re PR c++/12815 (Code compiled with optimization behaves unexpectedly)

	PR c++/12816
	* class.c (build_vtbl_ref_1): Do not unconditionally mark vtable
	references as constant.

	PR c++/12815
	* g++.dg/rtti/typeid4.C: New test.

From-SVN: r75457

gcc/cp/ChangeLog

 2004-01-05  Mark Mitchell  <mark@codesourcery.com>
 
+	PR c++/12816
+	* class.c (build_vtbl_ref_1): Do not unconditionally mark vtable
+	references as constant.
+
 	PR c++/12132
 	* parser.c (cp_parser_explicit_instantiation): Improve error
 	recovery.

gcc/cp/class.c

@@ -455,7 +455,7 @@ build_vtbl_ref_1 (tree instance, tree idx)
   assemble_external (vtbl);
 
   aref = build_array_ref (vtbl, idx);
-  TREE_CONSTANT (aref) = 1;
+  TREE_CONSTANT (aref) |= TREE_CONSTANT (vtbl) && TREE_CONSTANT (idx);
 
   return aref;
 }

gcc/testsuite/ChangeLog

+2004-01-05  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/12815
+	* g++.dg/rtti/typeid4.C: New test.
+
 2004-01-05  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	* gcc.dg/compat/sdata-section.h: Declare 'abort'.

gcc/testsuite/g++.dg/rtti/typeid4.C

+// { dg-do run }
+// { dg-options "-O2" }
+
+#include <typeinfo>
+#include <iostream>
+
+struct A { virtual ~A () {} };
+
+struct APtr
+{ 
+  APtr (A* p)  : p_ (p) { }
+  A& operator* () const { return *p_; }
+  A* p_;
+};
+
+int main ()
+{ 
+  APtr ap (new A);
+  std::type_info const* const exp = &typeid (*ap);
+  for (bool cont = true; cont; cont = false)
+    { 
+      std::cout << "inner: cont " << cont << std::endl;
+      if (exp) ;
+    }
+}
+