[PATCH] D45015: [Preprocessor] Allow libc++ to detect when aligned allocation is unavailable.

[Eric Fiselier via Phabricator via cfe-commits]

EricWF added a comment.

In https://reviews.llvm.org/D45015#1121581, @ahatanak wrote:

> Could you elaborate on what kind of changes you are planning to make in libc++ after committing this patch?


Libc++ shouldn't actually need any changes if this current patch lands. Currently libc++ is in a "incorrect" state where
it generates calls to `__builtin_operator_new(size_t, align_val_t)` when `__cpp_aligned_new` is defined but when aligned new/delete
are actually unavailable.

If we change `__cpp_aligned_new` to no longer be defined when aligned new is unavailable, then libc++ will start doing the right thing.
See r328180 <https://github.com/llvm-mirror/libcxx/commit/a83128739983c83eaf1ba4c2bc0e3aa570082d15#diff-bd538fe75403fdbc4de9a1b97bc7c283> for the relevent commits which made these libc++ changes.


https://reviews.llvm.org/D45015