[PATCH] D40141: [ObjC][ARC] Honor noescape attribute for -Warc-retain-cycles

[Alex Lorenz via Phabricator via cfe-commits]

arphaman created this revision.

This patch ensures that -Warc-retain-cycles doesn't warn about captures in blocks that are passed into parameters that have a `noescape` attribute.


Repository:
  rL LLVM

https://reviews.llvm.org/D40141

Files:
  lib/Sema/SemaChecking.cpp
  test/SemaObjC/warn-retain-cycle.m


Index: test/SemaObjC/warn-retain-cycle.m
===================================================================
--- test/SemaObjC/warn-retain-cycle.m
+++ test/SemaObjC/warn-retain-cycle.m
@@ -198,3 +198,15 @@
    };
 
 }
+
+typedef void (^a_block_t)(void);
+
+ at interface HonorNoEscape
+- (void)addStuffUsingBlock:(__attribute__((noescape)) a_block_t)block;
+ at end
+
+void testNoEscape(HonorNoEscape *obj) {
+  [obj addStuffUsingBlock:^{
+    (void)obj; // ok.
+  }];
+}
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -11652,9 +11652,14 @@
   }
 
   // Check whether the receiver is captured by any of the arguments.
-  for (unsigned i = 0, e = msg->getNumArgs(); i != e; ++i)
+  const ObjCMethodDecl *MD = msg->getMethodDecl();
+  for (unsigned i = 0, e = msg->getNumArgs(); i != e; ++i) {
+    // noescape blocks should not be retained by the method.
+    if (MD && MD->parameters()[i]->hasAttr<NoEscapeAttr>())
+      continue;
     if (Expr *capturer = findCapturingExpr(*this, msg->getArg(i), owner))
       return diagnoseRetainCycle(*this, capturer, owner);
+  }
 }
 
 /// Check a property assign to see if it's likely to cause a retain cycle.


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