[gentoo-musl] Clang++ always defines _GNU_SOURCE

[Lei Zhang]

Hi,

I noticed that clang++ unconditionally defines _GNU_SOURCE on Linux,
even when I'm not including any headers in my code. Switching from
stdlibc++ to libc++ doesn't change this, either.

I understand that g++ does this because stdlibc++ heavily relies on
_GNU_SOURCE. But what is the reason for clang++ to do so when using
libc++? Does libc++ also rely on this macro to work on Linux?


Regards,
Lei