85 lines
3.0 KiB
ReStructuredText
85 lines
3.0 KiB
ReStructuredText
========================================================
|
|
llvm-libc: An ISO C-conformant Standard Library for LLVM
|
|
========================================================
|
|
|
|
**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:
|
|
|
|
Goals
|
|
=====
|
|
|
|
- C17 and upwards conformant.
|
|
- A modular libc with individual pieces implemented in the "as a
|
|
library" philosophy of the LLVM project.
|
|
- Ability to layer this libc over the system libc if possible and desired
|
|
for a platform.
|
|
- Provide POSIX extensions on POSIX compliant platforms.
|
|
- Provide system-specific extensions as appropriate. For example,
|
|
provide the Linux API on Linux.
|
|
- Designed and developed from the start to work with LLVM tooling, fuzz testing
|
|
and sanitizer-supported testing.
|
|
- Use source based implementations as far possible rather than
|
|
assembly. Will try to *fix* the compiler rather than use assembly
|
|
language workarounds.
|
|
- Extensive unit testing and standards conformance testing.
|
|
|
|
Why a new C Standard Library?
|
|
=============================
|
|
|
|
Implementing a libc is no small task and is not be taken lightly. A
|
|
natural question to ask is, "why a new implementation of the C
|
|
standard library?" Some of the major reasons are as follows:
|
|
|
|
- Rather than being built as a single monolithic codebase, llvm-libc is designed
|
|
from the beginning to enable picking and choosing pieces. This allows using
|
|
it as a minimum overlay for e.g. faster math functions than might be
|
|
available on the system library. This is useful where an application may
|
|
need to access improved CPU support over what's available on the system,
|
|
or may need guarantees in performance across different installs.
|
|
- Explicit support for building llvm-libc and code with sanitizer compiler
|
|
options.
|
|
- `Fuzzing`__
|
|
- Be useful for research and review. By avoiding assembly language, using C++
|
|
iterators, RAII and templates, llvm-libc aims to have clearly
|
|
readable code and to improve the compiler as needed to ensure that optimal
|
|
assembly is emitted.
|
|
- Enable fully static compiles.
|
|
|
|
.. __: 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
|
|
integration_test
|
|
layering
|
|
mechanics_of_public_api
|
|
redirectors
|
|
source_layout
|