Thread safety analysis: turn on checking within lock and unlock functions.
These checks are enabled with the -Wthread-safety-beta flag.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179046 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/AnalysisBasedWarnings.cpp b/lib/Sema/AnalysisBasedWarnings.cpp
index 00d3c47..1295339 100644
--- a/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1333,8 +1333,12 @@
       LocEndOfScope = FunEndLocation;
 
     PartialDiagnosticAt Warning(LocEndOfScope, S.PDiag(DiagID) << LockName);
-    PartialDiagnosticAt Note(LocLocked, S.PDiag(diag::note_locked_here));
-    Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
+    if (LocLocked.isValid()) {
+      PartialDiagnosticAt Note(LocLocked, S.PDiag(diag::note_locked_here));
+      Warnings.push_back(DelayedDiag(Warning, OptionalNotes(1, Note)));
+      return;
+    }
+    Warnings.push_back(DelayedDiag(Warning, OptionalNotes()));
   }