4 files changed, 19 insertions, 1 deletions
diff --git a/lib/Checker/CMakeLists.txt b/lib/Checker/CMakeLists.txt
index f93fcc91fd..e69808e48e 100644
--- a/lib/Checker/CMakeLists.txt
+++ b/lib/Checker/CMakeLists.txt
@@ -18,6 +18,7 @@ add_clang_library(clangChecker
   BugReporterVisitors.cpp
   BuiltinFunctionChecker.cpp
   CFRefCount.cpp
+  CStringChecker.cpp
   CallAndMessageChecker.cpp
   CastSizeChecker.cpp
   CastToStructChecker.cpp
@@ -29,7 +30,6 @@ add_clang_library(clangChecker
   Checker.cpp
   CheckerHelpers.cpp
   CocoaConventions.cpp
-  CStringChecker.cpp
   DereferenceChecker.cpp
   DivZeroChecker.cpp
   Environment.cpp
@@ -54,6 +54,7 @@ add_clang_library(clangChecker
   NSErrorChecker.cpp
   NoReturnFunctionChecker.cpp
   OSAtomicChecker.cpp
+  ObjCAtSyncChecker.cpp
   ObjCUnusedIVarsChecker.cpp
   PathDiagnostic.cpp
   PlistDiagnostics.cpp
diff --git a/lib/Checker/GRExprEngine.cpp b/lib/Checker/GRExprEngine.cpp
index 851f34e43b..160ee46d30 100644
--- a/lib/Checker/GRExprEngine.cpp
+++ b/lib/Checker/GRExprEngine.cpp
@@ -373,6 +373,7 @@ static void RegisterInternalChecks(GRExprEngine &Eng) {
   RegisterUndefCapturedBlockVarChecker(Eng);
   RegisterUndefResultChecker(Eng);
   RegisterStackAddrLeakChecker(Eng);
+  RegisterObjCAtSyncChecker(Eng);
 
   // This is not a checker yet.
   RegisterNoReturnFunctionChecker(Eng);
diff --git a/lib/Checker/GRExprEngineInternalChecks.h b/lib/Checker/GRExprEngineInternalChecks.h
index f91a759b32..740a914cfc 100644
--- a/lib/Checker/GRExprEngineInternalChecks.h
+++ b/lib/Checker/GRExprEngineInternalChecks.h
@@ -31,6 +31,7 @@ void RegisterDereferenceChecker(GRExprEngine &Eng);
 void RegisterDivZeroChecker(GRExprEngine &Eng);
 void RegisterFixedAddressChecker(GRExprEngine &Eng);
 void RegisterNoReturnFunctionChecker(GRExprEngine &Eng);
+void RegisterObjCAtSyncChecker(GRExprEngine &Eng);
 void RegisterPointerArithChecker(GRExprEngine &Eng);
 void RegisterPointerSubChecker(GRExprEngine &Eng);
 void RegisterReturnPointerRangeChecker(GRExprEngine &Eng);
diff --git a/test/Analysis/misc-ps.m b/test/Analysis/misc-ps.m
index 1d6e6f6153..09f397041f 100644
--- a/test/Analysis/misc-ps.m
+++ b/test/Analysis/misc-ps.m
@@ -1094,4 +1094,19 @@ void test_enum_cases_positive(enum Cases C) {
   *p = 0xDEADBEEF; // expected-warning{{Dereference of null pointer}}
 }
 
+// <rdar://problem/6351970> rule request: warn if synchronization mutex can be nil
+void rdar6351970() {
+  id x = 0;
+  @synchronized(x) {} // expected-warning{{Nil value used as mutex for @synchronized() (no synchronization will occur)}}
+}
+
+void rdar6351970_b(id x) {
+  if (!x)
+    @synchronized(x) {} // expected-warning{{Nil value used as mutex for @synchronized() (no synchronization will occur)}}
+}
+
+void rdar6351970_c() {
+  id x;
+  @synchronized(x) {} // expected-warning{{Uninitialized value used as mutex for @synchronized}}
+}