From: Ted Kremenek <kremenek@apple.com>
Date: Thu, 14 Nov 2013 01:42:17 +0000 (+0000)
Subject: Suppress -Wunused-variable when initializer uses bridge casts for memory management.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1f64cfc5b3d164c3cdf397d82035a6a92e543443;p=clang

Suppress -Wunused-variable when initializer uses bridge casts for memory management.

Fixes <rdar://problem/15432770>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194647 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 9281951a81..a7b37c55e9 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1313,6 +1313,28 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
       }
     }
 
+    // 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.
+    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:
+          return false;
+        default:
+          break;
+        }
+      }
+    }
+
     // TODO: __attribute__((unused)) templates?
   }
   
diff --git a/test/SemaObjC/arc-bridged-cast.m b/test/SemaObjC/arc-bridged-cast.m
index 439d382116..6f5f3782d5 100644
--- a/test/SemaObjC/arc-bridged-cast.m
+++ b/test/SemaObjC/arc-bridged-cast.m
@@ -62,3 +62,15 @@ CFTypeRef fixitsWithSpace(id obj) {
   // CHECK: fix-it:"{{.*}}":{59:9-59:9}:"(__bridge CFTypeRef)"
   // CHECK: fix-it:"{{.*}}":{59:9-59:9}:" CFBridgingRetain"
 }
+
+// <rdar://problem/15432770>
+// Suppressed -Wunused-variable when the initializer is a bridge 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}}
+}
+#pragma clang diagnostic pop