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Releases: fmtlib/fmt

8.1.1

06 Jan 22:52
@vitaut vitaut
8.1.1
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8.1.1
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8.1.0

02 Jan 17:17
@vitaut vitaut
8.1.0
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8.1.0
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8.0.1

02 Jul 23:23
@vitaut vitaut
8.0.1
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8.0.1
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8.0.0

21 Jun 13:16
@vitaut vitaut
8.0.0
9e8b86f
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8.0.0

  • Enabled compile-time format string check 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 (#2019, #2044, #2056, #2072, #2075, #2078, #2129, #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 (Alexey Ochapov).

  • 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 (#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 (#2043, #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 (Alexey Ochapov).

  • 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 (#2243, #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 (Alexey Ochapov).

  • Added format string compilation support to fmt::print (#2280, #2304). Thanks @alexezeder (Alexey Ochapov).

  • Added initial support for compiling {fmt} as a C++20 module (#2235, #2240, #2260, #2282, #2283, #2288, #2298, #2306, #2307, #2309, #2318, #2324, #2332, #2340). Thanks @DanielaE (Daniela Engert).

  • Made symbols private by default reducing shared library size (#2301). For example there was a ~15% reported reduction on one platform. Thanks @sergiud (Sergiu Deitsch).

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

  • Added support of ranges with non-const begin / end (#1953). Thanks @kitegi (sarah).

  • Added support of std::byte and other formattable types to fmt::join (#1981, #2040, #2050, #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 (Camille Bordignon).

  • Implemented the default format for std::chrono::system_clock (#2319, #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 (#2337, #2349, #2350). Thanks @phprus (Vladislav Shchapov).

  • 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.

  • Made parameter order in vformat_to consistent with format_to (#2327).

  • Added support for time points with arbitrary durations (#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 (#2305, #2310). Thanks @Liedtke (Matthias Liedtke).

  • Made the hexfloat formatting use the right alignment by default (#2308, #2317). Thanks @Liedtke (Matthias 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 and make_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 '+' spec...

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7.1.3

25 Nov 14:37
@vitaut vitaut
7.1.3
7bdf062
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7.1.3

  • Fixed handling of buffer boundaries in format_to_n (#1996, #2029).

  • Fixed linkage errors when linking with a shared library (#2011).

  • Reintroduced ostream support to range formatters (#2014).

  • Worked around an issue with mixing std versions in gcc (#2017).

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7.1.2

04 Nov 15:39
@vitaut vitaut
7.1.2
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7.1.2
  • Fixed floating point formatting with large precision (#1976).
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7.1.1

02 Nov 14:27
@vitaut vitaut
7.1.1
5f7f7b9
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7.1.1

  • Fixed ABI compatibility with 7.0.x (#1961).

  • Added the FMT_ARM_ABI_COMPATIBILITY macro to work around ABI incompatibility between GCC and Clang on ARM (#1919).

  • Worked around a SFINAE bug in GCC 8 (#1957).

  • Fixed linkage errors when building with GCC's LTO (#1955).

  • Fixed a compilation error when building without __builtin_clz or equivalent (#1968). Thanks @tohammer (Tobias Hammer).

  • Fixed a sign conversion warning (#1964). Thanks @OptoCloud.

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7.1.0

26 Oct 13:43
@vitaut vitaut
7.1.0
4fe0b11
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7.1.0

  • Switched from Grisu3 to Dragonbox for the default floating-point formatting which gives the shortest decimal representation with round-trip guarantee and correct rounding (#1882, #1887, #1894). This makes {fmt} up to 20-30x faster than common implementations of std::ostringstream and sprintf on dtoa-benchmark and faster than double-conversion and Ryū:It is possible to get even better performance at the cost of larger binary size by compiling with the FMT_USE_FULL_CACHE_DRAGONBOX macro set to 1. Thanks @jk-jeon (Junekey Jeon).

  • Added an experimental unsynchronized file output API which, together with format string compilation, can give 5-9 times speed up compared to fprintf on common platforms (godbolt):

    #include <fmt/os.h>

int main() {
  auto f = fmt::output_file("guide");
  f.print("The answer is {}.", 42);
}

  • Added a formatter for std::chrono::time_point<system_clock> (#1819, #1837). For example (godbolt):

    #include <fmt/chrono.h>

int main() {
  auto now = std::chrono::system_clock::now();
  fmt::print("The time is {:%H:%M:%S}.\n", now);
}

    Thanks @adamburgess (Adam Burgess).

  • Added support for ranges with non-const begin/end to fmt::join (#1784, #1786). For example (godbolt):

    #include <fmt/ranges.h>
#include <range/v3/view/filter.hpp>

int main() {
  using std::literals::string_literals::operator""s;
  auto strs = std::array{"a"s, "bb"s, "ccc"s};
  auto range = strs | ranges::views::filter(
    [] (const std::string &x) { return x.size() != 2; }
  );
  fmt::print("{}\n", fmt::join(range, ""));
}

    prints "accc". Thanks @tonyelewis (Tony E Lewis).

  • Added a memory_buffer::append overload that takes a range (#1806). Thanks @BRevzin (Barry Revzin).

  • Improved handling of single code units in FMT_COMPILE. For example:

    #include <fmt/compile.h>

char* f(char* buf) {
  return fmt::format_to(buf, FMT_COMPILE("x{}"), 42);
}

    compiles to just (godbolt):

    _Z1fPc:
  movb $120, (%rdi)
  xorl %edx, %edx
  cmpl $42, _ZN3fmt2v76detail10basic_dataIvE23zero_or_powers_of_10_32E+8(%rip)
  movl $3, %eax
  seta %dl
  subl %edx, %eax
  movzwl _ZN3fmt2v76detail10basic_dataIvE6digitsE+84(%rip), %edx
  cltq
  addq %rdi, %rax
  movw %dx, -2(%rax)
  ret

    Here a single mov instruction writes 'x' ($120) to the output buffer.

  • Added dynamic width support to format string compilation (#1809).

  • Improved error reporting for unformattable types: now you'll get the type name directly in the error message instead of the note:

    #include <fmt/core.h>

struct how_about_no {};

int main() {
  fmt::print("{}", how_about_no());
}

    Error (godbolt): fmt/core.h:1438:3: error: static_assert failed due to requirement 'fmt::v7::formattable<how_about_no>()' "Cannot format an argument. To make type T formattable provide a formatter<T> specialization: https://fmt.dev/latest/api.html#udt" ...

  • Added the make_args_checked function template that allows you to write formatting functions with compile-time format string checks and avoid binary code bloat (godbolt):

    void vlog(const char* file, int line, fmt::string_view format,
          fmt::format_args args) {
  fmt::print("{}: {}: ", file, line);
  fmt::vprint(format, args);
}

template <typename S, typename... Args>
void log(const char* file, int line, const S& format, Args&&... args) {
  vlog(file, line, format,
      fmt::make_args_checked<Args...>(format, args...));
}

#define MY_LOG(format, ...) \
  log(__FILE__, __LINE__, FMT_STRING(format), __VA_ARGS__)

MY_LOG("invalid squishiness: {}", 42);

  • Replaced snprintf fallback with a faster internal IEEE 754 float and double formatter for arbitrary precision. For example (godbolt):

    #include <fmt/core.h>

int main() {
  fmt::print("{:.500}\n", 4.9406564584124654E-324);
}

    prints 4.9406564584124654417656879286822137236505980261432476442558568250067550727020875186529983636163599237979656469544571773092665671035593979639877479601078187812630071319031140452784581716784898210368871863605699873072305000638740915356498438731247339727316961514003171538539807412623856559117102665855668676818703956031062493194527159149245532930545654440112748012970999954193198940908041656332452475714786901472678015935523861155013480352649347201937902681071074917033322268447533357208324319360923829e-324.

  • Made format_to_n and formatted_size part of the core API (godbolt):

    #include <fmt/core.h>

int main() {
  char buffer[10];
  auto result = fmt::format_to_n(buffer, sizeof(buffer), "{}", 42);
}

  • Added fmt::format_to_n overload with format string compilation (#1764, #1767, #1869). For example (godbolt):

    #include <fmt/compile.h>

int main() {
  char buffer[8];
  fmt::format_to_n(buffer, sizeof(buffer), FMT_COMPILE("{}"), 42);
}

    Thanks @Kurkin (Dmitry Kurkin), @alexezeder (Alexey Ochapov).

  • Added fmt::format_to overload that take text_style (#1593, #1842, #1843). For example (godbolt):

    #include <fmt/color.h>

int main() {
  std::string out;
  fmt::format_to(std::back_inserter(out),
                 fmt::emphasis::bold | fg(fmt::color::red),
                 "The answer is {}.", 42);
}

    Thanks @Naios (Denis Blank).

  • Made the # specifier emit trailing zeros in addition to the decimal point (#1797). For example (godbolt):

    #include <fmt/core.h>

int main() {
  fmt::print("{:#.2g}", 0.5);
}

    prints 0.50.

  • Changed the default floating point format to not include .0 for consistency with std::format and std::to_chars (#1893, #1943). It is possible to get the decimal point and trailing zero with the # specifier.

  • Fixed an issue with floating-point formatting that could result in addition of a non-significant trailing zero in rare cases e.g. 1.00e-34 instead of 1.0e-34 (#1873, #1917).

  • Made fmt::to_string fallback on ostream insertion operator if the formatter specialization is not provided (#1815, #1829). Thanks @alexezeder (Alexey Ochapov).

  • Added support for the append mode to the experimental file API and improved fcntl.h detection. (#1847, #1848). Thanks @t-wiser.

  • Fixed handling of types that have both an implicit conversion operator and an overloaded ostream insertion operator (#1766).

  • Fixed a slicing issue in an internal iterator type (#1822). Thanks @BRevzin (Barry Revzin).

  • Fixed an issue in locale-specific integer formatting (#1927).

  • Fixed handling of exotic code unit types (#1870, #1932).

  • Improved FMT_ALWAYS_INLINE (#1878). Thanks @jk-jeon (Junekey Jeon).

  • Removed dependency on windows.h (#1900). Thanks @bernd5 (Bernd Baumanns).

  • Optimized counting of decimal digits on MSVC (#1890). Thanks @mwinterb.

  • Improved documentation (#1772, #1775, #1792, #1838, #1888, #1918, #1939). Thanks @leolchat (Léonard Gérard), @pepsiman (Malcolm Parsons), @Klaim (Joël Lamotte), @ravijanjam (Ravi J), @francesco-st, @udnaan (Adnan).

  • Added the FMT_REDUCE_INT_INSTANTIATIONS CMake option that reduces the binary code size at the cost of some integer formatting performance. This can be useful for extremely memory-constrained embedded systems (#1778, #1781). Thanks @kammce (Khalil Estell).

  • Added the FMT_USE_INLINE_NAMESPACES macro to control usage of inline namespaces (#1945). Thanks @darklukee.

  • Improved build configuration (#1760, #1770, #1779, #1783, #1823). Thanks @dvetutnev (Dmitriy Vetutnev), @xvitaly (Vitaly Zaitsev), @tambry (Raul Tambre), @medithe, @martinwuehrer (Martin Wührer).

  • Fixed various warnings and compilation issues (#1790, #1802, #1808, #1810, #1811, #1812, #1814, #1816, #1817, #1818, #1825, #1836, #1855, #1856, #1860, #1877, #1879, #1880, #1896, #1897, #1898, #1904, #1908, #1911, #1912, #1928, #1929, #1935 #1937, #1942, #1949). Thanks @TheQwertiest, @medithe, [@martinwuehrer (Martin Wührer)](h...

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7.0.3

07 Aug 13:39
@vitaut vitaut
7.0.3
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7.0.3

  • Worked around broken numeric_limits for 128-bit integers (#1787).

  • Added error reporting on missing named arguments (#1796).

  • Stopped using 128-bit integers with clang-cl (#1800). Thanks @Kingcom.

  • Fixed issues in locale-specific integer formatting (#1782, #1801).

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7.0.2

29 Jul 15:50
@vitaut vitaut
7.0.2
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7.0.2

  • Worked around broken numeric_limits for 128-bit integers (#1725).

  • Fixed compatibility with CMake 3.4 (#1779).

  • Fixed handling of digit separators in locale-specific formatting (#1782).

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