New ObjC warning: circular containers.

This commit adds new warning to prevent user from creating 'circular containers'.

Mutable collections from NSFoundation allows user to add collection to itself, e.g.: 

NSMutableArray *a = [NSMutableArray new]; 
[a addObject:a]; 

The code above leads to really weird behaviour (crashes, 'endless' recursion) and 
retain cycles (collection retains itself) if ARC enabled.

Patch checks the following collections: 
  - NSMutableArray, 
  - NSMutableDictionary, 
  - NSMutableSet, 
  - NSMutableOrderedSet, 
  - NSCountedSet. 

llvm-svn: 231265

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index ebe6cbb45d5..7d7d3ecc3de 100644
--- a/clang/lib/Sema/SemaExprObjC.cpp
+++ b/clang/lib/Sema/SemaExprObjC.cpp
@@ -2799,7 +2799,9 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
       }
     }
   }
-  
+
+  CheckObjCCircularContainer(Result);
+
   return MaybeBindToTemporary(Result);
 }