Libc++ needs to know when aligned allocation is supported by clang, but is
otherwise unavailable at link time. Otherwise, libc++ will incorrectly end up
generating calls to `__builtin_operator_new`/`__builtin_operator_delete` with
alignment arguments.
This patch implements the following changes:
* The `__cpp_aligned_new` feature test macro to no longer be defined when
aligned allocation is otherwise enabled but unavailable.
* The Darwin driver no longer passes `-faligned-alloc-unavailable` when the
user manually specifies `-faligned-allocation` or `-fno-aligned-allocation`.
* Instead of a warning Clang now generates a hard error when an aligned
allocation or deallocation function is referenced but unavailable.
Patch by Eric Fiselier.
Reviewers: rsmith, vsapsai, erik.pilkington, ahatanak, dexonsmith
Reviewed By: rsmith
Subscribers: Quuxplusone, cfe-commits
Differential Revision: https://reviews.llvm.org/D45015
llvm-svn: 338934
Volodymyr Sapsai