fmt Files

• Added a C11 API that brings fast, type-safe formatting to C. The new fmt-c library and fmt/fmt-c.h header use _Generic to dispatch on argument types and outperform printf/sprintf. For example:

```c++ #include <fmt/fmt-c.h>

fmt_print(stdout, "The answer is {}.\n", 42); ```

(https://github.com/fmtlib/fmt/issues/4663, https://github.com/fmtlib/fmt/pull/4671, https://github.com/fmtlib/fmt/pull/4696, https://github.com/fmtlib/fmt/issues/4693, https://github.com/fmtlib/fmt/pull/4694, https://github.com/fmtlib/fmt/pull/4712, https://github.com/fmtlib/fmt/pull/4789). Thanks @Soumik15630m, @Ferdi265 and @localspook.

• Added a separate fmt::fmt-module CMake target for C++20 modules and a CI workflow that exercises module-based builds (https://github.com/fmtlib/fmt/issues/4684, https://github.com/fmtlib/fmt/pull/4685, https://github.com/fmtlib/fmt/issues/4707, https://github.com/fmtlib/fmt/pull/4708, https://github.com/fmtlib/fmt/pull/4702, https://github.com/fmtlib/fmt/pull/4709). Thanks @MathewBensonCode.

• Enabled the full Dragonbox lookup cache by default for floating-point formatting unless optimizing for binary size (__OPTIMIZE_SIZE__), giving a ~10–25% speedup. Thanks Matthias Kretz for the suggestion. Average time per double on Apple M1 Pro (clang 17, random digits, smaller is better) measured with dtoa-benchmark:

• Improved integer formatting performance by ~3% (https://github.com/fmtlib/fmt/pull/4630). Thanks @user202729.

• Optimized formatting into back-insert iterators by using bulk container append/insert methods (e.g. on std::vector<char> and custom string types) (https://github.com/fmtlib/fmt/pull/4679). Thanks @user202729.

• Reduced binary size of debug builds (~200k to ~85k in the bloat test) and improved compile speed when consteval is unavailable.

• Made path formatting lossless, preserving ill-formed UTF-16 sequences when converting std::filesystem::path to a narrow string.

• Added support for formatting std::unexpected (https://github.com/fmtlib/fmt/pull/4675). Thanks @17steen.

• Added overloads of fmt::println that take a fmt::text_style (https://github.com/fmtlib/fmt/pull/4782). Thanks @ahoarau.

• Added support for positional arguments as width and precision specifiers in fmt::printf (https://github.com/fmtlib/fmt/pull/4643). Thanks @KareemOtoum.

• Made FMT_STRING a no-op when FMT_USE_CONSTEVAL is enabled, since the consteval format-string constructor already provides compile-time validation (https://github.com/fmtlib/fmt/issues/4611, https://github.com/fmtlib/fmt/pull/4612). Thanks @friedkeenan.

• Promoted fmt::detail::named_arg to the public API as fmt::named_arg and deprecated the detail alias (https://github.com/fmtlib/fmt/issues/4683, https://github.com/fmtlib/fmt/pull/4687). Thanks @TPPPP72.

• Moved the std::byte formatter from fmt/format.h to fmt/std.h.

• Provided a default definition for fmt::is_contiguous (https://github.com/fmtlib/fmt/pull/4731, https://github.com/fmtlib/fmt/pull/4770). Thanks @user202729 and @phprus.

• Added the FMT_USE_FLOCKFILE macro to disable the use of flockfile (https://github.com/fmtlib/fmt/issues/4646, https://github.com/fmtlib/fmt/pull/4666). Thanks @mvastola.

• Added include_guard(GLOBAL) so that {fmt} can be used in multiple submodules of the same project (https://github.com/fmtlib/fmt/pull/4672). Thanks @torsten48.

• Improved constexpr support (https://github.com/fmtlib/fmt/pull/4659, https://github.com/fmtlib/fmt/pull/4591). Thanks @elbeno and @17steen.

• Deprecated the implicit conversion from fmt::format_string and fmt::basic_fstring to string_view to align with std::format_string; use format_string::get() instead.

• Opted out std::complex from tuple formatting so that the dedicated std::complex formatter is always used.

• Removed the fmt::say function.

• Deprecated the std::initializer_list overload of fmt::join and the array overload of fmt::vformat_to.

• Made the <fmt/core.h> header equivalent to <fmt/base.h> by default. Code that relied on <fmt/core.h> pulling in <fmt/format.h> must now either include <fmt/format.h> directly or define FMT_DEPRECATED_HEAVY_CORE to opt back in.

• Improved wchar_t support: fmt::join now accepts wchar_t and other non-char separators, and fmt::format_to_n now works with fmt::runtime on wchar_t (https://github.com/fmtlib/fmt/pull/4686, https://github.com/fmtlib/fmt/issues/4714, https://github.com/fmtlib/fmt/pull/4715). Thanks @Yancey2023 and @sunmy2019.

• Fixed formatting of std::tm with a null tm_zone (https://github.com/fmtlib/fmt/pull/4790). Thanks @Carmel0.

• Fixed compile-time formatting in fmt/ranges.h, fmt/style.h and fmt/std.h (https://github.com/fmtlib/fmt/pull/4759). Thanks @j4niwzis.

• Fixed an ambiguity between formatter<std::optional<T>> in fmt/std.h and fmt/ranges.h on C++26 (P3168R2) (https://github.com/fmtlib/fmt/pull/4761). Thanks @phprus.

• Fixed a GCC PCH breakage triggered by a scoped #pragma GCC optimize.

• Fixed a TSAN false positive in the locale handling code (https://github.com/fmtlib/fmt/issues/4755).

• Fixed compile-time format string checks truncating string literals at an embedded null byte (https://github.com/fmtlib/fmt/pull/4732). Thanks @user202729.

• Fixed out-of-bounds reads in printf formatting (https://github.com/fmtlib/fmt/issues/4741, https://github.com/fmtlib/fmt/pull/4742, https://github.com/fmtlib/fmt/pull/4800). Thanks @Algunenano and @aizu-m.

• Fixed the return type of the f(un)lockfile wrappers on Windows (https://github.com/fmtlib/fmt/pull/4739). Thanks @mvastola.

• Worked around a CUDA issue when handling UTF-32 literals (https://github.com/fmtlib/fmt/pull/4719). Thanks @Cazadorro.

• Fixed missing named-argument validation for compiled format strings (https://github.com/fmtlib/fmt/pull/4638). Thanks @JaeheonShim.

• Fixed fmt::format_to_n in <fmt/compile.h> failing to compile when <iterator> is not transitively included (https://github.com/fmtlib/fmt/issues/4615).

• Fixed handling of pointers in format string compilation with FMT_BUILTIN_TYPES=0.

• Stopped assuming nul termination of the format string in fmt::printf. Thanks @ZUENS2020 for reporting.

• Fixed a build error when locale support is disabled (https://github.com/fmtlib/fmt/pull/4627). Thanks @marcel-behlau-elfin.

• Fixed a fallback range formatter for types with a container_type member (https://github.com/fmtlib/fmt/issues/4123, https://github.com/fmtlib/fmt/pull/4660). Thanks @Soumik15630m.

• Fixed C++20 concept detection (https://github.com/fmtlib/fmt/pull/4653). Thanks @tearfur.

• Fixed a clang compilation failure (https://github.com/fmtlib/fmt/pull/4718). Thanks @mccakit.

• Fixed various MSVC warnings, including C4305 and conversion warnings on x86 (https://github.com/fmtlib/fmt/pull/4668, https://github.com/fmtlib/fmt/pull/4594). Thanks @kanren3 and @blizzard4591.

• Updated the Android Gradle Plugin to 9.x (https://github.com/fmtlib/fmt/issues/4651, https://github.com/fmtlib/fmt/pull/4658). Thanks @Soumik15630m.

• Made various code, build and test improvements (https://github.com/fmtlib/fmt/pull/4625, https://github.com/fmtlib/fmt/pull/4639, https://github.com/fmtlib/fmt/pull/4644, https://github.com/fmtlib/fmt/pull/4656, https://github.com/fmtlib/fmt/pull/4680, https://github.com/fmtlib/fmt/pull/4681, https://github.com/fmtlib/fmt/pull/4704, https://github.com/fmtlib/fmt/pull/4710, https://github.com/fmtlib/fmt/pull/4713, https://github.com/fmtlib/fmt/pull/4729, https://github.com/fmtlib/fmt/pull/4751, https://github.com/fmtlib/fmt/pull/4758, https://github.com/fmtlib/fmt/pull/4799). Thanks @ZephyrLykos, @togunchan, @kagancansit, @BerndPetrovitsch, @Skylion007, @st0rmbtw, @localspook and @EXtremeExploit.

• Improved documentation, including a rewrite of the format string syntax, better handling of doxygen tags, documenting output_file, fixing CSS so that whitespace is displayed properly, and various smaller fixes (https://github.com/fmtlib/fmt/pull/4622, https://github.com/fmtlib/fmt/pull/4626, https://github.com/fmtlib/fmt/pull/4631, https://github.com/fmtlib/fmt/pull/4667, https://github.com/fmtlib/fmt/pull/4616, https://github.com/fmtlib/fmt/pull/4748). Thanks @heavywatal, @ZephyrLykos, @user202729, @ssszcmawo, @bigmoonbit and @Powerbyte7.

• Added building of release artifacts and SLSA provenance in CI, added a CodeQL workflow, and added the security policy in .github/SECURITY.md.