re PR c++/5857 (C++ duplicate_decls shouldn't use common_type)

        PR c++/5857
        * decl.c (duplicate_decls): Use merge_types instead of common_type.
        * typeck.c (common_type): Just hand off to
        type_after_usual_arithmetic_conversions and
        composite_pointer_type.
        (merge_types): New fn.
        (commonparms): Use it instead of common_type.
        (type_after_usual_arithmetic_conversions): Also handle COMPLEX_TYPE.
        (composite_pointer_type): Also handle attributes.
        * cp-tree.h: Declare merge_types.

From-SVN: r50820

gcc/cp/ChangeLog

 2002-03-15  Jason Merrill  <jason@redhat.com>
 
+	PR c++/5857
+	* decl.c (duplicate_decls): Use merge_types instead of common_type.
+	* typeck.c (common_type): Just hand off to
+	type_after_usual_arithmetic_conversions and
+	composite_pointer_type.
+	(merge_types): New fn.
+	(commonparms): Use it instead of common_type.
+	(type_after_usual_arithmetic_conversions): Also handle COMPLEX_TYPE.
+	(composite_pointer_type): Also handle attributes.
+	* cp-tree.h: Declare merge_types.
+
 	* decl.c (make_rtl_for_nonlocal_decl): Also defer COMDAT
 	variables.
 	* decl2.c (maybe_make_one_only): Also mark the decl as needed.

gcc/cp/cp-tree.h

@@ -4355,6 +4355,7 @@ extern tree pfn_from_ptrmemfunc                 PARAMS ((tree));
 extern tree type_after_usual_arithmetic_conversions PARAMS ((tree, tree));
 extern tree composite_pointer_type              PARAMS ((tree, tree, tree, tree,
 						       const char*));
+extern tree merge_types				PARAMS ((tree, tree));
 extern tree check_return_expr                   PARAMS ((tree));
 #define cp_build_binary_op(code, arg1, arg2) \
   build_binary_op(code, arg1, arg2, 1)

gcc/cp/decl.c

@@ -3515,16 +3515,16 @@ duplicate_decls (newdecl, olddecl)
       tree newtype;
 
       /* Merge the data types specified in the two decls.  */
-      newtype = common_type (TREE_TYPE (newdecl), TREE_TYPE (olddecl));
+      newtype = merge_types (TREE_TYPE (newdecl), TREE_TYPE (olddecl));
 
-      /* If common_type produces a non-typedef type, just use the old type.  */
+      /* If merge_types produces a non-typedef type, just use the old type.  */
       if (TREE_CODE (newdecl) == TYPE_DECL
 	  && newtype == DECL_ORIGINAL_TYPE (newdecl))
 	newtype = oldtype;
 
       if (TREE_CODE (newdecl) == VAR_DECL)
 	DECL_THIS_EXTERN (newdecl) |= DECL_THIS_EXTERN (olddecl);
-      /* Do this after calling `common_type' so that default
+      /* Do this after calling `merge_types' so that default
 	 parameters don't confuse us.  */
       else if (TREE_CODE (newdecl) == FUNCTION_DECL
 	  && (TYPE_RAISES_EXCEPTIONS (TREE_TYPE (newdecl))

gcc/testsuite/g++.dg/other/redecl1.C

+// PR c++/5857
+// This testcase failed because during duplicate_decls the type was promoted
+// to int.
+
+// { dg-do compile }
+
+typedef char baz;
+extern const char foo[];
+const baz foo[] = "xyz";
+const char bar[] = "abc";