LLVM libc#

The $dir_pw_third_party/llvm_libc/ module provides various helpers to optionally use LLVM libc with pw_libc.

Using upstream LLVM libc#

If you want to use LLVM libc, you must do the following:

Submodule#

Add LLVM libc to your workspace with the following command.

$ git submodule add https://llvm.googlesource.com/llvm-project/libc \
> third_party/llvm_libc/src

Note

This Git repository is maintained by Google and is a slice of upstream LLVM including only the libc subdirectory.

GN#

Set the GN var dir_pw_third_party_llvm_libc to the location of the LLVM libc source. If you used the command above, this will be //third_party/llvm_libc/src.

This can be set in your args.gn or .gn file like:
```
dir_pw_third_party_llvm_libc = "//third_party/llvm_libc_src"
```

Status#

Currently, the llvm-libc integration in pw_libc only provides a pw_libc.a and is not suitable as a full replacement for libc. Not all functions used by projects are currently available to use from llvm-libc. Moreover, headers are provided from the sysroot libc. Startup files are also provided from the sysroot.

In the future, we hope to be able to fully replace the sysroot libc.