[c++ patch] packed fields

[Nathan Sidwell <nathan at codesourcery dot com>]

Hi,
this fixes a code generation problem with accessing packed
fields. We lost information about the unalignedness of the
field, leading to bus errors on architectures where it is
important.

built & tested on sparc-sun-solaris2.8, ok?

nathan
-- 
Dr Nathan Sidwell   ::   http://www.codesourcery.com   ::   CodeSourcery LLC
         'But that's a lie.' - 'Yes it is. What's your point?'
nathan@codesourcery.com : http://www.cs.bris.ac.uk/~nathan/ : nathan@acm.org
2002-08-07  Nathan Sidwell  <nathan@codesourcery.com>

	* typeck.c (build_component_addr): Remove.
	(build_unary_op): Just check it's not a bitfield, and then build
	an ADDR_EXPR.

Index: cp/typeck.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/typeck.c,v
retrieving revision 1.413
diff -c -3 -p -r1.413 typeck.c
*** cp/typeck.c	26 Jul 2002 20:10:43 -0000	1.413
--- cp/typeck.c	1 Aug 2002 11:40:36 -0000
*************** static int comp_array_types PARAMS ((int
*** 57,63 ****
  static tree common_base_type PARAMS ((tree, tree));
  static tree lookup_anon_field PARAMS ((tree, tree));
  static tree pointer_diff PARAMS ((tree, tree, tree));
- static tree build_component_addr PARAMS ((tree, tree));
  static tree qualify_type_recursive PARAMS ((tree, tree));
  static tree get_delta_difference PARAMS ((tree, tree, int));
  static int comp_cv_target_types PARAMS ((tree, tree, int));
--- 57,62 ----
*************** pointer_diff (op0, op1, ptrtype)
*** 4019,4068 ****
    return folded;
  }
  
- /* Handle the case of taking the address of a COMPONENT_REF.
-    Called by `build_unary_op'.
- 
-    ARG is the COMPONENT_REF whose address we want.
-    ARGTYPE is the pointer type that this address should have. */
- 
- static tree
- build_component_addr (arg, argtype)
-      tree arg, argtype;
- {
-   tree field = TREE_OPERAND (arg, 1);
-   tree basetype = decl_type_context (field);
-   tree rval = build_unary_op (ADDR_EXPR, TREE_OPERAND (arg, 0), 0);
- 
-   my_friendly_assert (TREE_CODE (field) == FIELD_DECL, 981018);
- 
-   if (DECL_C_BIT_FIELD (field))
-     {
-       error ("attempt to take address of bit-field structure member `%D'",
-                 field);
-       return error_mark_node;
-     }
- 
-   if (TREE_CODE (field) == FIELD_DECL
-       && TYPE_BASE_CONVS_MAY_REQUIRE_CODE_P (basetype))
-     {
-       /* Can't convert directly to ARGTYPE, since that
- 	 may have the same pointer type as one of our
- 	 baseclasses.  */
-       tree binfo = lookup_base (TREE_TYPE (TREE_TYPE (rval)), basetype,
- 				ba_check, NULL);
- 
-       rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
-       rval = build1 (NOP_EXPR, argtype, rval);
-       TREE_CONSTANT (rval) = TREE_CONSTANT (TREE_OPERAND (rval, 0));
-     }
-   else
-     /* This conversion is harmless.  */
-     rval = convert_force (argtype, rval, 0);
- 
-   return fold (build (PLUS_EXPR, argtype, rval,
- 		      cp_convert (argtype, byte_position (field))));
- }
-    
  /* Construct and perhaps optimize a tree representation
     for a unary operation.  CODE, a tree_code, specifies the operation
     and XARG is the operand.  */
--- 4018,4023 ----
*************** build_unary_op (code, xarg, noconvert)
*** 4549,4556 ****
        {
  	tree addr;
  
! 	if (TREE_CODE (arg) == COMPONENT_REF)
! 	  addr = build_component_addr (arg, argtype);
  	else
  	  addr = build1 (ADDR_EXPR, argtype, arg);
  
--- 4504,4516 ----
        {
  	tree addr;
  
! 	if (TREE_CODE (arg) == COMPONENT_REF
! 	    && DECL_C_BIT_FIELD (TREE_OPERAND (arg, 1)))
! 	  {
! 	    error ("attempt to take address of bit-field structure member `%D'",
! 		   TREE_OPERAND (arg, 1));
! 	    return error_mark_node;
! 	  }
  	else
  	  addr = build1 (ADDR_EXPR, argtype, arg);
  
// { dg-do run }

// Copyright (C) 2002 Free Software Foundation, Inc.
// Contributed by Nathan Sidwell 8 Aug 2002 <nathan@codesourcery.com>

// WRS SPR 63496, lost packed attribute when accessing a packed
// field. This matters on aligned architectures like sh

struct thing { int m; };

struct pod {char a; thing m __attribute__ ((packed)); };

int main ()
{
  thing t;
  pod p;
  
  p.m = t; /* runtime bus error here */

  return 0;
  
};