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6.1.1 - 2019-12-04

6.1.0 - 2019-12-01

6.0.0 - 2019-08-26

5.3.0 - 2018-12-28

  • Introduced experimental chrono formatting support:

    #include <fmt/chrono.h>
    int main() {
      using namespace std::literals::chrono_literals;
      fmt::print("Default format: {} {}\n", 42s, 100ms);
      fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);


    Default format: 42s 100ms
    strftime-like format: 03:15:30
  • Added experimental support for emphasis (bold, italic, underline, strikethrough), colored output to a file stream, and improved colored formatting API (#961, #967, #973):

    #include <fmt/color.h>
    int main() {
      print(fg(fmt::color::crimson) | fmt::emphasis::bold,
            "Hello, {}!\n", "world");
      print(fg(fmt::color::floral_white) | bg(fmt::color::slate_gray) |
            fmt::emphasis::underline, "Hello, {}!\n", "мир");
      print(fg(fmt::color::steel_blue) | fmt::emphasis::italic,
            "Hello, {}!\n", "世界");

    prints the following on modern terminals with RGB color support:

    Thanks @Rakete1111 (Nicolas).

  • Added support for 4-bit terminal colors (#968, #974)

    #include <fmt/color.h>
    int main() {
      print(fg(fmt::terminal_color::red), "stop\n");

    Note that these colors vary by terminal:

    Thanks @Rakete1111 (Nicolas).

  • Parameterized formatting functions on the type of the format string (#880, #881, #883, #885, #897, #920). Any object of type S that has an overloaded to_string_view(const S&) returning fmt::string_view can be used as a format string:

    namespace my_ns {
    inline string_view to_string_view(const my_string& s) {
      return {, s.length()};
    std::string message = fmt::format(my_string("The answer is {}."), 42);

    Thanks @DanielaE (Daniela Engert).

  • Made std::string_view work as a format string (#898):

    auto message = fmt::format(std::string_view("The answer is {}."), 42);

    Thanks @DanielaE (Daniela Engert).

  • Added wide string support to compile-time format string checks (#924):

    print(fmt(L"{:f}"), 42); // compile-time error: invalid type specifier

    Thanks @XZiar.

  • Made colored print functions work with wide strings (#867):

    #include <fmt/color.h>
    int main() {
      print(fg(fmt::color::red), L"{}\n", 42);

    Thanks @DanielaE (Daniela Engert).

  • Introduced experimental Unicode support (#628, #891):

    using namespace fmt::literals;
    auto s = fmt::format("{:*^5}"_u, "🤡"_u); // s == "**🤡**"_u
  • Improved locale support:

    #include <fmt/locale.h>
    struct numpunct : std::numpunct<char> {
      char do_thousands_sep() const override { return '~'; }
    std::locale loc;
    auto s = fmt::format(std::locale(loc, new numpunct()), "{:n}", 1234567);
    // s == "1~234~567"
  • Constrained formatting functions on proper iterator types (#921). Thanks @DanielaE (Daniela Engert).

  • Added make_printf_args and make_wprintf_args functions (#934). Thanks @tnovotny.

  • Deprecated fmt::visit, parse_context, and wparse_context. Use fmt::visit_format_arg, format_parse_context, and wformat_parse_context instead.

  • Removed undocumented basic_fixed_buffer which has been superseded by the iterator-based API (#873, #902). Thanks @superfunc (hollywood programmer).

  • Disallowed repeated leading zeros in an argument ID:

    fmt::print("{000}", 42); // error
  • Reintroduced support for gcc 4.4.

  • Fixed compilation on platforms with exotic double (#878).

  • Improved documentation (#164, #877, #901, #906, #979). Thanks @kookjr (Mathew Cucuzella), @DarkDimius (Dmitry Petrashko), @HecticSerenity.

  • Added pkgconfig support which makes it easier to consume the library from meson and other build systems (#916). Thanks @colemickens (Cole Mickens).

  • Various build improvements (#909, #926, #937, #953, #959). Thanks @tchaikov (Kefu Chai), @luncliff (Park DongHa), @AndreasSchoenle (Andreas Schönle), @hotwatermorning, @Zefz (JohanJansen).

  • Improved string_view construction performance (#914). Thanks @gabime (Gabi Melman).

  • Fixed non-matching char types (#895). Thanks @DanielaE (Daniela Engert).

  • Fixed format_to_n with std::back_insert_iterator (#913). Thanks @DanielaE (Daniela Engert).

  • Fixed locale-dependent formatting (#905).

  • Fixed various compiler warnings and errors (#882, #886, #933, #941, #931, #943, #954, #956, #962, #965, #977, #983, #989). Thanks @Luthaf (Guillaume Fraux), @stevenhoving (Steven Hoving), @christinaa (Kristina Brooks), @lgritz (Larry Gritz), @DanielaE (Daniela Engert), @0x8000-0000 (Sign Bit), @liuping1997.

5.2.1 - 2018-09-21

5.2.0 - 2018-09-13

  • Optimized format string parsing and argument processing which resulted in up to 5x speed up on long format strings and significant performance boost on various benchmarks. For example, version 5.2 is 2.22x faster than 5.1 on decimal integer formatting with format_to (macOS, clang-902.0.39.2):


    Time, s


    fmt::format 5.1



    fmt::format 5.2



    fmt::format_to 5.1



    fmt::format_to 5.2











  • Changed the fmt macro from opt-out to opt-in to prevent name collisions. To enable it define the FMT_STRING_ALIAS macro to 1 before including fmt/format.h:

    #define FMT_STRING_ALIAS 1
    #include <fmt/format.h>
    std::string answer = format(fmt("{}"), 42);
  • Added compile-time format string checks to format_to overload that takes fmt::memory_buffer (#783):

    fmt::memory_buffer buf;
    // Compile-time error: invalid type specifier.
    fmt::format_to(buf, fmt("{:d}"), "foo");
  • Moved experimental color support to fmt/color.h and enabled the new API by default. The old API can be enabled by defining the FMT_DEPRECATED_COLORS macro.

  • Added formatting support for types explicitly convertible to fmt::string_view:

    struct foo {
      explicit operator fmt::string_view() const { return "foo"; }
    auto s = format("{}", foo());

    In particular, this makes formatting function work with folly::StringPiece.

  • Implemented preliminary support for char*_t by replacing the format function overloads with a single function template parameterized on the string type.

  • Added support for dynamic argument lists (#814, #819). Thanks @MikePopoloski (Michael Popoloski).

  • Reduced executable size overhead for embedded targets using newlib nano by making locale dependency optional (#839). Thanks @teajay-fr (Thomas Benard).

  • Keep noexcept specifier when exceptions are disabled (#801, #810). Thanks @qis (Alexej Harm).

  • Fixed formatting of user-defined types providing operator<< with format_to_n (#806). Thanks @mkurdej (Marek Kurdej).

  • Fixed dynamic linkage of new symbols (#808).

  • Fixed global initialization issue (#807):

    // This works on compilers with constexpr support.
    static const std::string answer = fmt::format("{}", 42);
  • Fixed various compiler warnings and errors (#804, #809, #811, #822, #827, #830, #838, #843, #844, #851, #852, #854). Thanks @henryiii (Henry Schreiner), @medithe, and @eliasdaler (Elias Daler).

5.1.0 - 2018-07-05

  • Added experimental support for RGB color output enabled with the FMT_EXTENDED_COLORS macro:

    #define FMT_HEADER_ONLY // or compile fmt with FMT_EXTENDED_COLORS defined
    #include <fmt/format.h>
    fmt::print(fmt::color::steel_blue, "Some beautiful text");

    The old API (the print_colored and vprint_colored functions and the color enum) is now deprecated. (#762 #767). thanks @Remotion (Remo).

  • Added quotes to strings in ranges and tuples (#766). Thanks @Remotion (Remo).

  • Made format_to work with basic_memory_buffer (#776).

  • Added vformat_to_n and wchar_t overload of format_to_n (#764, #769).

  • Made is_range and is_tuple_like part of public (experimental) API to allow specialization for user-defined types (#751, #759). Thanks @drrlvn (Dror Levin).

  • Added more compilers to continuous integration and increased FMT_PEDANTIC warning levels (#736). Thanks @eliaskosunen (Elias Kosunen).

  • Fixed compilation with MSVC 2013.

  • Fixed handling of user-defined types in format_to (#793).

  • Forced linking of inline vformat functions into the library (#795).

  • Fixed incorrect call to on_align in '{:}=' (#750).

  • Fixed floating-point formatting to a non-back_insert_iterator with sign & numeric alignment specified (#756).

  • Fixed formatting to an array with format_to_n (#778).

  • Fixed formatting of more than 15 named arguments (#754).

  • Fixed handling of compile-time strings when including fmt/ostream.h. (#768).

  • Fixed various compiler warnings and errors (#742, #748, #752, #770, #775, #779, #780, #790, #792, #800). Thanks @Remotion (Remo), @gabime (Gabi Melman), @foonathan (Jonathan Müller), @Dark-Passenger (Dhruv Paranjape), and @0x8000-0000 (Sign Bit).

5.0.0 - 2018-05-21

  • Added a requirement for partial C++11 support, most importantly variadic templates and type traits, and dropped FMT_VARIADIC_* emulation macros. Variadic templates are available since GCC 4.4, Clang 2.9 and MSVC 18.0 (2013). For older compilers use {fmt} version 4.x which continues to be maintained and works with C++98 compilers.

  • Renamed symbols to follow standard C++ naming conventions and proposed a subset of the library for standardization in P0645R2 Text Formatting.

  • Implemented constexpr parsing of format strings and compile-time format string checks. For example

    #include <fmt/format.h>
    std::string s = format(fmt("{:d}"), "foo");

    gives a compile-time error because d is an invalid specifier for strings (godbolt):

    <source>:4:19: note: in instantiation of function template specialization 'fmt::v5::format<S, char [4]>' requested here
      std::string s = format(fmt("{:d}"), "foo");
    format.h:1337:13: note: non-constexpr function 'on_error' cannot be used in a constant expression
        handler.on_error("invalid type specifier");

    Compile-time checks require relaxed constexpr (C++14 feature) support. If the latter is not available, checks will be performed at runtime.

  • Separated format string parsing and formatting in the extension API to enable compile-time format string processing. For example

    struct Answer {};
    namespace fmt {
    template <>
    struct formatter<Answer> {
      constexpr auto parse(parse_context& ctx) {
        auto it = ctx.begin();
        spec = *it;
        if (spec != 'd' && spec != 's')
          throw format_error("invalid specifier");
        return ++it;
      template <typename FormatContext>
      auto format(Answer, FormatContext& ctx) {
        return spec == 's' ?
          format_to(ctx.begin(), "{}", "fourty-two") :
          format_to(ctx.begin(), "{}", 42);
      char spec = 0;
    std::string s = format(fmt("{:x}"), Answer());

    gives a compile-time error due to invalid format specifier (godbolt):

    <source>:12:45: error: expression '<throw-expression>' is not a constant expression
           throw format_error("invalid specifier");
  • Added iterator support:

    #include <vector>
    #include <fmt/format.h>
    std::vector<char> out;
    fmt::format_to(std::back_inserter(out), "{}", 42);
  • Added the format_to_n function that restricts the output to the specified number of characters (#298):

    char out[4];
    fmt::format_to_n(out, sizeof(out), "{}", 12345);
    // out == "1234" (without terminating '\0')
  • Added the formatted_size function for computing the output size:

    #include <fmt/format.h>
    auto size = fmt::formatted_size("{}", 12345); // size == 5
  • Improved compile times by reducing dependencies on standard headers and providing a lightweight core API:

    #include <fmt/core.h>
    fmt::print("The answer is {}.", 42);

    See Compile time and code bloat.

  • Added the make_format_args function for capturing formatting arguments:

    // Prints formatted error message.
    void vreport_error(const char *format, fmt::format_args args) {
      fmt::print("Error: ");
      fmt::vprint(format, args);
    template <typename... Args>
    void report_error(const char *format, const Args & ... args) {
      vreport_error(format, fmt::make_format_args(args...));
  • Added the make_printf_args function for capturing printf arguments (#687, #694). Thanks @Kronuz (Germán Méndez Bravo).

  • Added prefix v to non-variadic functions taking format_args to distinguish them from variadic ones:

    std::string vformat(string_view format_str, format_args args);
    template <typename... Args>
    std::string format(string_view format_str, const Args & ... args);
  • Added experimental support for formatting ranges, containers and tuple-like types in fmt/ranges.h (#735):

    #include <fmt/ranges.h>
    std::vector<int> v = {1, 2, 3};
    fmt::print("{}", v); // prints {1, 2, 3}

    Thanks @Remotion (Remo).

  • Implemented wchar_t date and time formatting (#712):

    #include <fmt/time.h>
    std::time_t t = std::time(nullptr);
    auto s = fmt::format(L"The date is {:%Y-%m-%d}.", *std::localtime(&t));

    Thanks @DanielaE (Daniela Engert).

  • Provided more wide string overloads (#724). Thanks @DanielaE (Daniela Engert).

  • Switched from a custom null-terminated string view class to string_view in the format API and provided fmt::string_view which implements a subset of std::string_view API for pre-C++17 systems.

  • Added support for std::experimental::string_view (#607):

    #include <fmt/core.h>
    #include <experimental/string_view>
    fmt::print("{}", std::experimental::string_view("foo"));

    Thanks @virgiliofornazin (Virgilio Alexandre Fornazin).

  • Allowed mixing named and automatic arguments:

    fmt::format("{} {two}", 1, fmt::arg("two", 2));
  • Removed the write API in favor of the format API with compile-time handling of format strings.

  • Disallowed formatting of multibyte strings into a wide character target (#606).

  • Improved documentation (#515, #614, #617, #661, #680). Thanks @ibell (Ian Bell), @mihaitodor (Mihai Todor), and @johnthagen.

  • Implemented more efficient handling of large number of format arguments.

  • Introduced an inline namespace for symbol versioning.

  • Added debug postfix d to the fmt library name (#636).

  • Removed unnecessary fmt/ prefix in includes (#397). Thanks @chronoxor (Ivan Shynkarenka).

  • Moved fmt/*.h to include/fmt/*.h to prevent irrelevant files and directories appearing on the include search paths when fmt is used as a subproject and moved source files to the src directory.

  • Added qmake project file support/ (#641). Thanks @cowo78 (Giuseppe Corbelli).

  • Added Gradle build file support/build.gradle (#649). Thanks @luncliff (Park DongHa).

  • Removed FMT_CPPFORMAT CMake option.

  • Fixed a name conflict with the macro CHAR_WIDTH in glibc (#616). Thanks @aroig (Abdó Roig-Maranges).

  • Fixed handling of nested braces in fmt::join (#638).

  • Added SOURCELINK_SUFFIX for compatibility with Sphinx 1.5 (#497). Thanks @ginggs (Graham Inggs).

  • Added a missing inline in the header-only mode (#626). Thanks @aroig (Abdó Roig-Maranges).

  • Fixed various compiler warnings (#640, #656, #679, #681, #705, #715, #717, #720, #723, #726, #730, #739). Thanks @peterbell10, @LarsGullik, @foonathan (Jonathan Müller), @eliaskosunen (Elias Kosunen), @christianparpart (Christian Parpart), @DanielaE (Daniela Engert), and @mwinterb.

  • Worked around an MSVC bug and fixed several warnings (#653). Thanks @alabuzhev (Alex Alabuzhev).

  • Worked around GCC bug 67371 (#682).

  • Fixed compilation with -fno-exceptions (#655). Thanks @chenxiaolong (Andrew Gunnerson).

  • Made constexpr remove_prefix gcc version check tighter (#648).

  • Renamed internal type enum constants to prevent collision with poorly written C libraries (#644).

  • Added detection of wostream operator<< (#650).

  • Fixed compilation on OpenBSD (#660). Thanks @hubslave.

  • Fixed compilation on FreeBSD 12 (#732). Thanks @dankm.

  • Fixed compilation when there is a mismatch between -std options between the library and user code (#664).

  • Fixed compilation with GCC 7 and -std=c++11 (#734).

  • Improved generated binary code on GCC 7 and older (#668).

  • Fixed handling of numeric alignment with no width (#675).

  • Fixed handling of empty strings in UTF8/16 converters (#676). Thanks @vgalka-sl (Vasili Galka).

  • Fixed formatting of an empty string_view (#689).

  • Fixed detection of string_view on libc++ (#686).

  • Fixed DLL issues (#696). Thanks @sebkoenig.

  • Fixed compile checks for mixing narrow and wide strings (#690).

  • Disabled unsafe implicit conversion to std::string (#729).

  • Fixed handling of reused format specs (as in fmt::join) for pointers (#725). Thanks @mwinterb.

  • Fixed installation of fmt/ranges.h (#738). Thanks @sv1990.

4.1.0 - 2017-12-20

4.0.0 - 2017-06-27

3.0.2 - 2017-06-14

3.0.1 - 2016-11-01

3.0.0 - 2016-05-07

  • The project has been renamed from C++ Format (cppformat) to fmt for consistency with the used namespace and macro prefix (#307). Library headers are now located in the fmt directory:

    #include "fmt/format.h"

    Including format.h from the cppformat directory is deprecated but works via a proxy header which will be removed in the next major version.

    The documentation is now available at

  • Added support for strftime-like date and time formatting (#283):

    #include "fmt/time.h"
    std::time_t t = std::time(nullptr);
    // Prints "The date is 2016-04-29." (with the current date)
    fmt::print("The date is {:%Y-%m-%d}.", *std::localtime(&t));
  • std::ostream support including formatting of user-defined types that provide overloaded operator<< has been moved to fmt/ostream.h:

    #include "fmt/ostream.h"
    class Date {
      int year_, month_, day_;
      Date(int year, int month, int day) : year_(year), month_(month), day_(day) {}
      friend std::ostream &operator<<(std::ostream &os, const Date &d) {
        return os << d.year_ << '-' << d.month_ << '-' << d.day_;
    std::string s = fmt::format("The date is {}", Date(2012, 12, 9));
    // s == "The date is 2012-12-9"
  • Added support for custom argument formatters (#235).

  • Added support for locale-specific integer formatting with the n specifier (#305):

    std::setlocale(LC_ALL, "en_US.utf8");
    fmt::print("cppformat: {:n}\n", 1234567); // prints 1,234,567
  • Sign is now preserved when formatting an integer with an incorrect printf format specifier (#265):

    fmt::printf("%lld", -42); // prints -42

    Note that it would be an undefined behavior in std::printf.

  • Length modifiers such as ll are now optional in printf formatting functions and the correct type is determined automatically (#255):

    fmt::printf("%d", std::numeric_limits<long long>::max());

    Note that it would be an undefined behavior in std::printf.

  • Added initial support for custom formatters (#231).

  • Fixed detection of user-defined literal support on Intel C++ compiler (#311, #312). Thanks to @dean0x7d (Dean Moldovan) and @speth (Ray Speth).

  • Reduced compile time (#243, #249, #317):

    Thanks to @dean0x7d (Dean Moldovan).

  • Compile test fixes (#313). Thanks to @dean0x7d (Dean Moldovan).

  • Documentation fixes (#239, #248, #252, #258, #260, #301, #309). Thanks to @ReadmeCritic @Gachapen (Magnus Bjerke Vik) and @jwilk (Jakub Wilk).

  • Fixed compiler and sanitizer warnings (#244, #256, #259, #263, #274, #277, #286, #291, #296, #308) Thanks to @mwinterb, @pweiskircher (Patrik Weiskircher), @Naios.

  • Improved compatibility with Windows Store apps (#280, #285) Thanks to @mwinterb.

  • Added tests of compatibility with older C++ standards (#273). Thanks to @niosHD.

  • Fixed Android build (#271). Thanks to @newnon.

  • Changed ArgMap to be backed by a vector instead of a map. (#261, #262). Thanks to @mwinterb.

  • Added fprintf overload that writes to a std::ostream (#251). Thanks to nickhutchinson (Nicholas Hutchinson).

  • Export symbols when building a Windows DLL (#245). Thanks to macdems (Maciek Dems).

  • Fixed compilation on Cygwin (#304).

  • Implemented a workaround for a bug in Apple LLVM version 4.2 of clang (#276).

  • Implemented a workaround for Google Test bug #705 on gcc 6 (#268). Thanks to octoploid.

  • Removed Biicode support because the latter has been discontinued.

2.1.1 - 2016-04-11

  • The install location for generated CMake files is now configurable via the FMT_CMAKE_DIR CMake variable (#299). Thanks to @niosHD.
  • Documentation fixes (#252).

2.1.0 - 2016-03-21

  • Project layout and build system improvements (#267):

    • The code have been moved to the cppformat directory. Including format.h from the top-level directory is deprecated but works via a proxy header which will be removed in the next major version.
    • C++ Format CMake targets now have proper interface definitions.
    • Installed version of the library now supports the header-only configuration.
    • Targets doc, install, and test are now disabled if C++ Format is included as a CMake subproject. They can be enabled by setting FMT_DOC, FMT_INSTALL, and FMT_TEST in the parent project.

    Thanks to @niosHD.

2.0.1 - 2016-03-13

2.0.0 - 2015-12-01


  • [Breaking] Named arguments (#169, #173, #174):

    fmt::print("The answer is {answer}.", fmt::arg("answer", 42));

    Thanks to @jamboree.

  • [Experimental] User-defined literals for format and named arguments (#204, #206, #207):

    using namespace fmt::literals;
    fmt::print("The answer is {answer}.", "answer"_a=42);

    Thanks to @dean0x7d (Dean Moldovan).

  • [Breaking] Formatting of more than 16 arguments is now supported when using variadic templates (#141). Thanks to @Shauren.

  • Runtime width specification (#168):

    fmt::format("{0:{1}}", 42, 5); // gives "   42"

    Thanks to @jamboree.

  • [Breaking] Enums are now formatted with an overloaded std::ostream insertion operator (operator<<) if available (#232).

  • [Breaking] Changed default bool format to textual, "true" or "false" (#170):

    fmt::print("{}", true); // prints "true"

    To print bool as a number use numeric format specifier such as d:

    fmt::print("{:d}", true); // prints "1"
  • fmt::printf and fmt::sprintf now support formatting of bool with the %s specifier giving textual output, "true" or "false" (#223):

    fmt::printf("%s", true); // prints "true"

    Thanks to @LarsGullik.

  • [Breaking] signed char and unsigned char are now formatted as integers by default (#217).

  • [Breaking] Pointers to C strings can now be formatted with the p specifier (#223):

    fmt::print("{:p}", "test"); // prints pointer value

    Thanks to @LarsGullik.

  • [Breaking] fmt::printf and fmt::sprintf now print null pointers as (nil) and null strings as (null) for consistency with glibc (#226). Thanks to @LarsGullik.

  • [Breaking] fmt::(s)printf now supports formatting of objects of user-defined types that provide an overloaded std::ostream insertion operator (operator<<) (#201):

    fmt::printf("The date is %s", Date(2012, 12, 9));
  • [Breaking] The Buffer template is now part of the public API and can be used to implement custom memory buffers (#140). Thanks to @polyvertex (Jean-Charles Lefebvre).

  • [Breaking] Improved compatibility between BasicStringRef and std::experimental::basic_string_view (#100, #159, #183):

    • Comparison operators now compare string content, not pointers
    • BasicStringRef::c_str replaced by BasicStringRef::data
    • BasicStringRef is no longer assumed to be null-terminated

    References to null-terminated strings are now represented by a new class, BasicCStringRef.

  • Dependency on pthreads introduced by Google Test is now optional (#185).

  • New CMake options FMT_DOC, FMT_INSTALL and FMT_TEST to control generation of doc, install and test targets respectively, on by default (#197, #198, #200). Thanks to @maddinat0r (Alex Martin).

  • noexcept is now used when compiling with MSVC2015 (#215). Thanks to @dmkrepo (Dmitriy).

  • Added an option to disable use of windows.h when FMT_USE_WINDOWS_H is defined as 0 before including format.h (#171). Thanks to @alfps (Alf P. Steinbach).

  • [Breaking] windows.h is now included with NOMINMAX unless FMT_WIN_MINMAX is defined. This is done to prevent breaking code using std::min and std::max and only affects the header-only configuration (#152, #153, #154). Thanks to @DevO2012.

  • Improved support for custom character types (#171). Thanks to @alfps (Alf P. Steinbach).

  • Added an option to disable use of IOStreams when FMT_USE_IOSTREAMS is defined as 0 before including format.h (#205, #208). Thanks to @JodiTheTigger.

  • Improved detection of isnan, isinf and signbit.


  • Made formatting of user-defined types more efficient with a custom stream buffer (#92, #230). Thanks to @NotImplemented.
  • Further improved performance of fmt::Writer on integer formatting and fixed a minor regression. Now it is ~7% faster than karma::generate on Karma's benchmark (#186).
  • [Breaking] Reduced compiled code size (#143, #149).




1.1.0 - 2015-03-06

  • Added BasicArrayWriter, a class template that provides operations for formatting and writing data into a fixed-size array (#105 and #122):

    char buffer[100];
    fmt::ArrayWriter w(buffer);
    w.write("The answer is {}", 42);
  • Added 0 A.D. and PenUltima Online (POL) to the list of notable projects using C++ Format.

  • C++ Format now uses MSVC intrinsics for better formatting performance (#115, #116, #118 and #121). Previously these optimizations where only used on GCC and Clang. Thanks to @CarterLi and @objectx.

  • CMake install target (#119). Thanks to @TrentHouliston.

    You can now install C++ Format with make install command.

  • Improved Biicode support (#98 and #104). Thanks to @MariadeAnton and @franramirez688.

  • Improved support for building with Android NDK (#107). Thanks to @newnon.

    The android-ndk-example repository provides and example of using C++ Format with Android NDK:
  • Improved documentation of SystemError and WindowsError (#54).

  • Various code improvements (#110, #111 #112). Thanks to @CarterLi.

  • Improved compile-time errors when formatting wide into narrow strings (#117).

  • Fixed BasicWriter::write without formatting arguments when C++11 support is disabled (#109).

  • Fixed header-only build on OS X with GCC 4.9 (#124).

  • Fixed packaging issues (#94).

  • Added changelog (#103).

1.0.0 - 2015-02-05

  • Add support for a header-only configuration when FMT_HEADER_ONLY is defined before including format.h:

    #define FMT_HEADER_ONLY
    #include "format.h"
  • Compute string length in the constructor of BasicStringRef instead of the size method (#79). This eliminates size computation for string literals on reasonable optimizing compilers.

  • Fix formatting of types with overloaded operator << for std::wostream (#86):

    fmt::format(L"The date is {0}", Date(2012, 12, 9));
  • Fix linkage of tests on Arch Linux (#89).

  • Allow precision specifier for non-float arguments (#90):

    fmt::print("{:.3}\n", "Carpet"); // prints "Car"
  • Fix build on Android NDK (#93)

  • Improvements to documentation build procedure.

  • Remove FMT_SHARED CMake variable in favor of standard BUILD_SHARED_LIBS.

  • Fix error handling in fmt::fprintf.

  • Fix a number of warnings.

0.12.0 - 2014-10-25

  • [Breaking] Improved separation between formatting and buffer management. Writer is now a base class that cannot be instantiated directly. The new MemoryWriter class implements the default buffer management with small allocations done on stack. So fmt::Writer should be replaced with fmt::MemoryWriter in variable declarations.

    Old code:

    fmt::Writer w;

    New code:

    fmt::MemoryWriter w;

    If you pass fmt::Writer by reference, you can continue to do so:

    void f(fmt::Writer &w);

    This doesn't affect the formatting API.

  • Support for custom memory allocators (#69)

  • Formatting functions now accept signed char and unsigned char strings as arguments (#73):

    auto s = format("GLSL version: {}", glGetString(GL_VERSION));
  • Reduced code bloat. According to the new benchmark results, cppformat is close to printf and by the order of magnitude better than Boost Format in terms of compiled code size.

  • Improved appearance of the documentation on mobile by using the Sphinx Bootstrap theme:





0.11.0 - 2014-08-21

  • Safe printf implementation with a POSIX extension for positional arguments:

    fmt::printf("Elapsed time: %.2f seconds", 1.23);
    fmt::printf("%1$s, %3$d %2$s", weekday, month, day);
  • Arguments of char type can now be formatted as integers (Issue #55):

    fmt::format("0x{0:02X}", 'a');
  • Deprecated parts of the API removed.

  • The library is now built and tested on MinGW with Appveyor in addition to existing test platforms Linux/GCC, OS X/Clang, Windows/MSVC.

0.10.0 - 2014-07-01

Improved API

  • All formatting methods are now implemented as variadic functions instead of using operator<< for feeding arbitrary arguments into a temporary formatter object. This works both with C++11 where variadic templates are used and with older standards where variadic functions are emulated by providing lightweight wrapper functions defined with the FMT_VARIADIC macro. You can use this macro for defining your own portable variadic functions:

    void report_error(const char *format, const fmt::ArgList &args) {
      fmt::print("Error: {}");
      fmt::print(format, args);
    FMT_VARIADIC(void, report_error, const char *)
    report_error("file not found: {}", path);

    Apart from a more natural syntax, this also improves performance as there is no need to construct temporary formatter objects and control arguments' lifetimes. Because the wrapper functions are very lightweight, this doesn't cause code bloat even in pre-C++11 mode.

  • Simplified common case of formatting an std::string. Now it requires a single function call:

    std::string s = format("The answer is {}.", 42);

    Previously it required 2 function calls:

    std::string s = str(Format("The answer is {}.") << 42);

    Instead of unsafe c_str function, fmt::Writer should be used directly to bypass creation of std::string:

    fmt::Writer w;
    w.write("The answer is {}.", 42);
    w.c_str();  // returns a C string

    This doesn't do dynamic memory allocation for small strings and is less error prone as the lifetime of the string is the same as for std::string::c_str which is well understood (hopefully).

  • Improved consistency in naming functions that are a part of the public API. Now all public functions are lowercase following the standard library conventions. Previously it was a combination of lowercase and CapitalizedWords. Issue #50.

  • Old functions are marked as deprecated and will be removed in the next release.

Other Changes

  • Experimental support for printf format specifications (work in progress):

    fmt::printf("The answer is %d.", 42);
    std::string s = fmt::sprintf("Look, a %s!", "string");
  • Support for hexadecimal floating point format specifiers a and A:

    print("{:a}", -42.0); // Prints -0x1.5p+5
    print("{:A}", -42.0); // Prints -0X1.5P+5
  • CMake option FMT_SHARED that specifies whether to build format as a shared library (off by default).

0.9.0 - 2014-05-13

  • More efficient implementation of variadic formatting functions.

  • Writer::Format now has a variadic overload:

    Writer out;
    out.Format("Look, I'm {}!", "variadic");
  • For efficiency and consistency with other overloads, variadic overload of the Format function now returns Writer instead of std::string. Use the str function to convert it to std::string:

    std::string s = str(Format("Look, I'm {}!", "variadic"));
  • Replaced formatter actions with output sinks: NoAction -> NullSink, Write -> FileSink, ColorWriter -> ANSITerminalSink. This improves naming consistency and shouldn't affect client code unless these classes are used directly which should be rarely needed.

  • Added ThrowSystemError function that formats a message and throws SystemError containing the formatted message and system-specific error description. For example, the following code

    FILE *f = fopen(filename, "r");
    if (!f)
      ThrowSystemError(errno, "Failed to open file '{}'") << filename;

    will throw SystemError exception with description "Failed to open file '<filename>': No such file or directory" if file doesn't exist.

  • Support for AppVeyor continuous integration platform.

  • Format now throws SystemError in case of I/O errors.

  • Improve test infrastructure. Print functions are now tested by redirecting the output to a pipe.

0.8.0 - 2014-04-14

  • Initial release
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