typeck.c (original_type): New function.

	* typeck.c (original_type): New function.
	(common_type): Use it to get the DECL_ORIGINAL_TYPE for T1 and T2,
	to see if they're actually the same.
	* cp-tree.h (original_type): Declare.
fix problem when you have multiple identical typedefs

From-SVN: r19744

gcc/cp/ChangeLog

+Thu May 14 12:27:34 1998  Brendan Kehoe  <brendan@cygnus.com>
+
+	* typeck.c (original_type): New function.
+	(common_type): Use it to get the DECL_ORIGINAL_TYPE for T1 and T2,
+	to see if they're actually the same.
+	* cp-tree.h (original_type): Declare.
+
 Wed May 13 12:54:30 1998  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* Makefile.in (lex.o): Depend on output.h.

gcc/cp/cp-tree.h

@@ -2760,6 +2760,7 @@ extern int type_unknown_p			PROTO((tree));
 extern int fntype_p				PROTO((tree));
 extern tree require_instantiated_type		PROTO((tree, tree, tree));
 extern tree commonparms				PROTO((tree, tree));
+extern tree original_type			PROTO((tree));
 extern tree common_type				PROTO((tree, tree));
 extern int compexcepttypes			PROTO((tree, tree));
 extern int comptypes				PROTO((tree, tree, int));

gcc/cp/typeck.c

@@ -292,6 +292,25 @@ commonparms (p1, p2)
   return newargs;
 }
 
+/* Given a type, perhaps copied for a typedef,
+   find the "original" version of it.  */
+tree
+original_type (t)
+     tree t;
+{
+  while (TYPE_NAME (t) != NULL_TREE)
+    {
+      tree x = TYPE_NAME (t);
+      if (TREE_CODE (x) != TYPE_DECL)
+	break;
+      x = DECL_ORIGINAL_TYPE (x);
+      if (x == NULL_TREE)
+	break;
+      t = x;
+    }
+  return t;
+}
+
 /* Return the common type of two types.
    We assume that comptypes has already been done and returned 1;
    if that isn't so, this may crash.
@@ -311,8 +330,12 @@ common_type (t1, t2)
   tree attributes;
 
   /* Save time if the two types are the same.  */
-
-  if (t1 == t2) return t1;
+  if (t1 == t2)
+    return t1;
+  t1 = original_type (t1);
+  t2 = original_type (t2);
+  if (t1 == t2)
+    return t1;
 
   /* If one type is nonsense, use the other.  */
   if (t1 == error_mark_node)