re PR c++/61020 (typeid(typeid(X)) produces 'ud2')

	PR c++/61020
	* varpool.c (ctor_for_folding): Handle uninitialized vtables.

From-SVN: r211178

gcc/ChangeLog

+2014-06-02  Jason Merrill  <jason@redhat.com>
+
+	PR c++/61020
+	* varpool.c (ctor_for_folding): Handle uninitialized vtables.
+
 2014-06-03  Alan Lawrence  <alan.lawrence@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_evpc_ext): allow and handle

gcc/testsuite/g++.dg/opt/typeinfo1.C

+// PR c++/61020
+// { dg-options "-O2" }
+// { dg-do run }
+
+#include <typeinfo>
+
+struct Base {
+  virtual ~Base() { }
+};
+
+struct Derived : public Base {
+};
+
+int compare(const Base& base)
+{
+  return typeid(base) == typeid(typeid(Derived));
+}
+
+int main()
+{
+  Base base;
+  Derived derived;
+
+  if (compare(base)) return 1;
+  if (compare(derived)) return 2;
+  return 0;
+}

gcc/varpool.c

@@ -306,7 +306,16 @@ ctor_for_folding (tree decl)
   if (DECL_VIRTUAL_P (real_decl))
     {
       gcc_checking_assert (TREE_READONLY (real_decl));
-      return DECL_INITIAL (real_decl);
+      if (DECL_INITIAL (real_decl))
+	return DECL_INITIAL (real_decl);
+      else
+	{
+	  /* The C++ front end creates VAR_DECLs for vtables of typeinfo
+	     classes not defined in the current TU so that it can refer
+	     to them from typeinfo objects.  Avoid returning NULL_TREE.  */
+	  gcc_checking_assert (!COMPLETE_TYPE_P (DECL_CONTEXT (real_decl)));
+	  return error_mark_node;
+	}
     }
 
   /* If there is no constructor, we have nothing to do.  */