10.2.1

• Fixed ABI compatibility with earlier 10.x versions (#3786). Thanks @saraedum.

10.2.0

• Added support for the %j specifier (the number of days) for std::chrono::duration (#3643, #3732). Thanks @intelfx.

• Added support for the chrono suffix for days and changed the suffix for minutes from "m" to the correct "min" (#3662, #3664). For example (godbolt):

  #include <fmt/chrono.h>
  
  int main() {
    fmt::print("{}\n", std::chrono::days(42)); // prints "42d"
  }

  Thanks @Richardk2n.

• Fixed an overflow in std::chrono::time_point formatting with large dates (#3725, #3727). Thanks @cschreib.

• Added a formatter for std::source_location (#3730). For example (godbolt):

  #include <source_location>
  #include <fmt/std.h>
  
  int main() {
    fmt::print("{}\n", std::source_location::current());
  }

  prints

  /app/example.cpp:5:51: int main()
  

  Thanks @felix642.

• Added a formatter for std::bitset (#3660). For example (godbolt):

  #include <bitset>
  #include <fmt/std.h>
  
  int main() {
    fmt::print("{}\n", std::bitset<6>(42)); // prints "101010"
  }

  Thanks @muggenhor.

• Added an experimental nested_formatter that provides an easy way of applying a formatter to one or more subobjects while automatically handling width, fill and alignment. 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)]
  

• Added the generic representation (g) to std::filesystem::path (#3715, #3729). For example:

  #include <filesystem>
  #include <fmt/std.h>
  
  int main() {
    fmt::print("{:g}\n", std::filesystem::path("C:\\foo"));
  }

  prints "C:/foo" on Windows.

  Thanks @js324.

• Made format_as work with references (#3739). Thanks @tchaikov.

• Fixed formatting of invalid UTF-8 with precision (#3284).

• Fixed an inconsistency between fmt::to_string and fmt::format (#3684).

• Disallowed unsafe uses of fmt::styled (#3625):

  auto s = fmt::styled(std::string("dangle"), fmt::emphasis::bold);
  fmt::print("{}\n", s); // compile error

  Pass fmt::styled(...) as a parameter instead.

• Added a null check when formatting a C string with the s specifier (#3706).

• Disallowed the c specifier for bool (#3726, #3734). Thanks @js324.

• Made the default formatting unlocalized in fmt::ostream_formatter for consistency with the rest of the library (#3460).

• Fixed localized formatting in bases other than decimal (#3693, #3750). Thanks @js324.

• Fixed a performance regression in experimental fmt::ostream::print (#3674).

• Added synchronization with the underlying output stream when writing to the Windows console (#3668, #3688, #3689). Thanks @Roman-Koshelev and @dimztimz.

• Changed to only export format_error when {fmt} is built as a shared library (#3626, #3627). Thanks @phprus.

• Made fmt::streamed constexpr. (#3650). Thanks @muggenhor.

• Enabled consteval on older versions of MSVC (#3757). Thanks @phprus.

• Added an option to build without wchar_t support on Windows (#3631, #3636). Thanks @glebm.

• Improved build and CI configuration (#3679, #3701, #3702, #3749). Thanks @jcar87, @pklima and @tchaikov.

• Fixed various warnings, compilation and test issues (#3607, #3610, #3624, #3630, #3634, #3638, #3645, #3646, #3647, #3652, #3654, #3663, #3670, #3680, #3694, #3695, #3699, #3705, #3710, #3712, #3713, #3714, #3716, #3723, #3738, #3740, #3741, #3743, #3745, #3747, #3748, #3751, #3754, #3755, #3760, #3762, #3763, #3764, #3774, #3779). Thanks @danakj, @vinayyadav3016, @cyyever, @phprus, @qimiko, @saschasc, @gsjaardema, @lazka, @Zhaojun-Liu, @carlsmedstad, @hotwatermorning, @cptFracassa, @kuguma, @PeterJohnson, @H1X4Dev, @asantoni, @eltociear, @msimberg, @tchaikov, @waywardmonkeys.

• Improved documentation and README (#2086, #3637, #3642, #3653, #3655, #3661, #3673, #3677, #3737, #3742, #3744). Thanks @idzm, @perlun, @joycebrum, @fennewald, @reinhardt1053, @GeorgeLS.

• Updated CI dependencies (#3615, #3622, #3623, #3666, #3696, #3697, #3759, #3782).

10.1.1

• Added formatters for std::atomic and atomic_flag (#3574, #3594). Thanks @wangzw (Zhanwei Wang) and @AlexGuteniev (Alex Guteniev).

• Fixed an error about partial specialization of formatter<string> after instantiation when compiled with gcc and C++20 (#3584).

• Fixed compilation as a C++20 module with gcc and clang (#3587, #3597, #3605). Thanks @MathewBensonCode (Mathew Benson).

• Made fmt::to_string work with types that have format_as overloads (#3575). Thanks @phprus (Vladislav Shchapov).

• Made formatted_size work with integral format specifiers at compile time (#3591). Thanks @elbeno (Ben Deane).

• Fixed a warning about the no_unique_address attribute on clang-cl (#3599). Thanks @lukester1975.

• Improved compatibility with the legacy GBK encoding (#3598, #3599). Thanks @YuHuanTin.

• Added OpenSSF Scorecard analysis (#3530, #3571). Thanks @joycebrum (Joyce).

• Updated CI dependencies (#3591, #3592, #3593, #3602).

Pull Requests

• Configure OpenSSF Scorecard Action by @joycebrum in #3571
• to_string supports types with format_as by @phprus in #3575
• Add formatter for std::atomic by @wangzw in #3574
• Bump github/codeql-action from 2.2.4 to 2.21.4 by @dependabot in #3591
• Bump ossf/scorecard-action from 2.1.2 to 2.2.0 by @dependabot in #3592
• Bump actions/upload-artifact from 3.1.0 to 3.1.2 by @dependabot in #3593
• Fix formatted_size with FMT_COMPILE and format specs by @elbeno in #3588
• fix issues #3598 by @YuHuanTin in #3599
• Fix for Compilation Error When Using FMT_MODULE by @MathewBensonCode in #3597
• Fix FMT_NO_UNIQUE_ADDRESS warning with clang-cl. by @lukester1975 in #3600
• Bump actions/checkout from 3.1.0 to 3.5.3 by @dependabot in #3602
• Fix for FMT_MODULE not compiling on GCC by @MathewBensonCode in #3605
• atomic_flag formatting by @AlexGuteniev in #3594

New Contributors

• @wangzw made their first contribution in #3574
• @elbeno made their first contribution in #3588
• @YuHuanTin made their first contribution in #3599
• @MathewBensonCode made their first contribution in #3597

10.1.0

• Optimized format string compilation resulting in up to 40% speed up in compiled format_to and ~4x speed up in compiled format_to_n on a concatenation benchmark (#3133, #3484).

  {fmt} 10.0:

  ---------------------------------------------------------
  Benchmark               Time             CPU   Iterations
  ---------------------------------------------------------
  BM_format_to         78.9 ns         78.9 ns      8881746
  BM_format_to_n        568 ns          568 ns      1232089
  

  {fmt} 10.1:

  ---------------------------------------------------------
  Benchmark               Time             CPU   Iterations
  ---------------------------------------------------------
  BM_format_to         54.9 ns         54.9 ns     12727944
  BM_format_to_n        133 ns          133 ns      5257795
  

• Optimized storage of an empty allocator in basic_memory_buffer (#3485). Thanks @Minty-Meeo.

• Added formatters for proxy references to elements of std::vector<bool> and std::bitset<N> (#3567, #3570). For example (godbolt):

  #include <vector>
  #include <fmt/std.h>
  
  int main() {
    auto v = std::vector<bool>{true};
    fmt::print("{}", v[0]);
  }

  Thanks @phprus (Vladislav Shchapov) and @felix642 (Félix-Antoine Constantin).

• Fixed an ambiguous formatter specialization for containers that look like container adaptors such as boost::flat_set (#3556, #3561). Thanks @5chmidti.

• Fixed compilation when formatting durations not convertible from std::chrono::seconds (#3430). Thanks @patlkli (Patrick Geltinger).

• Made the formatter specialization for char* const-correct (#3432). Thanks @timsong-cpp.

• Made {} and {:} handled consistently during compile-time checks (#3526).

• Disallowed passing temporaries to make_format_args to improve API safety by preventing dangling references.

• Improved the compile-time error for unformattable types (#3478). Thanks @BRevzin (Barry Revzin).

• Improved the floating-point formatter (#3448, #3450). Thanks @florimond-collette (Florimond Collette).

• Fixed handling of precision for long double larger than 64 bits. (#3539, #3564).

• Made floating-point and chrono tests less platform-dependent (#3337, #3433, #3434). Thanks @phprus (Vladislav Shchapov).

• Removed the remnants of the Grisu floating-point formatter that has been replaced by Dragonbox in earlier versions.

• Added throw_format_error to the public API (#3551). Thanks @mjerabek (Martin Jeřábek).

• Made FMT_THROW assert even if assertions are disabled when compiling with exceptions disabled (#3418, #3439). Thanks @BRevzin (Barry Revzin).

• Added support for the ? format specifier to std::filesystem::path and made the default unescaped for consistency with strings.

• Made format_as and std::filesystem::path formatter work with exotic code unit types. (#3457, #3476). Thanks @gix (Nico Rieck), @hmbj (Hans-Martin B. Jensen).

• Deprecated the wide stream overload of printf.

• Removed unused basic_printf_parse_context.

• Improved RTTI detection used when formatting exceptions (#3468). Thanks @danakj (Dana Jansens).

• Improved compatibility with VxWorks7 (#3467). Thanks @wenshan1 (Bin Lan).

• Improved documentation (#3174, #3423, #3454, #3458, #3461, #3487, #3515). Thanks @zencatalyst (Kasra Hashemi), @rlalik, @mikecrowe (Mike Crowe).

• Improved build and CI configurations (#3449, #3451, #3452, #3453, #3459, #3481, #3486, #3489, #3496, #3517, #3523, #3563). Thanks @joycebrum (Joyce), @glebm (Gleb Mazovetskiy), @phprus (Vladislav Shchapov), @petrmanek (Petr Mánek), @setoye (Alta), @abouvier (Alexandre Bouvier).

• Fixed various warnings and compilation issues (#3408, #3424, #3444, #3446, #3475, #3482, #3492, #3493, #3508, #3509, #3533, #3542, #3543, #3540, #3544, #3548, #3549, #3550, #3552). Thanks @adesitter (Arnaud Desitter), @hmbj (Hans-Martin B. Jensen), @Minty-Meeo, @phprus (Vladislav Shchapov), @TobiSchluter (Tobias Schlüter), @kieranclancy (Kieran Clancy), @alexeedm (Dmitry Alexeev), @jurihock (Jürgen Hock), @Ozomahtli, @razaqq.

Pull Requests

• Fix time_point formatting for durations with certain ratios by @patlkli in #3430
• Make hex float test more stable by @phprus in #3434
• Always assert in FMT_THROW by @brevzin in #3439
• format-inl.h: address implicit int to bool conversion by @adesitter in #3446
• remove code duplication by @florimond-collette in #3448
• replace mod_inv_25 by explicit value as a fix for VS warning C4307 by @florimond-collette in #3450
• Fix parameter type of formatter<char*> by @timsong-cpp in #3432
• Hash pin Github Workflows by @joycebrum in #3451
• Create dependabot.yml by @joycebrum in #3452
• Update README.rst by @zencatalyst in #3454
• CMake: Do not fail on unknown compiler features by @glebm in #3453
• Fix example for user-defined types in documentation for 10.0.0 by @rlalik in #3461
• Make constexpr ceil by @phprus in #3459
• Pass correct Char to base format_as formatter by @gix in #3457
• Add VxWorks7 user space and kernel space support by @wenshan1 in #3467
• Only use typeid() in std.h when it is available by @danakj in #3468
• Fix MSVC warning in std::chrono::time_point formatter by @hmbj in #3475
• Use correct Char type in std::filesystem::path formatter by @hmbj in #3476
• Use FMT_TRY and FMT_CATCH in std.h by @Minty-Meeo in #3482
• Bump actions/checkout from 3.5.2 to 3.5.3 by @dependabot in #3486
• Give basic_memory_buffer allocator [[no_unique_address]] by @Minty-Meeo in #3485
• Fix for issue #3492 by @phprus in #3493
• Revert ae25f79 to restore capability to cmake --install when included as a subproject by @petrmanek in #3496
• Fix typo in assert message. by @TobiSchluter in #3508
• README: Add link to merged clang-tidy check by @mikecrowe in #3515
• Trying to improve errors in the unformattable case. by @brevzin in #3478
• fix missing header files when using CMake install by @setoye in #3523
• Fix format_string_checker initialisation order by @kieranclancy in #3542
• Turn off error-producing NVCC workaround when using c++20 by @alexeedm in #3544
• Remove std::copy usage. by @Ozomahtli in #3550
• expose detail::throw_format_error by @mjerabek in #3551
• Use the U literal for unsigned integer constants. by @jurihock in #3549
• Add missing inline specifier by @razaqq in #3552
• cmake: fix FMT_PKGCONFIG_DIR path by @abouvier in #3563
• fix ambiguous formatter lookup for flat_set by @5chmidti in #3561
• Added formatter for bit_reference-like types by @phprus in #3570

New Contributors

• @adesitter made their first contribution in #3446
• @florimond-collette made their first contribution in #3448
• @zencatalyst made their first contribution in #3454
• @rlalik made their first contribution in #3461
• @gix made their first contribution in #3457
• @wenshan1 made their first contribution in #3467
• @danakj made their first contribution in #3468
• @Minty-Meeo made their first contribution in #3482
• @dependabot made their first contribution in #3486
• @petrmanek made their first contr...

10.0.0

• Replaced Grisu with a new floating-point formatting algorithm for given precision (#3262, #2750, #3269, #3276). The new algorithm is based on Dragonbox already used for the shortest representation and gives substantial performance improvement:

  • Red: new algorithm

  • Green: new algorithm with FMT_USE_FULL_CACHE_DRAGONBOX defined to 1

  • Blue: old algorithm

  Thanks @jk-jeon (Junekey Jeon).

• Replaced snprintf-based hex float formatter with an internal implementation (#3179, #3203). This removes the last usage of s(n)printf in {fmt}. Thanks @phprus (Vladislav Shchapov).

• Fixed alignment of floating-point numbers with localization (#3263, #3272). Thanks @ShawnZhong (Shawn Zhong).

• Made handling of # consistent with std::format.

• Improved C++20 module support (#3134, #3254, #3386, #3387, #3388, #3392, #3397, #3399, #3400). Thanks @laitingsheng (Tinson Lai), @Orvid (Orvid King), @DanielaE (Daniela Engert). Switched to the modules CMake library which allows building {fmt} as a C++20 module with clang:

  CXX=clang++ cmake -DFMT_MODULE=ON .
  make
  

• Made format_as work with any user-defined type and not just enums. For example (godbolt):

  #include <fmt/format.h>
  
  struct floaty_mc_floatface {
    double value;
  };
  
  auto format_as(floaty_mc_floatface f) { return f.value; }
  
  int main() {
    fmt::print("{:8}\n", floaty_mc_floatface{0.42}); // prints "    0.42"
  }

• Removed deprecated implicit conversions for enums and conversions to primitive types for compatibility with std::format and to prevent potential ODR violations. Use format_as instead.

• Added support for fill, align and width to the time point formatter (#3237, #3260, #3275). For example (godbolt):

  #include <fmt/chrono.h>
  
  int main() {
    // prints "    2023"
    fmt::print("{:>8%Y}\n", std::chrono::system_clock::now());
  }

  Thanks @ShawnZhong (Shawn Zhong).

• Implemented formatting of subseconds (#2207, #3117, #3115, #3143, #3144, #3349). For example (godbolt):

  #include <fmt/chrono.h>
  
  int main() {
    // prints 01.234567
    fmt::print("{:%S}\n", std::chrono::microseconds(1234567));
  }

  Thanks @patrickroocks (Patrick Roocks) @phprus (Vladislav Shchapov), @BRevzin (Barry Revzin).

• Added precision support to %S (#3148). Thanks @SappyJoy (Stepan Ponomaryov)

• Added support for std::utc_time (#3098, #3110). Thanks @patrickroocks (Patrick Roocks).

• Switched formatting of std::chrono::system_clock from local time to UTC for compatibility with the standard (#3199, #3230). Thanks @ned14 (Niall Douglas).

• Added support for %Ez and %Oz to chrono formatters. (#3220, #3222). Thanks @phprus (Vladislav Shchapov).

• Improved validation of format specifiers for std::chrono::duration (#3219, #3232). Thanks @ShawnZhong (Shawn Zhong).

• Fixed formatting of time points before the epoch (#3117, #3261). For example (godbolt):

  #include <fmt/chrono.h>
  
  int main() {
    auto t = std::chrono::system_clock::from_time_t(0) -
             std::chrono::milliseconds(250);
    fmt::print("{:%S}\n", t); // prints 59.750000000
  }

  Thanks @ShawnZhong (Shawn Zhong).

• Experimental: implemented glibc extension for padding seconds, minutes and hours (#2959, #3271). Thanks @ShawnZhong (Shawn Zhong).

• Added a formatter for std::exception (#2977, #3012, #3062, #3076, #3119). For example (godbolt):

  #include <fmt/std.h>
  #include <vector>
  
  int main() {
    try {
      std::vector<bool>().at(0);
    } catch(const std::exception& e) {
      fmt::print("{}", e);
    }
  }

  prints:

  vector<bool>::_M_range_check: __n (which is 0) >= this->size() (which is 0)
  

  on libstdc++. Thanks @zach2good (Zach Toogood) and @phprus (Vladislav Shchapov).

• Moved std::error_code formatter from fmt/os.h to fmt/std.h. (#3125). Thanks @phprus (Vladislav Shchapov).

• Added formatters for standard container adapters: std::priority_queue, std::queue and std::stack (#3215, #3279). For example (godbolt):

  #include <fmt/ranges.h>
  #include <stack>
  #include <vector>
  
  int main() {
    auto s = std::stack<bool, std::vector<bool>>();
    for (auto b: {true, false, true}) s.push(b);
    fmt::print("{}\n", s); // prints [true, false, true]
  }

  Thanks @ShawnZhong (Shawn Zhong).

• Added a formatter for std::optional to fmt/std.h. Thanks @tom-huntington.

• Fixed formatting of valueless by exception variants (#3347). Thanks @TheOmegaCarrot.

• Made fmt::ptr accept unique_ptr with a custom deleter (#3177). Thanks @hmbj (Hans-Martin B. Jensen).

• Fixed formatting of noncopyable ranges and nested ranges of chars (#3158 #3286, #3290). Thanks @BRevzin (Barry Revzin).

• Fixed issues with formatting of paths and ranges of paths (#3319, #3321 #3322). Thanks @phprus (Vladislav Shchapov).

• Improved handling of invalid Unicode in paths.

• Enabled compile-time checks on Apple clang 14 and later (#3331). Thanks @cloyce (Cloyce D. Spradling).

• Improved compile-time checks of named arguments (#3105, #3214). Thanks @rbrich (Radek Brich).

• Fixed formatting when both alignment and 0 are given (#3236, #3248). Thanks @ShawnZhong (Shawn Zhong).

• Improved Unicode support in the experimental file API on Windows (#3234, #3293). Thanks @Fros1er (Froster).

• Unified UTF transcoding (#3416). Thanks @phprus (Vladislav Shchapov).

• Added support for UTF-8 digit separators via an experimental locale facet (#1861). For example (godbolt):

  auto loc = std::locale(
    std::locale(), new fmt::format_facet<std::locale>("’"));
  auto s = fmt::format(loc, "{:L}", 1000);

  where ’ is U+2019 used as a digit separator in the de_CH locale.

• Added an overload of formatted_size that takes a locale (#3084, #3087). Thanks @gerboengels.

• Removed the deprecated FMT_DEPRECATED_OSTREAM.

• Fixed a UB when using a null std::string_view with fmt::to_string or format string compilation (#3241, #3244). Thanks @phprus (Vladislav Shchapov).

• Added starts_with to the fallback string_view implementation (#3080). Thanks @phprus (Vladislav Shchapov).

• Added fmt::basic_format_string::get() for compatibility with basic_format_string (#3111). Thanks @huangqinjin.

• Added println for compatibility with C++23 (#3267). Thanks @ShawnZhong (Shawn Zhong).

• Renamed the FMT_EXPORT macro for shared library usage to FMT_LIB_EXPORT.

• Improved documentation (#3108, #3169, #3243). #3404). Thanks @Cleroth and @Vertexwahn.

• Improved build configuration and tests (#3118, #3120, #3188, #3189, #3198, #3205, #3207, #3210, #3240, #3256, #3264, #3299, #3302, #3312, #3317, #3328, #3333, #3369, #3373, #3395, #3406, #3411). Thanks @dimztimz (Dimitrij Mijoski), @phprus (Vladislav Shchapov), @DavidKorczynski, @ChrisThrasher (Chris Thrasher), @FrancoisCarouge (François Carouge), @kennyweiss (Kenny Weiss), @luzpaz, @codeinred (Alecto Irene Perez), @Mixaill (Mikhail Paulyshka), @joycebrum (Joyce), @kevinhwang (Kevin Hwang), @Vertexwahn.

• Fixed a regression in handling empty format specifiers after a colon ({:}) (#3086). Thanks @oxidase (Michael Krasnyk).

• Worked around a broken implementation of std::is_constant_evaluated in some versions of libstdc++ on clang (#3247, #3281). Thanks [@phprus (Vladislav Shc...

9.1.0

• fmt::formatted_size now works at compile time (#3026). For example (godbolt):

  #include <fmt/compile.h>
  
  int main() {
    using namespace fmt::literals;
    constexpr size_t n = fmt::formatted_size("{}"_cf, 42);
    fmt::print("{}\n", n); // prints 2
  }

  Thanks @marksantaniello (Mark Santaniello).

• Fixed handling of invalid UTF-8 (#3038, #3044, #3056). Thanks @phprus (Vladislav Shchapov) and @skeeto (Christopher Wellons).

• Improved Unicode support in ostream overloads of print (#2994, #3001, #3025). Thanks @dimztimz (Dimitrij Mijoski).

• Fixed handling of the sign specifier in localized formatting on systems with 32-bit wchar_t (#3041).

• Added support for wide streams to fmt::streamed (#2994). Thanks @phprus (Vladislav Shchapov).

• Added the n specifier that disables the output of delimiters when formatting ranges (#2981, #2983). For example (godbolt):

  #include <fmt/ranges.h>
  #include <vector>
  
  int main() {
    auto v = std::vector{1, 2, 3};
    fmt::print("{:n}\n", v); // prints 1, 2, 3
  }

  Thanks @BRevzin (Barry Revzin).

• Worked around problematic std::string_view constructors introduced in C++23 (#3030, #3050). Thanks @strega-nil-ms (nicole mazzuca).

• Improve handling (exclusion) of recursive ranges (#2968, #2974). Thanks @Dani-Hub (Daniel Krügler).

• Improved error reporting in format string compilation (#3055).

• Improved the implementation of Dragonbox, the algorithm used for the default floating-point formatting (#2984). Thanks @jk-jeon (Junekey Jeon).

• Fixed issues with floating-point formatting on exotic platforms.

• Improved the implementation of chrono formatting (#3010). Thanks @phprus (Vladislav Shchapov).

• Improved documentation (#2966, #3009, #3020, #3037). Thanks @mwinterb, @jcelerier (Jean-Michaël Celerier) and @remiburtin (Rémi Burtin).

• Improved build configuration (#2991, #2995, #3004, #3007, #3040). Thanks @dimztimz (Dimitrij Mijoski) and @hwhsu1231 (Haowei Hsu).

• Fixed various warnings and compilation issues (#2969, #2971, #2975, #2982, #2985, #2988, #3000, #3006, #3014, #3015, #3021, #3023, #3024, #3029, #3043, #3052, #3053, #3054). Thanks @h-friederich (Hannes Friederich), @dimztimz (Dimitrij Mijoski), @olupton (Olli Lupton), @bernhardmgruber (Bernhard Manfred Gruber), @phprus (Vladislav Shchapov).

Pull Requests

• Add xchar support for fmt::streamed(). by @phprus in #2961
• Fixed typo in changelog example by @mwinterb in #2966
• Exclude recursive ranges from the formatter specialization for ranges by @Dani-Hub in #2974
• Pointless comparison warnings by @federico-busato in #2971
• The n specifier for ranges. by @brevzin in #2981
• Fix for EDG frontend (Intel, NVHPC compilers) by @phprus in #2982
• Yet another simplification of Dragonbox by @jk-jeon in #2984
• Add additional search paths for doxygen on Windows by @hwhsu1231 in #2991
• Fixes IBM XLC behavior with uint128 fallback by @federico-busato in #2985
• Reduce filesize of the tests on MinGW by @dimztimz in #2995
• Improve Unicode handling when writing to an ostream on Windows by @dimztimz in #2994
• Add fmt:: namespace to doc by @jcelerier in #3009
• Range formatter by @brevzin in #2983
• Fix Unicode handling for ostream under Windows with libc++. by @dimztimz in #3001
• Improve CI on Windows, deprecate AppVeyor by @dimztimz in #3007
• Simplify and improve chrono formatting by @phprus in #3010
• Suppress unused typedef warning by @h-friederich in #3021
• Remove -Wl,--as-needed linker option by @phprus in #3024
• Use is_utf8() in print(std::ostream&, ...) by @dimztimz in #3025
• Constexpr formatted_size by @marksantaniello in #3026
• Fix testsuite on MinGW + MSVCRT by @dimztimz in #3029
• Fix docs by @remiburtin in #3037
• Prepare for deprecating FindPythonInterp module. by @hwhsu1231 in #3040
• nvhpc/22.3: workaround for c++17 mode by @olupton in #3043
• Fix decoder on broken utf8 sequences. by @phprus in #3044
• Disable non-type template args for nvhpc by @bernhardmgruber in #3053
• Disable bogus -Wstringop-overflow on GCC 11 by @phprus in #3054
• Fix bugs in utf8 decoder by @phprus in #3056

New Contributors

• @hwhsu1231 made their first contribution in #2991
• @dimztimz made their first contribution in #2995
• @h-friederich made their first contribution in #3021
• @marksantaniello made their first contribution in #3026
• @remiburtin made their first contribution in #3037
• @bernhardmgruber made their first contribution in #3053

Full Changelog: 9.0.0...9.1.0

9.0.0

• Switched to the internal floating point formatter for all decimal presentation formats. In particular this results in consistent rounding on all platforms and removing the s[n]printf fallback for decimal FP formatting.

• Compile-time floating point formatting no longer requires the header-only mode. For example (godbolt):

  #include <array>
  #include <fmt/compile.h>
  
  consteval auto compile_time_dtoa(double value) -> std::array<char, 10> {
    auto result = std::array<char, 10>();
    fmt::format_to(result.data(), FMT_COMPILE("{}"), value);
    return result;
  }
  
  constexpr auto answer = compile_time_dtoa(0.42);

  works with the default settings.

• Improved the implementation of Dragonbox, the algorithm used for the default floating-point formatting (#2713, #2750). Thanks @jk-jeon (Junekey Jeon).

• Made fmt::to_string work with __float128. This uses the internal FP formatter and works even on system without __float128 support in [s]printf.

• Disabled automatic std::ostream insertion operator (operator<<) discovery when fmt/ostream.h is included to prevent ODR violations. You can get the old behavior by defining FMT_DEPRECATED_OSTREAM but this will be removed in the next major release. Use fmt::streamed or fmt::ostream_formatter to enable formatting via std::ostream instead.

• Added fmt::ostream_formatter that can be used to write formatter specializations that perform formatting via std::ostream. For example (godbolt):

  #include <fmt/ostream.h>
  
  struct date {
    int year, month, day;
  
    friend std::ostream& operator<<(std::ostream& os, const date& d) {
      return os << d.year << '-' << d.month << '-' << d.day;
    }
  };
  
  template <> struct fmt::formatter<date> : ostream_formatter {};
  
  std::string s = fmt::format("The date is {}", date{2012, 12, 9});
  // s == "The date is 2012-12-9"

• Added the fmt::streamed function that takes an object and formats it via std::ostream. For example (godbolt):

  #include <thread>
  #include <fmt/ostream.h>
  
  int main() {
    fmt::print("Current thread id: {}\n",
               fmt::streamed(std::this_thread::get_id()));
  }

  Note that fmt/std.h provides a formatter specialization for std::thread::id so you don't need to format it via std::ostream.

• Deprecated implicit conversions of unscoped enums to integers for consistency with scoped enums.

• Added an argument-dependent lookup based format_as extension API to simplify formatting of enums.

• Added experimental std::variant formatting support (#2941). For example (godbolt):

  #include <variant>
  #include <fmt/std.h>
  
  int main() {
    auto v = std::variant<int, std::string>(42);
    fmt::print("{}\n", v);
  }

  prints:

  variant(42)
  

  Thanks @jehelset.

• Added experimental std::filesystem::path formatting support (#2865, #2902, #2917, #2918). For example (godbolt):

  #include <filesystem>
  #include <fmt/std.h>
  
  int main() {
    fmt::print("There is no place like {}.", std::filesystem::path("/home"));
  }

  prints:

  There is no place like "/home".
  

  Thanks @phprus (Vladislav Shchapov).

• Added a std::thread::id formatter to fmt/std.h. For example (godbolt):

  #include <thread>
  #include <fmt/std.h>
  
  int main() {
    fmt::print("Current thread id: {}\n", std::this_thread::get_id());
  }

• Added fmt::styled that applies a text style to an individual argument (#2793). For example (godbolt):

  #include <fmt/chrono.h>
  #include <fmt/color.h>
  
  int main() {
    auto now = std::chrono::system_clock::now();
    fmt::print(
      "[{}] {}: {}\n",
      fmt::styled(now, fmt::emphasis::bold),
      fmt::styled("error", fg(fmt::color::red)),
      "something went wrong");
  }

  prints

  Thanks @rbrugo (Riccardo Brugo).

• Made fmt::print overload for text styles correctly handle UTF-8 (#2681, #2701). Thanks @AlexGuteniev (Alex Guteniev).

• Fixed Unicode handling when writing to an ostream.

• Added support for nested specifiers to range formatting (#2673). For example (godbolt):

  #include <vector>
  #include <fmt/ranges.h>
  
  int main() {
    fmt::print("{::#x}\n", std::vector{10, 20, 30});
  }

  prints [0xa, 0x14, 0x1e].

  Thanks @BRevzin (Barry Revzin).

• Implemented escaping of wide strings in ranges (#2904). Thanks @phprus (Vladislav Shchapov).

• Added support for ranges with begin / end found via the argument-dependent lookup (#2807). Thanks @rbrugo (Riccardo Brugo).

• Fixed formatting of certain kinds of ranges of ranges (#2787). Thanks @BRevzin (Barry Revzin).

• Fixed handling of maps with element types other than std::pair (#2944). Thanks @BrukerJWD (Jonathan W).

• Made tuple formatter enabled only if elements are formattable (#2939, #2940). Thanks @jehelset.

• Made fmt::join compatible with format string compilation (#2719, #2720). Thanks @phprus (Vladislav Shchapov).

• Made compile-time checks work with named arguments of custom types and std::ostream print overloads (#2816, #2817, #2819). Thanks @timsong-cpp.

• Removed make_args_checked because it is no longer needed for compile-time checks (#2760). Thanks @phprus (Vladislav Shchapov).

• Removed the following deprecated APIs: _format, arg_join, the format_to overload that takes a memory buffer, [v]fprintf that takes an ostream.

• Removed the deprecated implicit conversion of [const] signed char* and [const] unsigned char* to C strings.

• Removed the deprecated fmt/locale.h.

• Replaced the deprecated fileno() with descriptor() in buffered_file.

• Moved to_string_view to the detail namespace since it's an implementation detail.

• Made access mode of a created file consistent with fopen by setting S_IWGRP and S_IWOTH (#2733). Thanks @arogge (Andreas Rogge).

• Removed a redundant buffer resize when formatting to std::ostream (#2842, #2843). Thanks @jcelerier (Jean-Michaël Celerier).

• Made precision computation for strings consistent with width (#2888).

• Fixed handling of locale separators in floating point formatting (#2830).

• Made sign specifiers work with __int128_t (#2773).

• Improved support for systems such as CHERI with extra data stored in pointers (#2932). Thanks @davidchisnall (David Chisnall).

• Improved documentation (#2706, #2712, #2789, #2803, #2805, #2815, #2924). Thanks @BRevzin (Barry Revzin), @Pokechu22, @setoye (Alta), @rtobar, @rbrugo (Riccardo Brugo), @anoonD (cre), @leha-bot (Alex).

• Improved build configuration (#2766, #2772, #2836, #2852, #2907, #2913, #2914). Thanks @kambala-decapitator (Andrey Filipenkov), @mattiasljungstrom (Mattias Ljungström), @kieselnb (Nick Kiesel), @nathannaveen, @Vertexwahn.

• Fixed various warnings and compilation issues (#2408, #2507, #2697, #2715, #2717, #2722, #2724, #2725, #2726, #2728, #2732, #2738, #2742, #2744, #2745, #2746, #2754, #2755, #2757, #2758, #2761, #2762, #2763, #2765, #2769, #2770, #2771, #2777, #2779, #2782, #2783, #2794, #2796, #2797, #2801, #2802, #2808, #2818, #2819, #2829, #2835, #2848, #2860, #2861, #2882, #2886, #2891, #2892, #2895, #2896, #2903, #2906, #2908, #2909, #2920, #2922, #2927, #2929, #2936, #2937, #2938, #2951, #2954, #2957, #2958, #2960). Thanks @matrackif @Tobi823 (Tobias Hellmann), @ivan-volnov (Ivan Volnov), @VasiliPupkin256, @federico-busato (Federico), @barcharcraz (Charlie Barto), @jk-jeon (Junekey Jeon), @HazardyKnusperkeks (Björn Schäpers), @dalboris (Boris Dalstein), @seanm (Sean McBride), @gsjaardema (Greg Sjaardema), @timsong-cpp, [@seanm (Sean Mc...

8.1.1

• Restored ABI compatibility with version 8.0.x (#2695, #2696). Thanks @saraedum (Julian Rüth).

• Fixed chrono formatting on big endian systems (#2698, #2699). Thanks @phprus (Vladislav Shchapov) and @xvitaly (Vitaly Zaitsev).

• Fixed a linkage error with mingw (#2691, #2692). Thanks @rbberger (Richard Berger).

8.1.0

• Optimized chrono formatting (#2500, #2537, #2541, #2544, #2550, #2551, #2576, #2577, #2586, #2591, #2594, #2602, #2617, #2628, #2633, #2670, #2671).

  Processing of some specifiers such as %z and %Y is now up to 10-20 times faster, for example on GCC 11 with libstdc++:

  ----------------------------------------------------------------------------
  Benchmark                                  Before             After
  ----------------------------------------------------------------------------
  FMTFormatter_z                             261 ns             26.3 ns
  FMTFormatterCompile_z                      246 ns             11.6 ns
  FMTFormatter_Y                             263 ns             26.1 ns
  FMTFormatterCompile_Y                      244 ns             10.5 ns
  ----------------------------------------------------------------------------
  

  Thanks @phprus (Vladislav Shchapov) and @toughengineer (Pavel Novikov).

• Implemented subsecond formatting for chrono durations (#2623). For example (godbolt):

  #include <fmt/chrono.h>
  
  int main() {
    fmt::print("{:%S}", std::chrono::milliseconds(1234));
  }

  prints "01.234".

  Thanks @matrackif.

• Fixed handling of precision 0 when formatting chrono durations (#2587, #2588). Thanks @lukester1975.

• Fixed an overflow on invalid inputs in the tm formatter (#2564). Thanks @phprus (Vladislav Shchapov).

• Added fmt::group_digits that formats integers with a non-localized digit separator (comma) for groups of three digits. For example (godbolt):

  #include <fmt/format.h>
  
  int main() {
    fmt::print("{} dollars", fmt::group_digits(1000000));
  }

  prints "1,000,000 dollars".

• Added support for faint, conceal, reverse and blink text styles (#2394):

  blink.mp4

  Thanks @benit8 (Benoît Lormeau) and @data-man (Dmitry Atamanov).

• Added experimental support for compile-time floating point formatting (#2426, #2470). It is currently limited to the header-only mode. Thanks @alexezeder (Alexey Ochapov).

• Added UDL-based named argument support to compile-time format string checks (#2640, #2649). For example (godbolt):

  #include <fmt/format.h>
  
  int main() {
    using namespace fmt::literals;
    fmt::print("{answer:s}", "answer"_a=42);
  }

  gives a compile-time error on compilers with C++20 consteval and non-type template parameter support (gcc 10+) because s is not a valid format specifier for an integer.

  Thanks @alexezeder (Alexey Ochapov).

• Implemented escaping of string range elements. For example (godbolt):

  #include <fmt/ranges.h>
  #include <vector>
  
  int main() {
    fmt::print("{}", std::vector<std::string>{"\naan"});
  }

  is now printed as:

  ["\naan"]
  

  instead of:

  ["
  aan"]
  

• Switched to JSON-like representation of maps and sets for consistency with Python's str.format. For example (godbolt):

  #include <fmt/ranges.h>
  #include <map>
  
  int main() {
    fmt::print("{}", std::map<std::string, int>{{"answer", 42}});
  }

  is now printed as:

  {"answer": 42}
  

• Extended fmt::join to support C++20-only ranges (#2549). Thanks @BRevzin (Barry Revzin).

• Optimized handling of non-const-iterable ranges and implemented initial support for non-const-formattable types.

• Disabled implicit conversions of scoped enums to integers that was accidentally introduced in earlier versions (#1841).

• Deprecated implicit conversion of [const] signed char* and [const] unsigned char* to C strings.

• Deprecated _format, a legacy UDL-based format API (#2646). Thanks @alexezeder (Alexey Ochapov).

• Marked format, formatted_size and to_string as [[nodiscard]] (#2612). @0x8000-0000 (Florin Iucha).

• Added missing diagnostic when trying to format function and member pointers as well as objects convertible to pointers which is explicitly disallowed (#2598, #2609, #2610). Thanks @AlexGuteniev (Alex Guteniev).

• Optimized writing to a contiguous buffer with format_to_n (#2489). Thanks @Roman-Koshelev.

• Optimized writing to non-char buffers (#2477). Thanks @Roman-Koshelev.

• Decimal point is now localized when using the L specifier.

• Improved floating point formatter implementation (#2498, #2499). Thanks @Roman-Koshelev.

• Fixed handling of very large precision in fixed format (#2616).

• Made a table of cached powers used in FP formatting static (#2509). Thanks @jk-jeon (Junekey Jeon).

• Resolved a lookup ambiguity with C++20 format-related functions due to ADL (#2639, #2641). Thanks @mkurdej (Marek Kurdej).

• Removed unnecessary inline namespace qualification (#2642, #2643). Thanks @mkurdej (Marek Kurdej).

• Implemented argument forwarding in format_to_n (#2462, #2463). Thanks @owent (WenTao Ou).

• Fixed handling of implicit conversions in fmt::to_string and format string compilation (#2565).

• Changed the default access mode of files created by fmt::output_file to -rw-r--r-- for consistency with fopen (#2530).

• Make fmt::ostream::flush public (#2435).

• Improved C++14/17 attribute detection (#2615). Thanks @AlexGuteniev (Alex Guteniev).

• Improved consteval detection for MSVC (#2559). Thanks @DanielaE (Daniela Engert).

• Improved documentation (#2406, #2446, #2493, #2513, #2515, #2522, #2562, #2575, #2606, #2620, #2676). Thanks @sobolevn (Nikita Sobolev), @UnePierre (Max FERGER), @zhsj, @phprus (Vladislav Shchapov), @ericcurtin (Eric Curtin), @Lounarok.

• Improved fuzzers and added a fuzzer for chrono timepoint formatting (#2461, #2469). @pauldreik (Paul Dreik),

• Added the FMT_SYSTEM_HEADERS CMake option setting which marks {fmt}'s headers as system. It can be used to suppress warnings (#2644, #2651). Thanks @alexezeder (Alexey Ochapov).

• Added the Bazel build system support (#2505, #2516). Thanks @Vertexwahn.

• Improved build configuration and tests (#2437, #2558, #2648, #2650, #2663, #2677). Thanks @DanielaE (Daniela Engert), @alexezeder (Alexey Ochapov), @phprus (Vladislav Shchapov).

• Fixed various warnings and compilation issues (#2353, #2356, #2399, #2408, #2414, #2427, #2432, #2442, #2434, #2439, #2447, #2450, #2455, #2465, #2472, #2474, #2476, #2478, #2479, #2481, #2482, #2483, #2490, #2491, #2510, #2518, #2528, #2529, #2539, #2540, #2545, #2555, #2557, #2570, #2573, #2582, #2605, #2611, #2647, #2627, #2630, #2635, #2638, #2653, #2654, #2661, #2664, #2684). Thanks @DanielaE (Daniela Engert), @mwinterb, @cdacamar (Cameron DaCamara), @TrebledJ (Johnathan), @bodomartin (brm), @cquammen (Cory Quammen), @white238 (Chris White), @mmarkeloff (Max), @palacaze (Pierre-Antoine Lacaze), @jcelerier (Jean-Michaël Celerier), @mborn-adi (Mathias Born), @BrukerJWD (Jonathan W), @spyridon97 (Spiros Tsalikis), @phprus (Vladislav Shchapov), @oliverlee (Oliver Lee), @joshessman-llnl (Josh Essman), @akohlmey (Axel Kohlmeyer), @timkalu, @olupton (Olli Lupton), @Acretock, @alexezeder (Alexey Ochapov), @andrewcorrigan (Andrew Corrigan), @lucpelletier, @HazardyKnusperkeks (Björn Schäpers).

8.0.1

• Fixed the version number in the inline namespace (#2374).

• Added a missing presentation type check for std::string (#2402).

• Fixed a linkage error when mixing code built with clang and gcc (#2377).

• Fixed documentation issues (#2396, #2403, #2406). Thanks @mkurdej (Marek Kurdej).

• Removed dead code in FP formatter ( #2398). Thanks @javierhonduco (Javier Honduvilla Coto).

• Fixed various warnings and compilation issues (#2351, #2359, #2365, #2368, #2370, #2376, #2381, #2382, #2386, #2389, #2395, #2397, #2400 #2401, #2407). Thanks @zx2c4 (Jason A. Donenfeld), @AidanSun05 (Aidan Sun), @mattiasljungstrom (Mattias Ljungström), @joemmett (Jonathan Emmett), @erengy (Eren Okka), @patlkli (Patrick Geltinger), @gsjaardema (Greg Sjaardema), @phprus (Vladislav Shchapov).