[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



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@338934 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/Driver/ToolChains/Darwin.cpp b/lib/Driver/ToolChains/Darwin.cpp
index 9205dd52de..dc540688d2 100644
--- a/lib/Driver/ToolChains/Darwin.cpp
+++ b/lib/Driver/ToolChains/Darwin.cpp
@@ -2035,7 +2035,11 @@ bool Darwin::isAlignedAllocationUnavailable() const {
 void Darwin::addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
                                    llvm::opt::ArgStringList &CC1Args,
                                    Action::OffloadKind DeviceOffloadKind) const {
-  if (isAlignedAllocationUnavailable())
+  // Pass "-faligned-alloc-unavailable" only when the user hasn't manually
+  // enabled or disabled aligned allocations.
+  if (!DriverArgs.hasArgNoClaim(options::OPT_faligned_allocation,
+                                options::OPT_fno_aligned_allocation) &&
+      isAlignedAllocationUnavailable())
     CC1Args.push_back("-faligned-alloc-unavailable");
 }