• Fixed compatibility with non-POSIX systems (#4054, #4060).

• Fixed performance regressions when using std::back_insert_iterator with fmt::format_to (#4070).

• Fixed handling of std::generator and move-only iterators (#4053, #4057). Thanks @Arghnews.

• Made formatter<std::string_view>::parse work with types convertible to std::string_view (#4036, #4055). Thanks @Arghnews.

• Made volatile void* formattable (#4049, #4056). Thanks @Arghnews.

• Made Glib::ustring not be confused with std::string (#4052).

• Made fmt::context iterator compatible with STL algorithms that rely on iterator category (#4079).

• Fixed version number in the inline namespace (#4047).

• Fixed disabling Unicode support via CMake (#4051).

• Fixed deprecated visit_format_arg (#4043). Thanks @nebkat.

• Fixed handling of a sign and improved the std::complex formater (#4034, #4050). Thanks @tesch1 and @phprus.

• Fixed ADL issues in fmt::printf when using C++20 (#4042). Thanks @toge.

• Removed a redundant check in the formatter for std::expected (#4040). Thanks @phprus.

• Added fmt/base.h which provides a subset of the API with minimal include dependencies and enough functionality to replace all uses of the printf family of functions. This brings the compile time of code using {fmt} much closer to the equivalent printf code as shown on the following benchmark that compiles 100 source files:

  Method	Compile Time (s)
  printf	1.6
  IOStreams	25.9
  fmt 10.x	19.0
  fmt 11.0	4.8
  tinyformat	29.1
  Boost Format	55.0

  This gives almost 4x improvement in build speed compared to version 10. Note that the benchmark is purely formatting code and includes. In real projects the difference from printf will be smaller partly because common standard headers will be included in almost any translation unit (TU) anyway. In particular, in every case except printf above ~1s is spent in total on including <type_traits> in all TUs.

• Optimized includes in other headers such as fmt/format.h which is now roughly equivalent to the old fmt/core.h in terms of build speed.

• Migrated the documentation at https://fmt.dev/ from Sphinx to MkDocs.

• Improved C++20 module support (#3990, #3991, #3993, #3994, #3997, #3998, #4004, #4005, #4006, #4013, #4027, #4029). In particular, native CMake support for modules is now used if available. Thanks @yujincheng08 and @matt77hias.

• Added an option to replace standard includes with import std enabled via the FMT_IMPORT_STD macro (#3921, #3928). Thanks @matt77hias.

• Exported fmt::range_format, fmt::range_format_kind and fmt::compiled_string from the fmt module (#3970, #3999). Thanks @matt77hias and @yujincheng08.

• Improved integration with stdio in fmt::print, enabling direct writes into a C stream buffer in common cases. This may give significant performance improvements ranging from tens of percent to 2x and eliminates dynamic memory allocations on the buffer level. It is currently enabled for built-in and string types with wider availability coming up in future releases.

  For example, it gives ~24% improvement on a simple benchmark compiled with Apple clang version 15.0.0 (clang-1500.1.0.2.5) and run on macOS 14.2.1:

  -------------------------------------------------------
  Benchmark             Time             CPU   Iterations
  -------------------------------------------------------
  printf             81.8 ns         81.5 ns      8496899
  fmt::print (10.x)  63.8 ns         61.9 ns     11524151
  fmt::print (11.0)  51.3 ns         51.0 ns     13846580
  

• Improved safety of fmt::format_to when writing to an array (#3805). For example (godbolt):

  auto volkswagen = char[4];
  auto result = fmt::format_to(volkswagen, "elephant");

  no longer results in a buffer overflow. Instead the output will be truncated and you can get the end iterator and whether truncation occurred from the result object. Thanks @ThePhD.

• Enabled Unicode support by default in MSVC, bringing it on par with other compilers and making it unnecessary for users to enable it explicitly. Most of {fmt} is encoding-agnostic but this prevents mojibake in places where encoding matters such as path formatting and terminal output. You can control the Unicode support via the CMake FMT_UNICODE option. Note that some {fmt} packages such as the one in vcpkg have already been compiled with Unicode enabled.

• Added a formatter for std::expected (#3834). Thanks @dominicpoeschko.

• Added a formatter for std::complex (#1467, #3886, #3892, #3900). Thanks @phprus.

• Added a formatter for std::type_info (#3978). Thanks @matt77hias.

• Specialized formatter for std::basic_string types with custom traits and allocators (#3938, #3943). Thanks @dieram3.

• Added formatters for std::chrono::day, std::chrono::month, std::chrono::year and std::chrono::year_month_day (#3758, #3772, #3906, #3913). For example:

  #include <fmt/chrono.h>
  #include <fmt/color.h>
  
  int main() {
    fmt::print(fg(fmt::color::green), "{}\n", std::chrono::day(7));
  }

  prints a green day:

  

  Thanks @zivshek.

• Fixed handling of precision in %S (#3794, #3814). Thanks @js324.

• Added support for the - specifier (glibc strftime extension) to day of the month (%d) and week of the year (%W, %U, %V) specifiers (#3976). Thanks @ZaheenJ.

• Fixed the scope of the - extension in chrono formatting so that it doesn't apply to subsequent specifiers (#3811, #3812). Thanks @phprus.

• Improved handling of time_point::min() (#3282).

• Added support for character range formatting (#3857, #3863). Thanks @js324.

• Added string and debug_string range formatters (#3973, #4024). Thanks @matt77hias.

• Enabled ADL for begin and end in fmt::join (#3813, #3824). Thanks @bbolli.

• Made contiguous iterator optimizations apply to std::basic_string iterators (#3798). Thanks @phprus.

• Added support for ranges with mutable begin and end (#3752, #3800, #3955). Thanks @tcbrindle and @Arghnews.

• Added support for move-only iterators to fmt::join (#3802, #3946). Thanks @Arghnews.

• Moved range and iterator overloads of fmt::join to fmt/ranges.h, next to other overloads.

• Fixed handling of types with begin returning void such as Eigen matrices (#3839, #3964). Thanks @Arghnews.

• Added an fmt::formattable concept (#3974). Thanks @matt77hias.

• Added support for __float128 (#3494).

• Fixed rounding issues when formatting long double with fixed precision (#3539).

• Made fmt::isnan not trigger floating-point exception for NaN values (#3948, #3951). Thanks @alexdewar.

• Removed dependency on <memory> for std::allocator_traits when possible (#3804). Thanks @phprus.

• Enabled compile-time checks in formatting functions that take text colors and styles.

• Deprecated wide stream overloads of fmt::print that take text styles.

• Made format string compilation work with clang 12 and later despite only partial non-type template parameter support (#4000, #4001). Thanks @yujincheng08.

• Made fmt::iterator_buffer's move constructor noexcept (#3808). Thanks @waywardmonkeys.

• Started enforcing that formatter::format is const for compatibility with std::format (#3447).

• Added fmt::basic_format_arg::visit and deprecated fmt::visit_format_arg.

• Made fmt::basic_string_view not constructible from nullptr for consistency with std::string_view in C++23 (#3846). Thanks @dalle.

• Fixed fmt::group_digits for negative integers (#3891, #3901). Thanks @phprus.

• Fixed handling of negative ids in fmt::basic_format_args::get (#3945). Thanks @marlenecota.

• Improved named argument validation (#3817).

• Disabled copy construction/assignment for fmt::format_arg_store and fixed moved construction (#3833). Thanks @ivafanas.

• Worked around a locale issue in RHEL/devtoolset (#3858, #3859). Thanks @g199209.

• Added RTTI detection for MSVC (#3821, #3963). Thanks @edo9300.

• Migrated the documentation from Sphinx to MkDocs.

• Improved documentation and README (https://...

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

• 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).

• 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

• 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...

• 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...

• 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

• 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...