ext-fmt/ChangeLog.md

11.0.0 - TBD

• Added fmt/base.h which provides a subset of the API with minimal include dependencies and enough functionality to replace all uses of *printf. 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	4.8
  tinyformat	29.1
  Boost Format	55.0

  Note that this is purely formatting code and includes. In real projects the difference will be smaller partly because common standard headers will be included in almost any translation unit anyway.

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

• Improved C++20 module support (https://github.com/fmtlib/fmt/issues/3990, https://github.com/fmtlib/fmt/pull/3991, https://github.com/fmtlib/fmt/issues/3993, https://github.com/fmtlib/fmt/pull/3997, https://github.com/fmtlib/fmt/pull/3998, https://github.com/fmtlib/fmt/pull/4004, https://github.com/fmtlib/fmt/pull/4005). Thanks @yujincheng08.

• Added an option to replace standard includes with import std enabled via the FMT_IMPORT_STD macro (https://github.com/fmtlib/fmt/issues/3921, https://github.com/fmtlib/fmt/pull/3928). Thanks @matt77hias.

• Exported fmt::range_format, fmt::range_format_kind and fmt::compiled_string from the fmt module (https://github.com/fmtlib/fmt/pull/3970, https://github.com/fmtlib/fmt/pull/3999). Thanks @matt77hias and @yujincheng08.

• Replaced double buffering with writing directly to a C stream buffer in std::print. This may give significant performance improvements ranging from tens of percent to 2x and elimates dynamic memory allocation of the buffer. It is currently enabled for common types with more to come in the upcoming releases.

• Improved safety of format_to when writting to an array (https://github.com/fmtlib/fmt/pull/3805). For example (godbolt):

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

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

• Added formatters for std::chrono::day, std::chrono::month, std::chrono::year and std::chrono::year_month_day (https://github.com/fmtlib/fmt/issues/3758, https://github.com/fmtlib/fmt/issues/3772, https://github.com/fmtlib/fmt/pull/3906, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/3794, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/pull/3976). Thanks @ZaheenJ.

• Fixed the scope of the - extension in chrono formatting so that it doesn't apply to subsequent specifiers (https://github.com/fmtlib/fmt/issues/3811, https://github.com/fmtlib/fmt/pull/3812). Thanks @phprus.

• Improved handling of time_point::min() (https://github.com/fmtlib/fmt/issues/3282).

• Added a formatter for std::expected (https://github.com/fmtlib/fmt/pull/3834. Thanks @dominicpoeschko.

• Added a formatter for std::complex (https://github.com/fmtlib/fmt/issues/1467, https://github.com/fmtlib/fmt/issues/3886, https://github.com/fmtlib/fmt/pull/3892, https://github.com/fmtlib/fmt/pull/3900). Thanks @phprus.

• Added a formatter for std::type_info (https://github.com/fmtlib/fmt/pull/3978). Thanks @matt77hias.

• Specialized formatter for std::basic_string types with custom traits and allocators (https://github.com/fmtlib/fmt/issues/3938, https://github.com/fmtlib/fmt/pull/3943). Thanks @dieram3.

• Added support for character range formatting (https://github.com/fmtlib/fmt/issues/3857, https://github.com/fmtlib/fmt/pull/3863). Thanks @js324.

• Enabled ADL for begin and end in fmt::join (https://github.com/fmtlib/fmt/issues/3813, https://github.com/fmtlib/fmt/pull/3824). Thanks @bbolli.

• Made contiguous iterator optimizations apply to std::basic_string iterators (https://github.com/fmtlib/fmt/pull/3798). Thanks @phprus.

• Added support for ranges with mutable begin and end (https://github.com/fmtlib/fmt/issues/3752, https://github.com/fmtlib/fmt/pull/3800, https://github.com/fmtlib/fmt/pull/3955). Thanks @tcbrindle and @Arghnews.

• Added support for move-only iterators to fmt::join (https://github.com/fmtlib/fmt/issues/3802, https://github.com/fmtlib/fmt/pull/3946). Thanks @Arghnews.

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

• Fixed hanling of types with begin returning void such as Eigen matrices (https://github.com/fmtlib/fmt/issues/3839, https://github.com/fmtlib/fmt/pull/3964). Thanks @Arghnews.

• Added a formattable concept (https://github.com/fmtlib/fmt/pull/3974). Thanks @matt77hias.

• Added support for __float128 (https://github.com/fmtlib/fmt/issues/3494).

• Fixed rounding issues when formatting long double with fixed precision (https://github.com/fmtlib/fmt/issues/3539).

• Made fmt::isnan not trigger floating-point exception for NaN values (https://github.com/fmtlib/fmt/issues/3948, https://github.com/fmtlib/fmt/pull/3951). Thanks @alexdewar.

• Removed dependency on <memory> for std::allocator_traits when possible (https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/4000, https://github.com/fmtlib/fmt/pull/4001). Thanks @yujincheng08.

• Made iterator_buffer's move constructor noexcept (https://github.com/fmtlib/fmt/pull/3808). Thanks @waywardmonkeys.

• Started enforcing that formatter::format is const for compatibility with std::format (https://github.com/fmtlib/fmt/issues/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 (https://github.com/fmtlib/fmt/pull/3846). Thanks @dalle.

• Fixed group_digits for negative integers (https://github.com/fmtlib/fmt/issues/3891, https://github.com/fmtlib/fmt/pull/3901). Thanks @phprus.

• Fixed handling of negative ids in basic_format_args::get (https://github.com/fmtlib/fmt/pull/3945). Thanks @marlenecota.

• Improved named argument validation (https://github.com/fmtlib/fmt/issues/3817).

• Disabled copy contruction/assignment for format_arg_store and fixed moved construction (https://github.com/fmtlib/fmt/pull/3833). Thanks @ivafanas.

• Worked around a locale issue in RHEL/devtoolset (https://github.com/fmtlib/fmt/issues/3858, https://github.com/fmtlib/fmt/pull/3859). Thanks @g199209.

• Added RTTI detection for MSVC (https://github.com/fmtlib/fmt/pull/3821, https://github.com/fmtlib/fmt/pull/3963). Thanks @edo9300.

• Improved documentation and README (https://github.com/fmtlib/fmt/issues/3775, https://github.com/fmtlib/fmt/pull/3784, https://github.com/fmtlib/fmt/issues/3788, https://github.com/fmtlib/fmt/pull/3789, https://github.com/fmtlib/fmt/pull/3793, https://github.com/fmtlib/fmt/issues/3818, https://github.com/fmtlib/fmt/pull/3820, https://github.com/fmtlib/fmt/pull/3822, https://github.com/fmtlib/fmt/pull/3843, https://github.com/fmtlib/fmt/pull/3890, https://github.com/fmtlib/fmt/issues/3894, https://github.com/fmtlib/fmt/pull/3895, https://github.com/fmtlib/fmt/pull/3905, https://github.com/fmtlib/fmt/issues/3942, https://github.com/fmtlib/fmt/pull/4008). Thanks @zencatalyst, WolleTD, @tupaschoal, @Dobiasd, @frank-weinberg, @bbolli, @phprus, @waywardmonkeys, @js324 and @tchaikov.

• Improved CI and tests (https://github.com/fmtlib/fmt/issues/3878, https://github.com/fmtlib/fmt/pull/3883, https://github.com/fmtlib/fmt/issues/3897, https://github.com/fmtlib/fmt/pull/3979, https://github.com/fmtlib/fmt/pull/3980, https://github.com/fmtlib/fmt/pull/3988, https://github.com/fmtlib/fmt/pull/4010). Thanks @vgorrX, @waywardmonkeys, @tchaikov and @phprus.

• Fixed buffer overflow when using format string compilation with debug format and std::back_insert_iterator (https://github.com/fmtlib/fmt/issues/3795, https://github.com/fmtlib/fmt/pull/3797). Thanks @phprus.

• Improved Bazel support (https://github.com/fmtlib/fmt/pull/3792, https://github.com/fmtlib/fmt/pull/3801, https://github.com/fmtlib/fmt/pull/3962, https://github.com/fmtlib/fmt/pull/3965). Thanks @Vertexwahn.

• Improved/fixed the CMake config (https://github.com/fmtlib/fmt/issues/3777, https://github.com/fmtlib/fmt/pull/3783, https://github.com/fmtlib/fmt/issues/3847, https://github.com/fmtlib/fmt/pull/3907). Thanks @phprus and @xTachyon.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/3685, https://github.com/fmtlib/fmt/issues/3769, https://github.com/fmtlib/fmt/issues/3796, https://github.com/fmtlib/fmt/issues/3803, https://github.com/fmtlib/fmt/pull/3806, https://github.com/fmtlib/fmt/pull/3807, https://github.com/fmtlib/fmt/issues/3809, https://github.com/fmtlib/fmt/pull/3810, https://github.com/fmtlib/fmt/issues/3830, https://github.com/fmtlib/fmt/pull/3832, https://github.com/fmtlib/fmt/issues/3835, https://github.com/fmtlib/fmt/pull/3844, https://github.com/fmtlib/fmt/issues/3854, https://github.com/fmtlib/fmt/pull/3856, https://github.com/fmtlib/fmt/pull/3865, https://github.com/fmtlib/fmt/pull/3866, https://github.com/fmtlib/fmt/pull/3880, https://github.com/fmtlib/fmt/issues/3881, https://github.com/fmtlib/fmt/issues/3884, https://github.com/fmtlib/fmt/issues/3898, https://github.com/fmtlib/fmt/pull/3899, https://github.com/fmtlib/fmt/pull/3909, https://github.com/fmtlib/fmt/pull/3917, https://github.com/fmtlib/fmt/pull/3923, https://github.com/fmtlib/fmt/pull/3924, https://github.com/fmtlib/fmt/issues/3925, https://github.com/fmtlib/fmt/pull/3930, https://github.com/fmtlib/fmt/pull/3931, https://github.com/fmtlib/fmt/pull/3933, https://github.com/fmtlib/fmt/issues/3935, https://github.com/fmtlib/fmt/pull/3937, https://github.com/fmtlib/fmt/pull/3967, https://github.com/fmtlib/fmt/pull/3968, https://github.com/fmtlib/fmt/pull/3972, https://github.com/fmtlib/fmt/pull/3983). Thanks @hmbj, @phprus, @res2k, @Baardi, @matt77hias, @waywardmonkeys, @hmbj, @yakra, @prlw1, @Arghnews, @mtillmann0, @ShifftC, @eepp and @jimmy-park.

10.2.1 - 2024-01-04

• Fixed ABI compatibility with earlier 10.x versions (https://github.com/fmtlib/fmt/issues/3785, https://github.com/fmtlib/fmt/pull/3786). Thanks @saraedum.

10.2.0 - 2024-01-01

• Added support for the %j specifier (the number of days) for std::chrono::duration (https://github.com/fmtlib/fmt/issues/3643, https://github.com/fmtlib/fmt/pull/3732). Thanks @intelfx.

• Added support for the chrono suffix for days and changed the suffix for minutes from "m" to the correct "min" (https://github.com/fmtlib/fmt/issues/3662, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/3725, https://github.com/fmtlib/fmt/pull/3727). Thanks @cschreib.

• Added a formatter for std::source_location (https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/3715, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/pull/3739). Thanks @tchaikov.

• Fixed formatting of invalid UTF-8 with precision (https://github.com/fmtlib/fmt/issues/3284).

• Fixed an inconsistency between fmt::to_string and fmt::format (https://github.com/fmtlib/fmt/issues/3684).

• Disallowed unsafe uses of fmt::styled (https://github.com/fmtlib/fmt/issues/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 (https://github.com/fmtlib/fmt/issues/3706).

• Disallowed the c specifier for bool (https://github.com/fmtlib/fmt/issues/3726, https://github.com/fmtlib/fmt/pull/3734). Thanks @js324.

• Made the default formatting unlocalized in fmt::ostream_formatter for consistency with the rest of the library (https://github.com/fmtlib/fmt/issues/3460).

• Fixed localized formatting in bases other than decimal (https://github.com/fmtlib/fmt/issues/3693, https://github.com/fmtlib/fmt/pull/3750). Thanks @js324.

• Fixed a performance regression in experimental fmt::ostream::print (https://github.com/fmtlib/fmt/issues/3674).

• Added synchronization with the underlying output stream when writing to the Windows console (https://github.com/fmtlib/fmt/pull/3668, https://github.com/fmtlib/fmt/issues/3688, https://github.com/fmtlib/fmt/pull/3689). Thanks @Roman-Koshelev and @dimztimz.

• Changed to only export format_error when {fmt} is built as a shared library (https://github.com/fmtlib/fmt/issues/3626, https://github.com/fmtlib/fmt/pull/3627). Thanks @phprus.

• Made fmt::streamed constexpr. (https://github.com/fmtlib/fmt/pull/3650). Thanks @muggenhor.

• Enabled consteval on older versions of MSVC (https://github.com/fmtlib/fmt/pull/3757). Thanks @phprus.

• Added an option to build without wchar_t support on Windows (https://github.com/fmtlib/fmt/issues/3631, https://github.com/fmtlib/fmt/pull/3636). Thanks @glebm.

• Improved build and CI configuration (https://github.com/fmtlib/fmt/pull/3679, https://github.com/fmtlib/fmt/issues/3701, https://github.com/fmtlib/fmt/pull/3702, https://github.com/fmtlib/fmt/pull/3749). Thanks @jcar87, @pklima and @tchaikov.

• Fixed various warnings, compilation and test issues (https://github.com/fmtlib/fmt/issues/3607, https://github.com/fmtlib/fmt/pull/3610, https://github.com/fmtlib/fmt/pull/3624, https://github.com/fmtlib/fmt/pull/3630, https://github.com/fmtlib/fmt/pull/3634, https://github.com/fmtlib/fmt/pull/3638, https://github.com/fmtlib/fmt/issues/3645, https://github.com/fmtlib/fmt/issues/3646, https://github.com/fmtlib/fmt/pull/3647, https://github.com/fmtlib/fmt/pull/3652, https://github.com/fmtlib/fmt/issues/3654, https://github.com/fmtlib/fmt/pull/3663, https://github.com/fmtlib/fmt/issues/3670, https://github.com/fmtlib/fmt/pull/3680, https://github.com/fmtlib/fmt/issues/3694, https://github.com/fmtlib/fmt/pull/3695, https://github.com/fmtlib/fmt/pull/3699, https://github.com/fmtlib/fmt/issues/3705, https://github.com/fmtlib/fmt/issues/3710, https://github.com/fmtlib/fmt/issues/3712, https://github.com/fmtlib/fmt/pull/3713, https://github.com/fmtlib/fmt/issues/3714, https://github.com/fmtlib/fmt/pull/3716, https://github.com/fmtlib/fmt/pull/3723, https://github.com/fmtlib/fmt/issues/3738, https://github.com/fmtlib/fmt/issues/3740, https://github.com/fmtlib/fmt/pull/3741, https://github.com/fmtlib/fmt/pull/3743, https://github.com/fmtlib/fmt/issues/3745, https://github.com/fmtlib/fmt/pull/3747, https://github.com/fmtlib/fmt/pull/3748, https://github.com/fmtlib/fmt/pull/3751, https://github.com/fmtlib/fmt/pull/3754, https://github.com/fmtlib/fmt/pull/3755, https://github.com/fmtlib/fmt/issues/3760, https://github.com/fmtlib/fmt/pull/3762, https://github.com/fmtlib/fmt/issues/3763, https://github.com/fmtlib/fmt/pull/3764, https://github.com/fmtlib/fmt/issues/3774, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/2086, https://github.com/fmtlib/fmt/issues/3637, https://github.com/fmtlib/fmt/pull/3642, https://github.com/fmtlib/fmt/pull/3653, https://github.com/fmtlib/fmt/pull/3655, https://github.com/fmtlib/fmt/pull/3661, https://github.com/fmtlib/fmt/issues/3673, https://github.com/fmtlib/fmt/pull/3677, https://github.com/fmtlib/fmt/pull/3737, https://github.com/fmtlib/fmt/issues/3742, https://github.com/fmtlib/fmt/pull/3744). Thanks @idzm, @perlun, @joycebrum, @fennewald, @reinhardt1053, @GeorgeLS.

• Updated CI dependencies (https://github.com/fmtlib/fmt/pull/3615, https://github.com/fmtlib/fmt/pull/3622, https://github.com/fmtlib/fmt/pull/3623, https://github.com/fmtlib/fmt/pull/3666, https://github.com/fmtlib/fmt/pull/3696, https://github.com/fmtlib/fmt/pull/3697, https://github.com/fmtlib/fmt/pull/3759, https://github.com/fmtlib/fmt/pull/3782).

10.1.1 - 2023-08-28

• Added formatters for std::atomic and atomic_flag (https://github.com/fmtlib/fmt/pull/3574, https://github.com/fmtlib/fmt/pull/3594). Thanks @wangzw and @AlexGuteniev.
• Fixed an error about partial specialization of formatter<string> after instantiation when compiled with gcc and C++20 (https://github.com/fmtlib/fmt/issues/3584).
• Fixed compilation as a C++20 module with gcc and clang (https://github.com/fmtlib/fmt/issues/3587, https://github.com/fmtlib/fmt/pull/3597, https://github.com/fmtlib/fmt/pull/3605). Thanks @MathewBensonCode.
• Made fmt::to_string work with types that have format_as overloads (https://github.com/fmtlib/fmt/pull/3575). Thanks @phprus.
• Made formatted_size work with integral format specifiers at compile time (https://github.com/fmtlib/fmt/pull/3591). Thanks @elbeno.
• Fixed a warning about the no_unique_address attribute on clang-cl (https://github.com/fmtlib/fmt/pull/3599). Thanks @lukester1975.
• Improved compatibility with the legacy GBK encoding (https://github.com/fmtlib/fmt/issues/3598, https://github.com/fmtlib/fmt/pull/3599). Thanks @YuHuanTin.
• Added OpenSSF Scorecard analysis (https://github.com/fmtlib/fmt/issues/3530, https://github.com/fmtlib/fmt/pull/3571). Thanks @joycebrum.
• Updated CI dependencies (https://github.com/fmtlib/fmt/pull/3591, https://github.com/fmtlib/fmt/pull/3592, https://github.com/fmtlib/fmt/pull/3593, https://github.com/fmtlib/fmt/pull/3602).

10.1.0 - 2023-08-12

• 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 (https://github.com/fmtlib/fmt/issues/3133, https://github.com/fmtlib/fmt/issues/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 (https://github.com/fmtlib/fmt/pull/3485). Thanks @Minty-Meeo.

• Added formatters for proxy references to elements of std::vector<bool> and std::bitset<N> (https://github.com/fmtlib/fmt/issues/3567, https://github.com/fmtlib/fmt/pull/3570). For example (godbolt):

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

  Thanks @phprus and @felix642.

• Fixed an ambiguous formatter specialization for containers that look like container adaptors such as boost::flat_set (https://github.com/fmtlib/fmt/issues/3556, https://github.com/fmtlib/fmt/pull/3561). Thanks @5chmidti.

• Fixed compilation when formatting durations not convertible from std::chrono::seconds (https://github.com/fmtlib/fmt/pull/3430). Thanks @patlkli.

• Made the formatter specialization for char* const-correct (https://github.com/fmtlib/fmt/pull/3432). Thanks @timsong-cpp.

• Made {} and {:} handled consistently during compile-time checks (https://github.com/fmtlib/fmt/issues/3526).

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

• Improved the compile-time error for unformattable types (https://github.com/fmtlib/fmt/pull/3478). Thanks @BRevzin.

• Improved the floating-point formatter (https://github.com/fmtlib/fmt/pull/3448, https://github.com/fmtlib/fmt/pull/3450). Thanks @florimond-collette.

• Fixed handling of precision for long double larger than 64 bits. (https://github.com/fmtlib/fmt/issues/3539, https://github.com/fmtlib/fmt/issues/3564).

• Made floating-point and chrono tests less platform-dependent (https://github.com/fmtlib/fmt/issues/3337, https://github.com/fmtlib/fmt/issues/3433, https://github.com/fmtlib/fmt/pull/3434). Thanks @phprus.

• 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 (https://github.com/fmtlib/fmt/pull/3551). Thanks @mjerabek.

• Made FMT_THROW assert even if assertions are disabled when compiling with exceptions disabled (https://github.com/fmtlib/fmt/issues/3418, https://github.com/fmtlib/fmt/pull/3439). Thanks @BRevzin.

• Made format_as and std::filesystem::path formatter work with exotic code unit types. (https://github.com/fmtlib/fmt/pull/3457, https://github.com/fmtlib/fmt/pull/3476). Thanks @gix and @hmbj.

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

• Deprecated the wide stream overload of printf.

• Removed unused basic_printf_parse_context.

• Improved RTTI detection used when formatting exceptions (https://github.com/fmtlib/fmt/pull/3468). Thanks @danakj.

• Improved compatibility with VxWorks7 (https://github.com/fmtlib/fmt/pull/3467). Thanks @wenshan1.

• Improved documentation (https://github.com/fmtlib/fmt/issues/3174, https://github.com/fmtlib/fmt/issues/3423, https://github.com/fmtlib/fmt/pull/3454, https://github.com/fmtlib/fmt/issues/3458, https://github.com/fmtlib/fmt/pull/3461, https://github.com/fmtlib/fmt/issues/3487, https://github.com/fmtlib/fmt/pull/3515). Thanks @zencatalyst, @rlalik and @mikecrowe.

• Improved build and CI configurations (https://github.com/fmtlib/fmt/issues/3449, https://github.com/fmtlib/fmt/pull/3451, https://github.com/fmtlib/fmt/pull/3452, https://github.com/fmtlib/fmt/pull/3453, https://github.com/fmtlib/fmt/pull/3459, https://github.com/fmtlib/fmt/issues/3481, https://github.com/fmtlib/fmt/pull/3486, https://github.com/fmtlib/fmt/issues/3489, https://github.com/fmtlib/fmt/pull/3496, https://github.com/fmtlib/fmt/issues/3517, https://github.com/fmtlib/fmt/pull/3523, https://github.com/fmtlib/fmt/pull/3563). Thanks @joycebrum, @glebm, @phprus, @petrmanek, @setoye and @abouvier.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/3408, https://github.com/fmtlib/fmt/issues/3424, https://github.com/fmtlib/fmt/issues/3444, https://github.com/fmtlib/fmt/pull/3446, https://github.com/fmtlib/fmt/pull/3475, https://github.com/fmtlib/fmt/pull/3482, https://github.com/fmtlib/fmt/issues/3492, https://github.com/fmtlib/fmt/pull/3493, https://github.com/fmtlib/fmt/pull/3508, https://github.com/fmtlib/fmt/issues/3509, https://github.com/fmtlib/fmt/issues/3533, https://github.com/fmtlib/fmt/pull/3542, https://github.com/fmtlib/fmt/issues/3543, https://github.com/fmtlib/fmt/issues/3540, https://github.com/fmtlib/fmt/pull/3544, https://github.com/fmtlib/fmt/issues/3548, https://github.com/fmtlib/fmt/pull/3549, https://github.com/fmtlib/fmt/pull/3550, https://github.com/fmtlib/fmt/pull/3552). Thanks @adesitter, @hmbj, @Minty-Meeo, @phprus, @TobiSchluter, @kieranclancy, @alexeedm, @jurihock, @Ozomahtli and @razaqq.

10.0.0 - 2023-05-09

• Replaced Grisu with a new floating-point formatting algorithm for given precision (https://github.com/fmtlib/fmt/issues/3262, https://github.com/fmtlib/fmt/issues/2750, https://github.com/fmtlib/fmt/pull/3269, https://github.com/fmtlib/fmt/pull/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.

• Replaced snprintf-based hex float formatter with an internal implementation (https://github.com/fmtlib/fmt/pull/3179, https://github.com/fmtlib/fmt/pull/3203). This removes the last usage of s(n)printf in {fmt}. Thanks @phprus.

• Fixed alignment of floating-point numbers with localization (https://github.com/fmtlib/fmt/issues/3263, https://github.com/fmtlib/fmt/pull/3272). Thanks @ShawnZhong.

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

• Improved C++20 module support (https://github.com/fmtlib/fmt/pull/3134, https://github.com/fmtlib/fmt/pull/3254, https://github.com/fmtlib/fmt/pull/3386, https://github.com/fmtlib/fmt/pull/3387, https://github.com/fmtlib/fmt/pull/3388, https://github.com/fmtlib/fmt/pull/3392, https://github.com/fmtlib/fmt/pull/3397, https://github.com/fmtlib/fmt/pull/3399, https://github.com/fmtlib/fmt/pull/3400). Thanks @laitingsheng, @Orvid and @DanielaE.

• 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 (https://github.com/fmtlib/fmt/issues/3237, https://github.com/fmtlib/fmt/pull/3260, https://github.com/fmtlib/fmt/pull/3275). For example (godbolt):

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

  Thanks @ShawnZhong.

• Implemented formatting of subseconds (https://github.com/fmtlib/fmt/issues/2207, https://github.com/fmtlib/fmt/issues/3117, https://github.com/fmtlib/fmt/pull/3115, https://github.com/fmtlib/fmt/pull/3143, https://github.com/fmtlib/fmt/pull/3144, https://github.com/fmtlib/fmt/pull/3349). For example (godbolt):

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

  Thanks @patrickroocks @phprus and @BRevzin.

• Added precision support to %S (https://github.com/fmtlib/fmt/pull/3148). Thanks @SappyJoy

• Added support for std::utc_time (https://github.com/fmtlib/fmt/issues/3098, https://github.com/fmtlib/fmt/pull/3110). Thanks @patrickroocks.

• Switched formatting of std::chrono::system_clock from local time to UTC for compatibility with the standard (https://github.com/fmtlib/fmt/issues/3199, https://github.com/fmtlib/fmt/pull/3230). Thanks @ned14.

• Added support for %Ez and %Oz to chrono formatters. (https://github.com/fmtlib/fmt/issues/3220, https://github.com/fmtlib/fmt/pull/3222). Thanks @phprus.

• Improved validation of format specifiers for std::chrono::duration (https://github.com/fmtlib/fmt/issues/3219, https://github.com/fmtlib/fmt/pull/3232). Thanks @ShawnZhong.

• Fixed formatting of time points before the epoch (https://github.com/fmtlib/fmt/issues/3117, https://github.com/fmtlib/fmt/pull/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.

• Experimental: implemented glibc extension for padding seconds, minutes and hours (https://github.com/fmtlib/fmt/issues/2959, https://github.com/fmtlib/fmt/pull/3271). Thanks @ShawnZhong.

• Added a formatter for std::exception (https://github.com/fmtlib/fmt/issues/2977, https://github.com/fmtlib/fmt/issues/3012, https://github.com/fmtlib/fmt/pull/3062, https://github.com/fmtlib/fmt/pull/3076, https://github.com/fmtlib/fmt/pull/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 and @phprus.

• Moved std::error_code formatter from fmt/os.h to fmt/std.h. (https://github.com/fmtlib/fmt/pull/3125). Thanks @phprus.

• Added formatters for standard container adapters: std::priority_queue, std::queue and std::stack (https://github.com/fmtlib/fmt/issues/3215, https://github.com/fmtlib/fmt/pull/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.

• Added a formatter for std::optional to fmt/std.h (https://github.com/fmtlib/fmt/issues/1367, https://github.com/fmtlib/fmt/pull/3303). Thanks @tom-huntington.

• Fixed formatting of valueless by exception variants (https://github.com/fmtlib/fmt/pull/3347). Thanks @TheOmegaCarrot.

• Made fmt::ptr accept unique_ptr with a custom deleter (https://github.com/fmtlib/fmt/pull/3177). Thanks @hmbj.

• Fixed formatting of noncopyable ranges and nested ranges of chars (https://github.com/fmtlib/fmt/pull/3158 https://github.com/fmtlib/fmt/issues/3286, https://github.com/fmtlib/fmt/pull/3290). Thanks @BRevzin.

• Fixed issues with formatting of paths and ranges of paths (https://github.com/fmtlib/fmt/issues/3319, https://github.com/fmtlib/fmt/pull/3321 https://github.com/fmtlib/fmt/issues/3322). Thanks @phprus.

• Improved handling of invalid Unicode in paths.

• Enabled compile-time checks on Apple clang 14 and later (https://github.com/fmtlib/fmt/pull/3331). Thanks @cloyce.

• Improved compile-time checks of named arguments (https://github.com/fmtlib/fmt/issues/3105, https://github.com/fmtlib/fmt/pull/3214). Thanks @rbrich.

• Fixed formatting when both alignment and 0 are given (https://github.com/fmtlib/fmt/issues/3236, https://github.com/fmtlib/fmt/pull/3248). Thanks @ShawnZhong.

• Improved Unicode support in the experimental file API on Windows (https://github.com/fmtlib/fmt/issues/3234, https://github.com/fmtlib/fmt/pull/3293). Thanks @Fros1er.

• Unified UTF transcoding (https://github.com/fmtlib/fmt/pull/3416). Thanks @phprus.

• Added support for UTF-8 digit separators via an experimental locale facet (https://github.com/fmtlib/fmt/issues/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 (https://github.com/fmtlib/fmt/issues/3084, https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/3241, https://github.com/fmtlib/fmt/pull/3244). Thanks @phprus.

• Added starts_with to the fallback string_view implementation (https://github.com/fmtlib/fmt/pull/3080). Thanks @phprus.

• Added fmt::basic_format_string::get() for compatibility with basic_format_string (https://github.com/fmtlib/fmt/pull/3111). Thanks @huangqinjin.

• Added println for compatibility with C++23 (https://github.com/fmtlib/fmt/pull/3267). Thanks @ShawnZhong.

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

• Improved documentation (https://github.com/fmtlib/fmt/issues/3108, https://github.com/fmtlib/fmt/issues/3169, https://github.com/fmtlib/fmt/pull/3243). https://github.com/fmtlib/fmt/pull/3404, https://github.com/fmtlib/fmt/pull/4002). Thanks @Cleroth, @Vertexwahn and @yujincheng08.

• Improved build configuration and tests (https://github.com/fmtlib/fmt/pull/3118, https://github.com/fmtlib/fmt/pull/3120, https://github.com/fmtlib/fmt/pull/3188, https://github.com/fmtlib/fmt/issues/3189, https://github.com/fmtlib/fmt/pull/3198, https://github.com/fmtlib/fmt/pull/3205, https://github.com/fmtlib/fmt/pull/3207, https://github.com/fmtlib/fmt/pull/3210, https://github.com/fmtlib/fmt/pull/3240, https://github.com/fmtlib/fmt/pull/3256, https://github.com/fmtlib/fmt/pull/3264, https://github.com/fmtlib/fmt/issues/3299, https://github.com/fmtlib/fmt/pull/3302, https://github.com/fmtlib/fmt/pull/3312, https://github.com/fmtlib/fmt/issues/3317, https://github.com/fmtlib/fmt/pull/3328, https://github.com/fmtlib/fmt/pull/3333, https://github.com/fmtlib/fmt/pull/3369, https://github.com/fmtlib/fmt/issues/3373, https://github.com/fmtlib/fmt/pull/3395, https://github.com/fmtlib/fmt/pull/3406, https://github.com/fmtlib/fmt/pull/3411). Thanks @dimztimz, @phprus, @DavidKorczynski, @ChrisThrasher, @FrancoisCarouge, @kennyweiss, @luzpaz, @codeinred, @Mixaill, @joycebrum, @kevinhwang and @Vertexwahn.

• Fixed a regression in handling empty format specifiers after a colon ({:}) (https://github.com/fmtlib/fmt/pull/3086). Thanks @oxidase.

• Worked around a broken implementation of std::is_constant_evaluated in some versions of libstdc++ on clang (https://github.com/fmtlib/fmt/issues/3247, https://github.com/fmtlib/fmt/pull/3281). Thanks @phprus.

• Fixed formatting of volatile variables (https://github.com/fmtlib/fmt/pull/3068).

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/pull/3057, https://github.com/fmtlib/fmt/pull/3066, https://github.com/fmtlib/fmt/pull/3072, https://github.com/fmtlib/fmt/pull/3082, https://github.com/fmtlib/fmt/pull/3091, https://github.com/fmtlib/fmt/issues/3092, https://github.com/fmtlib/fmt/pull/3093, https://github.com/fmtlib/fmt/pull/3095, https://github.com/fmtlib/fmt/issues/3096, https://github.com/fmtlib/fmt/pull/3097, https://github.com/fmtlib/fmt/issues/3128, https://github.com/fmtlib/fmt/pull/3129, https://github.com/fmtlib/fmt/pull/3137, https://github.com/fmtlib/fmt/pull/3139, https://github.com/fmtlib/fmt/issues/3140, https://github.com/fmtlib/fmt/pull/3142, https://github.com/fmtlib/fmt/issues/3149, https://github.com/fmtlib/fmt/pull/3150, https://github.com/fmtlib/fmt/issues/3154, https://github.com/fmtlib/fmt/issues/3163, https://github.com/fmtlib/fmt/issues/3178, https://github.com/fmtlib/fmt/pull/3184, https://github.com/fmtlib/fmt/pull/3196, https://github.com/fmtlib/fmt/issues/3204, https://github.com/fmtlib/fmt/pull/3206, https://github.com/fmtlib/fmt/pull/3208, https://github.com/fmtlib/fmt/issues/3213, https://github.com/fmtlib/fmt/pull/3216, https://github.com/fmtlib/fmt/issues/3224, https://github.com/fmtlib/fmt/issues/3226, https://github.com/fmtlib/fmt/issues/3228, https://github.com/fmtlib/fmt/pull/3229, https://github.com/fmtlib/fmt/pull/3259, https://github.com/fmtlib/fmt/issues/3274, https://github.com/fmtlib/fmt/issues/3287, https://github.com/fmtlib/fmt/pull/3288, https://github.com/fmtlib/fmt/issues/3292, https://github.com/fmtlib/fmt/pull/3295, https://github.com/fmtlib/fmt/pull/3296, https://github.com/fmtlib/fmt/issues/3298, https://github.com/fmtlib/fmt/issues/3325, https://github.com/fmtlib/fmt/pull/3326, https://github.com/fmtlib/fmt/issues/3334, https://github.com/fmtlib/fmt/issues/3342, https://github.com/fmtlib/fmt/pull/3343, https://github.com/fmtlib/fmt/issues/3351, https://github.com/fmtlib/fmt/pull/3352, https://github.com/fmtlib/fmt/pull/3362, https://github.com/fmtlib/fmt/issues/3365, https://github.com/fmtlib/fmt/pull/3366, https://github.com/fmtlib/fmt/pull/3374, https://github.com/fmtlib/fmt/issues/3377, https://github.com/fmtlib/fmt/pull/3378, https://github.com/fmtlib/fmt/issues/3381, https://github.com/fmtlib/fmt/pull/3398, https://github.com/fmtlib/fmt/pull/3413, https://github.com/fmtlib/fmt/issues/3415). Thanks @phprus, @gsjaardema, @NewbieOrange, @EngineLessCC, @asmaloney, @HazardyKnusperkeks, @sergiud, @Youw, @thesmurph, @czudziakm, @Roman-Koshelev, @chronoxor, @ShawnZhong, @russelltg, @glebm, @tmartin-gh, @Zhaojun-Liu, @louiswins and @mogemimi.

9.1.0 - 2022-08-27

• fmt::formatted_size now works at compile time (https://github.com/fmtlib/fmt/pull/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.

• Fixed handling of invalid UTF-8 (https://github.com/fmtlib/fmt/pull/3038, https://github.com/fmtlib/fmt/pull/3044, https://github.com/fmtlib/fmt/pull/3056). Thanks @phprus and @skeeto.

• Improved Unicode support in ostream overloads of print (https://github.com/fmtlib/fmt/pull/2994, https://github.com/fmtlib/fmt/pull/3001, https://github.com/fmtlib/fmt/pull/3025). Thanks @dimztimz.

• Fixed handling of the sign specifier in localized formatting on systems with 32-bit wchar_t (https://github.com/fmtlib/fmt/issues/3041).

• Added support for wide streams to fmt::streamed (https://github.com/fmtlib/fmt/pull/2994). Thanks @phprus.

• Added the n specifier that disables the output of delimiters when formatting ranges (https://github.com/fmtlib/fmt/pull/2981, https://github.com/fmtlib/fmt/pull/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.

• Worked around problematic std::string_view constructors introduced in C++23 (https://github.com/fmtlib/fmt/issues/3030, https://github.com/fmtlib/fmt/issues/3050). Thanks @strega-nil-ms.

• Improve handling (exclusion) of recursive ranges (https://github.com/fmtlib/fmt/issues/2968, https://github.com/fmtlib/fmt/pull/2974). Thanks @Dani-Hub.

• Improved error reporting in format string compilation (https://github.com/fmtlib/fmt/issues/3055).

• Improved the implementation of Dragonbox, the algorithm used for the default floating-point formatting (https://github.com/fmtlib/fmt/pull/2984). Thanks @jk-jeon.

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

• Improved the implementation of chrono formatting (https://github.com/fmtlib/fmt/pull/3010). Thanks @phprus.

• Improved documentation (https://github.com/fmtlib/fmt/pull/2966, https://github.com/fmtlib/fmt/pull/3009, https://github.com/fmtlib/fmt/issues/3020, https://github.com/fmtlib/fmt/pull/3037). Thanks @mwinterb, @jcelerier and @remiburtin.

• Improved build configuration (https://github.com/fmtlib/fmt/pull/2991, https://github.com/fmtlib/fmt/pull/2995, https://github.com/fmtlib/fmt/issues/3004, https://github.com/fmtlib/fmt/pull/3007, https://github.com/fmtlib/fmt/pull/3040). Thanks @dimztimz and @hwhsu1231.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/2969, https://github.com/fmtlib/fmt/pull/2971, https://github.com/fmtlib/fmt/issues/2975, https://github.com/fmtlib/fmt/pull/2982, https://github.com/fmtlib/fmt/pull/2985, https://github.com/fmtlib/fmt/issues/2988, https://github.com/fmtlib/fmt/issues/2989, https://github.com/fmtlib/fmt/issues/3000, https://github.com/fmtlib/fmt/issues/3006, https://github.com/fmtlib/fmt/issues/3014, https://github.com/fmtlib/fmt/issues/3015, https://github.com/fmtlib/fmt/pull/3021, https://github.com/fmtlib/fmt/issues/3023, https://github.com/fmtlib/fmt/pull/3024, https://github.com/fmtlib/fmt/pull/3029, https://github.com/fmtlib/fmt/pull/3043, https://github.com/fmtlib/fmt/issues/3052, https://github.com/fmtlib/fmt/pull/3053, https://github.com/fmtlib/fmt/pull/3054). Thanks @h-friederich, @dimztimz, @olupton, @bernhardmgruber and @phprus.

9.0.0 - 2022-07-04

• 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 (https://github.com/fmtlib/fmt/pull/2713, https://github.com/fmtlib/fmt/pull/2750). Thanks @jk-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 (https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/2865, https://github.com/fmtlib/fmt/pull/2902, https://github.com/fmtlib/fmt/issues/2917, https://github.com/fmtlib/fmt/pull/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.

• 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 (https://github.com/fmtlib/fmt/pull/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.

• Made fmt::print overload for text styles correctly handle UTF-8 (https://github.com/fmtlib/fmt/issues/2681, https://github.com/fmtlib/fmt/pull/2701). Thanks @AlexGuteniev.

• Fixed Unicode handling when writing to an ostream.

• Added support for nested specifiers to range formatting (https://github.com/fmtlib/fmt/pull/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.

• Implemented escaping of wide strings in ranges (https://github.com/fmtlib/fmt/pull/2904). Thanks @phprus.

• Added support for ranges with begin / end found via the argument-dependent lookup (https://github.com/fmtlib/fmt/pull/2807). Thanks @rbrugo.

• Fixed formatting of certain kinds of ranges of ranges (https://github.com/fmtlib/fmt/pull/2787). Thanks @BRevzin.

• Fixed handling of maps with element types other than std::pair (https://github.com/fmtlib/fmt/pull/2944). Thanks @BrukerJWD.

• Made tuple formatter enabled only if elements are formattable (https://github.com/fmtlib/fmt/issues/2939, https://github.com/fmtlib/fmt/pull/2940). Thanks @jehelset.

• Made fmt::join compatible with format string compilation (https://github.com/fmtlib/fmt/issues/2719, https://github.com/fmtlib/fmt/pull/2720). Thanks @phprus.

• Made compile-time checks work with named arguments of custom types and std::ostream print overloads (https://github.com/fmtlib/fmt/issues/2816, https://github.com/fmtlib/fmt/issues/2817, https://github.com/fmtlib/fmt/pull/2819). Thanks @timsong-cpp.

• Removed make_args_checked because it is no longer needed for compile-time checks (https://github.com/fmtlib/fmt/pull/2760). Thanks @phprus.

• 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 (https://github.com/fmtlib/fmt/pull/2733). Thanks @arogge.

• Removed a redundant buffer resize when formatting to std::ostream (https://github.com/fmtlib/fmt/issues/2842, https://github.com/fmtlib/fmt/pull/2843). Thanks @jcelerier.

• Made precision computation for strings consistent with width (https://github.com/fmtlib/fmt/issues/2888).

• Fixed handling of locale separators in floating point formatting (https://github.com/fmtlib/fmt/issues/2830).

• Made sign specifiers work with __int128_t (https://github.com/fmtlib/fmt/issues/2773).

• Improved support for systems such as CHERI with extra data stored in pointers (https://github.com/fmtlib/fmt/pull/2932). Thanks @davidchisnall.

• Improved documentation (https://github.com/fmtlib/fmt/pull/2706, https://github.com/fmtlib/fmt/pull/2712, https://github.com/fmtlib/fmt/pull/2789, https://github.com/fmtlib/fmt/pull/2803, https://github.com/fmtlib/fmt/pull/2805, https://github.com/fmtlib/fmt/pull/2815, https://github.com/fmtlib/fmt/pull/2924). Thanks @BRevzin, @Pokechu22, @setoye, @rtobar, @rbrugo, @anoonD and @leha-bot.

• Improved build configuration (https://github.com/fmtlib/fmt/pull/2766, https://github.com/fmtlib/fmt/pull/2772, https://github.com/fmtlib/fmt/pull/2836, https://github.com/fmtlib/fmt/pull/2852, https://github.com/fmtlib/fmt/pull/2907, https://github.com/fmtlib/fmt/pull/2913, https://github.com/fmtlib/fmt/pull/2914). Thanks @kambala-decapitator, @mattiasljungstrom, @kieselnb, @nathannaveen and @Vertexwahn.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/2408, https://github.com/fmtlib/fmt/issues/2507, https://github.com/fmtlib/fmt/issues/2697, https://github.com/fmtlib/fmt/issues/2715, https://github.com/fmtlib/fmt/issues/2717, https://github.com/fmtlib/fmt/pull/2722, https://github.com/fmtlib/fmt/pull/2724, https://github.com/fmtlib/fmt/pull/2725, https://github.com/fmtlib/fmt/issues/2726, https://github.com/fmtlib/fmt/pull/2728, https://github.com/fmtlib/fmt/pull/2732, https://github.com/fmtlib/fmt/issues/2738, https://github.com/fmtlib/fmt/pull/2742, https://github.com/fmtlib/fmt/issues/2744, https://github.com/fmtlib/fmt/issues/2745, https://github.com/fmtlib/fmt/issues/2746, https://github.com/fmtlib/fmt/issues/2754, https://github.com/fmtlib/fmt/pull/2755, https://github.com/fmtlib/fmt/issues/2757, https://github.com/fmtlib/fmt/pull/2758, https://github.com/fmtlib/fmt/issues/2761, https://github.com/fmtlib/fmt/pull/2762, https://github.com/fmtlib/fmt/issues/2763, https://github.com/fmtlib/fmt/pull/2765, https://github.com/fmtlib/fmt/issues/2769, https://github.com/fmtlib/fmt/pull/2770, https://github.com/fmtlib/fmt/issues/2771, https://github.com/fmtlib/fmt/issues/2777, https://github.com/fmtlib/fmt/pull/2779, https://github.com/fmtlib/fmt/pull/2782, https://github.com/fmtlib/fmt/pull/2783, https://github.com/fmtlib/fmt/issues/2794, https://github.com/fmtlib/fmt/issues/2796, https://github.com/fmtlib/fmt/pull/2797, https://github.com/fmtlib/fmt/pull/2801, https://github.com/fmtlib/fmt/pull/2802, https://github.com/fmtlib/fmt/issues/2808, https://github.com/fmtlib/fmt/issues/2818, https://github.com/fmtlib/fmt/pull/2819, https://github.com/fmtlib/fmt/issues/2829, https://github.com/fmtlib/fmt/issues/2835, https://github.com/fmtlib/fmt/issues/2848, https://github.com/fmtlib/fmt/issues/2860, https://github.com/fmtlib/fmt/pull/2861, https://github.com/fmtlib/fmt/pull/2882, https://github.com/fmtlib/fmt/issues/2886, https://github.com/fmtlib/fmt/issues/2891, https://github.com/fmtlib/fmt/pull/2892, https://github.com/fmtlib/fmt/issues/2895, https://github.com/fmtlib/fmt/issues/2896, https://github.com/fmtlib/fmt/pull/2903, https://github.com/fmtlib/fmt/issues/2906, https://github.com/fmtlib/fmt/issues/2908, https://github.com/fmtlib/fmt/pull/2909, https://github.com/fmtlib/fmt/issues/2920, https://github.com/fmtlib/fmt/pull/2922, https://github.com/fmtlib/fmt/pull/2927, https://github.com/fmtlib/fmt/pull/2929, https://github.com/fmtlib/fmt/issues/2936, https://github.com/fmtlib/fmt/pull/2937, https://github.com/fmtlib/fmt/pull/2938, https://github.com/fmtlib/fmt/pull/2951, https://github.com/fmtlib/fmt/issues/2954, https://github.com/fmtlib/fmt/pull/2957, https://github.com/fmtlib/fmt/issues/2958, https://github.com/fmtlib/fmt/pull/2960). Thanks @matrackif @Tobi823, @ivan-volnov, @VasiliPupkin256, @federico-busato, @barcharcraz, @jk-jeon, @HazardyKnusperkeks, @dalboris, @seanm, @gsjaardema, @timsong-cpp, @seanm, @frithrah, @chronoxor, @Agga, @madmaxoft, @JurajX, @phprus and @Dani-Hub.

8.1.1 - 2022-01-06

• Restored ABI compatibility with version 8.0.x (https://github.com/fmtlib/fmt/issues/2695, https://github.com/fmtlib/fmt/pull/2696). Thanks @saraedum.
• Fixed chrono formatting on big endian systems (https://github.com/fmtlib/fmt/issues/2698, https://github.com/fmtlib/fmt/pull/2699). Thanks @phprus and @xvitaly.
• Fixed a linkage error with mingw (https://github.com/fmtlib/fmt/issues/2691, https://github.com/fmtlib/fmt/pull/2692). Thanks @rbberger.

8.1.0 - 2022-01-02

• Optimized chrono formatting (https://github.com/fmtlib/fmt/pull/2500, https://github.com/fmtlib/fmt/pull/2537, https://github.com/fmtlib/fmt/issues/2541, https://github.com/fmtlib/fmt/pull/2544, https://github.com/fmtlib/fmt/pull/2550, https://github.com/fmtlib/fmt/pull/2551, https://github.com/fmtlib/fmt/pull/2576, https://github.com/fmtlib/fmt/issues/2577, https://github.com/fmtlib/fmt/pull/2586, https://github.com/fmtlib/fmt/pull/2591, https://github.com/fmtlib/fmt/pull/2594, https://github.com/fmtlib/fmt/pull/2602, https://github.com/fmtlib/fmt/pull/2617, https://github.com/fmtlib/fmt/issues/2628, https://github.com/fmtlib/fmt/pull/2633, https://github.com/fmtlib/fmt/issues/2670, https://github.com/fmtlib/fmt/pull/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 and @toughengineer.

• Implemented subsecond formatting for chrono durations (https://github.com/fmtlib/fmt/pull/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 (https://github.com/fmtlib/fmt/issues/2587, https://github.com/fmtlib/fmt/pull/2588). Thanks @lukester1975.

• Fixed an overflow on invalid inputs in the tm formatter (https://github.com/fmtlib/fmt/pull/2564). Thanks @phprus.

• 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 (https://github.com/fmtlib/fmt/pull/2394):

  https://user-images.githubusercontent.com/576385/147710227-c68f5317-f8fa-42c3-9123-7c4ba3c398cb.mp4

  Thanks @benit8 and @data-man.

• Added experimental support for compile-time floating point formatting (https://github.com/fmtlib/fmt/pull/2426, https://github.com/fmtlib/fmt/pull/2470). It is currently limited to the header-only mode. Thanks @alexezeder.

• Added UDL-based named argument support to compile-time format string checks (https://github.com/fmtlib/fmt/issues/2640, https://github.com/fmtlib/fmt/pull/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.

• 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"]
  

• Added an experimental ? specifier for escaping strings. (https://github.com/fmtlib/fmt/pull/2674). Thanks @BRevzin.

• 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 (https://github.com/fmtlib/fmt/pull/2549). Thanks @BRevzin.

• 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 (https://github.com/fmtlib/fmt/pull/1841).

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

• Deprecated _format, a legacy UDL-based format API (https://github.com/fmtlib/fmt/pull/2646). Thanks @alexezeder.

• Marked format, formatted_size and to_string as [[nodiscard]] (https://github.com/fmtlib/fmt/pull/2612). @0x8000-0000.

• Added missing diagnostic when trying to format function and member pointers as well as objects convertible to pointers which is explicitly disallowed (https://github.com/fmtlib/fmt/issues/2598, https://github.com/fmtlib/fmt/pull/2609, https://github.com/fmtlib/fmt/pull/2610). Thanks @AlexGuteniev.

• Optimized writing to a contiguous buffer with format_to_n (https://github.com/fmtlib/fmt/pull/2489). Thanks @Roman-Koshelev.

• Optimized writing to non-char buffers (https://github.com/fmtlib/fmt/pull/2477). Thanks @Roman-Koshelev.

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

• Improved floating point formatter implementation (https://github.com/fmtlib/fmt/pull/2498, https://github.com/fmtlib/fmt/pull/2499). Thanks @Roman-Koshelev.

• Fixed handling of very large precision in fixed format (https://github.com/fmtlib/fmt/pull/2616).

• Made a table of cached powers used in FP formatting static (https://github.com/fmtlib/fmt/pull/2509). Thanks @jk-jeon.

• Resolved a lookup ambiguity with C++20 format-related functions due to ADL (https://github.com/fmtlib/fmt/issues/2639, https://github.com/fmtlib/fmt/pull/2641). Thanks @mkurdej.

• Removed unnecessary inline namespace qualification (https://github.com/fmtlib/fmt/issues/2642, https://github.com/fmtlib/fmt/pull/2643). Thanks @mkurdej.

• Implemented argument forwarding in format_to_n (https://github.com/fmtlib/fmt/issues/2462, https://github.com/fmtlib/fmt/pull/2463). Thanks @owent.

• Fixed handling of implicit conversions in fmt::to_string and format string compilation (https://github.com/fmtlib/fmt/issues/2565).

• Changed the default access mode of files created by fmt::output_file to -rw-r--r-- for consistency with fopen (https://github.com/fmtlib/fmt/issues/2530).

• Make fmt::ostream::flush public (https://github.com/fmtlib/fmt/issues/2435).

• Improved C++14/17 attribute detection (https://github.com/fmtlib/fmt/pull/2615). Thanks @AlexGuteniev.

• Improved consteval detection for MSVC (https://github.com/fmtlib/fmt/pull/2559). Thanks @DanielaE.

• Improved documentation (https://github.com/fmtlib/fmt/issues/2406, https://github.com/fmtlib/fmt/pull/2446, https://github.com/fmtlib/fmt/issues/2493, https://github.com/fmtlib/fmt/issues/2513, https://github.com/fmtlib/fmt/pull/2515, https://github.com/fmtlib/fmt/issues/2522, https://github.com/fmtlib/fmt/pull/2562, https://github.com/fmtlib/fmt/pull/2575, https://github.com/fmtlib/fmt/pull/2606, https://github.com/fmtlib/fmt/pull/2620, https://github.com/fmtlib/fmt/issues/2676). Thanks @sobolevn, @UnePierre, @zhsj, @phprus, @ericcurtin and @Lounarok.

• Improved fuzzers and added a fuzzer for chrono timepoint formatting (https://github.com/fmtlib/fmt/pull/2461, https://github.com/fmtlib/fmt/pull/2469). @pauldreik,

• Added the FMT_SYSTEM_HEADERS CMake option setting which marks {fmt}'s headers as system. It can be used to suppress warnings (https://github.com/fmtlib/fmt/issues/2644, https://github.com/fmtlib/fmt/pull/2651). Thanks @alexezeder.

• Added the Bazel build system support (https://github.com/fmtlib/fmt/pull/2505, https://github.com/fmtlib/fmt/pull/2516). Thanks @Vertexwahn.

• Improved build configuration and tests (https://github.com/fmtlib/fmt/issues/2437, https://github.com/fmtlib/fmt/pull/2558, https://github.com/fmtlib/fmt/pull/2648, https://github.com/fmtlib/fmt/pull/2650, https://github.com/fmtlib/fmt/pull/2663, https://github.com/fmtlib/fmt/pull/2677). Thanks @DanielaE, @alexezeder and @phprus.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/pull/2353, https://github.com/fmtlib/fmt/pull/2356, https://github.com/fmtlib/fmt/pull/2399, https://github.com/fmtlib/fmt/issues/2408, https://github.com/fmtlib/fmt/pull/2414, https://github.com/fmtlib/fmt/pull/2427, https://github.com/fmtlib/fmt/pull/2432, https://github.com/fmtlib/fmt/pull/2442, https://github.com/fmtlib/fmt/pull/2434, https://github.com/fmtlib/fmt/issues/2439, https://github.com/fmtlib/fmt/pull/2447, https://github.com/fmtlib/fmt/pull/2450, https://github.com/fmtlib/fmt/issues/2455, https://github.com/fmtlib/fmt/issues/2465, https://github.com/fmtlib/fmt/issues/2472, https://github.com/fmtlib/fmt/issues/2474, https://github.com/fmtlib/fmt/pull/2476, https://github.com/fmtlib/fmt/issues/2478, https://github.com/fmtlib/fmt/issues/2479, https://github.com/fmtlib/fmt/issues/2481, https://github.com/fmtlib/fmt/pull/2482, https://github.com/fmtlib/fmt/pull/2483, https://github.com/fmtlib/fmt/issues/2490, https://github.com/fmtlib/fmt/pull/2491, https://github.com/fmtlib/fmt/pull/2510, https://github.com/fmtlib/fmt/pull/2518, https://github.com/fmtlib/fmt/issues/2528, https://github.com/fmtlib/fmt/pull/2529, https://github.com/fmtlib/fmt/pull/2539, https://github.com/fmtlib/fmt/issues/2540, https://github.com/fmtlib/fmt/pull/2545, https://github.com/fmtlib/fmt/pull/2555, https://github.com/fmtlib/fmt/issues/2557, https://github.com/fmtlib/fmt/issues/2570, https://github.com/fmtlib/fmt/pull/2573, https://github.com/fmtlib/fmt/pull/2582, https://github.com/fmtlib/fmt/issues/2605, https://github.com/fmtlib/fmt/pull/2611, https://github.com/fmtlib/fmt/pull/2647, https://github.com/fmtlib/fmt/issues/2627, https://github.com/fmtlib/fmt/pull/2630, https://github.com/fmtlib/fmt/issues/2635, https://github.com/fmtlib/fmt/issues/2638, https://github.com/fmtlib/fmt/issues/2653, https://github.com/fmtlib/fmt/issues/2654, https://github.com/fmtlib/fmt/issues/2661, https://github.com/fmtlib/fmt/pull/2664, https://github.com/fmtlib/fmt/pull/2684). Thanks @DanielaE, @mwinterb, @cdacamar, @TrebledJ, @bodomartin, @cquammen, @white238, @mmarkeloff, @palacaze, @jcelerier, @mborn-adi, @BrukerJWD, @spyridon97, @phprus, @oliverlee, @joshessman-llnl, @akohlmey, @timkalu, @olupton, @Acretock, @alexezeder, @andrewcorrigan, @lucpelletier and @HazardyKnusperkeks.

8.0.1 - 2021-07-02

• Fixed the version number in the inline namespace (https://github.com/fmtlib/fmt/issues/2374).
• Added a missing presentation type check for std::string (https://github.com/fmtlib/fmt/issues/2402).
• Fixed a linkage error when mixing code built with clang and gcc (https://github.com/fmtlib/fmt/issues/2377).
• Fixed documentation issues (https://github.com/fmtlib/fmt/pull/2396, https://github.com/fmtlib/fmt/issues/2403, https://github.com/fmtlib/fmt/issues/2406). Thanks @mkurdej.
• Removed dead code in FP formatter ( https://github.com/fmtlib/fmt/pull/2398). Thanks @javierhonduco.
• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/2351, https://github.com/fmtlib/fmt/issues/2359, https://github.com/fmtlib/fmt/pull/2365, https://github.com/fmtlib/fmt/issues/2368, https://github.com/fmtlib/fmt/pull/2370, https://github.com/fmtlib/fmt/pull/2376, https://github.com/fmtlib/fmt/pull/2381, https://github.com/fmtlib/fmt/pull/2382, https://github.com/fmtlib/fmt/issues/2386, https://github.com/fmtlib/fmt/pull/2389, https://github.com/fmtlib/fmt/pull/2395, https://github.com/fmtlib/fmt/pull/2397, https://github.com/fmtlib/fmt/issues/2400, https://github.com/fmtlib/fmt/issues/2401, https://github.com/fmtlib/fmt/pull/2407). Thanks @zx2c4, @AidanSun05, @mattiasljungstrom, @joemmett, @erengy, @patlkli, @gsjaardema and @phprus.

8.0.0 - 2021-06-21

• Enabled compile-time format string checks by default. For example (godbolt):

  #include <fmt/core.h>
  
  int main() {
    fmt::print("{:d}", "I am not a number");
  }
  

  gives a compile-time error on compilers with C++20 consteval support (gcc 10+, clang 11+) because d is not a valid format specifier for a string.

  To pass a runtime string wrap it in fmt::runtime:

  fmt::print(fmt::runtime("{:d}"), "I am not a number");
  

• Added compile-time formatting (https://github.com/fmtlib/fmt/pull/2019, https://github.com/fmtlib/fmt/pull/2044, https://github.com/fmtlib/fmt/pull/2056, https://github.com/fmtlib/fmt/pull/2072, https://github.com/fmtlib/fmt/pull/2075, https://github.com/fmtlib/fmt/issues/2078, https://github.com/fmtlib/fmt/pull/2129, https://github.com/fmtlib/fmt/pull/2326). For example (godbolt):

  #include <fmt/compile.h>
  
  consteval auto compile_time_itoa(int 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_itoa(42);
  

  Most of the formatting functionality is available at compile time with a notable exception of floating-point numbers and pointers. Thanks @alexezeder.

• Optimized handling of format specifiers during format string compilation. For example, hexadecimal formatting ("{:x}") is now 3-7x faster than before when using format_to with format string compilation and a stack-allocated buffer (https://github.com/fmtlib/fmt/issues/1944).

  Before (7.1.3):

  ----------------------------------------------------------------------------
  Benchmark                                  Time             CPU   Iterations
  ----------------------------------------------------------------------------
  FMTCompileOld/0                         15.5 ns         15.5 ns     43302898
  FMTCompileOld/42                        16.6 ns         16.6 ns     43278267
  FMTCompileOld/273123                    18.7 ns         18.6 ns     37035861
  FMTCompileOld/9223372036854775807       19.4 ns         19.4 ns     35243000
  ----------------------------------------------------------------------------
  

  After (8.x):

  ----------------------------------------------------------------------------
  Benchmark                                  Time             CPU   Iterations
  ----------------------------------------------------------------------------
  FMTCompileNew/0                         1.99 ns         1.99 ns    360523686
  FMTCompileNew/42                        2.33 ns         2.33 ns    279865664
  FMTCompileNew/273123                    3.72 ns         3.71 ns    190230315
  FMTCompileNew/9223372036854775807       5.28 ns         5.26 ns    130711631
  ----------------------------------------------------------------------------
  

  It is even faster than std::to_chars from libc++ compiled with clang on macOS:

  ----------------------------------------------------------------------------
  Benchmark                                  Time             CPU   Iterations
  ----------------------------------------------------------------------------
  ToChars/0                               4.42 ns         4.41 ns    160196630
  ToChars/42                              5.00 ns         4.98 ns    140735201
  ToChars/273123                          7.26 ns         7.24 ns     95784130
  ToChars/9223372036854775807             8.77 ns         8.75 ns     75872534
  ----------------------------------------------------------------------------
  

  In other cases, especially involving std::string construction, the speed up is usually lower because handling format specifiers takes a smaller fraction of the total time.

• Added the _cf user-defined literal to represent a compiled format string. It can be used instead of the FMT_COMPILE macro (https://github.com/fmtlib/fmt/pull/2043, https://github.com/fmtlib/fmt/pull/2242):

  #include <fmt/compile.h>
  
  using namespace fmt::literals;
  auto s = fmt::format(FMT_COMPILE("{}"), 42); // 🙁 not modern
  auto s = fmt::format("{}"_cf, 42);           // 🙂 modern as hell
  

  It requires compiler support for class types in non-type template parameters (a C++20 feature) which is available in GCC 9.3+. Thanks @alexezeder.

• Format string compilation now requires format functions of formatter specializations for user-defined types to be const:

  template <> struct fmt::formatter<my_type>: formatter<string_view> {
    template <typename FormatContext>
    auto format(my_type obj, FormatContext& ctx) const {  // Note const here.
      // ...
    }
  };
  

• Added UDL-based named argument support to format string compilation (https://github.com/fmtlib/fmt/pull/2243, https://github.com/fmtlib/fmt/pull/2281). For example:

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

  Here the argument named "answer" is resolved at compile time with no runtime overhead. Thanks @alexezeder.

• Added format string compilation support to fmt::print (https://github.com/fmtlib/fmt/issues/2280, https://github.com/fmtlib/fmt/pull/2304). Thanks @alexezeder.

• Added initial support for compiling {fmt} as a C++20 module (https://github.com/fmtlib/fmt/pull/2235, https://github.com/fmtlib/fmt/pull/2240, https://github.com/fmtlib/fmt/pull/2260, https://github.com/fmtlib/fmt/pull/2282, https://github.com/fmtlib/fmt/pull/2283, https://github.com/fmtlib/fmt/pull/2288, https://github.com/fmtlib/fmt/pull/2298, https://github.com/fmtlib/fmt/pull/2306, https://github.com/fmtlib/fmt/pull/2307, https://github.com/fmtlib/fmt/pull/2309, https://github.com/fmtlib/fmt/pull/2318, https://github.com/fmtlib/fmt/pull/2324, https://github.com/fmtlib/fmt/pull/2332, https://github.com/fmtlib/fmt/pull/2340). Thanks @DanielaE.

• Made symbols private by default reducing shared library size (https://github.com/fmtlib/fmt/pull/2301). For example there was a ~15% reported reduction on one platform. Thanks @sergiud.

• Optimized includes making the result of preprocessing fmt/format.h ~20% smaller with libstdc++/C++20 and slightly improving build times (https://github.com/fmtlib/fmt/issues/1998).

• Added support of ranges with non-const begin / end (https://github.com/fmtlib/fmt/pull/1953). Thanks @kitegi.

• Added support of std::byte and other formattable types to fmt::join (https://github.com/fmtlib/fmt/issues/1981, https://github.com/fmtlib/fmt/issues/2040, https://github.com/fmtlib/fmt/pull/2050, https://github.com/fmtlib/fmt/issues/2262). For example:

  #include <fmt/format.h>
  #include <cstddef>
  #include <vector>
  
  int main() {
    auto bytes = std::vector{std::byte(4), std::byte(2)};
    fmt::print("{}", fmt::join(bytes, ""));
  }
  

  prints "42".

  Thanks @kamibo.

• Implemented the default format for std::chrono::system_clock (https://github.com/fmtlib/fmt/issues/2319, https://github.com/fmtlib/fmt/pull/2345). For example:

  #include <fmt/chrono.h>
  
  int main() {
    fmt::print("{}", std::chrono::system_clock::now());
  }
  

  prints "2021-06-18 15:22:00" (the output depends on the current date and time). Thanks @sunmy2019.

• Made more chrono specifiers locale independent by default. Use the 'L' specifier to get localized formatting. For example:

  #include <fmt/chrono.h>
  
  int main() {
    std::locale::global(std::locale("ru_RU.UTF-8"));
    auto monday = std::chrono::weekday(1);
    fmt::print("{}\n", monday);   // prints "Mon"
    fmt::print("{:L}\n", monday); // prints "пн"
  }
  

• Improved locale handling in chrono formatting (https://github.com/fmtlib/fmt/issues/2337, https://github.com/fmtlib/fmt/pull/2349, https://github.com/fmtlib/fmt/pull/2350). Thanks @phprus.

• Deprecated fmt/locale.h moving the formatting functions that take a locale to fmt/format.h (char) and fmt/xchar (other overloads). This doesn't introduce a dependency on <locale> so there is virtually no compile time effect.

• Deprecated an undocumented format_to overload that takes basic_memory_buffer.

• Made parameter order in vformat_to consistent with format_to (https://github.com/fmtlib/fmt/issues/2327).

• Added support for time points with arbitrary durations (https://github.com/fmtlib/fmt/issues/2208). For example:

  #include <fmt/chrono.h>
  
  int main() {
    using tp = std::chrono::time_point<
      std::chrono::system_clock, std::chrono::seconds>;
    fmt::print("{:%S}", tp(std::chrono::seconds(42)));
  }
  

  prints "42".

• Formatting floating-point numbers no longer produces trailing zeros by default for consistency with std::format. For example:

  #include <fmt/core.h>
  
  int main() {
    fmt::print("{0:.3}", 1.1);
  }
  

  prints "1.1". Use the '#' specifier to keep trailing zeros.

• Dropped a limit on the number of elements in a range and replaced {} with [] as range delimiters for consistency with Python's str.format.

• The 'L' specifier for locale-specific numeric formatting can now be combined with presentation specifiers as in std::format. For example:

  #include <fmt/core.h>
  #include <locale>
  
  int main() {
    std::locale::global(std::locale("fr_FR.UTF-8"));
    fmt::print("{0:.2Lf}", 0.42);
  }
  

  prints "0,42". The deprecated 'n' specifier has been removed.

• Made the 0 specifier ignored for infinity and NaN (https://github.com/fmtlib/fmt/issues/2305, https://github.com/fmtlib/fmt/pull/2310). Thanks @Liedtke.

• Made the hexfloat formatting use the right alignment by default (https://github.com/fmtlib/fmt/issues/2308, https://github.com/fmtlib/fmt/pull/2317). Thanks @Liedtke.

• Removed the deprecated numeric alignment ('='). Use the '0' specifier instead.

• Removed the deprecated fmt/posix.h header that has been replaced with fmt/os.h.

• Removed the deprecated format_to_n_context, format_to_n_args and make_format_to_n_args. They have been replaced with format_context, format_args` andmake_format_args`` respectively.

• Moved wchar_t-specific functions and types to fmt/xchar.h. You can define FMT_DEPRECATED_INCLUDE_XCHAR to automatically include fmt/xchar.h from fmt/format.h but this will be disabled in the next major release.

• Fixed handling of the '+' specifier in localized formatting (https://github.com/fmtlib/fmt/issues/2133).

• Added support for the 's' format specifier that gives textual representation of bool (https://github.com/fmtlib/fmt/issues/2094, https://github.com/fmtlib/fmt/pull/2109). For example:

  #include <fmt/core.h>
  
  int main() {
    fmt::print("{:s}", true);
  }
  

  prints "true". Thanks @powercoderlol.

• Made fmt::ptr work with function pointers (https://github.com/fmtlib/fmt/pull/2131). For example:

  #include <fmt/format.h>
  
  int main() {
    fmt::print("My main: {}\n", fmt::ptr(main));
  }
  

  Thanks @mikecrowe.

• The undocumented support for specializing formatter for pointer types has been removed.

• Fixed fmt::formatted_size with format string compilation (https://github.com/fmtlib/fmt/pull/2141, https://github.com/fmtlib/fmt/pull/2161). Thanks @alexezeder.

• Fixed handling of empty format strings during format string compilation (https://github.com/fmtlib/fmt/issues/2042):

  auto s = fmt::format(FMT_COMPILE(""));
  

  Thanks @alexezeder.

• Fixed handling of enums in fmt::to_string (https://github.com/fmtlib/fmt/issues/2036).

• Improved width computation (https://github.com/fmtlib/fmt/issues/2033, https://github.com/fmtlib/fmt/issues/2091). For example:

  #include <fmt/core.h>
  
  int main() {
    fmt::print("{:-<10}{}\n", "你好", "世界");
    fmt::print("{:-<10}{}\n", "hello", "world");
  }
  

  prints

  

  on a modern terminal.

• The experimental fast output stream (fmt::ostream) is now truncated by default for consistency with fopen (https://github.com/fmtlib/fmt/issues/2018). For example:

  #include <fmt/os.h>
  
  int main() {
    fmt::ostream out1 = fmt::output_file("guide");
    out1.print("Zaphod");
    out1.close();
    fmt::ostream out2 = fmt::output_file("guide");
    out2.print("Ford");
  }
  

  writes "Ford" to the file "guide". To preserve the old file content if any pass fmt::file::WRONLY | fmt::file::CREATE flags to fmt::output_file.

• Fixed moving of fmt::ostream that holds buffered data (https://github.com/fmtlib/fmt/issues/2197, https://github.com/fmtlib/fmt/pull/2198). Thanks @vtta.

• Replaced the fmt::system_error exception with a function of the same name that constructs std::system_error (https://github.com/fmtlib/fmt/issues/2266).

• Replaced the fmt::windows_error exception with a function of the same name that constructs std::system_error with the category returned by fmt::system_category() (https://github.com/fmtlib/fmt/issues/2274, https://github.com/fmtlib/fmt/pull/2275). The latter is similar to std::system_category but correctly handles UTF-8. Thanks @phprus.

• Replaced fmt::error_code with std::error_code and made it formattable (https://github.com/fmtlib/fmt/issues/2269, https://github.com/fmtlib/fmt/pull/2270, https://github.com/fmtlib/fmt/pull/2273). Thanks @phprus.

• Added speech synthesis support (https://github.com/fmtlib/fmt/pull/2206).

• Made format_to work with a memory buffer that has a custom allocator (https://github.com/fmtlib/fmt/pull/2300). Thanks @voxmea.

• Added Allocator::max_size support to basic_memory_buffer. (https://github.com/fmtlib/fmt/pull/1960). Thanks @phprus.

• Added wide string support to fmt::join (https://github.com/fmtlib/fmt/pull/2236). Thanks @crbrz.

• Made iterators passed to formatter specializations via a format context satisfy C++20 std::output_iterator requirements (https://github.com/fmtlib/fmt/issues/2156, https://github.com/fmtlib/fmt/pull/2158, https://github.com/fmtlib/fmt/issues/2195, https://github.com/fmtlib/fmt/pull/2204). Thanks @randomnetcat.

• Optimized the printf implementation (https://github.com/fmtlib/fmt/pull/1982, https://github.com/fmtlib/fmt/pull/1984, https://github.com/fmtlib/fmt/pull/2016, https://github.com/fmtlib/fmt/pull/2164). Thanks @rimathia and @moiwi.

• Improved detection of constexpr char_traits (https://github.com/fmtlib/fmt/pull/2246, https://github.com/fmtlib/fmt/pull/2257). Thanks @phprus.

• Fixed writing to stdout when it is redirected to NUL on Windows (https://github.com/fmtlib/fmt/issues/2080).

• Fixed exception propagation from iterators (https://github.com/fmtlib/fmt/issues/2097).

• Improved strftime error handling (https://github.com/fmtlib/fmt/issues/2238, https://github.com/fmtlib/fmt/pull/2244). Thanks @yumeyao.

• Stopped using deprecated GCC UDL template extension.

• Added fmt/args.h to the install target (https://github.com/fmtlib/fmt/issues/2096).

• Error messages are now passed to assert when exceptions are disabled (https://github.com/fmtlib/fmt/pull/2145). Thanks @NobodyXu.

• Added the FMT_MASTER_PROJECT CMake option to control build and install targets when {fmt} is included via add_subdirectory (https://github.com/fmtlib/fmt/issues/2098, https://github.com/fmtlib/fmt/pull/2100). Thanks @randomizedthinking.

• Improved build configuration (https://github.com/fmtlib/fmt/pull/2026, https://github.com/fmtlib/fmt/pull/2122). Thanks @luncliff and @ibaned.

• Fixed various warnings and compilation issues (https://github.com/fmtlib/fmt/issues/1947, https://github.com/fmtlib/fmt/pull/1959, https://github.com/fmtlib/fmt/pull/1963, https://github.com/fmtlib/fmt/pull/1965, https://github.com/fmtlib/fmt/issues/1966, https://github.com/fmtlib/fmt/pull/1974, https://github.com/fmtlib/fmt/pull/1975, https://github.com/fmtlib/fmt/pull/1990, https://github.com/fmtlib/fmt/issues/2000, https://github.com/fmtlib/fmt/pull/2001, https://github.com/fmtlib/fmt/issues/2002, https://github.com/fmtlib/fmt/issues/2004, https://github.com/fmtlib/fmt/pull/2006, https://github.com/fmtlib/fmt/pull/2009, https://github.com/fmtlib/fmt/pull/2010, https://github.com/fmtlib/fmt/issues/2038, https://github.com/fmtlib/fmt/issues/2039, https://github.com/fmtlib/fmt/issues/2047, https://github.com/fmtlib/fmt/pull/2053, https://github.com/fmtlib/fmt/issues/2059, https://github.com/fmtlib/fmt/pull/2065, https://github.com/fmtlib/fmt/pull/2067, https://github.com/fmtlib/fmt/pull/2068, https://github.com/fmtlib/fmt/pull/2073, https://github.com/fmtlib/fmt/issues/2103, https://github.com/fmtlib/fmt/issues/2105, https://github.com/fmtlib/fmt/pull/2106, https://github.com/fmtlib/fmt/pull/2107, https://github.com/fmtlib/fmt/issues/2116, https://github.com/fmtlib/fmt/pull/2117, https://github.com/fmtlib/fmt/issues/2118, https://github.com/fmtlib/fmt/pull/2119, https://github.com/fmtlib/fmt/issues/2127, https://github.com/fmtlib/fmt/pull/2128, https://github.com/fmtlib/fmt/issues/2140, https://github.com/fmtlib/fmt/issues/2142, https://github.com/fmtlib/fmt/pull/2143, https://github.com/fmtlib/fmt/pull/2144, https://github.com/fmtlib/fmt/issues/2147, https://github.com/fmtlib/fmt/issues/2148, https://github.com/fmtlib/fmt/issues/2149, https://github.com/fmtlib/fmt/pull/2152, https://github.com/fmtlib/fmt/pull/2160, https://github.com/fmtlib/fmt/issues/2170, https://github.com/fmtlib/fmt/issues/2175, https://github.com/fmtlib/fmt/issues/2176, https://github.com/fmtlib/fmt/pull/2177, https://github.com/fmtlib/fmt/issues/2178, https://github.com/fmtlib/fmt/pull/2179, https://github.com/fmtlib/fmt/issues/2180, https://github.com/fmtlib/fmt/issues/2181, https://github.com/fmtlib/fmt/pull/2183, https://github.com/fmtlib/fmt/issues/2184, https://github.com/fmtlib/fmt/issues/2185, https://github.com/fmtlib/fmt/pull/2186, https://github.com/fmtlib/fmt/pull/2187, https://github.com/fmtlib/fmt/pull/2190, https://github.com/fmtlib/fmt/pull/2192, https://github.com/fmtlib/fmt/pull/2194, https://github.com/fmtlib/fmt/pull/2205, https://github.com/fmtlib/fmt/issues/2210, https://github.com/fmtlib/fmt/pull/2211, https://github.com/fmtlib/fmt/pull/2215, https://github.com/fmtlib/fmt/pull/2216, https://github.com/fmtlib/fmt/pull/2218, https://github.com/fmtlib/fmt/pull/2220, https://github.com/fmtlib/fmt/issues/2228, https://github.com/fmtlib/fmt/pull/2229, https://github.com/fmtlib/fmt/pull/2230, https://github.com/fmtlib/fmt/issues/2233, https://github.com/fmtlib/fmt/pull/2239, https://github.com/fmtlib/fmt/issues/2248, https://github.com/fmtlib/fmt/issues/2252, https://github.com/fmtlib/fmt/pull/2253, https://github.com/fmtlib/fmt/pull/2255, https://github.com/fmtlib/fmt/issues/2261, https://github.com/fmtlib/fmt/issues/2278, https://github.com/fmtlib/fmt/issues/2284, https://github.com/fmtlib/fmt/pull/2287, https://github.com/fmtlib/fmt/pull/2289, https://github.com/fmtlib/fmt/pull/2290, https://github.com/fmtlib/fmt/pull/2293, https://github.com/fmtlib/fmt/issues/2295, https://github.com/fmtlib/fmt/pull/2296, https://github.com/fmtlib/fmt/pull/2297, https://github.com/fmtlib/fmt/issues/2311, https://github.com/fmtlib/fmt/pull/2313, https://github.com/fmtlib/fmt/pull/2315, https://github.com/fmtlib/fmt/issues/2320, https://github.com/fmtlib/fmt/pull/2321, https://github.com/fmtlib/fmt/pull/2323, https://github.com/fmtlib/fmt/issues/2328, https://github.com/fmtlib/fmt/pull/2329, https://github.com/fmtlib/fmt/pull/2333, https://github.com/fmtlib/fmt/pull/2338, https://github.com/fmtlib/fmt/pull/2341). Thanks @darklukee, @fagg, @killerbot242, @jgopel, @yeswalrus, @Finkman, @HazardyKnusperkeks, @dkavolis, @concatime, @chronoxor, @summivox, @yNeo, @Apache-HB, @alexezeder, @toojays, @Brainy0207, @vadz, @imsherlock, @phprus, @white238, @yafshar, @BillyDonahue, @jstaahl, @denchat, @DanielaE, @ilyakurdyukov, @ilmai, @JessyDL, @sergiud, @mwinterb, @sven-herrmann, @jmelas, @twoixter, @crbrz and @upsj.

• Improved documentation (https://github.com/fmtlib/fmt/issues/1986, https://github.com/fmtlib/fmt/pull/2051, https://github.com/fmtlib/fmt/issues/2057, https://github.com/fmtlib/fmt/pull/2081, https://github.com/fmtlib/fmt/issues/2084, https://github.com/fmtlib/fmt/pull/2312). Thanks @imba-tjd, @0x416c69 and @mordante.

• Continuous integration and test improvements (https://github.com/fmtlib/fmt/issues/1969, https://github.com/fmtlib/fmt/pull/1991, https://github.com/fmtlib/fmt/pull/2020, https://github.com/fmtlib/fmt/pull/2110, https://github.com/fmtlib/fmt/pull/2114, https://github.com/fmtlib/fmt/issues/2196, https://github.com/fmtlib/fmt/pull/2217, https://github.com/fmtlib/fmt/pull/2247, https://github.com/fmtlib/fmt/pull/2256, https://github.com/fmtlib/fmt/pull/2336, https://github.com/fmtlib/fmt/pull/2346). Thanks @jgopel, @alexezeder and @DanielaE.

The change log for versions 0.8.0 - 7.1.3 is available here.