relibc_openlibm

OpenLibm

OpenLibm is an effort to have a high quality, portable, standalone C mathematical library (libm). It can be used standalone in applications and programming language implementations.

The project was born out of a need to have a good libm for the Julia programming language that worked consistently across compilers and operating systems, and in 32-bit and 64-bit environments.

Platform support

OpenLibm builds on Linux, macOS, Windows, FreeBSD, OpenBSD, NetBSD, and DragonFly BSD. It builds with both GCC and clang. Although largely tested and widely used on the x86 and x86-64 architectures, OpenLibm also supports arm, aarch64, ppc64le, mips, wasm32, riscv, s390(x) and loongarch64.

Build instructions

GNU Make

1. Use GNU Make to build OpenLibm. This is make on most systems, but gmake on BSDs.
2. Use make USEGCC=1 to build with GCC. This is the default on Linux and Windows.
3. Use make USECLANG=1 to build with clang. This is the default on OS X, FreeBSD, and OpenBSD.
4. Use make ARCH=wasm32 to build the wasm32 library with clang.
5. Architectures are auto-detected. Use make ARCH=i386 to force a build for i386. Other supported architectures are i486, i586, and i686. GCC 4.8 is the minimum requirement for correct codegen on older 32-bit architectures.

Cross Build Take riscv64 as example:

1. install qemu-riscv64-static, gcc-riscv64-linux-gnu

2. Cross build:

   ARCH=riscv64
   TRIPLE=$ARCH-linux-gnu
   make ARCH=$ARCH TOOLPREFIX=$TRIPLE-  -j
   make -C test ARCH=$ARCH TOOLPREFIX=$TRIPLE-  -j
   

3. Run test with qemu:

   qemu-$ARCH-static -L . -L /usr/$TRIPLE/  test/test-float
   qemu-$ARCH-static -L . -L /usr/$TRIPLE/  test/test-double
   

CMake

1. Create build directory with mkdir build and navigate into it with cd build.
2. Run CMake to configure project and generate native build system with cmake /path/to/openlibm/ or generate project with build system of choice e.g. cmake /path/to/openlib/ -G "MinGW Makefiles".
3. Build with the build system with cmake --build ..

Default CMake configuration builds a shared library, this can easily be configured using BUILD_SHARED_LIBS configuration option.

Acknowledgements

PowerPC support for openlibm was graciously sponsored by IBM.