Warn if a __weak variable is initialized with an Objective-C object literal.

Such variables may immediately become nil or may have unpredictable
behavior.

Fixes <rdar://problem/12569201>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170763 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 1 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 96e911d17b..9ca7782164 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -6780,13 +6780,30 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
     // we do not warn to warn spuriously when 'x' and 'y' are on separate
     // paths through the function. This should be revisited if
     // -Wrepeated-use-of-weak is made flow-sensitive.
-    if (VDecl->getType().getObjCLifetime() == Qualifiers::OCL_Strong) {
+    Qualifiers::ObjCLifetime Lifetime = VDecl->getType().getObjCLifetime();
+    if (Lifetime == Qualifiers::OCL_Strong) {
       DiagnosticsEngine::Level Level =
         Diags.getDiagnosticLevel(diag::warn_arc_repeated_use_of_weak,
                                  Init->getLocStart());
       if (Level != DiagnosticsEngine::Ignored)
         getCurFunction()->markSafeWeakUse(Init);
     }
+    else if (Lifetime == Qualifiers::OCL_Weak) {
+      // Check if we are initializing a __weak variable with an Objective-C
+      // object literal.  Since there is no other strong reference, the
+      // __weak variable may immediately become nil.
+      Expr *InitSansParen = Init->IgnoreParenImpCasts();
+      switch (InitSansParen->getStmtClass()) {
+        default: break;
+        case Stmt::BlockExprClass:
+        case Stmt::ObjCArrayLiteralClass:
+        case Stmt::ObjCDictionaryLiteralClass:
+        case Stmt::ObjCStringLiteralClass:
+          Diag(VDecl->getLocation(), diag::warn_attribute_weak_objc_literal)
+            << Init->getSourceRange();
+          break;
+      }
+    }
   }
 
   Init = MaybeCreateExprWithCleanups(Init);