Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -5359,6 +5359,8 @@
   InGroup<DiagGroup<"void-ptr-dereference">>;
 def warn_indirection_through_null : Warning<
   "indirection of non-volatile null pointer will be deleted, not trap">, InGroup<NullDereference>;
+def warn_binding_null_to_reference : Warning<
+  "binding null pointer to reference has undefined behavior">, InGroup<NullDereference>;
 def note_indirection_through_null : Note<
   "consider using __builtin_trap() or qualifying pointer with 'volatile'">;
 def warn_pointer_indirection_from_incompatible_type : Warning<
Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -3510,6 +3510,23 @@
   return CandidateSet.BestViableFunction(S, DeclLoc, Best);
 }
 
+static void CheckForNullPointerDereference(Sema &S, Expr *E) {
+  // Check to see if we are dereferencing a null pointer.  If so,
+  // and if not volatile-qualified, this is undefined behavior that the
+  // optimizer will delete, so warn about it.  People sometimes try to use this
+  // to get a deterministic trap and are surprised by clang's behavior.  This
+  // only handles the pattern "*null", which is a very syntactic check.
+  if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
+    if (UO->getOpcode() == UO_Deref &&
+        UO->getSubExpr()->IgnoreParenCasts()->
+          isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull) &&
+        !UO->getType().isVolatileQualified()) {
+    S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
+                          S.PDiag(diag::warn_binding_null_to_reference)
+                            << UO->getSubExpr()->getSourceRange());
+  }
+}
+
 /// \brief Attempt initialization by constructor (C++ [dcl.init]), which
 /// enumerates the constructors of the initialized entity and performs overload
 /// resolution to select the best.
@@ -3629,6 +3646,10 @@
     return;
   }
 
+  for (Expr *Arg : Args) {
+    CheckForNullPointerDereference(S, Arg);
+  }
+
   // Add the constructor initialization step. Any cv-qualification conversion is
   // subsumed by the initialization.
   bool HadMultipleCandidates = (CandidateSet.size() > 1);
Index: test/CXX/expr/expr.prim/expr.prim.lambda/p5.cpp
===================================================================
--- test/CXX/expr/expr.prim/expr.prim.lambda/p5.cpp
+++ test/CXX/expr/expr.prim/expr.prim.lambda/p5.cpp
@@ -11,7 +11,7 @@
 
 template<typename T>
 struct bogus_override_if_virtual : public T {
-  bogus_override_if_virtual() : T(*(T*)0) { }
+  bogus_override_if_virtual() : T(*(T*)0) { } // expected-warning {{binding null pointer to reference has undefined behavior}}
   int operator()() const;
 };
 
@@ -36,7 +36,7 @@
   lv(); // expected-error{{no matching function for call to object of type}}
   mlv(); // expected-error{{no matching function for call to object of type}}
 
-  bogus_override_if_virtual<decltype(l)> bogus;
+  bogus_override_if_virtual<decltype(l)> bogus; // expected-note{{in instantiation of member function 'bogus_override_if_virtual<(lambda}}
 }
 
 // Core issue 974: default arguments (8.3.6) may be specified in the
Index: test/Parser/cxx-casting.cpp
===================================================================
--- test/Parser/cxx-casting.cpp
+++ test/Parser/cxx-casting.cpp
@@ -37,7 +37,7 @@
 // This was being incorrectly tentatively parsed.
 namespace test1 {
   template <class T> class A {}; // expected-note 2{{here}}
-  void foo() { A<int>(*(A<int>*)0); }
+  void foo() { A<int>(*(A<int>*)0); } // expected-warning {{binding null pointer to reference has undefined behavior}}
 }
 
 typedef char* c;