re PR c++/31449 ([4.1] static_cast can remove const-ness)

	PR c++/31449
	* class.c (build_base_path): Ensure that the converted pointer has
	the same cv-qualification as the input.
	PR c++/31449
	* g++.dg/init/const5.C: New test.

From-SVN: r123679

gcc/cp/ChangeLog

+2007-04-09  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/31449
+	* class.c (build_base_path): Ensure that the converted pointer has
+	the same cv-qualification as the input.
+
 2007-04-09  Paolo Carlini  <pcarlini@suse.de>
 
 	* tree.c (cp_tree_equal): Deal with TRAIT_EXPR.

gcc/cp/class.c

@@ -303,7 +303,18 @@ build_base_path (enum tree_code code,
 	 field, because other parts of the compiler know that such
 	 expressions are always non-NULL.  */
       if (!virtual_access && integer_zerop (offset))
-	return build_nop (build_pointer_type (target_type), expr);
+	{
+	  tree class_type;
+	  /* TARGET_TYPE has been extracted from BINFO, and, is
+	     therefore always cv-unqualified.  Extract the
+	     cv-qualifiers from EXPR so that the expression returned
+	     matches the input.  */
+	  class_type = TREE_TYPE (TREE_TYPE (expr));
+	  target_type
+	    = cp_build_qualified_type (target_type,
+				       cp_type_quals (class_type));
+	  return build_nop (build_pointer_type (target_type), expr);
+	}
       null_test = error_mark_node;
     }
 

gcc/testsuite/ChangeLog

+2007-04-09  Mark Mitchell  <mark@codesourcery.com>
+
+	PR c++/31449
+	* g++.dg/init/const5.C: New test.
+
 2007-04-09  Jan Hubicka  <jh@suse.cz>
 
 	* gcc.dg/tree-ssa/foldaddr-3.c: New file.

gcc/testsuite/g++.dg/init/const5.C

+// PR c++/31449
+
+class Foo {};
+class Bar : public Foo {};
+static const Foo *foo = 0;
+
+static Bar *bar = static_cast<const Bar*>(foo); // { dg-error "conversion" }
+
+void func(const Foo *foo) {
+  Bar *bar = static_cast<const Bar*>(foo);  // { dg-error "conversion" }
+}