re PR c++/38543 ([C++0x] Cannot specialize variadic template function)

	PR c++/38543
	* pt.c (determine_specialization): Instead of comparing the number
	of parms, check that tsubst gives the right answer.

From-SVN: r186522

gcc/cp/ChangeLog

 2012-04-16  Jason Merrill  <jason@redhat.com>
 
+	PR c++/38543
+	* pt.c (determine_specialization): Instead of comparing the number
+	of parms, check that tsubst gives the right answer.
+
 	PR c++/52008
 	* pt.c (process_partial_specialization): Complain about a partial
 	specialization with fewer args than primary template parms.

gcc/cp/pt.c

@@ -1839,6 +1839,7 @@ determine_specialization (tree template_id,
 	{
 	  tree decl_arg_types;
 	  tree fn_arg_types;
+	  tree insttype;
 
 	  /* In case of explicit specialization, we need to check if
 	     the number of template headers appearing in the specialization
@@ -1900,15 +1901,6 @@ determine_specialization (tree template_id,
 	  fn_arg_types 
 	    = skip_artificial_parms_for (fn, fn_arg_types);
 
-	  /* Check that the number of function parameters matches.
-	     For example,
-	       template <class T> void f(int i = 0);
-	       template <> void f<int>();
-	     The specialization f<int> is invalid but is not caught
-	     by get_bindings below.  */
-	  if (list_length (fn_arg_types) != list_length (decl_arg_types))
-	    continue;
-
 	  /* Function templates cannot be specializations; there are
 	     no partial specializations of functions.  Therefore, if
 	     the type of DECL does not match FN, there is no
@@ -1929,6 +1921,15 @@ determine_specialization (tree template_id,
 	       specialize TMPL will produce DECL.  */
 	    continue;
 
+	  /* Make sure that the deduced arguments actually work.  */
+	  insttype = tsubst (TREE_TYPE (fn), targs, tf_none, NULL_TREE);
+	  if (insttype == error_mark_node)
+	    continue;
+	  fn_arg_types
+	    = skip_artificial_parms_for (fn, TYPE_ARG_TYPES (insttype));
+	  if (!compparms (fn_arg_types, decl_arg_types))
+	    continue;
+
 	  /* Save this template, and the arguments deduced.  */
 	  templates = tree_cons (targs, fn, templates);
 	}

gcc/testsuite/ChangeLog

 2012-04-16  Jason Merrill  <jason@redhat.com>
 
+	PR c++/38543
+	* g++.dg/cpp0x/variadic131.C: New.
+
 	PR c++/52008
 	* g++.dg/cpp0x/variadic130.C: New.
 

gcc/testsuite/g++.dg/cpp0x/variadic131.C

+// PR c++/38543
+// { dg-do compile { target c++11 } }
+
+template< typename ... T > void foo( T ... args );
+template<> void foo( ){}
+template<> void foo(int,double){}
+int main()
+{
+  foo( 0, 0.0 );
+  return 55;
+}