[PATCH] D73245: Depend stddef.h to provide max_align_t for C++11 and provide better fallback in <new>

[Joerg Sonnenberger via Phabricator via llvm-commits]

joerg added a comment.

libc++ has no idea what a correct max_align_t is. The internal definition works due to historic requirements that all three fundamental types are supported for new/delete, but we don't have any such guarantees for every other context. A correctly implemented stddef.h does not provide max_align_t in C++03 mode, since that would pollute the global namespace. This means that libc++ currently has two failure modes: on NetBSD, it outright tries to use a non-existing symbol. On other platforms it silently defines max_align_t in a way that can be subtle wrong.

I should add that e.g. libstdc++ doesn't provide it either, so at least somewhat portable C++03 code can not depend on the presence anyway.


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https://reviews.llvm.org/D73245