r194663 - Refine -Wunused-variable to only suppress warning for __bridge_transfer, not all bridge casts.

[Ted Kremenek]

Author: kremenek
Date: Wed Nov 13 22:27:00 2013
New Revision: 194663

URL: http://llvm.org/viewvc/llvm-project?rev=194663&view=rev
Log:
Refine -Wunused-variable to only suppress warning for __bridge_transfer, not all bridge casts.

Also refine test case to capture the intention of this suppression.  Essentially
some developers use __bridge_transfer as if it were a safe CFRelease.

Modified:
    cfe/trunk/lib/Sema/SemaDecl.cpp
    cfe/trunk/test/SemaObjC/arc-bridged-cast.m

Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=194663&r1=194662&r2=194663&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDecl.cpp Wed Nov 13 22:27:00 2013
@@ -1313,26 +1313,16 @@ static bool ShouldDiagnoseUnusedDecl(con
       }
     }
 
-    // Under ARC, bridged casts can have side-effects on memory
-    // management semantics.  Some users assign a bridged
-    // value to a temporary to adjust reference counts.
+    // Under ARC, some users use __bridge_transfer to automate memory
+    // reclamation of objects that were referenced via C pointers.
     const Expr *Init = VD->getInit();
     if (Init) {
       if (const ExprWithCleanups *EC = dyn_cast<ExprWithCleanups>(Init))
         Init = EC->getSubExpr();
       Init = Init->IgnoreParens();
-      if (const ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(Init)) {
-        switch (IC->getCastKind()) {
-        case CK_ARCProduceObject:
-        case CK_ARCConsumeObject:
-        case CK_ARCReclaimReturnedObject:
-        case CK_ARCExtendBlockObject:
-        case CK_CopyAndAutoreleaseBlockObject:
+      if (const ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(Init))
+        if (IC->getCastKind() == CK_ARCConsumeObject)
           return false;
-        default:
-          break;
-        }
-      }
     }
 
     // TODO: __attribute__((unused)) templates?

Modified: cfe/trunk/test/SemaObjC/arc-bridged-cast.m
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjC/arc-bridged-cast.m?rev=194663&r1=194662&r2=194663&view=diff
==============================================================================
--- cfe/trunk/test/SemaObjC/arc-bridged-cast.m (original)
+++ cfe/trunk/test/SemaObjC/arc-bridged-cast.m Wed Nov 13 22:27:00 2013
@@ -64,13 +64,12 @@ CFTypeRef fixitsWithSpace(id obj) {
 }
 
 // <rdar://problem/15432770>
-// Suppressed -Wunused-variable when the initializer is a bridge cast.
+// Suppressed -Wunused-variable when the initializer is a __bridge_transfer cast.
 #pragma clang diagnostic push
 #pragma clang diagnostic warning "-Wunused-variable"
-void rdar15432770() {
-  void (^block1)() = ^ { };
-  void *ptr = (__bridge_retained void *)(block1);
-  void (^block2)() = (__bridge_transfer void(^)())ptr; // no-warning
-  int x = 1; // expected-warning {{unused variable}}
+void rdar15432770_ptr_release(const void *ptr) {
+  void (^block)() = (__bridge_transfer void(^)())ptr; // no-warning
+  // Test that warning is active.
+  int x = 1; // expected-warning {{unused}}
 }
 #pragma clang diagnostic pop