[llvm-branch-commits] [clang] release/18.x: [Headers] Don't declare unreachable() from stddef.h in C++ (#86748) (PR #87696)

[Ian Anderson via llvm-branch-commits]

ian-twilightcoder wrote:

Nominating for backport because this is a C++ regression that was caused by https://reviews.llvm.org/D157757

https://github.com/llvm/llvm-project/pull/87696