zig/std/special/compiler_rt/README.md

This compiler-rt library is ported from LLVM.

It's needed because LLVM emits library calls to compiler-rt when hardware lacks functionality, for example, 64-bit integer multiplication on 32-bit x86.

This library is automatically built as-needed for the compilation target and then statically linked and therefore is a transparent dependency for the programmer.

Any bugs should be solved by trying to duplicate the bug upstream.

• If the bug exists upstream, get it fixed with the LLVM team and then port the fix downstream to Zig.
• If the bug only exists in Zig, something went wrong porting the code, and you can run the C code and Zig code side by side in a debugger to figure out what's happening differently.

To test Zig's compiler-rt, run this command from the build directory:

make install && ./zig test ../std/special/compiler_rt/index.zig --library c

The --library c argument omits compiler-rt from the generated test program, which prevents duplicate symbol linker errors for all the compiler-rt builtins.