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

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

1 files changed, 3 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index a1168fa34d5..22f13280c38 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1741,9 +1741,9 @@ static void diagnoseUnavailableAlignedAllocation(const FunctionDecl &FD,
     StringRef OSName = AvailabilityAttr::getPlatformNameSourceSpelling(
         S.getASTContext().getTargetInfo().getPlatformName());
 
-    S.Diag(Loc, diag::warn_aligned_allocation_unavailable)
-         << IsDelete << FD.getType().getAsString() << OSName
-         << alignedAllocMinVersion(T.getOS()).getAsString();
+    S.Diag(Loc, diag::err_aligned_allocation_unavailable)
+        << IsDelete << FD.getType().getAsString() << OSName
+        << alignedAllocMinVersion(T.getOS()).getAsString();
     S.Diag(Loc, diag::note_silence_unligned_allocation_unavailable);
   }
 }