[PATCH] D71082: Allow system header to provide their own implementation of some builtin

[serge via Phabricator via cfe-commits]

serge-sans-paille added a comment.

In D71082#1822925 <https://reviews.llvm.org/D71082#1822925>, @akhuang wrote:

> This caused a linker error in chromium:
>
>   ld.lld: error: undefined symbol: __warn_memset_zero_len
>
>
> Apparently now that the glibc memset is being used, __warn_memset_zero_len gets called from libc++ code (https://github.com/llvm/llvm-project/blob/b72a8c65e4e34779b6bc9e466203f553f5294486/libcxx/include/__bit_reference#L371).


I can reproduce the behavior locally, but without the linker error. On my system, (RHEL7.5) libc_nonshared.a provides that symbol. I've checked on other systems and it's available in that library on Ubuntu 14.04.

On other systems, this symbol is not available, neither in the lib nor in the header, because the associated gcc version is high enough. Can you try to reproduce with:

  clang -S -O2 -fgnuc-version=5.0 t.cpp  -o - -stdlib=libc++ -D_FORTIFY_SOURCE=1 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71082/new/

https://reviews.llvm.org/D71082