[PATCH] remove some TYPE_ARG_TYPES usage in objc/

[Nathan Froyd]

This patch removes one of the two remaining uses of TYPE_ARG_TYPES in
the ObjC/C++ frontends.  (The other one should be addressed in a
different manner.)  Given the constraints of the function_args_iterator
interface, I thought rewriting the logic of the loop would make things
slightly clearer.

Tested on x86_64-unknown-linux-gnu with ObjC/C++.  OK to commit?

-Nathan

gcc/objc/
        * objc-act.c (objc_compare_types): Use function_args_iterator
        instead of TYPE_ARG_TYPES to compare function argument types.

diff --git a/gcc/objc/objc-act.c b/gcc/objc/objc-act.c
index 7e69b0d..0e15fe5 100644
--- a/gcc/objc/objc-act.c
+++ b/gcc/objc/objc-act.c
@@ -2420,6 +2420,8 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, tree 
callee)
      lenient than C or C++ on this.  */
   if (TREE_CODE (ltyp) == FUNCTION_TYPE && TREE_CODE (rtyp) == FUNCTION_TYPE)
     {
+      function_args_iterator liter, riter;
+
       /* Return types must be covariant.  */
       if (!comptypes (TREE_TYPE (ltyp), TREE_TYPE (rtyp))
          && !objc_compare_types (TREE_TYPE (ltyp), TREE_TYPE (rtyp),
@@ -2427,16 +2429,31 @@ objc_compare_types (tree ltyp, tree rtyp, int argno, 
tree callee)
       return false;
 
       /* Argument types must be contravariant.  */
-      for (ltyp = TYPE_ARG_TYPES (ltyp), rtyp = TYPE_ARG_TYPES (rtyp);
-          ltyp && rtyp; ltyp = TREE_CHAIN (ltyp), rtyp = TREE_CHAIN (rtyp))
+      function_args_iter_init (&liter, ltyp);
+      function_args_iter_init (&riter, rtyp);
+
+      while (1)
        {
-         if (!comptypes (TREE_VALUE (rtyp), TREE_VALUE (ltyp))
-             && !objc_compare_types (TREE_VALUE (rtyp), TREE_VALUE (ltyp),
-                                     argno, callee))
+         ltyp = function_args_iter_cond (&liter);
+         rtyp = function_args_iter_cond (&riter);
+
+         /* If we've exhaused both lists simulateously, we're done.  */
+         if (ltyp == NULL_TREE && rtyp == NULL_TREE)
+           break;
+
+         /* If one list is shorter than the other, they fail to match.  */
+         if (ltyp == NULL_TREE || rtyp == NULL_TREE)
            return false;
-      }
 
-      return (ltyp == rtyp);
+         if (!comptypes (rtyp, ltyp)
+             && !objc_compare_types (rtyp, ltyp, argno, callee))
+           return false;
+
+         function_args_iter_next (&liter);
+         function_args_iter_next (&riter);
+       }
+
+      return true;
     }
 
   /* Past this point, we are only interested in ObjC class instances,