Release 10.0.0 · fmtlib/fmt

Replaced Grisu with a new floating-point formatting algorithm for given precision (#3262, #2750, #3269, #3276). The new algorithm is based on Dragonbox already used for the shortest representation and gives substantial performance improvement:
- Red: new algorithm
- Green: new algorithm with FMT_USE_FULL_CACHE_DRAGONBOX defined to 1
- Blue: old algorithm
Thanks @jk-jeon (Junekey Jeon).
Replaced snprintf-based hex float formatter with an internal implementation (#3179, #3203). This removes the last usage of s(n)printf in {fmt}. Thanks @phprus (Vladislav Shchapov).
Fixed alignment of floating-point numbers with localization (#3263, #3272). Thanks @ShawnZhong (Shawn Zhong).
Made handling of # consistent with std::format.
Improved C++20 module support (#3134, #3254, #3386, #3387, #3388, #3392, #3397, #3399, #3400). Thanks @laitingsheng (Tinson Lai), @Orvid (Orvid King), @DanielaE (Daniela Engert). Switched to the modules CMake library which allows building {fmt} as a C++20 module with clang:
```
CXX=clang++ cmake -DFMT_MODULE=ON .
make
```

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

#include <fmt/format.h>

struct floaty_mc_floatface {
  double value;
};

auto format_as(floaty_mc_floatface f) { return f.value; }

int main() {
  fmt::print("{:8}\n", floaty_mc_floatface{0.42}); // prints "    0.42"
}

Removed deprecated implicit conversions for enums and conversions to primitive types for compatibility with std::format and to prevent potential ODR violations. Use format_as instead.
Added support for fill, align and width to the time point formatter (#3237, #3260, #3275). For example (godbolt):
```
#include <fmt/chrono.h>

int main() {
  // prints "    2023"
  fmt::print("{:>8%Y}\n", std::chrono::system_clock::now());
}
```
Thanks @ShawnZhong (Shawn Zhong).
Implemented formatting of subseconds (#2207, #3117, #3115, #3143, #3144, #3349). For example (godbolt):
```
#include <fmt/chrono.h>

int main() {
  // prints 01.234567
  fmt::print("{:%S}\n", std::chrono::microseconds(1234567));
}
```
Thanks @patrickroocks (Patrick Roocks) @phprus (Vladislav Shchapov), @BRevzin (Barry Revzin).
Added precision support to %S (#3148). Thanks @SappyJoy (Stepan Ponomaryov)
Added support for std::utc_time (#3098, #3110). Thanks @patrickroocks (Patrick Roocks).
Switched formatting of std::chrono::system_clock from local time to UTC for compatibility with the standard (#3199, #3230). Thanks @ned14 (Niall Douglas).
Added support for %Ez and %Oz to chrono formatters. (#3220, #3222). Thanks @phprus (Vladislav Shchapov).
Improved validation of format specifiers for std::chrono::duration (#3219, #3232). Thanks @ShawnZhong (Shawn Zhong).

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

#include <fmt/chrono.h>

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

Thanks @ShawnZhong (Shawn Zhong).

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

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

#include <fmt/std.h>
#include <vector>

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

prints:

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

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

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

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

#include <fmt/ranges.h>
#include <stack>
#include <vector>

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

Thanks @ShawnZhong (Shawn Zhong).

Added a formatter for std::optional to fmt/std.h. Thanks @tom-huntington.
Fixed formatting of valueless by exception variants (#3347). Thanks @TheOmegaCarrot.
Made fmt::ptr accept unique_ptr with a custom deleter (#3177). Thanks @hmbj (Hans-Martin B. Jensen).
Fixed formatting of noncopyable ranges and nested ranges of chars (#3158 #3286, #3290). Thanks @BRevzin (Barry Revzin).
Fixed issues with formatting of paths and ranges of paths (#3319, #3321 #3322). Thanks @phprus (Vladislav Shchapov).
Improved handling of invalid Unicode in paths.
Enabled compile-time checks on Apple clang 14 and later (#3331). Thanks @cloyce (Cloyce D. Spradling).
Improved compile-time checks of named arguments (#3105, #3214). Thanks @rbrich (Radek Brich).
Fixed formatting when both alignment and 0 are given (#3236, #3248). Thanks @ShawnZhong (Shawn Zhong).
Improved Unicode support in the experimental file API on Windows (#3234, #3293). Thanks @Fros1er (Froster).
Unified UTF transcoding (#3416). Thanks @phprus (Vladislav Shchapov).
Added support for UTF-8 digit separators via an experimental locale facet (#1861). For example (godbolt):
```
auto loc = std::locale(
  std::locale(), new fmt::format_facet<std::locale>("’"));
auto s = fmt::format(loc, "{:L}", 1000);
```
where ’ is U+2019 used as a digit separator in the de_CH locale.
Added an overload of formatted_size that takes a locale (#3084, #3087). Thanks @gerboengels.
Removed the deprecated FMT_DEPRECATED_OSTREAM.
Fixed a UB when using a null std::string_view with fmt::to_string or format string compilation (#3241, #3244). Thanks @phprus (Vladislav Shchapov).
Added starts_with to the fallback string_view implementation (#3080). Thanks @phprus (Vladislav Shchapov).
Added fmt::basic_format_string::get() for compatibility with basic_format_string (#3111). Thanks @huangqinjin.
Added println for compatibility with C++23 (#3267). Thanks @ShawnZhong (Shawn Zhong).
Renamed the FMT_EXPORT macro for shared library usage to FMT_LIB_EXPORT.
Improved documentation (#3108, #3169, #3243). #3404). Thanks @Cleroth and @Vertexwahn.
Improved build configuration and tests (#3118, #3120, #3188, #3189, #3198, #3205, #3207, #3210, #3240, #3256, #3264, #3299, #3302, #3312, #3317, #3328, #3333, #3369, #3373, #3395, #3406, #3411). Thanks @dimztimz (Dimitrij Mijoski), @phprus (Vladislav Shchapov), @DavidKorczynski, @ChrisThrasher (Chris Thrasher), @FrancoisCarouge (François Carouge), @kennyweiss (Kenny Weiss), @luzpaz, @codeinred (Alecto Irene Perez), @Mixaill (Mikhail Paulyshka), @joycebrum (Joyce), @kevinhwang (Kevin Hwang), @Vertexwahn.
Fixed a regression in handling empty format specifiers after a colon ({:}) (#3086). Thanks @oxidase (Michael Krasnyk).
Worked around a broken implementation of std::is_constant_evaluated in some versions of libstdc++ on clang (#3247, #3281). Thanks @phprus (Vladislav Shchapov).
Fixed formatting of volatile variables (#3068).
Fixed various warnings and compilation issues (#3057, #3066, #3072, #3082, #3091, #3092, #3093, #3095, #3096, #3097, #3128, #3129, #3137, #3139, #3140, #3142, #3149, #3150, #3154, #3163, #3178, #3184, #3196, #3204, #3206, #3208, #3213, #3216, #3224, #3226, #3228, #3229, #3259, #3274, #3287, #3288, #3292, #3295, #3296, #3298, #3325, #3326, #3334, #3342, #3343, #3351, #3352, #3362, #3365, #3366, #3374, #3377, #3378, #3381, #3398, #3413, #3415). Thanks @phprus (Vladislav Shchapov), @gsjaardema (Greg Sjaardema), @NewbieOrange, @EngineLessCC (VivyaCC), @asmaloney (Andy Maloney), @HazardyKnusperkeks (Björn Schäpers), @sergiud (Sergiu Deitsch), @Youw (Ihor Dutchak), @thesmurph, @czudziakm (Maksymilian Czudziak), @Roman-Koshelev, @chronoxor (Ivan Shynkarenka), @ShawnZhong (Shawn Zhong), @russelltg (Russell Greene), @glebm (Gleb Mazovetskiy), @tmartin-gh, @Zhaojun-Liu (June Liu), @louiswins (Louis Wilson), @mogemimi.

Pull Requests

Added workarounds for compilers with EDG frontend (LCC and Nvidia) by @phprus in #3057
Fix compilation error with gcc-7.2.0 by @gsjaardema in #3066
Add formatter for std::exception by @zach2good in #3062
Simplify is_variant_like_ check, fix compile error before GCC 11 by @NewbieOrange in #3072
Add starts_with to fmt::basic_string_view. by @phprus in #3080
Fix intellisense on Windows by @enginelesscc in #3082
Add locale overload for formatted_size (#3084) by @gerboengels in #3087
Add class name output to formatter for std::exception by @phprus in #3076
Fix compilation with FMT_ENFORCE_COMPILE_STRING and FMT_WERROR by @asmaloney in #3091
Fix build error on GCC-9 by @phprus in #3093
fix gcc <= 7.1 compile errors by @sergiud in #3097
Fix warnings by @HazardyKnusperkeks in #3095
Add basic_format_string::get() by @huangqinjin in #3111
Update CI to Ubuntu 20.04 and to newer versions of actions by @dimztimz in #3118
Support formatting of time_point with utc_clock by @patrickroocks in #3110
Set CMAKE_RUNTIME_OUTPUT_DIRECTORY relative to CMAKE_CURRENT_BINARY_DIR by @phprus in #3120
Normalization of stdlib inline namespace names by @phprus in #3119
Move formatterstd::error_code from fmt/os.h to fmt/std.h by @phprus in #3125
Fix broken condition by @phprus in #3129
Fix options for C++20 experimental module in CMake by @laitingsheng in #3134
Avoid using uint as a type name by @Youw in #3137
Support formatting of subseconds by @patrickroocks in #3115
Remove duplicate template parameter. by @phprus in #3142
Fix overflow error by @phprus in #3143
Remove duplicate implementation by @phprus in #3144
Mention MariaDB amongst the projects that use fmt by @federico-razzoli in #3145
Fix warning: conditional expression is constant. by @phprus in #3150
Add locale getter in tm_writer by @SappyJoy in #3147
fmt::ostream - aggregate buffer instead of inheriting it by @Youw in #3139
Fixing formatting of range of range of char. by @brevzin in #3158
Add precision modifier for seconds in chrono format by @SappyJoy in #3148
Replace format with FMT_STRING. by @phprus in #3162
Format unique_ptr with custom deleter by @hmbj in #3177
This skips the scan-test if strptime isn't defined. by @thesmurph in #3184
Improve CI by @phprus in #3188
Fix warnings for compilers with EDG frontend by @phprus in #3196
Replacing snprintf-based hex float formatter with internal implementation by @phprus in #3179
CI linux: add CIFuzz Github action by @DavidKorczynski in #3198
Rename leading_v -> leading_xdigit by @phprus in #3203
Use target_compile_features to specify C++ standard requirement by @ChrisThrasher in #3205
Skip only strptime dependent test in scan-test by @phprus in #3206
Remove workaround for GTest bug by @phprus in #3207
Bump tested CMake version to 3.25 by @phprus in #3210
Add countl_zero function by @phprus in #3216
fix #3105 - Compile-time error when mixing named argument with automatic indexing by @rbrich in #3214
Implement %Ez, %Oz for chrono formatter by @phprus in #3222
Fix for issue #3228 by @phprus in #3229
Check chrono spec starts with % by @ShawnZhong in #3232
small typo in syntax.rst by @Cleroth in #3243
Fix for issue #3241 by @phprus in #3244
Ignore 0 character when align is present by @ShawnZhong in #3248
Remove empty semicolon by @ShawnZhong in #3249
Improve timezone tests by @phprus in #3240
Fix build with MSVC C++20 modules by @Orvid in #3254
Support fill, align & width for time point by @ShawnZhong in #3260
Fix standard default installation target presence by @FrancoisCarouge in #3264
Fix negative subsec for time_point by @ShawnZhong in #3261
Bugfix for fmt::printf on Power9 architecture with the XL compiler by @kennyweiss in #3256
Implement a new formatting algorithm for small given precision by @jk-jeon in #3269
Fix localized format for float-point numbers by @ShawnZhong in #3272
Fix spec "{:}" for time point by @ShawnZhong in #3275
Refactor countl_zero fallback by @jk-jeon in #3276
Workaround for incompatibility between libstdc++ consteval-based std::is_constant_evaluated() implementation and clang-14 by @phprus in #3281
Implement println by @ShawnZhong in #3267
Visual Studio 2022: fmt/format-inl.h(1145,60): warning C4310: cast truncates constant value #3287 by @chronoxor in #3288
Allowing formatting non-copyable ranges. by @brevzin in #3290
Fix errors setting of FMT_USE_FLOAT128 by @Roman-Koshelev in #3259
Implement glibc ext for sec, min, and hour by @ShawnZhong in #3271
Add formatters for container adapters by @ShawnZhong in #3279
Fix OpenBSD build error by @ShawnZhong in #3295
Add ubuntu mirrors by @phprus in #3302
change sopen_s to wsopen_s (#3234) by @Fros1er in #3293
Fix various typos by @luzpaz in #3312
Add Optional Support by @tom-huntington in #3303
Fix for issue #3325 by @phprus in #3326
chore: set permission to cifuzz.yml by @joycebrum in #3328
Enable consteval for Xcode 14 and later by @cloyce in #3331
Fix for issue #3319. by @phprus in #3321
Cleanup dead variable by @ShawnZhong in #3338
write_floating_seconds: Fall back to ::round by @glebm in #3343
Fix CUDA nvcc warning by @tmartin-gh in #3352
fix case of variant which is valueless by exception by @TheOmegaCarrot in #3347
%T is %H:%M:%S by @brevzin in #3349
Force use a signed char (On ARM char is unsigned by default) by @phprus in #3362
Workaround a double-double hexfloat format by @phprus in #3366
fix compilation for MS-DOS by @Mixaill in #3369
ranges: Fix extra semi by @HazardyKnusperkeks in #3374
Fix error C2668 on msvc by @Zhaojun-Liu in #3378
fix and improve module by @DanielaE in #3386
Feature/remove obsolete workarounds by @DanielaE in #3388
Update tests to use recommended MOCK_METHOD by @kevinhwang in #3395
Fix MSVC C4365 warning (signed/unsigned mismatch) on 32-bit Windows by @louiswins in #3398
names declared to be exported at the point of introduction into a nam… by @DanielaE in #3392
Feature/attach to gmf by @DanielaE in #3387
Name vfprintf clashes with the identically named declaration in 'st… by @DanielaE in #3400
Remove myself from maintainer list by @foonathan in #3402
Fix spelling by @Vertexwahn in #3404
Bazel support by @Vertexwahn in #3406
Remove .bazelrc mention from Bazel related readme by @Vertexwahn in #3411
towards better module testing by @DanielaE in #3397
Add FMT_STRING for format_to() call with clang-cl by @mogemimi in #3413
modules missing pieces by @DanielaE in #3399
Unification utf16/utf32 to utf8 conversion by @phprus in #3416

New Contributors

@zach2good made their first contribution in #3062
@NewbieOrange made their first contribution in #3072
@enginelesscc made their first contribution in #3082
@gerboengels made their first contribution in #3087
@asmaloney made their first contribution in #3091
@huangqinjin made their first contribution in #3111
@patrickroocks made their first contribution in #3110
@laitingsheng made their first contribution in #3134
@Youw made their first contribution in #3137
@federico-razzoli made their first contribution in #3145
@SappyJoy made their first contribution in #3147
@hmbj made their first contribution in #3177
@thesmurph made their first contribution in #3184
@DavidKorczynski made their first contribution in #3198
@ChrisThrasher made their first contribution in #3205
@rbrich made their first contribution in #3214
@ShawnZhong made their first contribution in #3232
@Cleroth made their first contribution in #3243
@Orvid made their first contribution in #3254
@FrancoisCarouge made their first contribution in #3264
@kennyweiss made their first contribution in #3256
@Fros1er made their first contribution in #3293
@luzpaz made their first contribution in #3312
@tom-huntington made their first contribution in #3303
@joycebrum made their first contribution in #3328
@cloyce made their first contribution in #3331
@glebm made their first contribution in #3343
@tmartin-gh made their first contribution in #3352
@TheOmegaCarrot made their first contribution in #3347
@Mixaill made their first contribution in #3369
@Zhaojun-Liu made their first contribution in #3378
@kevinhwang made their first contribution in #3395
@louiswins made their first contribution in #3398
@mogemimi made their first contribution in #3413

Full Changelog: 9.1.0...10.0.0

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10.0.0

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