Change RetainCountChecker to eagerly "escape" retained objects when they are

assigned to a struct.  This is fallout from inlining results, which expose
far more patterns where people stuff CF objects into structs and pass them
around (and we can reason about it).  The problem is that we don't have
a general way to detect when values have escaped, so as an intermediate step
we need to eagerly prune out such tracking.

Fixes <rdar://problem/11104566>.

llvm-svn: 153489

clang/lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp

@@ -3341,6 +3341,12 @@ void RetainCountChecker::checkBind(SVal loc, SVal val, const Stmt *S,
       // the binding).
       escapes = (state == (state->bindLoc(*regionLoc, val)));
     }
+    if (!escapes) {
+      // Case 4: We do not currently model what happens when a symbol is
+      // assigned to a struct field, so be conservative here and let the symbol
+      // go. TODO: This could definitely be improved upon.
+      escapes = !isa<VarRegion>(regionLoc->getRegion());
+    }
   }
 
   // If our store can represent the binding and we aren't storing to something

clang/test/Analysis/retain-release-region-store.m

@@ -100,6 +100,10 @@ struct foo {
   NSDate* f;
 };
 
+// FIXME: We should be warning about a use-after-free here, but we
+// temporarily "escape" retain counted objects stored to structs very eagerly
+// until we can properly tell whether they have escaped via a return value
+// or not.
 CFAbsoluteTime f4() {
   struct foo x;
   
@@ -110,7 +114,8 @@ CFAbsoluteTime f4() {
   CFDateGetAbsoluteTime(date); // no-warning
   x.f = (NSDate*) date;  
   [((NSDate*) date) release];
-  t = CFDateGetAbsoluteTime(date);   // expected-warning{{Reference-counted object is used after it is released}}
+  // FIXME: the following line should warn.
+  t = CFDateGetAbsoluteTime(date);   // no-warning
   return t;
 }
 

clang/test/Analysis/retain-release.m

@@ -1667,6 +1667,29 @@ void rdar_10824732() {
   }
 }
 
+//===----------------------------------------------------------------------===//
+// Test returning allocated memory in a struct.
+// 
+// We currently don't have a general way to track pointers that "escape".
+// Here we test that RetainCountChecker doesn't get excited about returning
+// allocated CF objects in struct fields.
+//===----------------------------------------------------------------------===//
+void *malloc(size_t);
+struct rdar11104566 { CFStringRef myStr; };
+struct rdar11104566 test_rdar11104566() {
+  CFStringRef cf = CFStringCreateWithCString( ((CFAllocatorRef)0), "test", kCFStringEncodingUTF8 ); // no-warning
+  struct rdar11104566 V;
+  V.myStr = cf;
+  return V; // no-warning
+}
+
+struct rdar11104566 *test_2_rdar11104566() {
+  CFStringRef cf = CFStringCreateWithCString( ((CFAllocatorRef)0), "test", kCFStringEncodingUTF8 ); // no-warning
+  struct rdar11104566 *V = (struct rdar11104566 *) malloc(sizeof(*V));
+  V->myStr = cf;
+  return V; // no-warning
+}
+
 //===----------------------------------------------------------------------===//
 // ObjC literals support.
 //===----------------------------------------------------------------------===//