[llvm-branch-commits] [libcxx] release/18.x: [libc++] Simplify the implementation of <stddef.h> (#86843) (PR #87374)

[Nico Weber via llvm-branch-commits]

nico wrote:

As mentioned on #86843, this breaks using `-pedantic` in code that includes libc++ headers. Since this got cherry-picked (…why? doesn't seem urgent?), we also must cherry-pick #88214.

https://github.com/llvm/llvm-project/pull/87374