[MS Compat] Don't crash if __GetExceptionInfo is in global scope

__GetExceptionInfo triggered Sema::LazilyCreateBuiltin which tries to
create a non-templated function decl.  This is unnecessary and
ill-advised, there is no need for us to create a declaration for such a
builtin.

This fixes PR26298.

llvm-svn: 258762

clang/lib/AST/Decl.cpp

@@ -2708,8 +2708,7 @@ unsigned FunctionDecl::getBuiltinID() const {
     // declaration, for instance "extern "C" { namespace std { decl } }".
     if (!LinkageDecl) {
       if (BuiltinID == Builtin::BI__GetExceptionInfo &&
-          Context.getTargetInfo().getCXXABI().isMicrosoft() &&
+          Context.getTargetInfo().getCXXABI().isMicrosoft())
-          isInStdNamespace())
         return Builtin::BI__GetExceptionInfo;
       return 0;
     }

clang/lib/Sema/SemaDecl.cpp

@@ -1748,6 +1748,9 @@ NamedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID,
           << Context.BuiltinInfo.getName(ID);
   }
 
+  if (R.isNull())
+    return nullptr;
+
   DeclContext *Parent = Context.getTranslationUnitDecl();
   if (getLangOpts().CPlusPlus) {
     LinkageSpecDecl *CLinkageDecl =

clang/test/CodeGenCXX/microsoft-abi-throw.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -emit-llvm -o - -triple=i386-pc-win32 -std=c++11 %s -fcxx-exceptions -fms-extensions | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -o - -triple=i386-pc-win32 -std=c++11 %s -fcxx-exceptions -fms-extensions -DSTD | FileCheck %s
 
 // CHECK-DAG: @"\01??_R0?AUY@@@8" = linkonce_odr global %rtti.TypeDescriptor7 { i8** @"\01??_7type_info@@6B@", i8* null, [8 x i8] c".?AUY@@\00" }, comdat
 // CHECK-DAG: @"_CT??_R0?AUY@@@8??0Y@@QAE@ABU0@@Z8" = linkonce_odr unnamed_addr constant %eh.CatchableType { i32 4, i8* bitcast (%rtti.TypeDescriptor7* @"\01??_R0?AUY@@@8" to i8*), i32 0, i32 -1, i32 0, i32 8, i8* bitcast (%struct.Y* (%struct.Y*, %struct.Y*, i32)* @"\01??0Y@@QAE@ABU0@@Z" to i8*) }, section ".xdata", comdat
@@ -97,19 +98,25 @@ void h() {
   throw nullptr;
 }
 
+#ifdef STD
 namespace std {
 template <typename T>
 void *__GetExceptionInfo(T);
 }
+#else
+template <typename T>
+void *__GetExceptionInfo(T);
+#endif
+using namespace std;
 
 void *GetExceptionInfo_test0() {
 // CHECK-LABEL: @"\01?GetExceptionInfo_test0@@YAPAXXZ"
 // CHECK:  ret i8* bitcast (%eh.ThrowInfo* @_TI1H to i8*)
-  return std::__GetExceptionInfo(0);
+  return __GetExceptionInfo(0);
 }
 
 void *GetExceptionInfo_test1() {
 // CHECK-LABEL: @"\01?GetExceptionInfo_test1@@YAPAXXZ"
 // CHECK:  ret i8* bitcast (%eh.ThrowInfo* @_TI1P6AXXZ to i8*)
-  return std::__GetExceptionInfo<void (*)()>(&h);
+  return __GetExceptionInfo<void (*)()>(&h);
 }