Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -360,6 +360,15 @@
   // semantic analysis and code generation.
   InitListExpr *getFullyStructuredList() const { return FullyStructuredList; }
 };
+
+bool IsContainedInNamespaceStd(Sema& S, CXXRecordDecl *R) {
+  for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext()); ND;
+       ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
+    if (S.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
+      return true;
+  }
+  return false;
+}
 } // end anonymous namespace
 
 ExprResult InitListChecker::PerformEmptyInit(Sema &SemaRef,
@@ -419,16 +428,8 @@
     if (CtorDecl->getMinRequiredArguments() == 0 &&
         CtorDecl->isExplicit() && R->getDeclName() &&
         SemaRef.SourceMgr.isInSystemHeader(CtorDecl->getLocation())) {
-
-
-      bool IsInStd = false;
-      for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext());
-           ND && !IsInStd; ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
-        if (SemaRef.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
-          IsInStd = true;
-      }
-
-      if (IsInStd && llvm::StringSwitch<bool>(R->getName()) 
+      if (IsContainedInNamespaceStd(SemaRef, R) &&
+          llvm::StringSwitch<bool>(R->getName())
               .Cases("basic_string", "deque", "forward_list", true)
               .Cases("list", "map", "multimap", "multiset", true)
               .Cases("priority_queue", "queue", "set", "stack", true)
@@ -3420,6 +3421,18 @@
   return CandidateSet.BestViableFunction(S, DeclLoc, Best);
 }
 
+static bool HasUninitializedFields(CXXRecordDecl* R) {
+  for (const auto *F : R->fields()) {
+    if (F->hasInClassInitializer() || F->isUnnamedBitfield())
+      continue;
+    if (CXXRecordDecl *FieldType = F->getType()->getAsCXXRecordDecl())
+      if (FieldType->hasDefaultConstructor())
+        continue;
+    return true;
+  }
+  return false;
+}
+
 /// \brief Attempt initialization by constructor (C++ [dcl.init]), which
 /// enumerates the constructors of the initialized entity and performs overload
 /// resolution to select the best.
@@ -3517,18 +3530,28 @@
   //   If a program calls for the default initialization of an object
   //   of a const-qualified type T, T shall be a class type with a
   //   user-provided default constructor.
+  CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
   if (Kind.getKind() == InitializationKind::IK_Default &&
-      Entity.getType().isConstQualified() &&
-      !cast<CXXConstructorDecl>(Best->Function)->isUserProvided()) {
-    if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
-      Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
-    return;
+      Entity.getType().isConstQualified() && !CtorDecl->isUserProvided()) {
+    // Some libstdc++ types use `MyType() = default;` which technically isn't
+    // a user-provided default constructor.  For types in system headers that
+    // are in namespace std and that only have fields that have default
+    // constructors, look the other way.  See also core issue 253.
+    CXXRecordDecl *R = CtorDecl->getParent();
+    bool AllowConstDefaultInit =
+        S.SourceMgr.isInSystemHeader(CtorDecl->getLocation()) &&
+        CtorDecl->isDefaulted() && IsContainedInNamespaceStd(S, R) &&
+        !HasUninitializedFields(R);
+    if (!AllowConstDefaultInit) {
+      if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
+        Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
+      return;
+    }
   }
 
   // C++11 [over.match.list]p1:
   //   In copy-list-initialization, if an explicit constructor is chosen, the
   //   initializer is ill-formed.
-  CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
   if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
     Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
     return;
Index: test/SemaCXX/cxx0x-const-defaulted-ctor-system-header.cpp
===================================================================
--- test/SemaCXX/cxx0x-const-defaulted-ctor-system-header.cpp
+++ test/SemaCXX/cxx0x-const-defaulted-ctor-system-header.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+// libstdc++5.3 uses `= default` for its container constructors.
+#ifdef BE_THE_HEADER
+#pragma clang system_header
+namespace std {
+template <class T>
+struct vector {
+  vector() = default;
+};
+}
+#else
+
+#define BE_THE_HEADER
+#include __FILE__
+const std::vector<int> empty_vector; // no diagnostic
+#endif