Index: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6351,6 +6351,15 @@
   "cannot use '%0' with exceptions disabled">;
 def err_objc_exceptions_disabled : Error<
   "cannot use '%0' with Objective-C exceptions disabled">;
+def warn_throw_in_noexcept_func 
+    : Warning<"%0 has a non-throwing exception specification but can still "
+      "throw, resulting in unexpected program termination">,
+      InGroup<Exceptions>;
+def note_throw_in_dtor 
+    : Note<"destructor or deallocator has a (possibly implicit) non-throwing "
+      "excepton specification">;
+def note_throw_in_function 
+    : Note<"non-throwing function declare here">;
 def err_seh_try_outside_functions : Error<
   "cannot use SEH '__try' in blocks, captured regions, or Obj-C method decls">;
 def err_mixing_cxx_try_seh_try : Error<
Index: cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
===================================================================
--- cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
+++ cfe/trunk/lib/Sema/AnalysisBasedWarnings.cpp
@@ -279,6 +279,150 @@
 }
 
 //===----------------------------------------------------------------------===//
+// Check for throw in a non-throwing function.
+//===----------------------------------------------------------------------===//
+enum ThrowState {
+  FoundNoPathForThrow,
+  FoundPathForThrow,
+  FoundPathWithNoThrowOutFunction,
+};
+
+static bool isThrowCaught(const CXXThrowExpr *Throw,
+                          const CXXCatchStmt *Catch) {
+  const Type *ThrowType = nullptr;
+  if (Throw->getSubExpr())
+    ThrowType = Throw->getSubExpr()->getType().getTypePtrOrNull();
+  if (!ThrowType)
+    return false;
+  const Type *CaughtType = Catch->getCaughtType().getTypePtrOrNull();
+  if (!CaughtType)
+    return true;
+  if (ThrowType->isReferenceType())
+    ThrowType = ThrowType->castAs<ReferenceType>()
+                    ->getPointeeType()
+                    ->getUnqualifiedDesugaredType();
+  if (CaughtType->isReferenceType())
+    CaughtType = CaughtType->castAs<ReferenceType>()
+                     ->getPointeeType()
+                     ->getUnqualifiedDesugaredType();
+  if (CaughtType == ThrowType)
+    return true;
+  const CXXRecordDecl *CaughtAsRecordType =
+      CaughtType->getPointeeCXXRecordDecl();
+  const CXXRecordDecl *ThrowTypeAsRecordType = ThrowType->getAsCXXRecordDecl();
+  if (CaughtAsRecordType && ThrowTypeAsRecordType)
+    return ThrowTypeAsRecordType->isDerivedFrom(CaughtAsRecordType);
+  return false;
+}
+
+static bool isThrowCaughtByHandlers(const CXXThrowExpr *CE,
+                                    const CXXTryStmt *TryStmt) {
+  for (unsigned H = 0, E = TryStmt->getNumHandlers(); H < E; ++H) {
+    if (isThrowCaught(CE, TryStmt->getHandler(H)))
+      return true;
+  }
+  return false;
+}
+
+static bool doesThrowEscapePath(CFGBlock Block, SourceLocation &OpLoc) {
+  for (const auto &B : Block) {
+    if (B.getKind() != CFGElement::Statement)
+      continue;
+    const auto *CE = dyn_cast<CXXThrowExpr>(B.getAs<CFGStmt>()->getStmt());
+    if (!CE)
+      continue;
+
+    OpLoc = CE->getThrowLoc();
+    for (const auto &I : Block.succs()) {
+      if (!I.isReachable())
+        continue;
+      if (const auto *Terminator =
+              dyn_cast_or_null<CXXTryStmt>(I->getTerminator()))
+        if (isThrowCaughtByHandlers(CE, Terminator))
+          return false;
+    }
+    return true;
+  }
+  return false;
+}
+
+static bool hasThrowOutNonThrowingFunc(SourceLocation &OpLoc, CFG *BodyCFG) {
+
+  unsigned ExitID = BodyCFG->getExit().getBlockID();
+
+  SmallVector<ThrowState, 16> States(BodyCFG->getNumBlockIDs(),
+                                     FoundNoPathForThrow);
+  States[BodyCFG->getEntry().getBlockID()] = FoundPathWithNoThrowOutFunction;
+
+  SmallVector<CFGBlock *, 16> Stack;
+  Stack.push_back(&BodyCFG->getEntry());
+  while (!Stack.empty()) {
+    CFGBlock *CurBlock = Stack.back();
+    Stack.pop_back();
+
+    unsigned ID = CurBlock->getBlockID();
+    ThrowState CurState = States[ID];
+    if (CurState == FoundPathWithNoThrowOutFunction) {
+      if (ExitID == ID)
+        continue;
+
+      if (doesThrowEscapePath(*CurBlock, OpLoc))
+        CurState = FoundPathForThrow;
+    }
+
+    // Loop over successor blocks and add them to the Stack if their state
+    // changes.
+    for (const auto &I : CurBlock->succs())
+      if (I.isReachable()) {
+        unsigned NextID = I->getBlockID();
+        if (NextID == ExitID && CurState == FoundPathForThrow) {
+          States[NextID] = CurState;
+        } else if (States[NextID] < CurState) {
+          States[NextID] = CurState;
+          Stack.push_back(I);
+        }
+      }
+  }
+  // Return true if the exit node is reachable, and only reachable through
+  // a throw expression.
+  return States[ExitID] == FoundPathForThrow;
+}
+
+static void EmitDiagForCXXThrowInNonThrowingFunc(Sema &S, SourceLocation OpLoc,
+                                                 const FunctionDecl *FD) {
+  if (!S.getSourceManager().isInSystemHeader(OpLoc)) {
+    S.Diag(OpLoc, diag::warn_throw_in_noexcept_func) << FD;
+    if (S.getLangOpts().CPlusPlus11 &&
+        (isa<CXXDestructorDecl>(FD) ||
+         FD->getDeclName().getCXXOverloadedOperator() == OO_Delete ||
+         FD->getDeclName().getCXXOverloadedOperator() == OO_Array_Delete))
+      S.Diag(FD->getLocation(), diag::note_throw_in_dtor);
+    else
+      S.Diag(FD->getLocation(), diag::note_throw_in_function);
+  }
+}
+
+static void checkThrowInNonThrowingFunc(Sema &S, const FunctionDecl *FD,
+                                        AnalysisDeclContext &AC) {
+  CFG *BodyCFG = AC.getCFG();
+  if (!BodyCFG)
+    return;
+  if (BodyCFG->getExit().pred_empty())
+    return;
+  SourceLocation OpLoc;
+  if (hasThrowOutNonThrowingFunc(OpLoc, BodyCFG))
+    EmitDiagForCXXThrowInNonThrowingFunc(S, OpLoc, FD);
+}
+
+static bool isNoexcept(const FunctionDecl *FD) {
+  const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+  if (FPT->getExceptionSpecType() != EST_None &&
+      FPT->isNothrow(FD->getASTContext()))
+    return true;
+  return false;
+}
+
+//===----------------------------------------------------------------------===//
 // Check for missing return value.
 //===----------------------------------------------------------------------===//
 
@@ -2127,6 +2271,12 @@
     }
   }
 
+  // Check for throw out of non-throwing function.
+  if (!Diags.isIgnored(diag::warn_throw_in_noexcept_func, D->getLocStart()))
+    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
+      if (S.getLangOpts().CPlusPlus && isNoexcept(FD))
+        checkThrowInNonThrowingFunc(S, FD, AC);
+
   // If none of the previous checks caused a CFG build, trigger one here
   // for -Wtautological-overlap-compare
   if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
Index: cfe/trunk/test/CXX/except/except.spec/p11.cpp
===================================================================
--- cfe/trunk/test/CXX/except/except.spec/p11.cpp
+++ cfe/trunk/test/CXX/except/except.spec/p11.cpp
@@ -1,12 +1,11 @@
 // RUN: %clang_cc1 -std=c++11 -fexceptions -fcxx-exceptions -fsyntax-only -verify %s
-// expected-no-diagnostics
 
 // This is the "let the user shoot themselves in the foot" clause.
-void f() noexcept {
-  throw 0; // no-error
+void f() noexcept { // expected-note {{non-throwing function declare here}}
+  throw 0; // expected-warning {{has a non-throwing exception specification but}} 
 }
-void g() throw() {
-  throw 0; // no-error
+void g() throw() { // expected-note {{non-throwing function declare here}}
+  throw 0; // expected-warning {{has a non-throwing exception specification but}} 
 }
 void h() throw(int) {
   throw 0.0; // no-error