re PR c++/26698 (g++ accepts const-incorrect code due to conversion function)

gcc/cp/

2007-10-12  Simon Martin  <simartin@users.sourceforge.net>

	PR c++/26698
	* call.c (build_user_type_conversion_1): Do not consider conversion
	functions to convert a (possibly cv-qualified) object to the (possibly
	cv-qualified) same object type (or a reference to it), to a (possibly
	cv-qualified) base class of that type (or a reference to it).

gcc/testsuite/

2007-10-12  Simon Martin  <simartin@users.sourceforge.net>

	PR c++/26698
	* g++.dg/conversion/op4.C: New test.

From-SVN: r129274

gcc/cp/ChangeLog

+2007-10-12  Simon Martin  <simartin@users.sourceforge.net>
+
+	PR c++/26698
+	* call.c (build_user_type_conversion_1): Do not consider conversion
+	functions to convert a (possibly cv-qualified) object to the (possibly
+	cv-qualified) same object type (or a reference to it), to a (possibly
+	cv-qualified) base class of that type (or a reference to it).
+
 2007-10-12  Paolo Carlini  <pcarlini@suse.de>
 
 	* pt.c (tsubst): Use template_parm_level_and_index.

gcc/cp/call.c

@@ -2601,7 +2601,21 @@ build_user_type_conversion_1 (tree totype, tree expr, int flags)
     ctors = lookup_fnfields (totype, complete_ctor_identifier, 0);
 
   if (IS_AGGR_TYPE (fromtype))
-    conv_fns = lookup_conversions (fromtype);
+    {
+      tree to_nonref = non_reference (totype);
+      if (same_type_ignoring_top_level_qualifiers_p (to_nonref, fromtype) ||
+	  (CLASS_TYPE_P (to_nonref) && CLASS_TYPE_P (fromtype)
+	   && DERIVED_FROM_P (to_nonref, fromtype)))
+	{
+	  /* [class.conv.fct] A conversion function is never used to
+	     convert a (possibly cv-qualified) object to the (possibly
+	     cv-qualified) same object type (or a reference to it), to a
+	     (possibly cv-qualified) base class of that type (or a
+	     reference to it)...  */
+	}
+      else
+	conv_fns = lookup_conversions (fromtype);
+    }
 
   candidates = 0;
   flags |= LOOKUP_NO_CONVERSION;

gcc/testsuite/ChangeLog

+2007-10-12  Simon Martin  <simartin@users.sourceforge.net>
+
+	PR c++/26698
+	* g++.dg/conversion/op4.C: New test.
+
 2007-10-12  Richard Sandiford  <rsandifo@nildram.co.uk>
 
 	* g++.dg/torture/pr33572.C (main): Allow argc to be zero.

gcc/testsuite/g++.dg/conversion/op4.C

+/* PR c++/26698 */
+/* { dg-do "compile" } */
+
+struct X {
+  int x;
+  X (int i = 0) : x (i) {}
+  operator X& (void) const {
+    return *(new X);
+  }
+};
+
+void add_one (X & ref) { /* { dg-error "in passing argument" } */
+  ++ ref.x;
+}
+
+void foo() {
+  X const a (2);
+  add_one(a); /* { dg-error "invalid initialization of reference of type" } */
+}