Define weak and __weak to mean ARC-style weak references, even in MRC.

Previously, __weak was silently accepted and ignored in MRC mode.
That makes this a potentially source-breaking change that we have to
roll out cautiously.  Accordingly, for the time being, actual support
for __weak references in MRC is experimental, and the compiler will
reject attempts to actually form such references.  The intent is to
eventually enable the feature by default in all non-GC modes.
(It is, of course, incompatible with ObjC GC's interpretation of
__weak.)

If you like, you can enable this feature with
  -Xclang -fobjc-weak
but like any -Xclang option, this option may be removed at any point,
e.g. if/when it is eventually enabled by default.

This patch also enables the use of the ARC __unsafe_unretained qualifier
in MRC.  Unlike __weak, this is being enabled immediately.  Since
variables are essentially __unsafe_unretained by default in MRC,
the only practical uses are (1) communication and (2) changing the
default behavior of by-value block capture.

As an implementation matter, this means that the ObjC ownership
qualifiers may appear in any ObjC language mode, and so this patch
removes a number of checks for getLangOpts().ObjCAutoRefCount
that were guarding the processing of these qualifiers.  I don't
expect this to be a significant drain on performance; it may even
be faster to just check for these qualifiers directly on a type
(since it's probably in a register anyway) than to do N dependent
loads to grab the LangOptions.

rdar://9674298

llvm-svn: 251041

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/ARCMigrate/ARCMT.cpp b/clang/lib/ARCMigrate/ARCMT.cpp
index 7eb01fb93db..82d8acd87e8 100644
--- a/clang/lib/ARCMigrate/ARCMT.cpp
+++ b/clang/lib/ARCMigrate/ARCMT.cpp
@@ -206,7 +206,8 @@ createInvocationForMigration(CompilerInvocation &origCI,
   WarnOpts.push_back("error=arc-unsafe-retained-assign");
   CInvok->getDiagnosticOpts().Warnings = std::move(WarnOpts);
 
-  CInvok->getLangOpts()->ObjCARCWeak = HasARCRuntime(origCI);
+  CInvok->getLangOpts()->ObjCWeakRuntime = HasARCRuntime(origCI);
+  CInvok->getLangOpts()->ObjCWeak = CInvok->getLangOpts()->ObjCWeakRuntime;
 
   return CInvok.release();
 }