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llvm-libc: An ISO C-conformant Standard Library
===============================================

**llvm-libc library is not complete.  If you need a fully functioning libc right
now, you should continue to use your standard system libc.**

.. contents:: Table of Contents
  :depth: 4
  :local:

Introduction
============

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

- Fully compliant with current C standards (C17 and upcoming C2x) and POSIX.
- 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`__

.. __: https://github.com/llvm/llvm-project/tree/main/libc/fuzzing

Platform Support
================

Most development is currently targeting x86_64 and aarch64 on Linux.  Several
functions in llvm-libc have been tested on Windows.  The Fuchsia platform is
slowly replacing functions from its bundled libc with functions from llvm-libc.

ABI Compatibility
=================

llvm-libc is written to be ABI independent.  Interfaces are generated using
LLVM's tablegen, so supporting arbitrary ABIs is possible.  In it's initial
stages llvm-libc is not offering ABI stability in any form.

Other Interesting Documentation
===============================

.. toctree::

    build_system
    clang_tidy_checks
    entrypoints
    fuzzing
    ground_truth_specification
    header_generation
    implementation_standard
    api_test
    layering
    mechanics_of_public_api
    redirectors
    source_layout
    strings
    runtimes_build
    stdio
    math