11.1.3

• Fixed compilation on GCC 9.4 (#4313).

• Worked around an internal compiler error when using C++20 modules with GCC 14.2 and earlier (#4295).

• Worked around a bug in GCC 6 (#4318).

• Fixed an issue caused by instantiating formatter<const T> (#4303, #4325). Thanks @timsong-cpp.

• Fixed formatting into std::ostreambuf_iterator when using format string compilation (#4309, #4312). Thanks @phprus.

• Restored a constraint on the map formatter so that it correctly reports as unformattable when the element is (#4326). Thanks @timsong-cpp.

• Reduced the size of format specs (#4298).

• Readded args() to fmt::format_context (#4307, #4310). Thanks @Erroneous1.

• Fixed a bogus MSVC warning (#4314, #4322). Thanks @ZehMatt.

• Fixed a pedantic mode error in the CMake config (#4327). Thanks @rlalik.

11.1.2

• Fixed ABI compatibility with earlier 11.x versions (#4292).

• Added wchar_t support to the std::bitset formatter (#4285, #4286, #4289, #4290). Thanks @phprus.

• Prefixed CMake components with fmt- to simplify usage of {fmt} via add_subdirectory (#4283).

• Updated docs for meson (#4291). Thanks @trim21.

• Fixed a compilation error in chrono on nvcc (#4297, #4301). Thanks @breyerml.

• Fixed various warnings (#4288, #4299). Thanks @GamesTrap and @edo9300.

11.1.1

• Fixed ABI compatibility with earlier 11.x versions (#4278).

• Defined CMake components (core and doc) to allow docs to be installed separately (#4276). Thanks @carlsmedstad.

11.1.0

• Improved C++20 module support (#4081, #4083, #4084, #4152, #4153, #4169, #4190, #4234, #4239). Thanks @kamrann and @Arghnews.

• Reduced debug (unoptimized) binary code size and the number of template instantiations when passing formatting arguments. For example, unoptimized binary code size for fmt::print("{}", 42) was reduced by ~40% on GCC and ~60% on clang (x86-64).

  GCC:

  • Before: 161 instructions of which 105 are in reusable functions (godbolt).
  • After: 116 instructions of which 60 are in reusable functions (godbolt).

  Clang:

  • Before: 310 instructions of which 251 are in reusable functions (godbolt).
  • After: 194 instructions of which 135 are in reusable functions (godbolt).

• Added an experimental fmt::writer API that can be used for writing to different destinations such as files or strings (#2354). For example (godbolt):

  #include <fmt/os.h>
  
  void write_text(fmt::writer w) {
    w.print("The answer is {}.", 42);
  }
  
  int main() {
    // Write to FILE.
    write_text(stdout);
  
    // Write to fmt::ostream.
    auto f = fmt::output_file("myfile");
    write_text(f);
  
    // Write to std::string.
    auto sb = fmt::string_buffer();
    write_text(sb);
    std::string s = sb.str();
  }

• Added width and alignment support to the formatter of std::error_code.

• Made std::expected<void, E> formattable (#4145, #4148). For example (godbolt):

  fmt::print("{}", std::expected<void, int>());

  prints

  expected()
  

  Thanks @phprus.

• Made fmt::is_formattable<void> SFINAE-friendly (#4147).

• Added support for _BitInt formatting when using clang (#4007, #4072, #4140, #4173, #4176). For example (godbolt):

  using int42 = _BitInt(42);
  fmt::print("{}", int42(100));

  Thanks @Arghnews.

• Added the n specifier for tuples and pairs (#4107). Thanks @someonewithpc.

• Added support for tuple-like types to fmt::join (#4226, #4230). Thanks @phprus.

• Made more types formattable at compile time (#4127). Thanks @AnthonyVH.

• Implemented a more efficient compile-time fmt::formatted_size (#4102, #4103). Thanks @phprus.

• Fixed compile-time formatting of some string types (#4065). Thanks @torshepherd.

• Made compiled version of fmt::format_to work with std::back_insert_iterator<std::vector<char>> (#4206, #4211). Thanks @phprus.

• Added a formatter for std::reference_wrapper (#4163, #4164). Thanks @yfeldblum and @phprus.

• Added experimental padding support (glibc strftime extension) to %m, %j and %Y (#4161). Thanks @KKhanhH.

• Made microseconds formatted as us instead of µs if the Unicode support is disabled (#4088).

• Fixed an unreleased regression in transcoding of surrogate pairs (#4094, #4095). Thanks @phprus.

• Made fmt::appender satisfy std::output_iterator concept (#4092, #4093). Thanks @phprus.

• Made std::iterator_traits<fmt::appender> standard-conforming (#4185). Thanks @CaseyCarter.

• Made it easier to reuse fmt::formatter<std::string_view> for types with an implicit conversion to std::string_view (#4036, #4055). Thanks @Arghnews.

• Made it possible to disable <filesystem> use via FMT_CPP_LIB_FILESYSTEM for compatibility with some video game console SDKs, e.g. Nintendo Switch SDK (#4257, #4258, #4259). Thanks @W4RH4WK and @phprus.

• Fixed compatibility with platforms that use 80-bit long double (#4245, #4246). Thanks @jsirpoma.

• Added support for UTF-32 code units greater than 0xFFFF in fill (#4201).

• Fixed handling of legacy encodings on Windows with GCC (#4162).

• Made fmt::to_string take fmt::basic_memory_buffer by const reference (#4261, #4262). Thanks @sascha-devel.

• Added fmt::dynamic_format_arg_store::size (#4270). Thanks @hannes-harnisch.

• Removed the ability to control locale usage via an undocumented FMT_STATIC_THOUSANDS_SEPARATOR in favor of FMT_USE_LOCALE.

• Renamed FMT_EXCEPTIONS to FMT_USE_EXCEPTIONS for consistency with other similar macros.

• Improved include directory ordering to reduce the chance of including incorrect headers when using multiple versions of {fmt} (#4116). Thanks @cdzhan.

• Made it possible to compile a subset of {fmt} without the C++ runtime.

• Improved documentation and README (#4066, #4117, #4203, #4235). Thanks @zyctree and @nikola-sh.

• Improved the documentation generator (#4110, #4115). Thanks @rturrado.

• Improved CI (#4155, #4151). Thanks @phprus.

• Fixed various warnings and compilation issues (#2708, #4091, #4109, #4113, #4125, #4129, #4130, #4131, #4132, #4133, #4144, #4150, #4158, #4159, #4160, #4170, #4177, #4187, #4188, #4194, #4200, #4205, #4207, #4208, #4210, #4220, #4231, #4232, #4233, #4236, #4267, #4271). Thanks @torsten48, @Arghnews, @tinfoilboy, @aminya, @Ottani, @zeroomega, @c4v4, @kongy, @vinayyadav3016, @sergio-nsk, @phprus and @YexuanXiao.

11.0.2

• 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).

11.0.1

• 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.

11.0.0

• 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://...

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