Index: cfe/trunk/lib/StaticAnalyzer/Checkers/UndefinedAssignmentChecker.cpp
===================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/UndefinedAssignmentChecker.cpp
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/UndefinedAssignmentChecker.cpp
@@ -51,17 +51,20 @@
   if (!N)
     return;
 
-  const char *str = "Assigned value is garbage or undefined";
-
+  static const char *const DefaultMsg =
+      "Assigned value is garbage or undefined";
   if (!BT)
-    BT.reset(new BuiltinBug(this, str));
+    BT.reset(new BuiltinBug(this, DefaultMsg));
 
   // Generate a report for this bug.
+  llvm::SmallString<128> Str;
+  llvm::raw_svector_ostream OS(Str);
+
   const Expr *ex = nullptr;
 
   while (StoreE) {
     if (const UnaryOperator *U = dyn_cast<UnaryOperator>(StoreE)) {
-      str = "The expression is an uninitialized value. "
+      OS << "The expression is an uninitialized value. "
             "The computed value will also be garbage";
 
       ex = U->getSubExpr();
@@ -71,7 +74,7 @@
     if (const BinaryOperator *B = dyn_cast<BinaryOperator>(StoreE)) {
       if (B->isCompoundAssignmentOp()) {
         if (C.getSVal(B->getLHS()).isUndef()) {
-          str = "The left expression of the compound assignment is an "
+          OS << "The left expression of the compound assignment is an "
                 "uninitialized value. The computed value will also be garbage";
           ex = B->getLHS();
           break;
@@ -87,10 +90,26 @@
       ex = VD->getInit();
     }
 
+    if (const auto *CD =
+            dyn_cast<CXXConstructorDecl>(C.getStackFrame()->getDecl())) {
+      if (CD->isImplicit()) {
+        for (auto I : CD->inits()) {
+          if (I->getInit()->IgnoreImpCasts() == StoreE) {
+            OS << "Value assigned to field '" << I->getMember()->getName()
+               << "' in implicit constructor is garbage or undefined";
+            break;
+          }
+        }
+      }
+    }
+
     break;
   }
 
-  auto R = llvm::make_unique<BugReport>(*BT, str, N);
+  if (OS.str().empty())
+    OS << DefaultMsg;
+
+  auto R = llvm::make_unique<BugReport>(*BT, OS.str(), N);
   if (ex) {
     R->addRange(ex->getSourceRange());
     bugreporter::trackNullOrUndefValue(N, ex, *R);
Index: cfe/trunk/test/Analysis/implicit-ctor-undef-value.cpp
===================================================================
--- cfe/trunk/test/Analysis/implicit-ctor-undef-value.cpp
+++ cfe/trunk/test/Analysis/implicit-ctor-undef-value.cpp
@@ -0,0 +1,75 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-output=text -verify %s
+
+namespace implicit_constructor {
+struct S {
+public:
+  S() {}
+  S(const S &) {}
+};
+
+// Warning is in a weird position because the body of the constructor is
+// missing. Specify which field is being assigned.
+class C { // expected-warning{{Value assigned to field 'y' in implicit constructor is garbage or undefined}}
+          // expected-note@-1{{Value assigned to field 'y' in implicit constructor is garbage or undefined}}
+  int x, y;
+  S s;
+
+public:
+  C(): x(0) {}
+};
+
+void test() {
+  C c1;
+  C c2(c1); // expected-note{{Calling implicit copy constructor for 'C'}}
+}
+} // end namespace implicit_constructor
+
+
+namespace explicit_constructor {
+class C {
+  int x, y;
+
+public:
+  C(): x(0) {}
+  // It is not necessary to specify which field is being assigned to.
+  C(const C &c):
+    x(c.x),
+    y(c.y) // expected-warning{{Assigned value is garbage or undefined}}
+           // expected-note@-1{{Assigned value is garbage or undefined}}
+  {}
+};
+
+void test() {
+  C c1;
+  C c2(c1); // expected-note{{Calling copy constructor for 'C'}}
+}
+} // end namespace explicit_constructor
+
+
+namespace base_class_constructor {
+struct S {
+public:
+  S() {}
+  S(const S &) {}
+};
+
+class C { // expected-warning{{Value assigned to field 'y' in implicit constructor is garbage or undefined}}
+          // expected-note@-1{{Value assigned to field 'y' in implicit constructor is garbage or undefined}}
+  int x, y;
+  S s;
+
+public:
+  C(): x(0) {}
+};
+
+class D: public C {
+public:
+  D(): C() {}
+};
+
+void test() {
+  D d1;
+  D d2(d1); // expected-note   {{Calling implicit copy constructor for 'D'}}
+            // expected-note@-1{{Calling implicit copy constructor for 'C'}}
+}
+} // end namespace base_class_constructor