[PATCH] Fix PR19195

[Karthik Bhat]

Hi rsmith, nicholas, bkramer,

Hi All,
A small patch ti fix PR19195. A call to getExpr from CXXDefaultInitExpr can return null in case we have not yet parsed and attached the in class initializer like in this test case.
Check if getExpr returns null and handle the same to prevent a crash during dynamic cast in StmtVisitor.
It would be great if someone could review the same and let me know if this is good for commit.

Thanks
Karthik Bhat

http://llvm-reviews.chandlerc.com/D3243

Files:
  test/CodeGenCXX/pr19195.cpp
  lib/CodeGen/CGExprScalar.cpp
  lib/CodeGen/CGDecl.cpp

Index: test/CodeGenCXX/pr19195.cpp
===================================================================
--- test/CodeGenCXX/pr19195.cpp
+++ test/CodeGenCXX/pr19195.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++11 -emit-llvm-only %s -o %t
+/* Testcase for PR19195 - clang hits assert during in class initialization */
+
+class Cls {
+  Cls();
+  template <typename> struct Templ {
+    Templ() {}
+    int initialized_member = 0;
+  };
+  Templ<int> trigger_instantiation;
+};
+Cls::Cls() {}
Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -349,6 +349,8 @@
   }
   Value *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
     CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
+    if(!DIE->getExpr())
+      return 0;
     return Visit(DIE->getExpr());
   }
   Value *VisitCXXThisExpr(CXXThisExpr *TE) {
Index: lib/CodeGen/CGDecl.cpp
===================================================================
--- lib/CodeGen/CGDecl.cpp
+++ lib/CodeGen/CGDecl.cpp
@@ -571,6 +571,8 @@
   Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime();
   if (!lifetime) {
     llvm::Value *value = EmitScalarExpr(init);
+    if (!value)
+      return;
     if (capturedByInit)
       drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
     EmitStoreThroughLValue(RValue::get(value), lvalue, true);
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