target-specific type attributes

[Richard Earnshaw <rearnsha at arm dot com>]

Currently 

struct f {char a, int b;} __attribute__((packed));

declares a packed structure as expected, but 

struct f {char a, int b;} __attribute__((md-specific-attr));

quietly fails to give the desired result.  This is because 
valid_machine_attribute creates a new type variant of struct f rather than 
modifying the base type.  It then promptly discards it.

If possible, I'd like the following patch to be in egcs-1.1;

<date>  Richard Earnshaw (rearnsha@arm.com)

	* tree.c (valid_machine_attribute): Only create a new type variant if
	there is a decl to use it.


Index: tree.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/tree.c,v
retrieving revision 1.36
diff -p -r1.36 tree.c
*** tree.c	1998/07/07 00:05:24	1.36
--- tree.c	1998/07/16 12:45:50
*************** valid_machine_attribute (attr_name, attr
*** 3391,3398 ****
  	}
        else
  	{
  	  type_attr_list = tree_cons (attr_name, attr_args, type_attr_list);
! 	  type = build_type_attribute_variant (type, type_attr_list);
  	}
        if (decl != 0)
  	TREE_TYPE (decl) = type;
--- 3391,3404 ----
  	}
        else
  	{
+ 	  /* If this is part of a declaration, create a type variant,
+ 	     otherwise, this is part of a type definition, so add it 
+ 	     to the base type.  */
  	  type_attr_list = tree_cons (attr_name, attr_args, type_attr_list);
! 	  if (decl != 0)
! 	    type = build_type_attribute_variant (type, type_attr_list);
! 	  else
! 	    TYPE_ATTRIBUTES (type) = type_attr_list;
  	}
        if (decl != 0)
  	TREE_TYPE (decl) = type;