re PR c++/42623 ([C++0x] Function template default arguments: Invalid expressions are allowed)

	PR c++/42623
	* c-common.c (c_sizeof_or_alignof_type): Return error_mark_node
	for incomplete type.

From-SVN: r158167

gcc/ChangeLog

 2010-04-09  Jason Merrill  <jason@redhat.com>
 
+	PR c++/42623
+	* c-common.c (c_sizeof_or_alignof_type): Return error_mark_node
+	for incomplete type.
+
 	PR c++/41788
 	* stor-layout.c (finalize_record_size): Don't change TYPE_PACKED
 	based on a warning flag.

gcc/c-common.c

@@ -4390,7 +4390,7 @@ c_sizeof_or_alignof_type (location_t loc,
       if (complain)
 	error_at (loc, "invalid application of %qs to incomplete type %qT ",
 		  op_name, type);
-      value = size_zero_node;
+      return error_mark_node;
     }
   else
     {

gcc/testsuite/ChangeLog

+2010-04-09  Jason Merrill  <jason@redhat.com>
+
+	PR c++/42623
+	* g++.dg/template/sizeof13.C: New.
+
 2010-04-09  Kai Tietz  <kai.tietz@onevision.com>
 
 	* g++.dg/other/pr35504.C: Add check for thiscall.

gcc/testsuite/g++.dg/template/sizeof13.C

+// PR c++/42623
+// We should choose f(B) because f(A<undef>) involves applying sizeof to
+// an incomplete class, so it is removed by SFINAE.
+// { dg-do link }
+
+struct undef;
+
+template <typename U, int N = sizeof(U)> struct A { A(int); };
+template <typename U> void f(A<U>);
+
+template <typename U> struct B { B(int) { } };
+template <typename U> void f(B<U>) { }
+
+int main()
+{
+  f<undef>(0);
+}