xft

A freestanding C23 systems library for Linux and Windows on x86_64 and aarch64.

xft replaces the parts of libc you would normally rely on and links with -nostdlib.

A hosted XFT_LIBC=ON flavor gives the same API on a normal toolchain.

• Everything is prefixed xft_
• Typedefs are fixed-width, alignment is encoded in the types
• Returns t_result (OK / KO) rather than errno

Build

Requires CMake >= 3.21 and GCC or Clang with C23 support. Ninja is the supported generator

On Windows, always pass -G Ninja (the Visual Studio generators ignore CMAKE_C_COMPILER)

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build

This produces build/libxft.a. Use cmake --install build --prefix /usr/local to install.

Option	Default	Effect
XFT_LIBC	OFF	Build against a libc instead of freestanding
XFT_NATIVE	ON	-march=native -mtune=native (turn off if shipping the binary)
XFT_LTO	ON	Link-time optimization (Clang + LTO wants lld)
XFT_FAST_MATH	ON	-ffast-math
XFT_SANITIZE	OFF	ASan + UBSan (forces XFT_LIBC=ON, disables LTO)
XFT_STRICT_ARCH	ON	Compile only the host's arch backends
XFT_RT	ON	xft entry point calling xft_main; OFF uses libc's and your main (forces XFT_LIBC=ON)
XFT_BUILD_TESTS	OFF	Unit tests (always sanitized)
XFT_BUILD_FUZZ	OFF	Fuzz targets (always sanitized)
XFT_BUILD_BENCH	OFF	Benchmarks (never sanitized)

Warnings are always errors. Release builds use -Wall -Wextra -Werror; every other build type uses the strict set in cmake/warnings_strict.cmake.

Usage

Link the xft::xft target, which carries the freestanding flags for you:

add_subdirectory(xft)
target_link_libraries(myprog PRIVATE xft::xft)

On Windows, xft calls into the system DLLs even in the freestanding flavor, so it depends on the kernel32, ntdll and shell32 import libraries. xft::xft links them for you; if you link libxft.lib by hand, add them yourself.

Programs include <xft.h> and define xft_main instead of main; it must end with xft_exit

Tests and benchmarks

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DXFT_BUILD_TESTS=ON -DXFT_BUILD_FUZZ=ON
cmake --build build
ctest --test-dir build --output-on-failure

cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DXFT_BUILD_BENCH=ON
cmake --build build --target run-bench

Benchmarks use the tailor harness (so it's linux-only).

On Windows, the sanitized tests and fuzz targets load clang_rt.asan_dynamic-<arch>.dll, which LLVM ships outside bin. Put its directory on PATH (or the binaries exit with 0xc0000135):

$res = & clang -print-resource-dir
$env:PATH = "$res\lib\windows;$env:PATH"

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LICENSE

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <https://unlicense.org/>