- Fixed handling of thousands seperator (#353)
- Fixed handling of
unsigned charstrings (#373) - Corrected buffer growth when formatting time (#367)
- Removed warnings under MSVC and clang (#318, #250, also merged #385 and #361). Thanks @jcelerier (Jean-Michaël Celerier) and @nmoehrle (Nils Moehrle).
- Fixed compilation issues under Android (#327, #345 and #381), FreeBSD (#358), Cygwin (#388), MinGW (#355) as well as other issues (#350, #366, #348, #402, #405). Thanks to @dpantele (Dmitry), @hghwng (Hugh Wang), @arvedarved (Tilman Keskinöz), @LogicalKnight (Sean) and @JanHellwig (Jan Hellwig).
- Fixed some documentation issues and extended specification (#320, #333, #347, #362). Thanks to @smellman (Taro Matsuzawa aka. btm).
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
fmtdirectory:#include "fmt/format.h"
Including
format.hfrom thecppformatdirectory is deprecated but works via a proxy header which will be removed in the next major version.The documentation is now available at http://fmtlib.net.
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::ostreamsupport including formatting of user-defined types that provide overloadedoperator<<has been moved tofmt/ostream.h:#include "fmt/ostream.h" class Date { int year_, month_, day_; public: 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
nspecifier (#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
printfformat specifier (#265):fmt::printf("%lld", -42); // prints -42
Note that it would be an undefined behavior in
std::printf.Length modifiers such as
llare 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.
Changed
ArgMapto be backed by a vector instead of a map. (#261, #262). Thanks to @mwinterb.Added
fprintfoverload that writes to astd::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.
- The install location for generated CMake files is now configurable via
the
FMT_CMAKE_DIRCMake variable (#299). Thanks to @niosHD. - Documentation fixes (#252).
Project layout and build system improvements (#267):
- The code have been moved to the
cppformatdirectory. Includingformat.hfrom 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, andtestare now disabled if C++ Format is included as a CMake subproject. They can be enabled by settingFMT_DOC,FMT_INSTALL, andFMT_TESTin the parent project.
Thanks to @niosHD.
- The code have been moved to the
- Improved CMake find and package support (#264). Thanks to @niosHD.
- Fix compile error with Android NDK and mingw32 (#241). Thanks to @Gachapen (Magnus Bjerke Vik).
- Documentation fixes (#248, #260).
[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::ostreaminsertion operator (operator<<) if available (#232).[Breaking] Changed default
boolformat to textual, "true" or "false" (#170):fmt::print("{}", true); // prints "true"
To print
boolas a number use numeric format specifier such asd:fmt::print("{:d}", true); // prints "1"
fmt::printfandfmt::sprintfnow support formatting ofboolwith the%sspecifier giving textual output, "true" or "false" (#223):fmt::printf("%s", true); // prints "true"
Thanks to @LarsGullik.
[Breaking]
signed charandunsigned charare now formatted as integers by default (#217).[Breaking] Pointers to C strings can now be formatted with the
pspecifier (#223):fmt::print("{:p}", "test"); // prints pointer value
Thanks to @LarsGullik.
[Breaking]
fmt::printfandfmt::sprintfnow print null pointers as(nil)and null strings as(null)for consistency with glibc (#226). Thanks to @LarsGullik.[Breaking]
fmt::(s)printfnow supports formatting of objects of user-defined types that provide an overloadedstd::ostreaminsertion operator (operator<<) (#201):fmt::printf("The date is %s", Date(2012, 12, 9));
[Breaking] The
Buffertemplate 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
BasicStringRefand std::experimental::basic_string_view (#100, #159, #183):- Comparison operators now compare string content, not pointers
BasicStringRef::c_strreplaced byBasicStringRef::dataBasicStringRefis 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_INSTALLandFMT_TESTto control generation ofdoc,installandtesttargets respectively, on by default (#197, #198, #200). Thanks to @maddinat0r (Alex Martin).noexceptis now used when compiling with MSVC2015 (#215). Thanks to @dmkrepo (Dmitriy).Added an option to disable use of
windows.hwhenFMT_USE_WINDOWS_His defined as 0 before includingformat.h(#171). Thanks to @alfps (Alf P. Steinbach).[Breaking]
windows.his now included withNOMINMAXunlessFMT_WIN_MINMAXis defined. This is done to prevent breaking code usingstd::minandstd::maxand 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_IOSTREAMSis defined as 0 before includingformat.h(#205, #208). Thanks to @JodiTheTigger.Improved detection of
isnan,isinfandsignbit.
- Made formatting of user-defined types more efficient with a custom stream buffer (#92, #230). Thanks to @NotImplemented.
- Further improved performance of
fmt::Writeron integer formatting and fixed a minor regression. Now it is ~7% faster thankarma::generateon Karma's benchmark (#186). - [Breaking] Reduced compiled code size (#143, #149).
[Breaking] Headers are now installed in
${CMAKE_INSTALL_PREFIX}/include/cppformat(#178). Thanks to @jackyf (Eugene V. Lyubimkin).[Breaking] Changed the library name from
formattocppformatfor consistency with the project name and to avoid potential conflicts (#178). Thanks to @jackyf (Eugene V. Lyubimkin).C++ Format is now available in Debian GNU/Linux (stretch, sid) and derived distributions such as Ubuntu 15.10 and later (#155):
$ sudo apt-get install libcppformat1-dev
Thanks to @jackyf (Eugene V. Lyubimkin).
Packages for Fedora and RHEL are now available. Thanks to Dave Johansen.
C++ Format can now be installed via Homebrew on OS X (#157):
$ brew install cppformat
Thanks to @ortho, Anatoliy Bulukin.
- Migrated from ReadTheDocs to GitHub Pages for better responsiveness and reliability (#128). New documentation address is http://cppformat.github.io/.
- Added Building the documentation section to the documentation.
- Documentation build script is now compatible with Python 3 and newer pip versions. (#189, #209). Thanks to @JodiTheTigger and @xentec.
- Documentation fixes and improvements (#36, #75, #125, #160, #161, #162, #165, #210). Thanks to @syohex (Syohei YOSHIDA) and bug reporters.
- Fixed out-of-tree documentation build (#177). Thanks to @jackyf (Eugene V. Lyubimkin).
Fixed
initializer_listdetection (#136). Thanks to @Gachapen (Magnus Bjerke Vik).[Breaking] Fixed formatting of enums with numeric format specifiers in
fmt::(s)printf(#131, #139):enum { ANSWER = 42 }; fmt::printf("%d", ANSWER);
Thanks to @Naios.
Improved compatibility with old versions of MinGW (#129, #130, #132). Thanks to @cstamford (Christopher Stamford).
Fixed a compile error on MSVC with disabled exceptions (#144).
Added a workaround for broken implementation of variadic templates in MSVC2012 (#148).
Placed the anonymous namespace within
fmtnamespace for the header-only configuration (#171). Thanks to @alfps (Alf P. Steinbach).Implemented a workaround for a name lookup bug in MSVC2010 (#188).
Fixed compiler warnings (#95, #96, #114, #135, #142, #145, #146, #158, #163, #175, #190, #191, #194, #196, #216, #218, #220, #229, #233, #234, #236, #281, #289). Thanks to @seanmiddleditch (Sean Middleditch), @dixlorenz (Dix Lorenz), @CarterLi (李通洲), @Naios, @fmatthew5876 (Matthew Fioravante), @LevskiWeng (Levski Weng), @rpopescu, @gabime (Gabi Melman), @cubicool (Jeremy Moles), @jkflying (Julian Kent), @LogicalKnight (Sean L), @inguin (Ingo van Lil) and @Jopie64 (Johan).
Fixed portability issues (mostly causing test failures) on ARM, ppc64, ppc64le, s390x and SunOS 5.11 i386 ( #138, #179, #180, #202, #225, Red Hat Bugzilla Bug 1260297). Thanks to @Naios, @jackyf (Eugene V. Lyubimkin) and Dave Johansen.
Fixed a name conflict with macro
freedefined incrtdbg.hwhen_CRTDBG_MAP_ALLOCis set (#211).Fixed shared library build on OS X (#212). Thanks to @dean0x7d (Dean Moldovan).
Fixed an overload conflict on MSVC when
/Zc:wchar_t-option is specified (#214). Thanks to @slavanap (Vyacheslav Napadovsky).Improved compatibility with MSVC 2008 (#236). Thanks to @Jopie64 (Johan).
Improved compatibility with bcc32 (#227).
Fixed
static_assertdetection on Clang (#228). Thanks to @dean0x7d (Dean Moldovan).
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 installcommand.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
SystemErrorandWindowsError(#54).Various code improvements (#110, #111 #112). Thanks to @CarterLi.
Improved compile-time errors when formatting wide into narrow strings (#117).
Fixed
BasicWriter::writewithout 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).
Add support for a header-only configuration when
FMT_HEADER_ONLYis defined before includingformat.h:#define FMT_HEADER_ONLY #include "format.h"
Compute string length in the constructor of
BasicStringRefinstead of thesizemethod (#79). This eliminates size computation for string literals on reasonable optimizing compilers.Fix formatting of types with overloaded
operator <<forstd::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_SHAREDCMake variable in favor of standard BUILD_SHARED_LIBS.Fix error handling in
fmt::fprintf.Fix a number of warnings.
[Breaking] Improved separation between formatting and buffer management.
Writeris now a base class that cannot be instantiated directly. The newMemoryWriterclass implements the default buffer management with small allocations done on stack. Sofmt::Writershould be replaced withfmt::MemoryWriterin variable declarations.Old code:
fmt::Writer w;
New code:
fmt::MemoryWriter w;
If you pass
fmt::Writerby 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
printfand 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:
Old
New
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
chartype 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.
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 theFMT_VARIADICmacro. 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_strfunction,fmt::Writershould be used directly to bypass creation ofstd::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_strwhich 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
aandA:print("{:a}", -42.0); // Prints -0x1.5p+5 print("{:A}", -42.0); // Prints -0X1.5P+5
CMake option
FMT_SHAREDthat specifies whether to build format as a shared library (off by default).
More efficient implementation of variadic formatting functions.
Writer::Formatnow has a variadic overload:Writer out; out.Format("Look, I'm {}!", "variadic");
For efficiency and consistency with other overloads, variadic overload of the
Formatfunction now returnsWriterinstead ofstd::string. Use thestrfunction to convert it tostd::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
ThrowSystemErrorfunction that formats a message and throwsSystemErrorcontaining the formatted message and system-specific error description. For example, the following codeFILE *f = fopen(filename, "r"); if (!f) ThrowSystemError(errno, "Failed to open file '{}'") << filename;
will throw
SystemErrorexception with description "Failed to open file '<filename>': No such file or directory" if file doesn't exist.Support for AppVeyor continuous integration platform.
Formatnow throwsSystemErrorin case of I/O errors.Improve test infrastructure. Print functions are now tested by redirecting the output to a pipe.
- Initial release

