Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -3492,13 +3492,15 @@
 
 static void fillAttributedTypeLoc(AttributedTypeLoc TL,
                                   const AttributeList *attrs) {
-  AttributedType::Kind kind = TL.getAttrKind();
+  if (!attrs)
+    return;
 
-  assert(attrs && "no type attributes in the expected location!");
+  AttributedType::Kind kind = TL.getAttrKind();
   AttributeList::Kind parsedKind = getAttrListKind(kind);
   while (attrs->getKind() != parsedKind) {
     attrs = attrs->getNext();
-    assert(attrs && "no matching attribute in expected location!");
+    if (!attrs)
+      return;
   }
 
   TL.setAttrNameLoc(attrs->getLoc());
Index: test/SemaCXX/cxx11-gnu-attrs.cpp
===================================================================
--- test/SemaCXX/cxx11-gnu-attrs.cpp
+++ test/SemaCXX/cxx11-gnu-attrs.cpp
@@ -8,6 +8,17 @@
 // expected-error@-1 {{'unused' attribute cannot be applied to types}}
 int *[[gnu::unused]] attr_on_ptr;
 // expected-warning@-1 {{attribute 'unused' ignored, because it cannot be applied to a type}}
+[[gnu::fastcall]] void pr17424_1();
+// expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
+[[gnu::fastcall]] [[gnu::stdcall]] void pr17424_2();
+// expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
+// expected-warning@-2 {{calling convention 'stdcall' ignored for this target}}
+[[gnu::fastcall]] __stdcall void pr17424_3();
+// expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
+// expected-warning@-2 {{calling convention '__stdcall' ignored for this target}}
+[[gnu::fastcall]] void pr17424_4() [[gnu::stdcall]];
+// expected-warning@-1 {{calling convention 'fastcall' ignored for this target}}
+// expected-warning@-2 {{attribute 'stdcall' ignored, because it cannot be applied to a type}}
 
 // Valid cases.