diff --git a/clang/lib/StaticAnalyzer/Checkers/UndefinedArraySubscriptChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/UndefinedArraySubscriptChecker.cpp
index be3a34f..176ee48 100644
--- a/clang/lib/StaticAnalyzer/Checkers/UndefinedArraySubscriptChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/UndefinedArraySubscriptChecker.cpp
@@ -34,18 +34,28 @@
 void 
 UndefinedArraySubscriptChecker::checkPreStmt(const ArraySubscriptExpr *A,
                                              CheckerContext &C) const {
-  if (C.getState()->getSVal(A->getIdx(), C.getLocationContext()).isUndef()) {
-    if (ExplodedNode *N = C.generateSink()) {
-      if (!BT)
-        BT.reset(new BuiltinBug("Array subscript is undefined"));
+  const Expr *Index = A->getIdx();
+  if (!C.getSVal(Index).isUndef())
+    return;
 
-      // Generate a report for this bug.
-      BugReport *R = new BugReport(*BT, BT->getName(), N);
-      R->addRange(A->getIdx()->getSourceRange());
-      bugreporter::trackNullOrUndefValue(N, A->getIdx(), *R);
-      C.emitReport(R);
-    }
-  }
+  // Sema generates anonymous array variables for copying array struct fields.
+  // Don't warn if we're in an implicitly-generated constructor.
+  const Decl *D = C.getLocationContext()->getDecl();
+  if (const CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(D))
+    if (Ctor->isImplicitlyDefined())
+      return;
+
+  ExplodedNode *N = C.generateSink();
+  if (!N)
+    return;
+  if (!BT)
+    BT.reset(new BuiltinBug("Array subscript is undefined"));
+
+  // Generate a report for this bug.
+  BugReport *R = new BugReport(*BT, BT->getName(), N);
+  R->addRange(A->getIdx()->getSourceRange());
+  bugreporter::trackNullOrUndefValue(N, A->getIdx(), *R);
+  C.emitReport(R);
 }
 
 void ento::registerUndefinedArraySubscriptChecker(CheckerManager &mgr) {