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, 2 deletions

diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index 5099867..4aecd08 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -489,9 +489,9 @@ CastsAwayConstness(Sema &Self, QualType SrcType, QualType DestType,
                    QualType *TheOffendingDestType = nullptr,
                    Qualifiers *CastAwayQualifiers = nullptr) {
   // If the only checking we care about is for Objective-C lifetime qualifiers,
-  // and we're not in ARC mode, there's nothing to check.
+  // and we're not in ObjC mode, there's nothing to check.
   if (!CheckCVR && CheckObjCLifetime && 
-      !Self.Context.getLangOpts().ObjCAutoRefCount)
+      !Self.Context.getLangOpts().ObjC1)
     return false;
     
   // Casting away constness is defined in C++ 5.2.11p8 with reference to