The LLVM C Library

Warning

LLVM-libc is not yet ABI stable; currently only static linking is supported. LLVM-libc developers retain the right to modify the ABI of types used throughout the library. Another libc should be preferred if ABI stability is a requirement.

Note

LLVM-libc is not fully complete right now. Some programs may fail to build due to missing functions. If you would like to help us finish LLVM-libc, check out “Contributing to the libc project” in the sidebar or ask on discord.

Introduction

LLVM-libc aspires to a unique place in the software ecosystem. The goals are:

  • Fully compliant with current C23 and POSIX.1-2024 standards.

  • Easily decomposed and embedded: Supplement or replace system C library functionality easily. This is useful to get consistent math precision across systems, or updated memory operations for newer microarchitectures. These pieces will work on Linux, MacOS, Windows, and Fuchsia.

  • The creation of fully static binaries without license implications.

  • Increase whole program optimization opportunities for static binaries through ability to inline math and memory operations.

  • Reduce coding errors by coding in modern C++ through the use of lightweight containers during coding that can be optimized away at runtime.

  • Permit fuzzing and sanitizer instrumentation of user binaries including the libc functions.

  • A complete testsuite that tests both the public interface and internal algorithms.

  • Fuzzing