 FMT_BEGIN_NAMESPACE
 template <> struct formatter<const_formattable> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }

@@ -732,7 +619,7 @@ template <> struct formatter<const_formattable> {
 };

 template <> struct formatter<nonconst_formattable> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }

@@ -754,7 +641,7 @@ struct convertible_to_pointer_formattable {

 FMT_BEGIN_NAMESPACE
 template <> struct formatter<convertible_to_pointer_formattable> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }

@@ -768,29 +655,17 @@ FMT_END_NAMESPACE

 enum class unformattable_scoped_enum {};

-namespace test {
-enum class formattable_scoped_enum {};
-auto format_as(formattable_scoped_enum) -> int { return 42; }
-
-struct convertible_to_enum {
-  operator formattable_scoped_enum() const { return {}; }
-};
-}  // namespace test
-
 TEST(core_test, is_formattable) {
-#if 0
-  // This should be enabled once corresponding map overloads are gone.
-  static_assert(fmt::is_formattable<signed char*>::value, "");
-  static_assert(fmt::is_formattable<unsigned char*>::value, "");
-  static_assert(fmt::is_formattable<const signed char*>::value, "");
-  static_assert(fmt::is_formattable<const unsigned char*>::value, "");
-#endif
  static_assert(!fmt::is_formattable<wchar_t>::value, "");
 #ifdef __cpp_char8_t
  static_assert(!fmt::is_formattable<char8_t>::value, "");
 #endif
  static_assert(!fmt::is_formattable<char16_t>::value, "");
  static_assert(!fmt::is_formattable<char32_t>::value, "");
+  static_assert(!fmt::is_formattable<signed char*>::value, "");
+  static_assert(!fmt::is_formattable<unsigned char*>::value, "");
+  static_assert(!fmt::is_formattable<const signed char*>::value, "");
+  static_assert(!fmt::is_formattable<const unsigned char*>::value, "");
  static_assert(!fmt::is_formattable<const wchar_t*>::value, "");
  static_assert(!fmt::is_formattable<const wchar_t[3]>::value, "");
  static_assert(!fmt::is_formattable<fmt::basic_string_view<wchar_t>>::value,
@@ -798,7 +673,8 @@ TEST(core_test, is_formattable) {
  static_assert(fmt::is_formattable<enabled_formatter>::value, "");
  static_assert(!fmt::is_formattable<enabled_ptr_formatter*>::value, "");
  static_assert(!fmt::is_formattable<disabled_formatter>::value, "");
-  static_assert(fmt::is_formattable<disabled_formatter_convertible>::value, "");
+  static_assert(!fmt::is_formattable<disabled_formatter_convertible>::value,
+                "");

  static_assert(fmt::is_formattable<const_formattable&>::value, "");
  static_assert(fmt::is_formattable<const const_formattable&>::value, "");
@@ -818,45 +694,47 @@ TEST(core_test, is_formattable) {
  static_assert(!fmt::is_formattable<int(s::*)>::value, "");
  static_assert(!fmt::is_formattable<int (s::*)()>::value, "");
  static_assert(!fmt::is_formattable<unformattable_scoped_enum>::value, "");
-  static_assert(fmt::is_formattable<test::formattable_scoped_enum>::value, "");
-  static_assert(!fmt::is_formattable<test::convertible_to_enum>::value, "");
+  static_assert(!fmt::is_formattable<unformattable_scoped_enum>::value, "");
 }

 TEST(core_test, format) { EXPECT_EQ(fmt::format("{}", 42), "42"); }

 TEST(core_test, format_to) {
-  std::string s;
+  auto s = std::string();
  fmt::format_to(std::back_inserter(s), "{}", 42);
  EXPECT_EQ(s, "42");
 }

-TEST(core_test, format_as) {
-  EXPECT_EQ(fmt::format("{}", test::formattable_scoped_enum()), "42");
+#ifdef __cpp_lib_byte
+TEST(core_test, format_byte) {
+  EXPECT_EQ(fmt::format("{}", std::byte(42)), "42");
 }
+#endif

 struct convertible_to_int {
  operator int() const { return 42; }
 };

-struct convertible_to_c_string {
+struct convertible_to_cstring {
  operator const char*() const { return "foo"; }
 };

 FMT_BEGIN_NAMESPACE
 template <> struct formatter<convertible_to_int> {
-  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }
-  auto format(convertible_to_int, format_context& ctx) -> decltype(ctx.out()) {
+  auto format(convertible_to_int, format_context& ctx) const
+      -> decltype(ctx.out()) {
    return std::copy_n("foo", 3, ctx.out());
  }
 };

-template <> struct formatter<convertible_to_c_string> {
+template <> struct formatter<convertible_to_cstring> {
  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
    return ctx.begin();
  }
-  auto format(convertible_to_c_string, format_context& ctx)
+  auto format(convertible_to_cstring, format_context& ctx) const
      -> decltype(ctx.out()) {
    return std::copy_n("bar", 3, ctx.out());
  }
@@ -865,7 +743,7 @@ FMT_END_NAMESPACE

 TEST(core_test, formatter_overrides_implicit_conversion) {
  EXPECT_EQ(fmt::format("{}", convertible_to_int()), "foo");
-  EXPECT_EQ(fmt::format("{}", convertible_to_c_string()), "bar");
+  EXPECT_EQ(fmt::format("{}", convertible_to_cstring()), "bar");
 }

 // Test that check is not found by ADL.
@@ -874,27 +752,26 @@ TEST(core_test, adl_check) {
  EXPECT_EQ(fmt::format("{}", test_struct()), "test");
 }

-TEST(core_test, to_string_view_foreign_strings) {
-  using namespace test_ns;
-  EXPECT_EQ(to_string_view(test_string<char>("42")), "42");
-  fmt::detail::type type =
-      fmt::detail::mapped_type_constant<test_string<char>,
-                                        fmt::format_context>::value;
-  EXPECT_EQ(type, fmt::detail::type::string_type);
-}
-
-struct implicitly_convertible_to_string {
-  operator std::string() const { return "foo"; }
-};
-
 struct implicitly_convertible_to_string_view {
  operator fmt::string_view() const { return "foo"; }
 };

-TEST(core_test, format_implicitly_convertible_to_string_view) {
-  EXPECT_EQ("foo", fmt::format("{}", implicitly_convertible_to_string_view()));
+TEST(core_test, no_implicit_conversion_to_string_view) {
+  EXPECT_FALSE(
+      fmt::is_formattable<implicitly_convertible_to_string_view>::value);
 }

+#ifdef FMT_USE_STRING_VIEW
+struct implicitly_convertible_to_std_string_view {
+  operator std::string_view() const { return "foo"; }
+};
+
+TEST(core_test, no_implicit_conversion_to_std_string_view) {
+  EXPECT_FALSE(
+      fmt::is_formattable<implicitly_convertible_to_std_string_view>::value);
+}
+#endif
+
 // std::is_constructible is broken in MSVC until version 2015.
 #if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1900
 struct explicitly_convertible_to_string_view {
@@ -923,25 +800,6 @@ TEST(core_test, format_explicitly_convertible_to_std_string_view) {
 #  endif
 #endif

-struct convertible_to_long_long {
-  operator long long() const { return 1LL << 32; }
-};
-
-TEST(format_test, format_convertible_to_long_long) {
-  EXPECT_EQ("100000000", fmt::format("{:x}", convertible_to_long_long()));
-}
-
-struct disabled_rvalue_conversion {
-  operator const char*() const& { return "foo"; }
-  operator const char*() & { return "foo"; }
-  operator const char*() const&& = delete;
-  operator const char*() && = delete;
-};
-
-TEST(core_test, disabled_rvalue_conversion) {
-  EXPECT_EQ("foo", fmt::format("{}", disabled_rvalue_conversion()));
-}
-
 namespace adl_test {
 template <typename... T> void make_format_args(const T&...) = delete;

@@ -973,3 +831,28 @@ TEST(core_test, has_const_formatter) {
 TEST(core_test, format_nonconst) {
  EXPECT_EQ(fmt::format("{}", nonconst_formattable()), "test");
 }
+
+struct its_a_trap {
+  template <typename T> operator T() const {
+    auto v = T();
+    v.x = 42;
+    return v;
+  }
+};
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<its_a_trap> {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  auto format(its_a_trap, format_context& ctx) const -> decltype(ctx.out()) {
+    auto s = string_view("42");
+    return std::copy(s.begin(), s.end(), ctx.out());
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(core_test, trappy_conversion) {
+  EXPECT_EQ(fmt::format("{}", its_a_trap()), "42");
+}
@@ -8,12 +8,14 @@
 #include <iterator>
 #include <vector>

+#define I 42  // simulate https://en.cppreference.com/w/c/numeric/complex/I
 #include "fmt/chrono.h"
 #include "fmt/color.h"
 #include "fmt/format.h"
 #include "fmt/ostream.h"
 #include "fmt/ranges.h"
 #include "fmt/xchar.h"
+#undef I

 // Exercise the API to verify that everything we expect to can compile.
 void test_format_api() {
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1...3.18)
+cmake_minimum_required(VERSION 3.8...3.25)

 project(fmt-test)

@@ -196,43 +196,6 @@ TEST(fp_test, multiply) {
  EXPECT_EQ(v.e, 4 + 8 + 64);
 }

-TEST(fp_test, get_cached_power) {
-  using limits = std::numeric_limits<double>;
-  for (auto exp = limits::min_exponent; exp <= limits::max_exponent; ++exp) {
-    int dec_exp = 0;
-    auto power = fmt::detail::get_cached_power(exp, dec_exp);
-    bigint exact, cache(power.f);
-    if (dec_exp >= 0) {
-      exact.assign_pow10(dec_exp);
-      if (power.e <= 0)
-        exact <<= -power.e;
-      else
-        cache <<= power.e;
-      exact.align(cache);
-      cache.align(exact);
-      auto exact_str = fmt::to_string(exact);
-      auto cache_str = fmt::to_string(cache);
-      EXPECT_EQ(exact_str.size(), cache_str.size());
-      EXPECT_EQ(exact_str.substr(0, 15), cache_str.substr(0, 15));
-      int diff = cache_str[15] - exact_str[15];
-      if (diff == 1)
-        EXPECT_GT(exact_str[16], '8');
-      else
-        EXPECT_EQ(diff, 0);
-    } else {
-      cache.assign_pow10(-dec_exp);
-      cache *= power.f + 1;  // Inexact check.
-      exact = 1;
-      exact <<= -power.e;
-      exact.align(cache);
-      auto exact_str = fmt::to_string(exact);
-      auto cache_str = fmt::to_string(cache);
-      EXPECT_EQ(exact_str.size(), cache_str.size());
-      EXPECT_EQ(exact_str.substr(0, 16), cache_str.substr(0, 16));
-    }
-  }
-}
-
 TEST(fp_test, dragonbox_max_k) {
  using fmt::detail::dragonbox::floor_log10_pow2;
  using float_info = fmt::detail::dragonbox::float_info<float>;
@@ -242,66 +205,18 @@ TEST(fp_test, dragonbox_max_k) {
          floor_log10_pow2(std::numeric_limits<float>::min_exponent -
                           fmt::detail::num_significand_bits<float>() - 1));
  using double_info = fmt::detail::dragonbox::float_info<double>;
-  EXPECT_EQ(
-      fmt::detail::const_check(double_info::max_k),
-      double_info::kappa -
-          floor_log10_pow2(std::numeric_limits<double>::min_exponent -
-                           fmt::detail::num_significand_bits<double>() - 1));
-}
-
-TEST(fp_test, get_round_direction) {
-  using fmt::detail::get_round_direction;
-  using fmt::detail::round_direction;
-  EXPECT_EQ(get_round_direction(100, 50, 0), round_direction::down);
-  EXPECT_EQ(get_round_direction(100, 51, 0), round_direction::up);
-  EXPECT_EQ(get_round_direction(100, 40, 10), round_direction::down);
-  EXPECT_EQ(get_round_direction(100, 60, 10), round_direction::up);
-  for (size_t i = 41; i < 60; ++i)
-    EXPECT_EQ(get_round_direction(100, i, 10), round_direction::unknown);
-  uint64_t max = max_value<uint64_t>();
-  EXPECT_THROW(get_round_direction(100, 100, 0), assertion_failure);
-  EXPECT_THROW(get_round_direction(100, 0, 100), assertion_failure);
-  EXPECT_THROW(get_round_direction(100, 0, 50), assertion_failure);
-  // Check that remainder + error doesn't overflow.
-  EXPECT_EQ(get_round_direction(max, max - 1, 2), round_direction::up);
-  // Check that 2 * (remainder + error) doesn't overflow.
-  EXPECT_EQ(get_round_direction(max, max / 2 + 1, max / 2),
-            round_direction::unknown);
-  // Check that remainder - error doesn't overflow.
-  EXPECT_EQ(get_round_direction(100, 40, 41), round_direction::unknown);
-  // Check that 2 * (remainder - error) doesn't overflow.
-  EXPECT_EQ(get_round_direction(max, max - 1, 1), round_direction::up);
-}
-
-TEST(fp_test, fixed_handler) {
-  struct handler : fmt::detail::gen_digits_handler {
-    char buffer[10];
-    handler(int prec = 0) : fmt::detail::gen_digits_handler() {
-      buf = buffer;
-      precision = prec;
-    }
-  };
-  handler().on_digit('0', 100, 99, 0, false);
-  EXPECT_THROW(handler().on_digit('0', 100, 100, 0, false), assertion_failure);
-  namespace digits = fmt::detail::digits;
-  EXPECT_EQ(handler(1).on_digit('0', 100, 10, 10, false), digits::error);
-  // Check that divisor - error doesn't overflow.
-  EXPECT_EQ(handler(1).on_digit('0', 100, 10, 101, false), digits::error);
-  // Check that 2 * error doesn't overflow.
-  uint64_t max = max_value<uint64_t>();
-  EXPECT_EQ(handler(1).on_digit('0', max, 10, max - 1, false), digits::error);
-}
-
-TEST(fp_test, grisu_format_compiles_with_on_ieee_double) {
-  auto buf = fmt::memory_buffer();
-  format_float(0.42, -1, fmt::detail::float_specs(), buf);
+  EXPECT_EQ(fmt::detail::const_check(double_info::max_k),
+            double_info::kappa -
+                floor_log10_pow2(
+                    std::numeric_limits<double>::min_exponent -
+                    2 * fmt::detail::num_significand_bits<double>() - 1));
 }

 TEST(format_impl_test, format_error_code) {
  std::string msg = "error 42", sep = ": ";
  {
    auto buffer = fmt::memory_buffer();
-    format_to(fmt::appender(buffer), "garbage");
+    fmt::format_to(fmt::appender(buffer), "garbage");
    fmt::detail::format_error_code(buffer, 42, "test");
    EXPECT_EQ(to_string(buffer), "test: " + msg);
  }
@@ -331,13 +246,6 @@ TEST(format_impl_test, format_error_code) {
  }
 }

-TEST(format_impl_test, compute_width) {
-  EXPECT_EQ(4,
-            fmt::detail::compute_width(
-                fmt::basic_string_view<fmt::detail::char8_type>(
-                    reinterpret_cast<const fmt::detail::char8_type*>("ёжик"))));
-}
-
 // Tests fmt::detail::count_digits for integer type Int.
 template <typename Int> void test_count_digits() {
  for (Int i = 0; i < 10; ++i) EXPECT_EQ(1u, fmt::detail::count_digits(i));
@@ -353,6 +261,16 @@ TEST(format_impl_test, count_digits) {
  test_count_digits<uint64_t>();
 }

+TEST(format_impl_test, countl_zero) {
+  constexpr auto num_bits = fmt::detail::num_bits<uint32_t>();
+  uint32_t n = 1u;
+  for (int i = 1; i < num_bits - 1; i++) {
+    n <<= 1;
+    EXPECT_EQ(fmt::detail::countl_zero(n - 1), num_bits - i);
+    EXPECT_EQ(fmt::detail::countl_zero(n), num_bits - i - 1);
+  }
+}
+
 #if FMT_USE_FLOAT128
 TEST(format_impl_test, write_float128) {
  auto s = std::string();
@@ -372,10 +290,22 @@ struct double_double {
  auto operator-() const -> double_double { return double_double(-a, -b); }
 };

+auto format_as(double_double d) -> double { return d; }
+
 bool operator>=(const double_double& lhs, const double_double& rhs) {
  return lhs.a + lhs.b >= rhs.a + rhs.b;
 }

+struct slow_float {
+  float value;
+
+  explicit constexpr slow_float(float val = 0) : value(val) {}
+  operator float() const { return value; }
+  auto operator-() const -> slow_float { return slow_float(-value); }
+};
+
+auto format_as(slow_float f) -> float { return f; }
+
 namespace std {
 template <> struct is_floating_point<double_double> : std::true_type {};
 template <> struct numeric_limits<double_double> {
@@ -383,17 +313,38 @@ template <> struct numeric_limits<double_double> {
  static constexpr bool is_iec559 = true;
  static constexpr int digits = 106;
 };
+
+template <> struct is_floating_point<slow_float> : std::true_type {};
+template <> struct numeric_limits<slow_float> : numeric_limits<float> {};
 }  // namespace std

+FMT_BEGIN_NAMESPACE
+namespace detail {
+template <> struct is_fast_float<slow_float> : std::false_type {};
+namespace dragonbox {
+template <> struct float_info<slow_float> {
+  using carrier_uint = uint32_t;
+  static const int exponent_bits = 8;
+};
+}  // namespace dragonbox
+}  // namespace detail
+FMT_END_NAMESPACE
+
 TEST(format_impl_test, write_double_double) {
  auto s = std::string();
  fmt::detail::write<char>(std::back_inserter(s), double_double(42), {});
-#ifndef _MSC_VER  // MSVC has an issue with specializing is_floating_point.
-  EXPECT_EQ(s, "42");
-#endif
+  // Specializing is_floating_point is broken in MSVC.
+  if (!FMT_MSC_VERSION) EXPECT_EQ(s, "42");
 }

-#ifdef _WIN32
+TEST(format_impl_test, write_dragon_even) {
+  auto s = std::string();
+  fmt::detail::write<char>(std::back_inserter(s), slow_float(33554450.0f), {});
+  // Specializing is_floating_point is broken in MSVC.
+  if (!FMT_MSC_VERSION) EXPECT_EQ(s, "33554450");
+}
+
+#if defined(_WIN32) && !defined(FMT_WINDOWS_NO_WCHAR)
 #  include <windows.h>

 TEST(format_impl_test, write_console_signature) {
@@ -401,3 +352,125 @@ TEST(format_impl_test, write_console_signature) {
  (void)p;
 }
 #endif
+
+// A public domain branchless UTF-8 decoder by Christopher Wellons:
+// https://github.com/skeeto/branchless-utf8
+constexpr bool unicode_is_surrogate(uint32_t c) {
+  return c >= 0xD800U && c <= 0xDFFFU;
+}
+
+FMT_CONSTEXPR char* utf8_encode(char* s, uint32_t c) {
+  if (c >= (1UL << 16)) {
+    s[0] = static_cast<char>(0xf0 | (c >> 18));
+    s[1] = static_cast<char>(0x80 | ((c >> 12) & 0x3f));
+    s[2] = static_cast<char>(0x80 | ((c >> 6) & 0x3f));
+    s[3] = static_cast<char>(0x80 | ((c >> 0) & 0x3f));
+    return s + 4;
+  } else if (c >= (1UL << 11)) {
+    s[0] = static_cast<char>(0xe0 | (c >> 12));
+    s[1] = static_cast<char>(0x80 | ((c >> 6) & 0x3f));
+    s[2] = static_cast<char>(0x80 | ((c >> 0) & 0x3f));
+    return s + 3;
+  } else if (c >= (1UL << 7)) {
+    s[0] = static_cast<char>(0xc0 | (c >> 6));
+    s[1] = static_cast<char>(0x80 | ((c >> 0) & 0x3f));
+    return s + 2;
+  } else {
+    s[0] = static_cast<char>(c);
+    return s + 1;
+  }
+}
+
+// Make sure it can decode every character
+TEST(format_impl_test, utf8_decode_decode_all) {
+  for (uint32_t i = 0; i < 0x10ffff; i++) {
+    if (!unicode_is_surrogate(i)) {
+      int e;
+      uint32_t c;
+      char buf[8] = {0};
+      char* end = utf8_encode(buf, i);
+      const char* res = fmt::detail::utf8_decode(buf, &c, &e);
+      EXPECT_EQ(end, res);
+      EXPECT_EQ(c, i);
+      EXPECT_EQ(e, 0);
+    }
+  }
+}
+
+// Reject everything outside of U+0000..U+10FFFF
+TEST(format_impl_test, utf8_decode_out_of_range) {
+  for (uint32_t i = 0x110000; i < 0x1fffff; i++) {
+    int e;
+    uint32_t c;
+    char buf[8] = {0};
+    utf8_encode(buf, i);
+    const char* end = fmt::detail::utf8_decode(buf, &c, &e);
+    EXPECT_NE(e, 0);
+    EXPECT_EQ(end - buf, 4);
+  }
+}
+
+// Does it reject all surrogate halves?
+TEST(format_impl_test, utf8_decode_surrogate_halves) {
+  for (uint32_t i = 0xd800; i <= 0xdfff; i++) {
+    int e;
+    uint32_t c;
+    char buf[8] = {0};
+    utf8_encode(buf, i);
+    fmt::detail::utf8_decode(buf, &c, &e);
+    EXPECT_NE(e, 0);
+  }
+}
+
+// How about non-canonical encodings?
+TEST(format_impl_test, utf8_decode_non_canonical_encodings) {
+  int e;
+  uint32_t c;
+  const char* end;
+
+  char buf2[8] = {char(0xc0), char(0xA4)};
+  end = fmt::detail::utf8_decode(buf2, &c, &e);
+  EXPECT_NE(e, 0);           // non-canonical len 2
+  EXPECT_EQ(end, buf2 + 2);  // non-canonical recover 2
+
+  char buf3[8] = {char(0xe0), char(0x80), char(0xA4)};
+  end = fmt::detail::utf8_decode(buf3, &c, &e);
+  EXPECT_NE(e, 0);           // non-canonical len 3
+  EXPECT_EQ(end, buf3 + 3);  // non-canonical recover 3
+
+  char buf4[8] = {char(0xf0), char(0x80), char(0x80), char(0xA4)};
+  end = fmt::detail::utf8_decode(buf4, &c, &e);
+  EXPECT_NE(e, 0);           // non-canonical encoding len 4
+  EXPECT_EQ(end, buf4 + 4);  // non-canonical recover 4
+}
+
+// Let's try some bogus byte sequences
+TEST(format_impl_test, utf8_decode_bogus_byte_sequences) {
+  int e;
+  uint32_t c;
+
+  // Invalid first byte
+  char buf0[4] = {char(0xff)};
+  auto len = fmt::detail::utf8_decode(buf0, &c, &e) - buf0;
+  EXPECT_NE(e, 0);    // "bogus [ff] 0x%02x U+%04lx", e, (unsigned long)c);
+  EXPECT_EQ(len, 1);  // "bogus [ff] recovery %d", len);
+
+  // Invalid first byte
+  char buf1[4] = {char(0x80)};
+  len = fmt::detail::utf8_decode(buf1, &c, &e) - buf1;
+  EXPECT_NE(e, 0);    // "bogus [80] 0x%02x U+%04lx", e, (unsigned long)c);
+  EXPECT_EQ(len, 1);  // "bogus [80] recovery %d", len);
+
+  // Looks like a two-byte sequence but second byte is wrong
+  char buf2[4] = {char(0xc0), char(0x0a)};
+  len = fmt::detail::utf8_decode(buf2, &c, &e) - buf2;
+  EXPECT_NE(e, 0);    // "bogus [c0 0a] 0x%02x U+%04lx", e, (unsigned long)c
+  EXPECT_EQ(len, 2);  // "bogus [c0 0a] recovery %d", len);
+}
+
+TEST(format_impl_test, to_utf8) {
+  auto s = std::string("ёжик");
+  auto u = fmt::detail::to_utf8<wchar_t>(L"\x0451\x0436\x0438\x043A");
+  EXPECT_EQ(s, u.str());
+  EXPECT_EQ(s.size(), u.size());
+}
@@ -22,7 +22,7 @@ function(add_fuzzer source)
  if (FMT_FUZZ_LDFLAGS)
    target_link_libraries(${name} PRIVATE ${FMT_FUZZ_LDFLAGS})
  endif ()
-  target_compile_features(${name} PRIVATE cxx_generic_lambdas)
+  target_compile_features(${name} PRIVATE cxx_std_14)
 endfunction()

 foreach (source chrono-duration.cc chrono-timepoint.cc float.cc named-arg.cc one-arg.cc two-args.cc)
@@ -201,6 +201,7 @@ TEST(gtest_extra_test, expect_write_streaming) {
 // EXPECT_THROW_MSG macro.
 TEST(gtest_extra_test, expect_throw_no_unreachable_code_warning) {
  int n = 0;
+  (void)n;
  using std::runtime_error;
  EXPECT_THROW_MSG(throw runtime_error(""), runtime_error, "");
  EXPECT_NONFATAL_FAILURE(EXPECT_THROW_MSG(n++, runtime_error, ""), "");
@@ -213,6 +214,7 @@ TEST(gtest_extra_test, expect_throw_no_unreachable_code_warning) {
 // EXPECT_SYSTEM_ERROR macro.
 TEST(gtest_extra_test, expect_system_error_no_unreachable_code_warning) {
  int n = 0;
+  (void)n;
  EXPECT_SYSTEM_ERROR(throw fmt::system_error(EDOM, "test"), EDOM, "test");
  EXPECT_NONFATAL_FAILURE(EXPECT_SYSTEM_ERROR(n++, EDOM, ""), "");
  EXPECT_NONFATAL_FAILURE(EXPECT_SYSTEM_ERROR(throw 1, EDOM, ""), "");
@@ -352,7 +354,7 @@ TEST(output_redirect_test, dup_error_in_ctor) {
  FMT_POSIX(close(fd));
  std::unique_ptr<output_redirect> redir{nullptr};
  EXPECT_SYSTEM_ERROR_NOASSERT(
-      redir.reset(new output_redirect(f.get())), EBADF,
+      redir.reset(new output_redirect(f.get(), false)), EBADF,
      fmt::format("cannot duplicate file descriptor {}", fd));
  copy.dup2(fd);  // "undo" close or dtor will fail
 }
@@ -11,8 +11,8 @@

 using fmt::file;

-output_redirect::output_redirect(FILE* f) : file_(f) {
-  flush();
+output_redirect::output_redirect(FILE* f, bool flush) : file_(f) {
+  if (flush) this->flush();
  int fd = FMT_POSIX(fileno(f));
  // Create a file object referring to the original file.
  original_ = file::dup(fd);
@@ -12,12 +12,7 @@

 #include <string>

-#ifdef FMT_MODULE_TEST
-import fmt;
-#else
-#  include "fmt/os.h"
-#endif  // FMG_MODULE_TEST
-
+#include "fmt/os.h"
 #include "gmock/gmock.h"

 #define FMT_TEST_THROW_(statement, expected_exception, expected_message, fail) \
@@ -82,7 +77,7 @@ class output_redirect {
  void restore();

 public:
-  explicit output_redirect(FILE* file);
+  explicit output_redirect(FILE* file, bool flush = true);
  ~output_redirect() noexcept;

  output_redirect(const output_redirect&) = delete;
@@ -9,6 +9,7 @@ add_library(gtest STATIC
  gmock-gtest-all.cc gmock/gmock.h gtest/gtest.h gtest/gtest-spi.h)
 target_compile_definitions(gtest PUBLIC GTEST_HAS_STD_WSTRING=1)
 target_include_directories(gtest SYSTEM PUBLIC .)
+target_compile_features(gtest PUBLIC cxx_std_11)

 find_package(Threads)
 if (Threads_FOUND)
@@ -17,13 +18,6 @@ else ()
  target_compile_definitions(gtest PUBLIC GTEST_HAS_PTHREAD=0)
 endif ()

-# Workaround GTest bug https://github.com/google/googletest/issues/705.
-fmt_check_cxx_compiler_flag(
-  -fno-delete-null-pointer-checks HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
-if (HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
-  target_compile_options(gtest PUBLIC -fno-delete-null-pointer-checks)
-endif ()
-
 if (MSVC)
  # Disable MSVC warnings of _CRT_INSECURE_DEPRECATE functions.
  target_compile_definitions(gtest PRIVATE _CRT_SECURE_NO_WARNINGS)
@@ -1912,7 +1912,7 @@ void AssertHelper::operator=(const Message& message) const {
 namespace {

 // When TEST_P is found without a matching INSTANTIATE_TEST_SUITE_P
-// to creates test cases for it, a syntetic test case is
+// to creates test cases for it, a synthetic test case is
 // inserted to report ether an error or a log message.
 //
 // This configuration bit will likely be removed at some point.
@@ -2202,7 +2202,7 @@ bool UnitTestOptions::MatchesFilter(const std::string& name_str,

    // Check if this pattern matches name_str.
    if (PatternMatchesString(name_str, pattern, pattern_end)) {
-      return true;
+      break;
    }

    // Give up on this pattern. However, if we found a pattern separator (:),
@@ -13778,7 +13778,7 @@ UntypedActionResultHolderBase* UntypedFunctionMockerBase::UntypedInvokeWith(

  UntypedActionResultHolderBase* result = nullptr;

-  auto perform_action = [&] {
+  auto perform_action = [&, this] {
    return untyped_action == nullptr
               ? this->UntypedPerformDefaultAction(untyped_args, ss.str())
               : this->UntypedPerformAction(untyped_action, untyped_args);
@@ -20,8 +20,8 @@ template <typename T> class mock_allocator {
  mock_allocator() {}
  mock_allocator(const mock_allocator&) {}
  using value_type = T;
-  MOCK_METHOD1_T(allocate, T*(size_t n));
-  MOCK_METHOD2_T(deallocate, void(T* p, size_t n));
+  MOCK_METHOD(T*, allocate, (size_t));
+  MOCK_METHOD(void, deallocate, (T*, size_t));
 };

 template <typename Allocator> class allocator_ref {
@@ -15,8 +15,6 @@
 #  define FMT_HIDE_MODULE_BUGS
 #endif

-#define FMT_MODULE_TEST
-
 #include <bit>
 #include <chrono>
 #include <exception>
@@ -41,7 +39,6 @@
 #else
 #  define FMT_POSIX(call) call
 #endif
-#define FMT_OS_H_  // don't pull in os.h directly or indirectly

 import fmt;

@@ -53,13 +50,8 @@ static bool macro_leaked =
    false;
 #endif

-// Include sources to pick up functions and classes from the module rather than
-// from the non-modular library which is baked into the 'test-main' library.
-// This averts linker problems:
-// - strong ownership model: missing linker symbols
-// - weak ownership model: duplicate linker symbols
-#include "gtest-extra.cc"
-#include "util.cc"
+#define FMT_OS_H_  // don't pull in os.h, neither directly nor indirectly
+#include "gtest-extra.h"

 // an implicitly exported namespace must be visible [module.interface]/2.2
 TEST(module_test, namespace) {
@@ -75,9 +67,8 @@ bool oops_detail_namespace_is_visible;
 namespace fmt {
 bool namespace_detail_invisible() {
 #if defined(FMT_HIDE_MODULE_BUGS) && defined(_MSC_FULL_VER) && \
-    ((_MSC_VER == 1929 && _MSC_FULL_VER <= 192930136) ||       \
-     (_MSC_VER == 1930 && _MSC_FULL_VER <= 193030704))
-  // bug in msvc up to 16.11.5 / 17.0-pre5:
+    _MSC_FULL_VER <= 193700000
+  // bug in msvc up to at least 17.7:

  // the namespace is visible even when it is neither
  // implicitly nor explicitly exported
@@ -111,7 +102,7 @@ TEST(module_test, macros) {
 // but rather visibility of all client-facing overloads, reachability of
 // non-exported entities, name lookup and overload resolution within
 // template instantitions.
-// Excercise all exported entities of the API at least once.
+// Exercise all exported entities of the API at least once.
 // Instantiate as many code paths as possible.

 TEST(module_test, to_string) {
@@ -140,7 +131,7 @@ TEST(module_test, format_to) {
  EXPECT_EQ("42", std::string_view(buffer));

  fmt::memory_buffer mb;
-  fmt::format_to(mb, "{}", 42);
+  fmt::format_to(std::back_inserter(mb), "{}", 42);
  EXPECT_EQ("42", std::string_view(buffer));

  std::wstring w;
@@ -152,7 +143,7 @@ TEST(module_test, format_to) {
  EXPECT_EQ(L"42", std::wstring_view(wbuffer));

  fmt::wmemory_buffer wb;
-  fmt::format_to(wb, L"{}", 42);
+  fmt::format_to(std::back_inserter(wb), L"{}", 42);
  EXPECT_EQ(L"42", std::wstring_view(wbuffer));
 }

@@ -211,8 +202,8 @@ TEST(module_test, dynamic_format_args) {

 TEST(module_test, vformat) {
  EXPECT_EQ("42", fmt::vformat("{}", fmt::make_format_args(42)));
-  EXPECT_EQ(L"42", fmt::vformat(fmt::to_string_view(L"{}"),
-                                fmt::make_wformat_args(42)));
+  EXPECT_EQ(L"42",
+            fmt::vformat(fmt::wstring_view(L"{}"), fmt::make_wformat_args(42)));
 }

 TEST(module_test, vformat_to) {
@@ -245,9 +236,9 @@ TEST(module_test, vformat_to_n) {
  auto wstore = fmt::make_wformat_args(12345);
  std::wstring w;
  auto wresult = fmt::vformat_to_n(std::back_inserter(w), 1,
-                                   fmt::to_string_view(L"{}"), wstore);
+                                   fmt::wstring_view(L"{}"), wstore);
  wchar_t wbuffer[4] = {0};
-  fmt::vformat_to_n(wbuffer, 3, fmt::to_string_view(L"{:}"), wstore);
+  fmt::vformat_to_n(wbuffer, 3, fmt::wstring_view(L"{:}"), wstore);
 }

 std::string as_string(std::wstring_view text) {
@@ -258,22 +249,18 @@ std::string as_string(std::wstring_view text) {
 TEST(module_test, print) {
  EXPECT_WRITE(stdout, fmt::print("{}µ", 42), "42µ");
  EXPECT_WRITE(stderr, fmt::print(stderr, "{}µ", 4.2), "4.2µ");
-  if (false) {
-    EXPECT_WRITE(stdout, fmt::print(L"{}µ", 42), as_string(L"42µ"));
-    EXPECT_WRITE(stderr, fmt::print(stderr, L"{}µ", 4.2), as_string(L"4.2µ"));
-  }
+  EXPECT_WRITE(stdout, fmt::print(L"{}µ", 42), as_string(L"42µ"));
+  EXPECT_WRITE(stderr, fmt::print(stderr, L"{}µ", 4.2), as_string(L"4.2µ"));
 }

 TEST(module_test, vprint) {
  EXPECT_WRITE(stdout, fmt::vprint("{:}µ", fmt::make_format_args(42)), "42µ");
  EXPECT_WRITE(stderr, fmt::vprint(stderr, "{}", fmt::make_format_args(4.2)),
               "4.2");
-  if (false) {
-    EXPECT_WRITE(stdout, fmt::vprint(L"{:}µ", fmt::make_wformat_args(42)),
-                 as_string(L"42µ"));
-    EXPECT_WRITE(stderr, fmt::vprint(stderr, L"{}", fmt::make_wformat_args(42)),
-                 as_string(L"42"));
-  }
+  EXPECT_WRITE(stdout, fmt::vprint(L"{:}µ", fmt::make_wformat_args(42)),
+               as_string(L"42µ"));
+  EXPECT_WRITE(stderr, fmt::vprint(stderr, L"{}", fmt::make_wformat_args(42)),
+               as_string(L"42"));
 }

 TEST(module_test, named_args) {
@@ -284,9 +271,7 @@ TEST(module_test, named_args) {
 TEST(module_test, literals) {
  using namespace fmt::literals;
  EXPECT_EQ("42", fmt::format("{answer}", "answer"_a = 42));
-  EXPECT_EQ("42", "{}"_format(42));
  EXPECT_EQ(L"42", fmt::format(L"{answer}", L"answer"_a = 42));
-  EXPECT_EQ(L"42", L"{}"_format(42));
 }

 TEST(module_test, locale) {
@@ -320,7 +305,7 @@ TEST(module_test, string_view) {

 TEST(module_test, memory_buffer) {
  fmt::basic_memory_buffer<char, fmt::inline_buffer_size> buffer;
-  fmt::format_to(buffer, "{}", "42");
+  fmt::format_to(std::back_inserter(buffer), "{}", "42");
  EXPECT_EQ("42", to_string(buffer));
  fmt::memory_buffer nbuffer(std::move(buffer));
  EXPECT_EQ("42", to_string(nbuffer));
@@ -395,27 +380,20 @@ struct test_formatter : fmt::formatter<char> {
  bool check() { return true; }
 };

-struct test_dynamic_formatter : fmt::dynamic_formatter<> {
-  bool check() { return true; }
-};
-
-TEST(module_test, formatter) {
-  EXPECT_TRUE(test_formatter{}.check());
-  EXPECT_TRUE(test_dynamic_formatter{}.check());
-}
+TEST(module_test, formatter) { EXPECT_TRUE(test_formatter{}.check()); }

 TEST(module_test, join) {
  int arr[3] = {1, 2, 3};
  std::vector<double> vec{1.0, 2.0, 3.0};
  std::initializer_list<int> il{1, 2, 3};
-  auto sep = fmt::to_string_view(", ");
+  auto sep = fmt::string_view(", ");
  EXPECT_EQ("1, 2, 3", to_string(fmt::join(arr + 0, arr + 3, sep)));
  EXPECT_EQ("1, 2, 3", to_string(fmt::join(arr, sep)));
  EXPECT_EQ("1, 2, 3", to_string(fmt::join(vec.begin(), vec.end(), sep)));
  EXPECT_EQ("1, 2, 3", to_string(fmt::join(vec, sep)));
  EXPECT_EQ("1, 2, 3", to_string(fmt::join(il, sep)));

-  auto wsep = fmt::to_string_view(L", ");
+  auto wsep = fmt::wstring_view(L", ");
  EXPECT_EQ(L"1, 2, 3", fmt::format(L"{}", fmt::join(arr + 0, arr + 3, wsep)));
  EXPECT_EQ(L"1, 2, 3", fmt::format(L"{}", fmt::join(arr, wsep)));
  EXPECT_EQ(L"1, 2, 3", fmt::format(L"{}", fmt::join(il, wsep)));
@@ -426,7 +404,6 @@ TEST(module_test, time) {
  EXPECT_TRUE(fmt::localtime(time_now).tm_year > 120);
  EXPECT_TRUE(fmt::gmtime(time_now).tm_year > 120);
  auto chrono_now = std::chrono::system_clock::now();
-  EXPECT_TRUE(fmt::localtime(chrono_now).tm_year > 120);
  EXPECT_TRUE(fmt::gmtime(chrono_now).tm_year > 120);
 }

@@ -453,34 +430,16 @@ TEST(module_test, weekday) {
  EXPECT_EQ("Mon", fmt::format(std::locale::classic(), "{}", fmt::weekday(1)));
 }

-TEST(module_test, to_string_view) {
-  using fmt::to_string_view;
-  fmt::string_view nsv{to_string_view("42")};
-  EXPECT_EQ("42", nsv);
-  fmt::wstring_view wsv{to_string_view(L"42")};
-  EXPECT_EQ(L"42", wsv);
-}
-
 TEST(module_test, printf) {
  EXPECT_WRITE(stdout, fmt::printf("%f", 42.123456), "42.123456");
  EXPECT_WRITE(stdout, fmt::printf("%d", 42), "42");
-  if (false) {
-    EXPECT_WRITE(stdout, fmt::printf(L"%f", 42.123456),
-                 as_string(L"42.123456"));
-    EXPECT_WRITE(stdout, fmt::printf(L"%d", 42), as_string(L"42"));
-  }
+  EXPECT_WRITE(stdout, fmt::printf(L"%f", 42.123456), as_string(L"42.123456"));
+  EXPECT_WRITE(stdout, fmt::printf(L"%d", 42), as_string(L"42"));
 }

 TEST(module_test, fprintf) {
  EXPECT_WRITE(stderr, fmt::fprintf(stderr, "%d", 42), "42");
-  std::ostringstream os;
-  fmt::fprintf(os, "%s", "bla");
-  EXPECT_EQ("bla", os.str());
-
  EXPECT_WRITE(stderr, fmt::fprintf(stderr, L"%d", 42), as_string(L"42"));
-  std::wostringstream ws;
-  fmt::fprintf(ws, L"%s", L"bla");
-  EXPECT_EQ(L"bla", ws.str());
 }

 TEST(module_test, sprintf) {
@@ -490,25 +449,15 @@ TEST(module_test, sprintf) {

 TEST(module_test, vprintf) {
  EXPECT_WRITE(stdout, fmt::vprintf("%d", fmt::make_printf_args(42)), "42");
-  if (false) {
-    EXPECT_WRITE(stdout, fmt::vprintf(L"%d", fmt::make_wprintf_args(42)),
-                 as_string(L"42"));
-  }
+  EXPECT_WRITE(stdout, fmt::vprintf(L"%d", fmt::make_wprintf_args(42)),
+               as_string(L"42"));
 }

 TEST(module_test, vfprintf) {
  auto args = fmt::make_printf_args(42);
  EXPECT_WRITE(stderr, fmt::vfprintf(stderr, "%d", args), "42");
-  std::ostringstream os;
-  fmt::vfprintf(os, "%d", args);
-  EXPECT_EQ("42", os.str());
  auto wargs = fmt::make_wprintf_args(42);
-  if (false) {
-    EXPECT_WRITE(stderr, fmt::vfprintf(stderr, L"%d", wargs), as_string(L"42"));
-  }
-  std::wostringstream ws;
-  fmt::vfprintf(ws, L"%d", wargs);
-  EXPECT_EQ(L"42", ws.str());
+  EXPECT_WRITE(stderr, fmt::vfprintf(stderr, L"%d", wargs), as_string(L"42"));
 }

 TEST(module_test, vsprintf) {
@@ -538,8 +487,13 @@ TEST(module_test, buffered_file) {
 }

 TEST(module_test, output_file) {
+#ifdef __clang__
+  fmt::println("\033[0;33m[=disabled=] {}\033[0;0m",
+               "Clang 16.0 emits multiple copies of vtables");
+#else
  fmt::ostream out = fmt::output_file("module-test", fmt::buffer_size = 1);
  out.close();
+#endif
 }

 struct custom_context {
@@ -552,21 +506,15 @@ TEST(module_test, custom_context) {
  EXPECT_TRUE(!custom_arg);
 }

-struct disabled_formatter {};
-
-TEST(module_test, has_formatter) {
-  EXPECT_FALSE(
-      (fmt::has_formatter<disabled_formatter, fmt::format_context>::value));
-}
-
-TEST(module_test, is_formattable) {
-  EXPECT_FALSE(fmt::is_formattable<disabled_formatter>::value);
-}
-
 TEST(module_test, compile_format_string) {
  using namespace fmt::literals;
+#ifdef __clang__
+  fmt::println("\033[0;33m[=disabled=] {}\033[0;0m",
+               "Clang 16.0 fails to import user-defined literals");
+#else
  EXPECT_EQ("42", fmt::format("{0:x}"_cf, 0x42));
  EXPECT_EQ(L"42", fmt::format(L"{:}"_cf, 42));
  EXPECT_EQ("4.2", fmt::format("{arg:3.1f}"_cf, "arg"_a = 4.2));
  EXPECT_EQ(L" 42", fmt::format(L"{arg:>3}"_cf, L"arg"_a = L"42"));
+#endif
 }
@@ -22,60 +22,6 @@ using wstring_view = fmt::basic_string_view<wchar_t>;

 #  include <windows.h>

-TEST(util_test, utf16_to_utf8) {
-  auto s = std::string("ёжик");
-  fmt::detail::utf16_to_utf8 u(L"\x0451\x0436\x0438\x043A");
-  EXPECT_EQ(s, u.str());
-  EXPECT_EQ(s.size(), u.size());
-}
-
-TEST(util_test, utf16_to_utf8_empty_string) {
-  std::string s = "";
-  fmt::detail::utf16_to_utf8 u(L"");
-  EXPECT_EQ(s, u.str());
-  EXPECT_EQ(s.size(), u.size());
-}
-
-template <typename Converter, typename Char>
-void check_utf_conversion_error(const char* message,
-                                fmt::basic_string_view<Char> str =
-                                    fmt::basic_string_view<Char>(nullptr, 1)) {
-  fmt::memory_buffer out;
-  fmt::detail::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
-  auto error = std::system_error(std::error_code());
-  try {
-    (Converter)(str);
-  } catch (const std::system_error& e) {
-    error = e;
-  }
-  EXPECT_EQ(ERROR_INVALID_PARAMETER, error.code().value());
-  EXPECT_THAT(error.what(), HasSubstr(fmt::to_string(out)));
-}
-
-TEST(util_test, utf16_to_utf8_error) {
-  check_utf_conversion_error<fmt::detail::utf16_to_utf8, wchar_t>(
-      "cannot convert string from UTF-16 to UTF-8");
-}
-
-TEST(util_test, utf16_to_utf8_convert) {
-  fmt::detail::utf16_to_utf8 u;
-  EXPECT_EQ(ERROR_INVALID_PARAMETER, u.convert(wstring_view(nullptr, 1)));
-  EXPECT_EQ(ERROR_INVALID_PARAMETER,
-            u.convert(wstring_view(L"foo", INT_MAX + 1u)));
-}
-
-TEST(os_test, format_std_error_code) {
-  EXPECT_EQ("generic:42",
-            fmt::format(FMT_STRING("{0}"),
-                        std::error_code(42, std::generic_category())));
-  EXPECT_EQ("system:42",
-            fmt::format(FMT_STRING("{0}"),
-                        std::error_code(42, fmt::system_category())));
-  EXPECT_EQ("system:-42",
-            fmt::format(FMT_STRING("{0}"),
-                        std::error_code(-42, fmt::system_category())));
-}
-
 TEST(os_test, format_windows_error) {
  LPWSTR message = nullptr;
  auto result = FormatMessageW(
@@ -83,7 +29,8 @@ TEST(os_test, format_windows_error) {
          FORMAT_MESSAGE_IGNORE_INSERTS,
      nullptr, ERROR_FILE_EXISTS, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
      reinterpret_cast<LPWSTR>(&message), 0, nullptr);
-  fmt::detail::utf16_to_utf8 utf8_message(wstring_view(message, result - 2));
+  auto utf8_message =
+      fmt::detail::to_utf8<wchar_t>(wstring_view(message, result - 2));
  LocalFree(message);
  fmt::memory_buffer actual_message;
  fmt::detail::format_windows_error(actual_message, ERROR_FILE_EXISTS, "test");
@@ -108,7 +55,8 @@ TEST(os_test, format_long_windows_error) {
    LocalFree(message);
    return;
  }
-  fmt::detail::utf16_to_utf8 utf8_message(wstring_view(message, result - 2));
+  auto utf8_message =
+      fmt::detail::to_utf8<wchar_t>(wstring_view(message, result - 2));
  LocalFree(message);
  fmt::memory_buffer actual_message;
  fmt::detail::format_windows_error(actual_message, provisioning_not_allowed,
@@ -139,6 +87,17 @@ TEST(os_test, report_windows_error) {
               fmt::to_string(out));
 }

+#  if FMT_USE_FCNTL && !defined(__MINGW32__)
+TEST(file_test, open_windows_file) {
+  using fmt::file;
+  file out = file::open_windows_file(L"test-file",
+                                     file::WRONLY | file::CREATE | file::TRUNC);
+  out.write("x", 1);
+  file in = file::open_windows_file(L"test-file", file::RDONLY);
+  EXPECT_READ(in, "x");
+}
+#  endif  // FMT_USE_FCNTL && !defined(__MINGW32__)
+
 #endif  // _WIN32

 #if FMT_USE_FCNTL
@@ -17,7 +17,7 @@ struct test {};
 // included after fmt/format.h.
 namespace fmt {
 template <> struct formatter<test> : formatter<int> {
-  auto format(const test&, format_context& ctx) -> decltype(ctx.out()) {
+  auto format(const test&, format_context& ctx) const -> decltype(ctx.out()) {
    return formatter<int>::format(42, ctx);
  }
 };
@@ -86,13 +86,13 @@ TEST(ostream_test, format_specs) {
  EXPECT_EQ(" def ", fmt::format("{0:^5}", test_string("def")));
  EXPECT_EQ("def**", fmt::format("{0:*<5}", test_string("def")));
  EXPECT_THROW_MSG((void)fmt::format(runtime("{0:+}"), test_string()),
-                   format_error, "format specifier requires numeric argument");
+                   format_error, "invalid format specifier");
  EXPECT_THROW_MSG((void)fmt::format(runtime("{0:-}"), test_string()),
-                   format_error, "format specifier requires numeric argument");
+                   format_error, "invalid format specifier");
  EXPECT_THROW_MSG((void)fmt::format(runtime("{0: }"), test_string()),
-                   format_error, "format specifier requires numeric argument");
+                   format_error, "invalid format specifier");
  EXPECT_THROW_MSG((void)fmt::format(runtime("{0:#}"), test_string()),
-                   format_error, "format specifier requires numeric argument");
+                   format_error, "invalid format specifier");
  EXPECT_THROW_MSG((void)fmt::format(runtime("{0:05}"), test_string()),
                   format_error, "format specifier requires numeric argument");
  EXPECT_EQ("test         ", fmt::format("{0:13}", test_string("test")));
@@ -106,9 +106,17 @@ TEST(ostream_test, empty_custom_output) {
 }

 TEST(ostream_test, print) {
-  std::ostringstream os;
-  fmt::print(os, "Don't {}!", "panic");
-  EXPECT_EQ("Don't panic!", os.str());
+  {
+    std::ostringstream os;
+    fmt::print(os, "Don't {}!", "panic");
+    EXPECT_EQ("Don't panic!", os.str());
+  }
+
+  {
+    std::ostringstream os;
+    fmt::println(os, "Don't {}!", "panic");
+    EXPECT_EQ("Don't panic!\n", os.str());
+  }
 }

 TEST(ostream_test, write_to_ostream) {
@@ -132,7 +140,7 @@ TEST(ostream_test, write_to_ostream_max_size) {
  } buffer(max_size);

  struct mock_streambuf : std::streambuf {
-    MOCK_METHOD2(xsputn, std::streamsize(const void* s, std::streamsize n));
+    MOCK_METHOD(std::streamsize, xsputn, (const void*, std::streamsize));
    auto xsputn(const char* s, std::streamsize n) -> std::streamsize override {
      const void* v = s;
      return xsputn(v, n);
@@ -218,45 +226,6 @@ TEST(ostream_test, format_to_n) {
  EXPECT_EQ("xabx", fmt::string_view(buffer, 4));
 }

-template <typename T> struct convertible {
-  T value;
-  explicit convertible(const T& val) : value(val) {}
-  operator T() const { return value; }
-};
-
-TEST(ostream_test, disable_builtin_ostream_operators) {
-  EXPECT_EQ("42", fmt::format("{:d}", convertible<unsigned short>(42)));
-  EXPECT_EQ("foo", fmt::format("{}", convertible<const char*>("foo")));
-}
-
-struct streamable_and_convertible_to_bool {
-  operator bool() const { return true; }
-};
-
-std::ostream& operator<<(std::ostream& os, streamable_and_convertible_to_bool) {
-  return os << "foo";
-}
-
-TEST(ostream_test, format_convertible_to_bool) {
-  // operator<< is intentionally not used because of potential ODR violations.
-  EXPECT_EQ(fmt::format("{}", streamable_and_convertible_to_bool()), "true");
-}
-
-struct streamable_and_convertible_to_string_view {
-  operator fmt::string_view() const { return "foo"; }
-};
-
-std::ostream& operator<<(std::ostream& os,
-                         streamable_and_convertible_to_string_view) {
-  return os << "bar";
-}
-
-TEST(ostream_test, format_convertible_to_string_vew) {
-  // operator<< is intentionally not used because of potential ODR violations.
-  EXPECT_EQ(fmt::format("{}", streamable_and_convertible_to_string_view()),
-            "foo");
-}
-
 struct copyfmt_test {};

 std::ostream& operator<<(std::ostream& os, copyfmt_test) {
@@ -320,3 +289,20 @@ TEST(ostream_test, closed_ofstream) {
  std::ofstream ofs;
  fmt::print(ofs, "discard");
 }
+
+struct unlocalized {};
+
+auto operator<<(std::ostream& os, unlocalized)
+    -> std::ostream& {
+  return os << 12345;
+}
+
+namespace fmt {
+template <> struct formatter<unlocalized> : ostream_formatter {};
+}  // namespace fmt
+
+TEST(ostream_test, unlocalized) {
+  auto loc = get_locale("en_US.UTF-8");
+  std::locale::global(loc);
+  EXPECT_EQ(fmt::format(loc, "{}", unlocalized()), "12345");
+}
@@ -72,12 +72,6 @@ int test::open(const char* path, int oflag, int mode) {
  EMULATE_EINTR(open, -1);
  return ::open(path, oflag, mode);
 }
-#else
-errno_t test::sopen_s(int* pfh, const char* filename, int oflag, int shflag,
-                      int pmode) {
-  EMULATE_EINTR(open, EINTR);
-  return _sopen_s(pfh, filename, oflag, shflag, pmode);
-}
 #endif

 #ifndef _WIN32
@@ -220,11 +214,11 @@ TEST(os_test, getpagesize) {
 }

 TEST(file_test, open_retry) {
+#  ifndef _WIN32
  write_file("temp", "there must be something here");
  std::unique_ptr<file> f{nullptr};
  EXPECT_RETRY(f.reset(new file("temp", file::RDONLY)), open,
               "cannot open file temp");
-#  ifndef _WIN32
  char c = 0;
  f->read(&c, 1);
 #  endif
@@ -30,15 +30,13 @@ namespace test {

 #ifndef _MSC_VER
 // Size type for read and write.
-typedef size_t size_t;
-typedef ssize_t ssize_t;
+using size_t = size_t;
+using ssize_t = ssize_t;
 int open(const char* path, int oflag, int mode);
 int fstat(int fd, struct stat* buf);
 #else
-typedef unsigned size_t;
-typedef int ssize_t;
-errno_t sopen_s(int* pfh, const char* filename, int oflag, int shflag,
-                int pmode);
+using size_t = unsigned;
+using ssize_t = int;
 #endif

 #ifndef _WIN32
@@ -225,10 +225,8 @@ TEST(printf_test, hash_flag) {
  EXPECT_PRINTF("-42.0000", "%#g", -42.0);
  EXPECT_PRINTF("-42.0000", "%#G", -42.0);

-  safe_sprintf(buffer, "%#a", 16.0);
-  EXPECT_PRINTF(buffer, "%#a", 16.0);
-  safe_sprintf(buffer, "%#A", 16.0);
-  EXPECT_PRINTF(buffer, "%#A", 16.0);
+  EXPECT_PRINTF("0x1.p+4", "%#a", 16.0);
+  EXPECT_PRINTF("0X1.P+4", "%#A", 16.0);

  // '#' flag is ignored for non-numeric types.
  EXPECT_PRINTF("x", "%#c", 'x');
@@ -239,7 +237,7 @@ TEST(printf_test, width) {

  // Width cannot be specified twice.
  EXPECT_THROW_MSG(test_sprintf("%5-5d", 42), format_error,
-                   "invalid type specifier");
+                   "invalid format specifier");

  EXPECT_THROW_MSG(test_sprintf(format("%{}d", big_num), 42), format_error,
                   "number is too big");
@@ -312,10 +310,10 @@ TEST(printf_test, dynamic_precision) {
  }
 }

-template <typename T> struct make_signed { typedef T type; };
+template <typename T> struct make_signed { using type = T; };

 #define SPECIALIZE_MAKE_SIGNED(T, S) \
-  template <> struct make_signed<T> { typedef S type; }
+  template <> struct make_signed<T> { using type = S; }

 SPECIALIZE_MAKE_SIGNED(char, signed char);
 SPECIALIZE_MAKE_SIGNED(unsigned char, signed char);
@@ -407,10 +405,7 @@ TEST(printf_test, length) {
  EXPECT_PRINTF(fmt::format("{:.6}", max), "%Lg", max);
 }

-TEST(printf_test, bool) {
-  EXPECT_PRINTF("1", "%d", true);
-  EXPECT_PRINTF("true", "%s", true);
-}
+TEST(printf_test, bool) { EXPECT_PRINTF("1", "%d", true); }

 TEST(printf_test, int) {
  EXPECT_PRINTF("-42", "%d", -42);
@@ -534,11 +529,12 @@ TEST(printf_test, wide_string) {
 }

 TEST(printf_test, vprintf) {
-  fmt::format_arg_store<fmt::printf_context, int> as{42};
-  fmt::basic_format_args<fmt::printf_context> args(as);
-  EXPECT_EQ(fmt::vsprintf("%d", args), "42");
-  EXPECT_WRITE(stdout, fmt::vprintf("%d", args), "42");
-  EXPECT_WRITE(stdout, fmt::vfprintf(stdout, "%d", args), "42");
+  int n = 42;
+  auto store = fmt::format_arg_store<fmt::printf_context, int>(n);
+  auto args = fmt::basic_format_args<fmt::printf_context>(store);
+  EXPECT_EQ(fmt::vsprintf(fmt::string_view("%d"), args), "42");
+  EXPECT_WRITE(stdout, fmt::vfprintf(stdout, fmt::string_view("%d"), args),
+               "42");
 }

 template <typename... Args>
@@ -554,31 +550,11 @@ TEST(printf_test, fixed_large_exponent) {
  EXPECT_EQ("1000000000000000000000", fmt::sprintf("%.*f", -13, 1e21));
 }

-TEST(printf_test, vsprintf_make_args_example) {
-  fmt::format_arg_store<fmt::printf_context, int, const char*> as{42,
-                                                                  "something"};
-  fmt::basic_format_args<fmt::printf_context> args(as);
-  EXPECT_EQ("[42] something happened", fmt::vsprintf("[%d] %s happened", args));
-  auto as2 = fmt::make_printf_args(42, "something");
-  fmt::basic_format_args<fmt::printf_context> args2(as2);
+TEST(printf_test, make_printf_args) {
  EXPECT_EQ("[42] something happened",
-            fmt::vsprintf("[%d] %s happened", args2));
-  EXPECT_EQ("[42] something happened",
-            fmt::vsprintf("[%d] %s happened",
+            fmt::vsprintf(fmt::string_view("[%d] %s happened"),
                          {fmt::make_printf_args(42, "something")}));
-}
-
-TEST(printf_test, vsprintf_make_wargs_example) {
-  fmt::format_arg_store<fmt::wprintf_context, int, const wchar_t*> as{
-      42, L"something"};
-  fmt::basic_format_args<fmt::wprintf_context> args(as);
  EXPECT_EQ(L"[42] something happened",
-            fmt::vsprintf(L"[%d] %s happened", args));
-  auto as2 = fmt::make_wprintf_args(42, L"something");
-  fmt::basic_format_args<fmt::wprintf_context> args2(as2);
-  EXPECT_EQ(L"[42] something happened",
-            fmt::vsprintf(L"[%d] %s happened", args2));
-  EXPECT_EQ(L"[42] something happened",
-            fmt::vsprintf(L"[%d] %s happened",
+            fmt::vsprintf(fmt::basic_string_view<wchar_t>(L"[%d] %s happened"),
                          {fmt::make_wprintf_args(42, L"something")}));
 }
@@ -1,20 +1,25 @@
-// Formatting library for C++ - the core API
+// Formatting library for C++ - ranges tests
 //
-// Copyright (c) 2012 - present, Victor Zverovich
+// Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors
 // All rights reserved.
 //
 // For the license information refer to format.h.
-//
-// Copyright (c) 2018 - present, Remotion (Igor Schulz)
-// All Rights Reserved
-// {fmt} support for ranges, containers and types tuple interface.

 #include "fmt/ranges.h"

+#include <list>
 #include <map>
+#include <numeric>
+#include <queue>
+#include <stack>
 #include <string>
+#include <utility>
 #include <vector>

+#if FMT_HAS_INCLUDE(<ranges>)
+#  include <ranges>
+#endif
+
 #include "gtest/gtest.h"

 #if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 601
@@ -40,6 +45,8 @@ TEST(ranges_test, format_2d_array) {
 TEST(ranges_test, format_array_of_literals) {
  const char* arr[] = {"1234", "abcd"};
  EXPECT_EQ(fmt::format("{}", arr), "[\"1234\", \"abcd\"]");
+  EXPECT_EQ(fmt::format("{:n}", arr), "\"1234\", \"abcd\"");
+  EXPECT_EQ(fmt::format("{:n:}", arr), "1234, abcd");
 }
 #endif  // FMT_RANGES_TEST_ENABLE_C_STYLE_ARRAY

@@ -47,17 +54,33 @@ TEST(ranges_test, format_vector) {
  auto v = std::vector<int>{1, 2, 3, 5, 7, 11};
  EXPECT_EQ(fmt::format("{}", v), "[1, 2, 3, 5, 7, 11]");
  EXPECT_EQ(fmt::format("{::#x}", v), "[0x1, 0x2, 0x3, 0x5, 0x7, 0xb]");
+  EXPECT_EQ(fmt::format("{:n:#x}", v), "0x1, 0x2, 0x3, 0x5, 0x7, 0xb");
+
+  auto vc = std::vector<char>{'a', 'b', 'c'};
+  auto vvc = std::vector<std::vector<char>>{vc, vc};
+  EXPECT_EQ(fmt::format("{}", vc), "['a', 'b', 'c']");
+  EXPECT_EQ(fmt::format("{}", vvc), "[['a', 'b', 'c'], ['a', 'b', 'c']]");
+  EXPECT_EQ(fmt::format("{:n}", vvc), "['a', 'b', 'c'], ['a', 'b', 'c']");
+  EXPECT_EQ(fmt::format("{:n:n}", vvc), "'a', 'b', 'c', 'a', 'b', 'c'");
+  EXPECT_EQ(fmt::format("{:n:n:}", vvc), "a, b, c, a, b, c");
 }

-TEST(ranges_test, format_vector2) {
+TEST(ranges_test, format_nested_vector) {
  auto v = std::vector<std::vector<int>>{{1, 2}, {3, 5}, {7, 11}};
  EXPECT_EQ(fmt::format("{}", v), "[[1, 2], [3, 5], [7, 11]]");
  EXPECT_EQ(fmt::format("{:::#x}", v), "[[0x1, 0x2], [0x3, 0x5], [0x7, 0xb]]");
+  EXPECT_EQ(fmt::format("{:n:n:#x}", v), "0x1, 0x2, 0x3, 0x5, 0x7, 0xb");
+}
+
+TEST(ranges_test, to_string_vector) {
+  auto v = std::vector<std::string>{"a", "b", "c"};
+  EXPECT_EQ(fmt::to_string(v), "[\"a\", \"b\", \"c\"]");
 }

 TEST(ranges_test, format_map) {
  auto m = std::map<std::string, int>{{"one", 1}, {"two", 2}};
  EXPECT_EQ(fmt::format("{}", m), "{\"one\": 1, \"two\": 2}");
+  EXPECT_EQ(fmt::format("{:n}", m), "\"one\": 1, \"two\": 2");
 }

 TEST(ranges_test, format_set) {
@@ -65,13 +88,41 @@ TEST(ranges_test, format_set) {
            "{\"one\", \"two\"}");
 }

+// Models std::flat_set close enough to test if no ambiguous lookup of a
+// formatter happens due to the flat_set type matching is_set and
+// is_container_adaptor_like.
+template <typename T> class flat_set {
+ public:
+  using key_type = T;
+  using container_type = std::vector<T>;
+
+  using iterator = typename std::vector<T>::iterator;
+  using const_iterator = typename std::vector<T>::const_iterator;
+
+  template <typename... Ts>
+  explicit flat_set(Ts&&... args) : c{std::forward<Ts>(args)...} {}
+
+  auto begin() -> iterator { return c.begin(); }
+  auto end() -> iterator { return c.end(); }
+
+  auto begin() const -> const_iterator { return c.begin(); }
+  auto end() const -> const_iterator { return c.end(); }
+
+ private:
+  std::vector<T> c;
+};
+
+TEST(ranges_test, format_flat_set) {
+  EXPECT_EQ(fmt::format("{}", flat_set<std::string>{"one", "two"}),
+            "{\"one\", \"two\"}");
+}
+
 namespace adl {
 struct box {
  int value;
 };

 auto begin(const box& b) -> const int* { return &b.value; }
-
 auto end(const box& b) -> const int* { return &b.value + 1; }
 }  // namespace adl

@@ -91,6 +142,7 @@ TEST(ranges_test, format_tuple) {
  auto t =
      std::tuple<int, float, std::string, char>(42, 1.5f, "this is tuple", 'i');
  EXPECT_EQ(fmt::format("{}", t), "(42, 1.5, \"this is tuple\", 'i')");
+
  EXPECT_EQ(fmt::format("{}", std::tuple<>()), "()");

  EXPECT_TRUE((fmt::is_formattable<std::tuple<>>::value));
@@ -103,16 +155,36 @@ TEST(ranges_test, format_tuple) {
  EXPECT_TRUE((fmt::is_formattable<std::tuple<int, float>>::value));
 }

+struct not_default_formattable {};
+struct bad_format {};
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<not_default_formattable> {
+  auto parse(format_parse_context&) -> const char* { throw bad_format(); }
+  auto format(not_default_formattable, format_context& ctx)
+      -> format_context::iterator {
+    return ctx.out();
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(ranges_test, tuple_parse_calls_element_parse) {
+  auto f = fmt::formatter<std::tuple<not_default_formattable>>();
+  auto ctx = fmt::format_parse_context("");
+  EXPECT_THROW(f.parse(ctx), bad_format);
+}
+
 #ifdef FMT_RANGES_TEST_ENABLE_FORMAT_STRUCT
 struct tuple_like {
  int i;
  std::string str;

-  template <size_t N> fmt::enable_if_t<N == 0, int> get() const noexcept {
+  template <size_t N>
+  auto get() const noexcept -> fmt::enable_if_t<N == 0, int> {
    return i;
  }
  template <size_t N>
-  fmt::enable_if_t<N == 1, fmt::string_view> get() const noexcept {
+  auto get() const noexcept -> fmt::enable_if_t<N == 1, fmt::string_view> {
    return str;
  }
 };
@@ -144,32 +216,24 @@ TEST(ranges_test, format_to) {
  EXPECT_STREQ(buf, "[1, 2, 3]");
 }

-struct path_like {
-  const path_like* begin() const;
-  const path_like* end() const;
+template <typename Char> struct path_like {
+  auto begin() const -> const path_like*;
+  auto end() const -> const path_like*;

-  operator std::string() const;
+  operator std::basic_string<Char>() const;
 };

-TEST(ranges_test, path_like) {
-  EXPECT_FALSE((fmt::is_range<path_like, char>::value));
+TEST(ranges_test, disabled_range_formatting_of_path) {
+  // Range formatting of path is disabled because of infinite recursion
+  // (path element is itself a path).
+  EXPECT_EQ((fmt::range_format_kind<path_like<char>, char>::value),
+            fmt::range_format::disabled);
+  EXPECT_EQ((fmt::range_format_kind<path_like<wchar_t>, char>::value),
+            fmt::range_format::disabled);
 }

-#ifdef FMT_USE_STRING_VIEW
-struct string_like {
-  const char* begin();
-  const char* end();
-  operator fmt::string_view() const { return "foo"; }
-  operator std::string_view() const { return "foo"; }
-};
-
-TEST(ranges_test, format_string_like) {
-  EXPECT_EQ(fmt::format("{}", string_like()), "foo");
-}
-#endif  // FMT_USE_STRING_VIEW
-
-// A range that provides non-const only begin()/end() to test fmt::join handles
-// that.
+// A range that provides non-const only begin()/end() to test fmt::join
+// handles that.
 //
 // Some ranges (e.g. those produced by range-v3's views::filter()) can cache
 // information during iteration so they only provide non-const begin()/end().
@@ -184,8 +248,8 @@ template <typename T> class non_const_only_range {
  explicit non_const_only_range(Args&&... args)
      : vec(std::forward<Args>(args)...) {}

-  const_iterator begin() { return vec.begin(); }
-  const_iterator end() { return vec.end(); }
+  auto begin() -> const_iterator { return vec.begin(); }
+  auto end() -> const_iterator { return vec.end(); }
 };

 template <typename T> class noncopyable_range {
@@ -193,7 +257,7 @@ template <typename T> class noncopyable_range {
  std::vector<T> vec;

 public:
-  using const_iterator = typename ::std::vector<T>::const_iterator;
+  using iterator = typename ::std::vector<T>::iterator;

  template <typename... Args>
  explicit noncopyable_range(Args&&... args)
@@ -202,16 +266,16 @@ template <typename T> class noncopyable_range {
  noncopyable_range(noncopyable_range const&) = delete;
  noncopyable_range(noncopyable_range&) = delete;

-  const_iterator begin() const { return vec.begin(); }
-  const_iterator end() const { return vec.end(); }
+  auto begin() -> iterator { return vec.begin(); }
+  auto end() -> iterator { return vec.end(); }
 };

 TEST(ranges_test, range) {
-  noncopyable_range<int> w(3u, 0);
+  auto&& w = noncopyable_range<int>(3u, 0);
  EXPECT_EQ(fmt::format("{}", w), "[0, 0, 0]");
  EXPECT_EQ(fmt::format("{}", noncopyable_range<int>(3u, 0)), "[0, 0, 0]");

-  non_const_only_range<int> x(3u, 0);
+  auto x = non_const_only_range<int>(3u, 0);
  EXPECT_EQ(fmt::format("{}", x), "[0, 0, 0]");
  EXPECT_EQ(fmt::format("{}", non_const_only_range<int>(3u, 0)), "[0, 0, 0]");

@@ -232,7 +296,6 @@ TEST(ranges_test, enum_range) {
 }

 #if !FMT_MSC_VERSION
-
 TEST(ranges_test, unformattable_range) {
  EXPECT_FALSE((fmt::has_formatter<std::vector<unformattable>,
                                   fmt::format_context>::value));
@@ -287,8 +350,8 @@ bool operator!=(const char* p, zstring_sentinel) { return *p != '\0'; }

 struct zstring {
  const char* p;
-  const char* begin() const { return p; }
-  zstring_sentinel end() const { return {}; }
+  auto begin() const -> const char* { return p; }
+  auto end() const -> zstring_sentinel { return {}; }
 };

 #  ifdef __cpp_lib_ranges
@@ -302,20 +365,22 @@ struct cpp20_only_range {

    iterator() = default;
    iterator(int i) : val(i) {}
-    int operator*() const { return val; }
-    iterator& operator++() {
+    auto operator*() const -> int { return val; }
+    auto operator++() -> iterator& {
      ++val;
      return *this;
    }
    void operator++(int) { ++*this; }
-    bool operator==(const iterator& rhs) const { return val == rhs.val; }
+    auto operator==(const iterator& rhs) const -> bool {
+      return val == rhs.val;
+    }
  };

  int lo;
  int hi;

-  iterator begin() const { return iterator(lo); }
-  iterator end() const { return iterator(hi); }
+  auto begin() const -> iterator { return iterator(lo); }
+  auto end() const -> iterator { return iterator(hi); }
 };

 static_assert(std::input_iterator<cpp20_only_range::iterator>);
@@ -329,12 +394,12 @@ TEST(ranges_test, join_sentinel) {
 }

 TEST(ranges_test, join_range) {
-  noncopyable_range<int> w(3u, 0);
+  auto&& w = noncopyable_range<int>(3u, 0);
  EXPECT_EQ(fmt::format("{}", fmt::join(w, ",")), "0,0,0");
  EXPECT_EQ(fmt::format("{}", fmt::join(noncopyable_range<int>(3u, 0), ",")),
            "0,0,0");

-  non_const_only_range<int> x(3u, 0);
+  auto x = non_const_only_range<int>(3u, 0);
  EXPECT_EQ(fmt::format("{}", fmt::join(x, ",")), "0,0,0");
  EXPECT_EQ(fmt::format("{}", fmt::join(non_const_only_range<int>(3u, 0), ",")),
            "0,0,0");
@@ -357,6 +422,17 @@ TEST(ranges_test, join_range) {
 }
 #endif  // FMT_RANGES_TEST_ENABLE_JOIN

+#if defined(__cpp_lib_ranges) && __cpp_lib_ranges >= 202302L
+TEST(ranges_test, nested_ranges) {
+  auto l = std::list{1, 2, 3};
+  auto r = std::views::iota(0, 3) | std::views::transform([&l](auto i) {
+             return std::views::take(std::ranges::subrange(l), i);
+           }) |
+           std::views::transform(std::views::reverse);
+  EXPECT_EQ(fmt::format("{}", r), "[[], [1], [2, 1]]");
+}
+#endif
+
 TEST(ranges_test, is_printable) {
  using fmt::detail::is_printable;
  EXPECT_TRUE(is_printable(0x0323));
@@ -364,7 +440,7 @@ TEST(ranges_test, is_printable) {
  EXPECT_FALSE(is_printable(0x110000));
 }

-TEST(ranges_test, escape_string) {
+TEST(ranges_test, escape) {
  using vec = std::vector<std::string>;
  EXPECT_EQ(fmt::format("{}", vec{"\n\r\t\"\\"}), "[\"\\n\\r\\t\\\"\\\\\"]");
  EXPECT_EQ(fmt::format("{}", vec{"\x07"}), "[\"\\x07\"]");
@@ -375,22 +451,22 @@ TEST(ranges_test, escape_string) {
    EXPECT_EQ(fmt::format("{}", vec{"\xcd\xb8"}), "[\"\\u0378\"]");
    // Unassigned Unicode code points.
    EXPECT_EQ(fmt::format("{}", vec{"\xf0\xaa\x9b\x9e"}), "[\"\\U0002a6de\"]");
+    // Broken utf-8.
    EXPECT_EQ(fmt::format("{}", vec{"\xf4\x8f\xbf\xc0"}),
              "[\"\\xf4\\x8f\\xbf\\xc0\"]");
-    EXPECT_EQ(fmt::format("{}", vec{"понедельник"}), "[\"понедельник\"]");
+    EXPECT_EQ(fmt::format("{}", vec{"\xf0\x28"}), "[\"\\xf0(\"]");
+    EXPECT_EQ(fmt::format("{}", vec{"\xe1\x28"}), "[\"\\xe1(\"]");
+    EXPECT_EQ(fmt::format("{}", vec{std::string("\xf0\x28\0\0anything", 12)}),
+              "[\"\\xf0(\\x00\\x00anything\"]");
+
+    // Correct utf-8.
+    EXPECT_EQ(fmt::format("{}", vec{"🦄"}), "[\"🦄\"]");
  }
-}

-#ifdef FMT_USE_STRING_VIEW
-struct convertible_to_string_view {
-  operator std::string_view() const { return "foo"; }
-};
-
-TEST(ranges_test, escape_convertible_to_string_view) {
-  EXPECT_EQ(fmt::format("{}", std::vector<convertible_to_string_view>(1)),
-            "[\"foo\"]");
+  EXPECT_EQ(fmt::format("{}", std::vector<std::vector<char>>{{'x'}}),
+            "[['x']]");
+  EXPECT_EQ(fmt::format("{}", std::tuple<std::vector<char>>{{'x'}}), "(['x'])");
 }
-#endif  // FMT_USE_STRING_VIEW

 template <typename R> struct fmt_ref_view {
  R* r;
@@ -400,9 +476,85 @@ template <typename R> struct fmt_ref_view {
 };

 TEST(ranges_test, range_of_range_of_mixed_const) {
-  std::vector<std::vector<int>> v = {{1, 2, 3}, {4, 5}};
+  auto v = std::vector<std::vector<int>>{{1, 2, 3}, {4, 5}};
  EXPECT_EQ(fmt::format("{}", v), "[[1, 2, 3], [4, 5]]");

-  fmt_ref_view<decltype(v)> r{&v};
+  auto r = fmt_ref_view<decltype(v)>{&v};
  EXPECT_EQ(fmt::format("{}", r), "[[1, 2, 3], [4, 5]]");
 }
+
+TEST(ranges_test, vector_char) {
+  EXPECT_EQ(fmt::format("{}", std::vector<char>{'a', 'b'}), "['a', 'b']");
+}
+
+TEST(ranges_test, container_adaptor) {
+  {
+    using fmt::detail::is_container_adaptor_like;
+    using T = std::nullptr_t;
+    static_assert(is_container_adaptor_like<std::stack<T>>::value, "");
+    static_assert(is_container_adaptor_like<std::queue<T>>::value, "");
+    static_assert(is_container_adaptor_like<std::priority_queue<T>>::value, "");
+    static_assert(!is_container_adaptor_like<std::vector<T>>::value, "");
+  }
+
+  {
+    auto s = std::stack<int>();
+    s.push(1);
+    s.push(2);
+    EXPECT_EQ(fmt::format("{}", s), "[1, 2]");
+    EXPECT_EQ(fmt::format("{}", const_cast<const decltype(s)&>(s)), "[1, 2]");
+  }
+
+  {
+    auto q = std::queue<int>();
+    q.push(1);
+    q.push(2);
+    EXPECT_EQ(fmt::format("{}", q), "[1, 2]");
+  }
+
+  {
+    auto q = std::priority_queue<int>();
+    q.push(3);
+    q.push(1);
+    q.push(2);
+    q.push(4);
+    EXPECT_EQ(fmt::format("{}", q), "[4, 3, 2, 1]");
+  }
+
+  {
+    auto s = std::stack<char, std::string>();
+    s.push('a');
+    s.push('b');
+    // See https://cplusplus.github.io/LWG/issue3881.
+    EXPECT_EQ(fmt::format("{}", s), "['a', 'b']");
+  }
+
+  {
+    struct my_container_adaptor {
+      using value_type = int;
+      using container_type = std::vector<value_type>;
+      void push(const value_type& v) { c.push_back(v); }
+
+     protected:
+      container_type c;
+    };
+
+    auto m = my_container_adaptor();
+    m.push(1);
+    m.push(2);
+    EXPECT_EQ(fmt::format("{}", m), "[1, 2]");
+  }
+}
+
+struct tieable {
+  int a = 3;
+  double b = 0.42;
+};
+
+auto format_as(const tieable& t) -> std::tuple<int, double> {
+  return std::tie(t.a, t.b);
+}
+
+TEST(ranges_test, format_as_tie) {
+  EXPECT_EQ(fmt::format("{}", tieable()), "(3, 0.42)");
+}
@@ -10,23 +10,29 @@
 #include <time.h>

 #include <climits>
+#include <thread>

+#include "fmt/os.h"
 #include "gmock/gmock.h"
 #include "gtest-extra.h"

 TEST(scan_test, read_text) {
-  auto s = fmt::string_view("foo");
+  fmt::string_view s = "foo";
  auto end = fmt::scan(s, "foo");
  EXPECT_EQ(end, s.end());
  EXPECT_THROW_MSG(fmt::scan("fob", "foo"), fmt::format_error, "invalid input");
 }

 TEST(scan_test, read_int) {
-  auto n = int();
+  int n = 0;
  fmt::scan("42", "{}", n);
  EXPECT_EQ(n, 42);
  fmt::scan("-42", "{}", n);
  EXPECT_EQ(n, -42);
+  fmt::scan("42", "{:}", n);
+  EXPECT_EQ(n, 42);
+  EXPECT_THROW_MSG(fmt::scan(std::to_string(INT_MAX + 1u), "{}", n),
+                   fmt::format_error, "number is too big");
 }

 TEST(scan_test, read_longlong) {
@@ -38,7 +44,7 @@ TEST(scan_test, read_longlong) {
 }

 TEST(scan_test, read_uint) {
-  auto n = unsigned();
+  unsigned n = 0;
  fmt::scan("42", "{}", n);
  EXPECT_EQ(n, 42);
  EXPECT_THROW_MSG(fmt::scan("-42", "{}", n), fmt::format_error,
@@ -53,52 +59,63 @@ TEST(scan_test, read_ulonglong) {
                   "invalid input");
 }

+TEST(scan_test, read_hex) {
+  unsigned n = 0;
+  fmt::scan("2a", "{:x}", n);
+  EXPECT_EQ(n, 42);
+  auto num_digits = std::numeric_limits<unsigned>::digits / 4;
+  EXPECT_THROW_MSG(fmt::scan(fmt::format("1{:0{}}", 0, num_digits), "{:x}", n),
+                   fmt::format_error, "number is too big");
+}
+
 TEST(scan_test, read_string) {
-  auto s = std::string();
+  std::string s;
  fmt::scan("foo", "{}", s);
  EXPECT_EQ(s, "foo");
 }

 TEST(scan_test, read_string_view) {
-  auto s = fmt::string_view();
+  fmt::string_view s;
  fmt::scan("foo", "{}", s);
  EXPECT_EQ(s, "foo");
 }

-#ifndef _WIN32
-namespace fmt {
-template <> struct scanner<tm> {
-  std::string format;
+TEST(scan_test, separator) {
+  int n1 = 0, n2 = 0;
+  fmt::scan("10 20", "{} {}", n1, n2);
+  EXPECT_EQ(n1, 10);
+  EXPECT_EQ(n2, 20);
+}

-  scan_parse_context::iterator parse(scan_parse_context& ctx) {
-    auto it = ctx.begin();
-    if (it != ctx.end() && *it == ':') ++it;
-    auto end = it;
-    while (end != ctx.end() && *end != '}') ++end;
-    format.reserve(detail::to_unsigned(end - it + 1));
-    format.append(it, end);
-    format.push_back('\0');
-    return end;
+struct num {
+  int value;
+};
+
+namespace fmt {
+template <> struct scanner<num> {
+  bool hex = false;
+
+  auto parse(scan_parse_context& ctx) -> scan_parse_context::iterator {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it != end && *it == 'x') hex = true;
+    if (it != end && *it != '}') throw_format_error("invalid format");
+    return it;
  }

  template <class ScanContext>
-  typename ScanContext::iterator scan(tm& t, ScanContext& ctx) {
-    auto result = strptime(ctx.begin(), format.c_str(), &t);
-    if (!result) throw format_error("failed to parse time");
-    return result;
+  auto scan(num& n, ScanContext& ctx) const -> typename ScanContext::iterator {
+    // TODO: handle specifier
+    return fmt::scan(ctx, "{}", n.value);
  }
 };
 }  // namespace fmt

 TEST(scan_test, read_custom) {
-  auto input = "Date: 1985-10-25";
-  auto t = tm();
-  fmt::scan(input, "Date: {0:%Y-%m-%d}", t);
-  EXPECT_EQ(t.tm_year, 85);
-  EXPECT_EQ(t.tm_mon, 9);
-  EXPECT_EQ(t.tm_mday, 25);
+  auto input = "42";
+  auto n = num();
+  fmt::scan(input, "{:}", n);
+  EXPECT_EQ(n.value, 42);
 }
-#endif

 TEST(scan_test, invalid_format) {
  EXPECT_THROW_MSG(fmt::scan("", "{}"), fmt::format_error,
@@ -108,9 +125,64 @@ TEST(scan_test, invalid_format) {
 }

 TEST(scan_test, example) {
-  auto key = std::string();
-  auto value = int();
+  std::string key;
+  int value = 0;
  fmt::scan("answer = 42", "{} = {}", key, value);
  EXPECT_EQ(key, "answer");
  EXPECT_EQ(value, 42);
 }
+
+TEST(scan_test, end_of_input) {
+  int value = 0;
+  fmt::scan("", "{}", value);
+}
+
+#if FMT_USE_FCNTL
+TEST(scan_test, file) {
+  fmt::file read_end, write_end;
+  fmt::file::pipe(read_end, write_end);
+
+  fmt::string_view input = "10 20";
+  write_end.write(input.data(), input.size());
+  write_end.close();
+
+  int n1 = 0, n2 = 0;
+  fmt::buffered_file f = read_end.fdopen("r");
+  fmt::scan(f.get(), "{} {}", n1, n2);
+  EXPECT_EQ(n1, 10);
+  EXPECT_EQ(n2, 20);
+}
+
+TEST(scan_test, lock) {
+  fmt::file read_end, write_end;
+  fmt::file::pipe(read_end, write_end);
+
+  std::thread producer([&]() {
+    fmt::string_view input = "42 ";
+    for (int i = 0; i < 1000; ++i) write_end.write(input.data(), input.size());
+    write_end.close();
+  });
+
+  std::atomic<int> count(0);
+  fmt::buffered_file f = read_end.fdopen("r");
+  auto fun = [&]() {
+    int value = 0;
+    while (fmt::scan(f.get(), "{}", value)) {
+      if (value != 42) {
+        read_end.close();
+        EXPECT_EQ(value, 42);
+        break;
+      }
+      ++count;
+    }
+  };
+  std::thread consumer1(fun);
+  std::thread consumer2(fun);
+  
+  producer.join();
+  consumer1.join();
+  consumer2.join();
+  EXPECT_EQ(count, 1000);
+
+}
+#endif  // FMT_USE_FCNTL
@@ -12,6 +12,264 @@
 #include "fmt/format.h"

 FMT_BEGIN_NAMESPACE
+namespace detail {
+
+inline auto is_whitespace(char c) -> bool { return c == ' ' || c == '\n'; }
+
+// If c is a hex digit returns its numeric value, othewise -1.
+inline auto to_hex_digit(char c) -> int {
+  if (c >= '0' && c <= '9') return c - '0';
+  if (c >= 'a' && c <= 'f') return c - 'a' + 10;
+  if (c >= 'A' && c <= 'F') return c - 'A' + 10;
+  return -1;
+}
+
+struct maybe_contiguous_range {
+  const char* begin;
+  const char* end;
+
+  explicit operator bool() const { return begin != nullptr; }
+};
+
+class scan_buffer {
+ private:
+  const char* ptr_;
+  const char* end_;
+  bool contiguous_;
+
+ protected:
+  scan_buffer(const char* ptr, const char* end, bool contiguous)
+      : ptr_(ptr), end_(end), contiguous_(contiguous) {}
+  ~scan_buffer() = default;
+
+  void set(string_view buf) {
+    ptr_ = buf.begin();
+    end_ = buf.end();
+  }
+
+  auto ptr() const -> const char* { return ptr_; }
+
+ public:
+  scan_buffer(const scan_buffer&) = delete;
+  void operator=(const scan_buffer&) = delete;
+
+  // Fills the buffer with more input if available.
+  virtual void consume() = 0;
+
+  class sentinel {};
+
+  class iterator {
+   private:
+    const char** ptr_;
+    scan_buffer* buf_;  // This could be merged with ptr_.
+    char value_;
+
+    static auto get_sentinel() -> const char** {
+      static const char* ptr = nullptr;
+      return &ptr;
+    }
+
+    friend class scan_buffer;
+
+    friend auto operator==(iterator lhs, sentinel) -> bool {
+      return *lhs.ptr_ == nullptr;
+    }
+    friend auto operator!=(iterator lhs, sentinel) -> bool {
+      return *lhs.ptr_ != nullptr;
+    }
+
+    iterator(scan_buffer* buf) : buf_(buf) {
+      if (buf->ptr_ == buf->end_) {
+        ptr_ = get_sentinel();
+        return;
+      }
+      ptr_ = &buf->ptr_;
+      value_ = *buf->ptr_;
+    }
+
+    friend scan_buffer& get_buffer(iterator it) { return *it.buf_; }
+
+   public:
+    iterator() : ptr_(get_sentinel()), buf_(nullptr) {}
+
+    auto operator++() -> iterator& {
+      if (!buf_->try_consume()) ptr_ = get_sentinel();
+      value_ = *buf_->ptr_;
+      return *this;
+    }
+    auto operator++(int) -> iterator {
+      iterator copy = *this;
+      ++*this;
+      return copy;
+    }
+    auto operator*() const -> char { return value_; }
+
+    auto base() const -> const char* { return buf_->ptr_; }
+
+    friend auto to_contiguous(iterator it) -> maybe_contiguous_range;
+    friend auto advance(iterator it, size_t n) -> iterator;
+  };
+
+  friend auto to_contiguous(iterator it) -> maybe_contiguous_range {
+    if (it.buf_->is_contiguous()) return {it.buf_->ptr_, it.buf_->end_};
+    return {nullptr, nullptr};
+  }
+  friend auto advance(iterator it, size_t n) -> iterator {
+    FMT_ASSERT(it.buf_->is_contiguous(), "");
+    const char*& ptr = it.buf_->ptr_;
+    ptr += n;
+    it.value_ = *ptr;
+    if (ptr == it.buf_->end_) it.ptr_ = iterator::get_sentinel();
+    return it;
+  }
+
+  auto begin() -> iterator { return this; }
+  auto end() -> sentinel { return {}; }
+
+  auto is_contiguous() const -> bool { return contiguous_; }
+
+  // Tries consuming a single code unit. Returns true iff there is more input.
+  auto try_consume() -> bool {
+    FMT_ASSERT(ptr_ != end_, "");
+    ++ptr_;
+    if (ptr_ != end_) return true;
+    consume();
+    return ptr_ != end_;
+  }
+};
+
+using scan_iterator = scan_buffer::iterator;
+using scan_sentinel = scan_buffer::sentinel;
+
+class string_scan_buffer : public scan_buffer {
+ private:
+  void consume() override {}
+
+ public:
+  explicit string_scan_buffer(string_view s)
+      : scan_buffer(s.begin(), s.end(), true) {}
+};
+
+#ifdef _WIN32
+void flockfile(FILE* f) { _lock_file(f); }
+void funlockfile(FILE* f) { _unlock_file(f); }
+int getc_unlocked(FILE* f) { return _fgetc_nolock(f); }
+#endif
+
+// A FILE wrapper. F is FILE defined as a template parameter to make
+// system-specific API detection work.
+template <typename F> class file_base {
+ protected:
+  F* file_;
+
+ public:
+  file_base(F* file) : file_(file) {}
+  operator F*() const { return file_; }
+
+  // Reads a code unit from the stream.
+  auto get() -> int {
+    int result = getc_unlocked(file_);
+    if (result == EOF && ferror(file_) != 0)
+      FMT_THROW(system_error(errno, FMT_STRING("getc failed")));
+    return result;
+  }
+
+  // Puts the code unit back into the stream buffer.
+  void unget(char c) {
+    if (ungetc(c, file_) == EOF)
+      FMT_THROW(system_error(errno, FMT_STRING("ungetc failed")));
+  }
+};
+
+// A FILE wrapper for glibc.
+template <typename F> class glibc_file : public file_base<F> {
+ public:
+  using file_base<F>::file_base;
+
+  // Returns the file's read buffer as a string_view.
+  auto buffer() const -> string_view {
+    return {this->file_->_IO_read_ptr,
+            to_unsigned(this->file_->_IO_read_end - this->file_->_IO_read_ptr)};
+  }
+};
+
+// A FILE wrapper for Apple's libc.
+template <typename F> class apple_file : public file_base<F> {
+ public:
+  using file_base<F>::file_base;
+
+  auto buffer() const -> string_view {
+    return {reinterpret_cast<char*>(this->file_->_p),
+            to_unsigned(this->file_->_r)};
+  }
+};
+
+// A fallback FILE wrapper.
+template <typename F> class fallback_file : public file_base<F> {
+ private:
+  char next_;  // The next unconsumed character in the buffer.
+  bool has_next_ = false;
+
+ public:
+  using file_base<F>::file_base;
+
+  auto buffer() const -> string_view { return {&next_, has_next_ ? 1u : 0u}; }
+
+  auto get() -> int {
+    has_next_ = false;
+    return file_base<F>::get();
+  }
+
+  void unget(char c) {
+    file_base<F>::unget(c);
+    next_ = c;
+    has_next_ = true;
+  }
+};
+
+class file_scan_buffer : public scan_buffer {
+ private:
+  template <typename F, FMT_ENABLE_IF(sizeof(F::_IO_read_ptr) != 0)>
+  static auto get_file(F* f, int) -> glibc_file<F> {
+    return f;
+  }
+  template <typename F, FMT_ENABLE_IF(sizeof(F::_p) != 0)>
+  static auto get_file(F* f, int) -> apple_file<F> {
+    return f;
+  }
+  static auto get_file(FILE* f, ...) -> fallback_file<FILE> { return f; }
+
+  decltype(get_file(static_cast<FILE*>(nullptr), 0)) file_;
+
+  // Fills the buffer if it is empty.
+  void fill() {
+    string_view buf = file_.buffer();
+    if (buf.size() == 0) {
+      int c = file_.get();
+      // Put the character back since we are only filling the buffer.
+      if (c != EOF) file_.unget(static_cast<char>(c));
+      buf = file_.buffer();
+    }
+    set(buf);
+  }
+
+  void consume() override {
+    // Consume the current buffer content.
+    size_t n = to_unsigned(ptr() - file_.buffer().begin());
+    for (size_t i = 0; i != n; ++i) file_.get();
+    fill();
+  }
+
+ public:
+  explicit file_scan_buffer(FILE* f)
+      : scan_buffer(nullptr, nullptr, false), file_(f) {
+    flockfile(f);
+    fill();
+  }
+  ~file_scan_buffer() { funlockfile(file_); }
+};
+}  // namespace detail
+
 template <typename T, typename Char = char> struct scanner {
  // A deleted default constructor indicates a disabled scanner.
  scanner() = delete;
@@ -27,31 +285,14 @@ class scan_parse_context {
  explicit FMT_CONSTEXPR scan_parse_context(string_view format)
      : format_(format) {}

-  FMT_CONSTEXPR iterator begin() const { return format_.begin(); }
-  FMT_CONSTEXPR iterator end() const { return format_.end(); }
+  FMT_CONSTEXPR auto begin() const -> iterator { return format_.begin(); }
+  FMT_CONSTEXPR auto end() const -> iterator { return format_.end(); }

  void advance_to(iterator it) {
    format_.remove_prefix(detail::to_unsigned(it - begin()));
  }
 };

-struct scan_context {
- private:
-  string_view input_;
-
- public:
-  using iterator = const char*;
-
-  explicit scan_context(string_view input) : input_(input) {}
-
-  iterator begin() const { return input_.data(); }
-  iterator end() const { return begin() + input_.size(); }
-
-  void advance_to(iterator it) {
-    input_.remove_prefix(detail::to_unsigned(it - begin()));
-  }
-};
-
 namespace detail {
 enum class scan_type {
  none_type,
@@ -64,178 +305,362 @@ enum class scan_type {
  custom_type
 };

-struct custom_scan_arg {
+template <typename Context> struct custom_scan_arg {
  void* value;
-  void (*scan)(void* arg, scan_parse_context& parse_ctx, scan_context& ctx);
-};
-
-class scan_arg {
- public:
-  scan_type type;
-  union {
-    int* int_value;
-    unsigned* uint_value;
-    long long* long_long_value;
-    unsigned long long* ulong_long_value;
-    std::string* string;
-    fmt::string_view* string_view;
-    custom_scan_arg custom;
-    // TODO: more types
-  };
-
-  scan_arg() : type(scan_type::none_type) {}
-  scan_arg(int& value) : type(scan_type::int_type), int_value(&value) {}
-  scan_arg(unsigned& value) : type(scan_type::uint_type), uint_value(&value) {}
-  scan_arg(long long& value)
-      : type(scan_type::long_long_type), long_long_value(&value) {}
-  scan_arg(unsigned long long& value)
-      : type(scan_type::ulong_long_type), ulong_long_value(&value) {}
-  scan_arg(std::string& value) : type(scan_type::string_type), string(&value) {}
-  scan_arg(fmt::string_view& value)
-      : type(scan_type::string_view_type), string_view(&value) {}
-  template <typename T> scan_arg(T& value) : type(scan_type::custom_type) {
-    custom.value = &value;
-    custom.scan = scan_custom_arg<T>;
-  }
-
- private:
-  template <typename T>
-  static void scan_custom_arg(void* arg, scan_parse_context& parse_ctx,
-                              scan_context& ctx) {
-    scanner<T> s;
-    parse_ctx.advance_to(s.parse(parse_ctx));
-    ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
-  }
+  void (*scan)(void* arg, scan_parse_context& parse_ctx, Context& ctx);
 };
 }  // namespace detail

+// A scan argument. Context is a template parameter for the compiled API where
+// output can be unbuffered.
+template <typename Context> class basic_scan_arg {
+ private:
+  using scan_type = detail::scan_type;
+  scan_type type_;
+  union {
+    int* int_value_;
+    unsigned* uint_value_;
+    long long* long_long_value_;
+    unsigned long long* ulong_long_value_;
+    std::string* string_;
+    string_view* string_view_;
+    detail::custom_scan_arg<Context> custom_;
+    // TODO: more types
+  };
+
+  template <typename T>
+  static void scan_custom_arg(void* arg, scan_parse_context& parse_ctx,
+                              Context& ctx) {
+    auto s = scanner<T>();
+    parse_ctx.advance_to(s.parse(parse_ctx));
+    ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
+  }
+
+ public:
+  FMT_CONSTEXPR basic_scan_arg()
+      : type_(scan_type::none_type), int_value_(nullptr) {}
+  FMT_CONSTEXPR basic_scan_arg(int& value)
+      : type_(scan_type::int_type), int_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(unsigned& value)
+      : type_(scan_type::uint_type), uint_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(long long& value)
+      : type_(scan_type::long_long_type), long_long_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(unsigned long long& value)
+      : type_(scan_type::ulong_long_type), ulong_long_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(std::string& value)
+      : type_(scan_type::string_type), string_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(string_view& value)
+      : type_(scan_type::string_view_type), string_view_(&value) {}
+  template <typename T>
+  FMT_CONSTEXPR basic_scan_arg(T& value) : type_(scan_type::custom_type) {
+    custom_.value = &value;
+    custom_.scan = scan_custom_arg<T>;
+  }
+
+  constexpr explicit operator bool() const noexcept {
+    return type_ != scan_type::none_type;
+  }
+
+  auto type() const -> detail::scan_type { return type_; }
+
+  template <typename Visitor>
+  auto visit(Visitor&& vis) -> decltype(vis(monostate())) {
+    switch (type_) {
+    case scan_type::none_type:
+      break;
+    case scan_type::int_type:
+      return vis(*int_value_);
+    case scan_type::uint_type:
+      return vis(*uint_value_);
+    case scan_type::long_long_type:
+      return vis(*long_long_value_);
+    case scan_type::ulong_long_type:
+      return vis(*ulong_long_value_);
+    case scan_type::string_type:
+      return vis(*string_);
+    case scan_type::string_view_type:
+      return vis(*string_view_);
+    case scan_type::custom_type:
+      break;
+    }
+    return vis(monostate());
+  }
+
+  auto scan_custom(const char* parse_begin, scan_parse_context& parse_ctx,
+                   Context& ctx) const -> bool {
+    if (type_ != scan_type::custom_type) return false;
+    parse_ctx.advance_to(parse_begin);
+    custom_.scan(custom_.value, parse_ctx, ctx);
+    return true;
+  }
+};
+
+class scan_context;
+using scan_arg = basic_scan_arg<scan_context>;
+
 struct scan_args {
  int size;
-  const detail::scan_arg* data;
+  const scan_arg* data;

  template <size_t N>
-  scan_args(const std::array<detail::scan_arg, N>& store)
+  FMT_CONSTEXPR scan_args(const std::array<scan_arg, N>& store)
      : size(N), data(store.data()) {
    static_assert(N < INT_MAX, "too many arguments");
  }
 };

+class scan_context {
+ private:
+  detail::scan_buffer& buf_;
+  scan_args args_;
+
+ public:
+  using iterator = detail::scan_iterator;
+  using sentinel = detail::scan_sentinel;
+
+  explicit FMT_CONSTEXPR scan_context(detail::scan_buffer& buf, scan_args args)
+      : buf_(buf), args_(args) {}
+
+  FMT_CONSTEXPR auto arg(int id) const -> scan_arg {
+    return id < args_.size ? args_.data[id] : scan_arg();
+  }
+
+  auto begin() const -> iterator { return buf_.begin(); }
+  auto end() const -> sentinel { return {}; }
+
+  void advance_to(iterator) { buf_.consume(); }
+};
+
 namespace detail {

+const char* parse_scan_specs(const char* begin, const char* end,
+                             format_specs<>& specs, scan_type) {
+  while (begin != end) {
+    switch (to_ascii(*begin)) {
+    // TODO: parse more scan format specifiers
+    case 'x':
+      specs.type = presentation_type::hex_lower;
+      ++begin;
+      break;
+    case '}':
+      return begin;
+    }
+  }
+  return begin;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
+auto read(scan_iterator it, T& value)
+    -> scan_iterator {
+  if (it == scan_sentinel()) return it;
+  char c = *it;
+  if (c < '0' || c > '9') throw_format_error("invalid input");
+
+  int num_digits = 0;
+  T n = 0, prev = 0;
+  char prev_digit = c;
+  do {
+    prev = n;
+    n = n * 10 + static_cast<unsigned>(c - '0');
+    prev_digit = c;
+    c = *++it;
+    ++num_digits;
+    if (c < '0' || c > '9') break;
+  } while (it != scan_sentinel());
+
+  // Check overflow.
+  if (num_digits <= std::numeric_limits<int>::digits10) {
+    value = n;
+    return it;
+  }
+  unsigned max = to_unsigned((std::numeric_limits<int>::max)());
+  if (num_digits == std::numeric_limits<int>::digits10 + 1 &&
+      prev * 10ull + unsigned(prev_digit - '0') <= max) {
+    value = n;
+  } else {
+    throw_format_error("number is too big");
+  }
+  return it;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
+auto read_hex(scan_iterator it, T& value)
+    -> scan_iterator {
+  if (it == scan_sentinel()) return it;
+  int digit = to_hex_digit(*it);
+  if (digit < 0) throw_format_error("invalid input");
+
+  int num_digits = 0;
+  T n = 0;
+  do {
+    n = (n << 4) + static_cast<unsigned>(digit);
+    ++num_digits;
+    digit = to_hex_digit(*++it);
+    if (digit < 0) break;
+  } while (it != scan_sentinel());
+
+  // Check overflow.
+  if (num_digits <= (std::numeric_limits<T>::digits >> 2))
+    value = n;
+  else
+    throw_format_error("number is too big");
+  return it;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
+auto read(scan_iterator it, T& value, const format_specs<>& specs)
+    -> scan_iterator {
+  if (specs.type == presentation_type::hex_lower)
+    return read_hex(it, value);
+  return read(it, value);
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_signed<T>::value)>
+auto read(scan_iterator it, T& value, const format_specs<>& = {})
+    -> scan_iterator {
+  bool negative = it != scan_sentinel() && *it == '-';
+  if (negative) {
+    ++it;
+    if (it == scan_sentinel()) throw_format_error("invalid input");
+  }
+  using unsigned_type = typename std::make_unsigned<T>::type;
+  unsigned_type abs_value = 0;
+  it = read(it, abs_value);
+  auto n = static_cast<T>(abs_value);
+  value = negative ? -n : n;
+  return it;
+}
+
+auto read(scan_iterator it, std::string& value, const format_specs<>& = {})
+    -> scan_iterator {
+  while (it != scan_sentinel() && *it != ' ') value.push_back(*it++);
+  return it;
+}
+
+auto read(scan_iterator it, string_view& value, const format_specs<>& = {})
+    -> scan_iterator {
+  auto range = to_contiguous(it);
+  // This could also be checked at compile time in scan.
+  if (!range) throw_format_error("string_view requires contiguous input");
+  auto p = range.begin;
+  while (p != range.end && *p != ' ') ++p;
+  size_t size = to_unsigned(p - range.begin);
+  value = {range.begin, size};
+  return advance(it, size);
+}
+
+auto read(scan_iterator it, monostate, const format_specs<>& = {})
+    -> scan_iterator {
+  return it;
+}
+
+// An argument scanner that uses the default format, e.g. decimal for integers.
+struct default_arg_scanner {
+  scan_iterator it;
+
+  template <typename T> FMT_INLINE auto operator()(T&& value) -> scan_iterator {
+    return read(it, value);
+  }
+};
+
+// An argument scanner with format specifiers.
+struct arg_scanner {
+  scan_iterator it;
+  const format_specs<>& specs;
+
+  template <typename T> auto operator()(T&& value) -> scan_iterator {
+    return read(it, value, specs);
+  }
+};
+
 struct scan_handler : error_handler {
 private:
  scan_parse_context parse_ctx_;
  scan_context scan_ctx_;
-  scan_args args_;
  int next_arg_id_;
-  scan_arg arg_;

-  template <typename T = unsigned> T read_uint() {
-    T value = 0;
-    auto it = scan_ctx_.begin(), end = scan_ctx_.end();
-    while (it != end) {
-      char c = *it++;
-      if (c < '0' || c > '9') on_error("invalid input");
-      // TODO: check overflow
-      value = value * 10 + static_cast<unsigned>(c - '0');
-    }
-    scan_ctx_.advance_to(it);
-    return value;
-  }
-
-  template <typename T = int> T read_int() {
-    auto it = scan_ctx_.begin(), end = scan_ctx_.end();
-    bool negative = it != end && *it == '-';
-    if (negative) ++it;
-    scan_ctx_.advance_to(it);
-    const auto value = read_uint<typename std::make_unsigned<T>::type>();
-    if (negative) return -static_cast<T>(value);
-    return static_cast<T>(value);
-  }
+  using sentinel = scan_buffer::sentinel;

 public:
-  scan_handler(string_view format, string_view input, scan_args args)
-      : parse_ctx_(format), scan_ctx_(input), args_(args), next_arg_id_(0) {}
+  FMT_CONSTEXPR scan_handler(string_view format, scan_buffer& buf,
+                             scan_args args)
+      : parse_ctx_(format), scan_ctx_(buf, args), next_arg_id_(0) {}

-  const char* pos() const { return scan_ctx_.begin(); }
+  auto pos() const -> scan_buffer::iterator { return scan_ctx_.begin(); }

  void on_text(const char* begin, const char* end) {
-    auto size = to_unsigned(end - begin);
+    if (begin == end) return;
    auto it = scan_ctx_.begin();
-    if (it + size > scan_ctx_.end() ||
-        !std::equal(begin, end, make_checked(it, size))) {
-      on_error("invalid input");
+    for (; begin != end; ++begin, ++it) {
+      if (it == sentinel() || *begin != *it) on_error("invalid input");
    }
-    scan_ctx_.advance_to(it + size);
+    scan_ctx_.advance_to(it);
  }

-  FMT_CONSTEXPR int on_arg_id() { return on_arg_id(next_arg_id_++); }
-  FMT_CONSTEXPR int on_arg_id(int id) {
-    if (id >= args_.size) on_error("argument index out of range");
-    arg_ = args_.data[id];
+  FMT_CONSTEXPR auto on_arg_id() -> int { return on_arg_id(next_arg_id_++); }
+  FMT_CONSTEXPR auto on_arg_id(int id) -> int {
+    if (!scan_ctx_.arg(id)) on_error("argument index out of range");
    return id;
  }
-  FMT_CONSTEXPR int on_arg_id(string_view id) {
+  FMT_CONSTEXPR auto on_arg_id(string_view id) -> int {
    if (id.data()) on_error("invalid format");
    return 0;
  }

-  void on_replacement_field(int, const char*) {
-    auto it = scan_ctx_.begin(), end = scan_ctx_.end();
-    switch (arg_.type) {
-    case scan_type::int_type:
-      *arg_.int_value = read_int();
-      break;
-    case scan_type::uint_type:
-      *arg_.uint_value = read_uint();
-      break;
-    case scan_type::long_long_type:
-      *arg_.long_long_value = read_int<long long>();
-      break;
-    case scan_type::ulong_long_type:
-      *arg_.ulong_long_value = read_uint<unsigned long long>();
-      break;
-    case scan_type::string_type:
-      while (it != end && *it != ' ') arg_.string->push_back(*it++);
-      scan_ctx_.advance_to(it);
-      break;
-    case scan_type::string_view_type: {
-      auto s = it;
-      while (it != end && *it != ' ') ++it;
-      *arg_.string_view = fmt::string_view(s, to_unsigned(it - s));
-      scan_ctx_.advance_to(it);
-      break;
-    }
-    case scan_type::none_type:
-    case scan_type::custom_type:
-      assert(false);
-    }
+  void on_replacement_field(int arg_id, const char*) {
+    scan_arg arg = scan_ctx_.arg(arg_id);
+    auto it = scan_ctx_.begin();
+    while (it != sentinel() && is_whitespace(*it)) ++it;
+    scan_ctx_.advance_to(arg.visit(default_arg_scanner{it}));
  }

-  const char* on_format_specs(int, const char* begin, const char*) {
-    if (arg_.type != scan_type::custom_type) return begin;
-    parse_ctx_.advance_to(begin);
-    arg_.custom.scan(arg_.custom.value, parse_ctx_, scan_ctx_);
-    return parse_ctx_.begin();
+  auto on_format_specs(int arg_id, const char* begin, const char* end) -> const
+      char* {
+    scan_arg arg = scan_ctx_.arg(arg_id);
+    if (arg.scan_custom(begin, parse_ctx_, scan_ctx_))
+      return parse_ctx_.begin();
+    auto specs = format_specs<>();
+    begin = parse_scan_specs(begin, end, specs, arg.type());
+    if (begin == end || *begin != '}') on_error("missing '}' in format string");
+    scan_ctx_.advance_to(arg.visit(arg_scanner{scan_ctx_.begin(), specs}));
+    return begin;
  }
+
+  void on_error(const char* message) { error_handler::on_error(message); }
 };
 }  // namespace detail

-template <typename... Args>
-std::array<detail::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
+template <typename... T>
+auto make_scan_args(T&... args) -> std::array<scan_arg, sizeof...(T)> {
  return {{args...}};
 }

-string_view::iterator vscan(string_view input, string_view format_str,
-                            scan_args args) {
-  detail::scan_handler h(format_str, input, args);
-  detail::parse_format_string<false>(format_str, h);
-  return input.begin() + (h.pos() - &*input.begin());
+void vscan(detail::scan_buffer& buf, string_view fmt, scan_args args) {
+  auto h = detail::scan_handler(fmt, buf, args);
+  detail::parse_format_string<false>(fmt, h);
 }

-template <typename... Args>
-string_view::iterator scan(string_view input, string_view format_str,
-                           Args&... args) {
-  return vscan(input, format_str, make_scan_args(args...));
+template <typename... T>
+auto scan(string_view input, string_view fmt, T&... args)
+    -> string_view::iterator {
+  auto&& buf = detail::string_scan_buffer(input);
+  vscan(buf, fmt, make_scan_args(args...));
+  return input.begin() + (buf.begin().base() - input.data());
 }
+
+template <typename InputRange, typename... T,
+          FMT_ENABLE_IF(!std::is_convertible<InputRange, string_view>::value)>
+auto scan(InputRange&& input, string_view fmt, T&... args)
+    -> decltype(std::begin(input)) {
+  auto it = std::begin(input);
+  vscan(get_buffer(it), fmt, make_scan_args(args...));
+  return it;
+}
+
+template <typename... T> bool scan(std::FILE* f, string_view fmt, T&... args) {
+  auto&& buf = detail::file_scan_buffer(f);
+  vscan(buf, fmt, make_scan_args(args...));
+  return buf.begin() != buf.end();
+}
+
 FMT_END_NAMESPACE
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1...3.18)
+cmake_minimum_required(VERSION 3.8...3.25)

 project(fmt-link CXX)

@@ -6,52 +6,152 @@
 // For the license information refer to format.h.

 #include "fmt/std.h"
-#include "fmt/ranges.h"

+#include <bitset>
+#include <stdexcept>
 #include <string>
 #include <vector>

-#include "gtest/gtest.h"
+#include "fmt/os.h"  // fmt::system_category
+#include "fmt/ranges.h"
+#include "gtest-extra.h"  // StartsWith

+#ifdef __cpp_lib_filesystem
 TEST(std_test, path) {
-// Test ambiguity problem described in #2954. We need to exclude compilers
-// where the ambiguity problem cannot be solved for now.
-#if defined(__cpp_lib_filesystem) && \
-    (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920)
-  EXPECT_EQ(fmt::format("{:8}", std::filesystem::path("foo")), "\"foo\"   ");
-  EXPECT_EQ(fmt::format("{}", std::filesystem::path("foo\"bar.txt")),
-            "\"foo\\\"bar.txt\"");
+  using std::filesystem::path;
+  EXPECT_EQ(fmt::format("{}", path("/usr/bin")), "/usr/bin");
+  EXPECT_EQ(fmt::format("{:?}", path("/usr/bin")), "\"/usr/bin\"");
+  EXPECT_EQ(fmt::format("{:8}", path("foo")), "foo     ");

+  EXPECT_EQ(fmt::format("{}", path("foo\"bar")), "foo\"bar");
+  EXPECT_EQ(fmt::format("{:?}", path("foo\"bar")), "\"foo\\\"bar\"");
+
+  EXPECT_EQ(fmt::format("{:g}", path("/usr/bin")), "/usr/bin");
 #  ifdef _WIN32
-  // File.txt in Russian.
-  const wchar_t unicode_path[] = {0x424, 0x430, 0x439, 0x43b, 0x2e,
-                                  0x74,  0x78,  0x74,  0};
-  const char unicode_u8path[] = {'"',        char(0xd0), char(0xa4), char(0xd0),
-                                 char(0xb0), char(0xd0), char(0xb9), char(0xd0),
-                                 char(0xbb), '.',        't',        'x',
-                                 't',        '"',        '\0'};
-  EXPECT_EQ(fmt::format("{}", std::filesystem::path(unicode_path)),
-            unicode_u8path);
+  EXPECT_EQ(fmt::format("{}", path("C:\\foo")), "C:\\foo");
+  EXPECT_EQ(fmt::format("{:g}", path("C:\\foo")), "C:/foo");
+
+  EXPECT_EQ(fmt::format("{}", path(L"\x0428\x0447\x0443\x0447\x044B\x043D\x0448"
+                                   L"\x0447\x044B\x043D\x0430")),
+            "Шчучыншчына");
+  EXPECT_EQ(fmt::format("{}", path(L"\xd800")), "�");
+  EXPECT_EQ(fmt::format("{:?}", path(L"\xd800")), "\"\\ud800\"");
 #  endif
-#endif
 }

+// Test ambiguity problem described in #2954.
 TEST(ranges_std_test, format_vector_path) {
-// Test ambiguity problem described in #2954. We need to exclude compilers
-// where the ambiguity problem cannot be solved for now.
-#if defined(__cpp_lib_filesystem) && \
-    (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1920)
  auto p = std::filesystem::path("foo/bar.txt");
  auto c = std::vector<std::string>{"abc", "def"};
  EXPECT_EQ(fmt::format("path={}, range={}", p, c),
-            "path=\"foo/bar.txt\", range=[\"abc\", \"def\"]");
-#endif
+            "path=foo/bar.txt, range=[\"abc\", \"def\"]");
 }

+// Test that path is not escaped twice in the debug mode.
+TEST(ranges_std_test, format_quote_path) {
+  auto vec =
+      std::vector<std::filesystem::path>{"path1/file1.txt", "path2/file2.txt"};
+  EXPECT_EQ(fmt::format("{}", vec),
+            "[\"path1/file1.txt\", \"path2/file2.txt\"]");
+#  ifdef __cpp_lib_optional
+  auto o = std::optional<std::filesystem::path>("path/file.txt");
+  EXPECT_EQ(fmt::format("{}", o), "optional(\"path/file.txt\")");
+  EXPECT_EQ(fmt::format("{:?}", o), "optional(\"path/file.txt\")");
+#  endif
+}
+#endif
+
 TEST(std_test, thread_id) {
  EXPECT_FALSE(fmt::format("{}", std::this_thread::get_id()).empty());
 }

+#ifdef __cpp_lib_source_location
+TEST(std_test, source_location) {
+  std::source_location loc = std::source_location::current();
+  EXPECT_EQ(fmt::format("{}", loc),
+            fmt::format("{}:{}:{}: {}", loc.file_name(), loc.line(),
+                        loc.column(), loc.function_name()));
+}
+#endif
+
+TEST(std_test, optional) {
+#ifdef __cpp_lib_optional
+  EXPECT_EQ(fmt::format("{}", std::optional<int>{}), "none");
+  EXPECT_EQ(fmt::format("{}", std::pair{1, "second"}), "(1, \"second\")");
+  EXPECT_EQ(fmt::format("{}", std::vector{std::optional{1}, std::optional{2},
+                                          std::optional{3}}),
+            "[optional(1), optional(2), optional(3)]");
+  EXPECT_EQ(
+      fmt::format("{}", std::optional<std::optional<const char*>>{{"nested"}}),
+      "optional(optional(\"nested\"))");
+  EXPECT_EQ(
+      fmt::format("{:<{}}", std::optional{std::string{"left aligned"}}, 30),
+      "optional(\"left aligned\"                )");
+  EXPECT_EQ(
+      fmt::format("{::d}", std::optional{std::vector{'h', 'e', 'l', 'l', 'o'}}),
+      "optional([104, 101, 108, 108, 111])");
+  EXPECT_EQ(fmt::format("{}", std::optional{std::string{"string"}}),
+            "optional(\"string\")");
+  EXPECT_EQ(fmt::format("{}", std::optional{'C'}), "optional(\'C\')");
+  EXPECT_EQ(fmt::format("{:.{}f}", std::optional{3.14}, 1), "optional(3.1)");
+
+  struct unformattable {};
+  EXPECT_FALSE((fmt::is_formattable<unformattable>::value));
+  EXPECT_FALSE((fmt::is_formattable<std::optional<unformattable>>::value));
+  EXPECT_TRUE((fmt::is_formattable<std::optional<int>>::value));
+#endif
+}
+
+namespace my_nso {
+enum class my_number {
+  one,
+  two,
+};
+auto format_as(my_number number) -> fmt::string_view {
+  return number == my_number::one ? "first" : "second";
+}
+
+class my_class {
+ public:
+  int av;
+
+ private:
+  friend auto format_as(const my_class& elm) -> std::string {
+    return fmt::to_string(elm.av);
+  }
+};
+}  // namespace my_nso
+TEST(std_test, optional_format_as) {
+#ifdef __cpp_lib_optional
+  EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_number>{}), "none");
+  EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_number::one}),
+            "optional(\"first\")");
+  EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_class>{}), "none");
+  EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class{7}}),
+            "optional(\"7\")");
+#endif
+}
+
+struct throws_on_move {
+  throws_on_move() = default;
+
+  [[noreturn]] throws_on_move(throws_on_move&&) {
+    throw std::runtime_error("Thrown by throws_on_move");
+  }
+
+  throws_on_move(const throws_on_move&) = default;
+};
+
+namespace fmt {
+template <> struct formatter<throws_on_move> : formatter<string_view> {
+  auto format(const throws_on_move&, format_context& ctx) const
+      -> decltype(ctx.out()) {
+    string_view str("<throws_on_move>");
+    return formatter<string_view>::format(str, ctx);
+  }
+};
+}  // namespace fmt
+
 TEST(std_test, variant) {
 #ifdef __cpp_lib_variant
  EXPECT_EQ(fmt::format("{}", std::monostate{}), "monostate");
@@ -80,5 +180,127 @@ TEST(std_test, variant) {

  EXPECT_EQ(fmt::format("{}", v4), "variant(monostate)");
  EXPECT_EQ(fmt::format("{}", v5), "variant(\"yes, this is variant\")");
+
+  volatile int i = 42;  // Test compile error before GCC 11 described in #3068.
+  EXPECT_EQ(fmt::format("{}", i), "42");
+
+  std::variant<std::monostate, throws_on_move> v6;
+
+  try {
+    throws_on_move thrower;
+    v6.emplace<throws_on_move>(std::move(thrower));
+  } catch (const std::runtime_error&) {
+  }
+  // v6 is now valueless by exception
+
+  EXPECT_EQ(fmt::format("{}", v6), "variant(valueless by exception)");
+
 #endif
 }
+
+TEST(std_test, error_code) {
+  EXPECT_EQ("generic:42",
+            fmt::format(FMT_STRING("{0}"),
+                        std::error_code(42, std::generic_category())));
+  EXPECT_EQ("system:42",
+            fmt::format(FMT_STRING("{0}"),
+                        std::error_code(42, fmt::system_category())));
+  EXPECT_EQ("system:-42",
+            fmt::format(FMT_STRING("{0}"),
+                        std::error_code(-42, fmt::system_category())));
+}
+
+template <typename Catch> void exception_test() {
+  try {
+    throw std::runtime_error("Test Exception");
+  } catch (const Catch& ex) {
+    EXPECT_EQ("Test Exception", fmt::format("{}", ex));
+    EXPECT_EQ("std::runtime_error: Test Exception", fmt::format("{:t}", ex));
+  }
+}
+
+namespace my_ns1 {
+namespace my_ns2 {
+struct my_exception : public std::exception {
+ private:
+  std::string msg;
+
+ public:
+  my_exception(const std::string& s) : msg(s) {}
+  const char* what() const noexcept override;
+};
+const char* my_exception::what() const noexcept { return msg.c_str(); }
+}  // namespace my_ns2
+}  // namespace my_ns1
+
+TEST(std_test, exception) {
+  using testing::StartsWith;
+  exception_test<std::exception>();
+  exception_test<std::runtime_error>();
+
+  try {
+    using namespace my_ns1::my_ns2;
+    throw my_exception("My Exception");
+  } catch (const std::exception& ex) {
+    EXPECT_EQ("my_ns1::my_ns2::my_exception: My Exception",
+              fmt::format("{:t}", ex));
+    EXPECT_EQ("My Exception", fmt::format("{:}", ex));
+  }
+
+  try {
+    throw std::system_error(std::error_code(), "message");
+  } catch (const std::system_error& ex) {
+    EXPECT_THAT(fmt::format("{:t}", ex), StartsWith("std::system_error: "));
+  }
+
+#ifdef __cpp_lib_filesystem
+  // Tests that the inline namespace is stripped out, e.g.
+  // std::filesystem::__cxx11::* -> std::filesystem::*.
+  try {
+    throw std::filesystem::filesystem_error("message", std::error_code());
+  } catch (const std::filesystem::filesystem_error& ex) {
+    EXPECT_THAT(fmt::format("{:t}", ex),
+                StartsWith("std::filesystem::filesystem_error: "));
+  }
+#endif
+}
+
+TEST(std_test, format_bit_reference) {
+  std::bitset<2> bs(1);
+  EXPECT_EQ(fmt::format("{} {}", bs[0], bs[1]), "true false");
+  std::vector<bool> v = {true, false};
+  EXPECT_EQ(fmt::format("{} {}", v[0], v[1]), "true false");
+}
+
+TEST(std_test, format_const_bit_reference) {
+  const std::bitset<2> bs(1);
+  EXPECT_EQ(fmt::format("{} {}", bs[0], bs[1]), "true false");
+  const std::vector<bool> v = {true, false};
+  EXPECT_EQ(fmt::format("{} {}", v[0], v[1]), "true false");
+}
+
+TEST(std_test, format_bitset) {
+  auto bs = std::bitset<6>(42);
+  EXPECT_EQ(fmt::format("{}", bs), "101010");
+  EXPECT_EQ(fmt::format("{:0>8}", bs), "00101010");
+  EXPECT_EQ(fmt::format("{:-^12}", bs), "---101010---");
+}
+
+TEST(std_test, format_atomic) {
+  std::atomic<bool> b(false);
+  EXPECT_EQ(fmt::format("{}", b), "false");
+
+  const std::atomic<bool> cb(true);
+  EXPECT_EQ(fmt::format("{}", cb), "true");
+}
+
+#ifdef __cpp_lib_atomic_flag_test
+TEST(std_test, format_atomic_flag) {
+  std::atomic_flag f = ATOMIC_FLAG_INIT;
+  (void)f.test_and_set();
+  EXPECT_EQ(fmt::format("{}", f), "true");
+
+  const std::atomic_flag cf = ATOMIC_FLAG_INIT;
+  EXPECT_EQ(fmt::format("{}", cf), "false");
+}
+#endif  // __cpp_lib_atomic_flag_test
@@ -18,12 +18,12 @@ using testing::Contains;
 TEST(unicode_test, is_utf8) { EXPECT_TRUE(fmt::detail::is_utf8()); }

 TEST(unicode_test, legacy_locale) {
-  auto loc = get_locale("ru_RU.CP1251", "Russian_Russia.1251");
+  auto loc = get_locale("be_BY.CP1251", "Belarusian_Belarus.1251");
  if (loc == std::locale::classic()) return;

  auto s = std::string();
  try {
-    s = fmt::format(loc, "День недели: {:L}", fmt::weekday(1));
+    s = fmt::format(loc, "Дзень тыдня: {:L}", fmt::weekday(1));
  } catch (const fmt::format_error& e) {
    // Formatting can fail due to an unsupported encoding.
    fmt::print("Format error: {}\n", e.what());
@@ -38,11 +38,11 @@ TEST(unicode_test, legacy_locale) {
  os << std::put_time(&tm, "%a");
  auto wd = os.str();
  if (wd == "??") {
-    EXPECT_EQ(s, "День недели: ??");
+    EXPECT_EQ(s, "Дзень тыдня: ??");
    fmt::print("std::locale gives ?? as a weekday.\n");
    return;
  }
 #endif
-  EXPECT_THAT((std::vector<std::string>{"День недели: пн", "День недели: Пн"}),
+  EXPECT_THAT((std::vector<std::string>{"Дзень тыдня: пн", "Дзень тыдня: Пан"}),
              Contains(s));
 }
@@ -37,9 +37,13 @@ std::locale do_get_locale(const char* name) {

 std::locale get_locale(const char* name, const char* alt_name) {
  auto loc = do_get_locale(name);
-  if (loc == std::locale::classic() && alt_name) {
+  if (loc == std::locale::classic() && alt_name)
    loc = do_get_locale(alt_name);
-  }
+#ifdef __OpenBSD__
+    // Locales are not working in OpenBSD:
+    // https://github.com/fmtlib/fmt/issues/3670.
+    loc = std::locale::classic();
+#endif
  if (loc == std::locale::classic())
    fmt::print(stderr, "{} locale is missing.\n", name);
  return loc;
@@ -10,11 +10,7 @@
 #include <locale>
 #include <string>

-#ifdef FMT_MODULE_TEST
-import fmt;
-#else
-#  include "fmt/os.h"
-#endif  // FMT_MODULE_TEST
+#include "fmt/os.h"

 #ifdef _MSC_VER
 #  define FMT_VSNPRINTF vsprintf_s
@@ -33,9 +29,9 @@ void safe_sprintf(char (&buffer)[SIZE], const char* format, ...) {
 extern const char* const file_content;

 // Opens a buffered file for reading.
-fmt::buffered_file open_buffered_file(FILE** fp = nullptr);
+auto open_buffered_file(FILE** fp = nullptr) -> fmt::buffered_file;

-inline FILE* safe_fopen(const char* filename, const char* mode) {
+inline auto safe_fopen(const char* filename, const char* mode) -> FILE* {
 #if defined(_WIN32) && !defined(__MINGW32__)
  // Fix MSVC warning about "unsafe" fopen.
  FILE* f = nullptr;
@@ -55,17 +51,17 @@ template <typename Char> class basic_test_string {
 public:
  explicit basic_test_string(const Char* value = empty) : value_(value) {}

-  const std::basic_string<Char>& value() const { return value_; }
+  auto value() const -> const std::basic_string<Char>& { return value_; }
 };

 template <typename Char> const Char basic_test_string<Char>::empty[] = {0};

-typedef basic_test_string<char> test_string;
-typedef basic_test_string<wchar_t> test_wstring;
+using test_string = basic_test_string<char>;
+using test_wstring = basic_test_string<wchar_t>;

 template <typename Char>
-std::basic_ostream<Char>& operator<<(std::basic_ostream<Char>& os,
-                                     const basic_test_string<Char>& s) {
+auto operator<<(std::basic_ostream<Char>& os, const basic_test_string<Char>& s)
+    -> std::basic_ostream<Char>& {
  os << s.value();
  return os;
 }
@@ -76,10 +72,12 @@ class date {
 public:
  date(int year, int month, int day) : year_(year), month_(month), day_(day) {}

-  int year() const { return year_; }
-  int month() const { return month_; }
-  int day() const { return day_; }
+  auto year() const -> int { return year_; }
+  auto month() const -> int { return month_; }
+  auto day() const -> int { return day_; }
 };

-// Returns a locale with the given name if available or classic locale othewise.
-std::locale get_locale(const char* name, const char* alt_name = nullptr);
+// Returns a locale with the given name if available or classic locale
+// otherwise.
+auto get_locale(const char* name, const char* alt_name = nullptr)
+    -> std::locale;
@@ -7,6 +7,7 @@

 #include "fmt/xchar.h"

+#include <algorithm>
 #include <complex>
 #include <cwchar>
 #include <vector>
@@ -15,31 +16,21 @@
 #include "fmt/color.h"
 #include "fmt/ostream.h"
 #include "fmt/ranges.h"
+#include "fmt/std.h"
 #include "gtest-extra.h"  // Contains
 #include "util.h"         // get_locale

 using fmt::detail::max_value;
 using testing::Contains;

-namespace test_ns {
-template <typename Char> class test_string {
- private:
-  std::basic_string<Char> s_;
-
- public:
-  test_string(const Char* s) : s_(s) {}
-  const Char* data() const { return s_.data(); }
-  size_t length() const { return s_.size(); }
-  operator const Char*() const { return s_.c_str(); }
-};
-
-template <typename Char>
-fmt::basic_string_view<Char> to_string_view(const test_string<Char>& s) {
-  return {s.data(), s.length()};
-}
+#if defined(__MINGW32__) && !defined(_UCRT)
+// Only C89 conversion specifiers when using MSVCRT instead of UCRT
+#  define FMT_HAS_C99_STRFTIME 0
+#else
+#  define FMT_HAS_C99_STRFTIME 1
+#endif

 struct non_string {};
-}  // namespace test_ns

 template <typename T> class is_string_test : public testing::Test {};

@@ -61,8 +52,7 @@ TYPED_TEST(is_string_test, is_string) {
  using fmt_string_view = fmt::detail::std_string_view<TypeParam>;
  EXPECT_TRUE(std::is_empty<fmt_string_view>::value !=
              fmt::detail::is_string<fmt_string_view>::value);
-  EXPECT_TRUE(fmt::detail::is_string<test_ns::test_string<TypeParam>>::value);
-  EXPECT_FALSE(fmt::detail::is_string<test_ns::non_string>::value);
+  EXPECT_FALSE(fmt::detail::is_string<non_string>::value);
 }

 // std::is_constructible is broken in MSVC until version 2015.
@@ -84,7 +74,7 @@ TEST(xchar_test, format) {
  EXPECT_EQ(L"4.2", fmt::format(L"{}", 4.2));
  EXPECT_EQ(L"abc", fmt::format(L"{}", L"abc"));
  EXPECT_EQ(L"z", fmt::format(L"{}", L'z'));
-  EXPECT_THROW(fmt::format(L"{:*\x343E}", 42), fmt::format_error);
+  EXPECT_THROW(fmt::format(fmt::runtime(L"{:*\x343E}"), 42), fmt::format_error);
  EXPECT_EQ(L"true", fmt::format(L"{}", true));
  EXPECT_EQ(L"a", fmt::format(L"{0}", 'a'));
  EXPECT_EQ(L"a", fmt::format(L"{0}", L'a'));
@@ -98,8 +88,9 @@ TEST(xchar_test, is_formattable) {
 }

 TEST(xchar_test, compile_time_string) {
+  EXPECT_EQ(fmt::format(fmt::wformat_string<int>(L"{}"), 42), L"42");
 #if defined(FMT_USE_STRING_VIEW) && FMT_CPLUSPLUS >= 201703L
-  EXPECT_EQ(L"42", fmt::format(FMT_STRING(std::wstring_view(L"{}")), 42));
+  EXPECT_EQ(fmt::format(FMT_STRING(std::wstring_view(L"{}")), 42), L"42");
 #endif
 }

@@ -111,10 +102,72 @@ struct custom_char {
  template <typename T>
  constexpr custom_char(T val) : value(static_cast<int>(val)) {}

-  operator int() const { return value; }
+  constexpr operator char() const {
+    return value <= 0xff ? static_cast<char>(value) : '\0';
+  }
+  constexpr bool operator<(custom_char c) const { return value < c.value; }
 };

-int to_ascii(custom_char c) { return c; }
+namespace std {
+
+template <> struct char_traits<custom_char> {
+  using char_type = custom_char;
+  using int_type = int;
+  using off_type = streamoff;
+  using pos_type = streampos;
+  using state_type = mbstate_t;
+
+  static constexpr void assign(char_type& r, const char_type& a) { r = a; }
+  static constexpr bool eq(char_type a, char_type b) { return a == b; }
+  static constexpr bool lt(char_type a, char_type b) { return a < b; }
+  static FMT_CONSTEXPR int compare(const char_type* s1, const char_type* s2,
+                                   size_t count) {
+    for (; count; count--, s1++, s2++) {
+      if (lt(*s1, *s2)) return -1;
+      if (lt(*s2, *s1)) return 1;
+    }
+    return 0;
+  }
+  static FMT_CONSTEXPR size_t length(const char_type* s) {
+    size_t count = 0;
+    while (!eq(*s++, custom_char(0))) count++;
+    return count;
+  }
+  static const char_type* find(const char_type*, size_t, const char_type&);
+  static FMT_CONSTEXPR char_type* move(char_type* dest, const char_type* src,
+                                       size_t count) {
+    if (count == 0) return dest;
+    char_type* ret = dest;
+    if (src < dest) {
+      dest += count;
+      src += count;
+      for (; count; count--) assign(*--dest, *--src);
+    } else if (src > dest)
+      copy(dest, src, count);
+    return ret;
+  }
+  static FMT_CONSTEXPR char_type* copy(char_type* dest, const char_type* src,
+                                       size_t count) {
+    char_type* ret = dest;
+    for (; count; count--) assign(*dest++, *src++);
+    return ret;
+  }
+  static FMT_CONSTEXPR char_type* assign(char_type* dest, std::size_t count,
+                                         char_type a) {
+    char_type* ret = dest;
+    for (; count; count--) assign(*dest++, a);
+    return ret;
+  }
+  static int_type not_eof(int_type);
+  static char_type to_char_type(int_type);
+  static int_type to_int_type(char_type);
+  static bool eq_int_type(int_type, int_type);
+  static int_type eof();
+};
+
+}  // namespace std
+
+auto to_ascii(custom_char c) -> char { return c; }

 FMT_BEGIN_NAMESPACE
 template <> struct is_char<custom_char> : std::true_type {};
@@ -134,18 +187,6 @@ template <typename S> std::string from_u8str(const S& str) {
  return std::string(str.begin(), str.end());
 }

-TEST(xchar_test, format_utf8_precision) {
-  using str_type = std::basic_string<fmt::detail::char8_type>;
-  auto format =
-      str_type(reinterpret_cast<const fmt::detail::char8_type*>(u8"{:.4}"));
-  auto str = str_type(reinterpret_cast<const fmt::detail::char8_type*>(
-      u8"caf\u00e9s"));  // cafés
-  auto result = fmt::format(format, str);
-  EXPECT_EQ(fmt::detail::compute_width(result), 4);
-  EXPECT_EQ(result.size(), 5);
-  EXPECT_EQ(from_u8str(result), from_u8str(str.substr(0, 5)));
-}
-
 TEST(xchar_test, format_to) {
  auto buf = std::vector<wchar_t>();
  fmt::format_to(std::back_inserter(buf), L"{}{}", 42, L'\0');
@@ -153,17 +194,21 @@ TEST(xchar_test, format_to) {
 }

 TEST(xchar_test, vformat_to) {
-  using wcontext = fmt::wformat_context;
-  fmt::basic_format_arg<wcontext> warg = fmt::detail::make_arg<wcontext>(42);
-  auto wargs = fmt::basic_format_args<wcontext>(&warg, 1);
+  auto args = fmt::make_wformat_args(42);
  auto w = std::wstring();
-  fmt::vformat_to(std::back_inserter(w), L"{}", wargs);
-  EXPECT_EQ(L"42", w);
-  w.clear();
-  fmt::vformat_to(std::back_inserter(w), FMT_STRING(L"{}"), wargs);
+  fmt::vformat_to(std::back_inserter(w), L"{}", args);
  EXPECT_EQ(L"42", w);
 }

+namespace test {
+struct struct_as_wstring_view {};
+auto format_as(struct_as_wstring_view) -> fmt::wstring_view { return L"foo"; }
+}  // namespace test
+
+TEST(xchar_test, format_as) {
+  EXPECT_EQ(fmt::format(L"{}", test::struct_as_wstring_view()), L"foo");
+}
+
 TEST(format_test, wide_format_to_n) {
  wchar_t buffer[4];
  buffer[3] = L'x';
@@ -199,7 +244,10 @@ TEST(xchar_test, named_arg_udl) {

 TEST(xchar_test, print) {
  // Check that the wide print overload compiles.
-  if (fmt::detail::const_check(false)) fmt::print(L"test");
+  if (fmt::detail::const_check(false)) {
+    fmt::print(L"test");
+    fmt::println(L"test");
+  }
 }

 TEST(xchar_test, join) {
@@ -229,11 +277,24 @@ TEST(xchar_test, enum) {
  EXPECT_EQ(L"0", fmt::format(L"{}", unstreamable_enum()));
 }

+struct streamable_and_unformattable {};
+
+auto operator<<(std::wostream& os, streamable_and_unformattable)
+    -> std::wostream& {
+  return os << L"foo";
+}
+
+TEST(xchar_test, streamed) {
+  EXPECT_FALSE(fmt::is_formattable<streamable_and_unformattable>());
+  EXPECT_EQ(fmt::format(L"{}", fmt::streamed(streamable_and_unformattable())),
+            L"foo");
+}
+
 TEST(xchar_test, sign_not_truncated) {
  wchar_t format_str[] = {
      L'{', L':',
      '+' | static_cast<wchar_t>(1 << fmt::detail::num_bits<char>()), L'}', 0};
-  EXPECT_THROW(fmt::format(format_str, 42), fmt::format_error);
+  EXPECT_THROW(fmt::format(fmt::runtime(format_str), 42), fmt::format_error);
 }

 TEST(xchar_test, chrono) {
@@ -269,8 +330,9 @@ std::wstring system_wcsftime(const std::wstring& format, const std::tm* timeptr,
 #endif
 }

-TEST(chrono_test, time_point) {
-  auto t1 = std::chrono::system_clock::now();
+TEST(chrono_test_wchar, time_point) {
+  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
+      std::chrono::system_clock::now());

  std::vector<std::wstring> spec_list = {
      L"%%",  L"%n",  L"%t",  L"%Y",  L"%EY", L"%y",  L"%Oy", L"%Ey", L"%C",
@@ -278,14 +340,36 @@ TEST(chrono_test, time_point) {
      L"%OU", L"%W",  L"%OW", L"%V",  L"%OV", L"%j",  L"%d",  L"%Od", L"%e",
      L"%Oe", L"%a",  L"%A",  L"%w",  L"%Ow", L"%u",  L"%Ou", L"%H",  L"%OH",
      L"%I",  L"%OI", L"%M",  L"%OM", L"%S",  L"%OS", L"%x",  L"%Ex", L"%X",
-      L"%EX", L"%D",  L"%F",  L"%R",  L"%T",  L"%p",  L"%z",  L"%Z"};
-  spec_list.push_back(L"%Y-%m-%d %H:%M:%S");
+      L"%EX", L"%D",  L"%F",  L"%R",  L"%T",  L"%p"};
 #ifndef _WIN32
  // Disabled on Windows, because these formats is not consistent among
  // platforms.
  spec_list.insert(spec_list.end(), {L"%c", L"%Ec", L"%r"});
+#elif !FMT_HAS_C99_STRFTIME
+  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
+  spec_list = {L"%%", L"%Y", L"%y", L"%b", L"%B", L"%m", L"%U",
+               L"%W", L"%j", L"%d", L"%a", L"%A", L"%w", L"%H",
+               L"%I", L"%M", L"%S", L"%x", L"%X", L"%p"};
 #endif
+  spec_list.push_back(L"%Y-%m-%d %H:%M:%S");

+  for (const auto& spec : spec_list) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    auto sys_output = system_wcsftime(spec, &tm);
+
+    auto fmt_spec = fmt::format(L"{{:{}}}", spec);
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
+  }
+
+  // Timezone formatters tests makes sense for localtime.
+#if FMT_HAS_C99_STRFTIME
+  spec_list = {L"%z", L"%Z"};
+#else
+  spec_list = {L"%Z"};
+#endif
  for (const auto& spec : spec_list) {
    auto t = std::chrono::system_clock::to_time_t(t1);
    auto tm = *std::localtime(&t);
@@ -293,8 +377,38 @@ TEST(chrono_test, time_point) {
    auto sys_output = system_wcsftime(spec, &tm);

    auto fmt_spec = fmt::format(L"{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt_spec, t1));
-    EXPECT_EQ(sys_output, fmt::format(fmt_spec, tm));
+    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
+
+    if (spec == L"%z") {
+      sys_output.insert(sys_output.end() - 2, 1, L':');
+      EXPECT_EQ(sys_output, fmt::format(L"{:%Ez}", tm));
+      EXPECT_EQ(sys_output, fmt::format(L"{:%Oz}", tm));
+    }
+  }
+
+  // Separate tests for UTC, since std::time_put can use local time and ignoring
+  // the timezone in std::tm (if it presents on platform).
+  if (fmt::detail::has_member_data_tm_zone<std::tm>::value) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    std::vector<std::wstring> tz_names = {L"GMT", L"UTC"};
+    EXPECT_THAT(tz_names, Contains(fmt::format(L"{:%Z}", t1)));
+    EXPECT_THAT(tz_names, Contains(fmt::format(L"{:%Z}", tm)));
+  }
+
+  if (fmt::detail::has_member_data_tm_gmtoff<std::tm>::value) {
+    auto t = std::chrono::system_clock::to_time_t(t1);
+    auto tm = *std::gmtime(&t);
+
+    EXPECT_EQ(L"+0000", fmt::format(L"{:%z}", t1));
+    EXPECT_EQ(L"+0000", fmt::format(L"{:%z}", tm));
+
+    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Ez}", t1));
+    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Ez}", tm));
+
+    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Oz}", t1));
+    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Oz}", tm));
  }
 }

@@ -305,9 +419,17 @@ TEST(xchar_test, color) {

 TEST(xchar_test, ostream) {
 #if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 409
-  std::wostringstream wos;
-  fmt::print(wos, L"Don't {}!", L"panic");
-  EXPECT_EQ(wos.str(), L"Don't panic!");
+  {
+    std::wostringstream wos;
+    fmt::print(wos, L"Don't {}!", L"panic");
+    EXPECT_EQ(wos.str(), L"Don't panic!");
+  }
+
+  {
+    std::wostringstream wos;
+    fmt::println(wos, L"Don't {}!", L"panic");
+    EXPECT_EQ(wos.str(), L"Don't panic!\n");
+  }
 #endif
 }

@@ -325,6 +447,7 @@ TEST(xchar_test, escape_string) {
 TEST(xchar_test, to_wstring) { EXPECT_EQ(L"42", fmt::to_wstring(42)); }

 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+
 template <typename Char> struct numpunct : std::numpunct<Char> {
 protected:
  Char do_decimal_point() const override { return '?'; }
@@ -360,6 +483,9 @@ TEST(locale_test, localized_double) {
  EXPECT_EQ(fmt::format(loc, "{:L}", 1234.5), "1~234?5");
  EXPECT_EQ(fmt::format(loc, "{:L}", 12000.0), "12~000");
  EXPECT_EQ(fmt::format(loc, "{:8L}", 1230.0), "   1~230");
+  EXPECT_EQ(fmt::format(loc, "{:15.6Lf}", 0.1), "       0?100000");
+  EXPECT_EQ(fmt::format(loc, "{:15.6Lf}", 1.0), "       1?000000");
+  EXPECT_EQ(fmt::format(loc, "{:15.6Lf}", 1e3), "   1~000?000000");
 }

 TEST(locale_test, format) {
@@ -368,8 +494,8 @@ TEST(locale_test, format) {
  EXPECT_EQ("1~234~567", fmt::format(loc, "{:L}", 1234567));
  EXPECT_EQ("-1~234~567", fmt::format(loc, "{:L}", -1234567));
  EXPECT_EQ("-256", fmt::format(loc, "{:L}", -256));
-  fmt::format_arg_store<fmt::format_context, int> as{1234567};
-  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:L}", fmt::format_args(as)));
+  auto n = 1234567;
+  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:L}", fmt::make_format_args(n)));
  auto s = std::string();
  fmt::format_to(std::back_inserter(s), loc, "{:L}", 1234567);
  EXPECT_EQ("1~234~567", s);
@@ -402,10 +528,9 @@ TEST(locale_test, wformat) {
  auto loc = std::locale(std::locale(), new numpunct<wchar_t>());
  EXPECT_EQ(L"1234567", fmt::format(std::locale(), L"{:L}", 1234567));
  EXPECT_EQ(L"1~234~567", fmt::format(loc, L"{:L}", 1234567));
-  using wcontext = fmt::buffer_context<wchar_t>;
-  fmt::format_arg_store<wcontext, int> as{1234567};
+  int n = 1234567;
  EXPECT_EQ(L"1~234~567",
-            fmt::vformat(loc, L"{:L}", fmt::basic_format_args<wcontext>(as)));
+            fmt::vformat(loc, L"{:L}", fmt::make_wformat_args(n)));
  EXPECT_EQ(L"1234567", fmt::format(std::locale("C"), L"{:L}", 1234567));

  auto no_grouping_loc = std::locale(std::locale(), new no_grouping<wchar_t>());
@@ -422,16 +547,16 @@ TEST(locale_test, wformat) {
            fmt::format(small_grouping_loc, L"{:L}", max_value<uint32_t>()));
 }

-TEST(locale_test, double_formatter) {
+TEST(locale_test, int_formatter) {
  auto loc = std::locale(std::locale(), new special_grouping<char>());
  auto f = fmt::formatter<int>();
  auto parse_ctx = fmt::format_parse_context("L");
  f.parse(parse_ctx);
-  char buf[10] = {};
-  fmt::basic_format_context<char*, char> format_ctx(
-      buf, {}, fmt::detail::locale_ref(loc));
-  *f.format(12345, format_ctx) = 0;
-  EXPECT_STREQ("12,345", buf);
+  auto buf = fmt::memory_buffer();
+  fmt::basic_format_context<fmt::appender, char> format_ctx(
+      fmt::appender(buf), {}, fmt::detail::locale_ref(loc));
+  f.format(12345, format_ctx);
+  EXPECT_EQ(fmt::to_string(buf), "12,345");
 }

 FMT_BEGIN_NAMESPACE
@@ -442,13 +567,10 @@ template <class charT> struct formatter<std::complex<double>, charT> {
 public:
  FMT_CONSTEXPR typename basic_format_parse_context<charT>::iterator parse(
      basic_format_parse_context<charT>& ctx) {
-    using handler_type =
-        detail::dynamic_specs_handler<basic_format_parse_context<charT>>;
-    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                detail::type::string_type);
-    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
-    detail::parse_float_type_spec(specs_, ctx.error_handler());
-    return it;
+    auto end = parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
+                                  detail::type::float_type);
+    detail::parse_float_type_spec(specs_);
+    return end;
  }

  template <class FormatContext>
@@ -465,9 +587,9 @@ template <class charT> struct formatter<std::complex<double>, charT> {
                            fmt::runtime("{:" + specs + "}"), c.imag());
    auto fill_align_width = std::string();
    if (specs_.width > 0) fill_align_width = fmt::format(">{}", specs_.width);
-    return format_to(ctx.out(), runtime("{:" + fill_align_width + "}"),
-                     c.real() != 0 ? fmt::format("({}+{}i)", real, imag)
-                                   : fmt::format("{}i", imag));
+    return fmt::format_to(ctx.out(), runtime("{:" + fill_align_width + "}"),
+                          c.real() != 0 ? fmt::format("({}+{}i)", real, imag)
+                                        : fmt::format("{}i", imag));
  }
 };
 FMT_END_NAMESPACE
@@ -480,19 +602,28 @@ TEST(locale_test, complex) {
 }

 TEST(locale_test, chrono_weekday) {
-  auto loc = get_locale("ru_RU.UTF-8", "Russian_Russia.1251");
+  auto loc = get_locale("es_ES.UTF-8", "Spanish_Spain.1252");
  auto loc_old = std::locale::global(loc);
-  auto mon = fmt::weekday(1);
-  EXPECT_EQ(fmt::format(L"{}", mon), L"Mon");
+  auto sat = fmt::weekday(6);
+  EXPECT_EQ(fmt::format(L"{}", sat), L"Sat");
  if (loc != std::locale::classic()) {
-    // {L"\x43F\x43D", L"\x41F\x43D", L"\x43F\x43D\x434", L"\x41F\x43D\x434"}
-    // {L"пн", L"Пн", L"пнд", L"Пнд"}
-    EXPECT_THAT(
-        (std::vector<std::wstring>{L"\x43F\x43D", L"\x41F\x43D",
-                                   L"\x43F\x43D\x434", L"\x41F\x43D\x434"}),
-        Contains(fmt::format(loc, L"{:L}", mon)));
+    // L'\xE1' is 'á'.
+    auto saturdays = std::vector<std::wstring>{L"s\xE1""b", L"s\xE1."};
+    EXPECT_THAT(saturdays, Contains(fmt::format(loc, L"{:L}", sat)));
  }
  std::locale::global(loc_old);
 }

+TEST(locale_test, sign) {
+  EXPECT_EQ(fmt::format(std::locale(), L"{:L}", -50), L"-50");
+}
+
+TEST(std_test_xchar, optional) {
+#  ifdef __cpp_lib_optional
+  EXPECT_EQ(fmt::format(L"{}", std::optional{L'C'}), L"optional(\'C\')");
+  EXPECT_EQ(fmt::format(L"{}", std::optional{std::wstring{L"wide string"}}),
+            L"optional(\"wide string\")");
+#  endif
+}
+
 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR
				`@@ -1 +0,0 @@`
				`build --symlink_prefix=/ # Out of source build`
@@ -1 +1 @@
 .1.1
 .1.2