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

[Volodymyr Sapsai via Phabricator via cfe-commits]

vsapsai added a comment.

In https://reviews.llvm.org/D45015#1105314, @rsmith wrote:

> That is: on old Darwin, we should not define `__cpp_aligned_allocation` (even in C++17), produce the "no aligned allocation support" warning in C++17 mode, and then not try to call the aligned allocation function. But if `-faligned-allocation` or `-fno-aligned-allocation` is specified explicitly, then the user knows what they're doing and they get no warning.


What when compiler has `__builtin_operator_new`, `__builtin_operator_delete`? If I build libc++ tests with recent Clang which has these builtins and run tests with libc++.dylib from old Darwin, there are no linkage errors. Should we define `__cpp_aligned_allocation` in this case?


Repository:
  rC Clang

https://reviews.llvm.org/D45015