[PATCH] Fix PR48269

[Richard Guenther]

This removes a double-accounting for MEM_REF offsets.  The code still
looks somewhat fishy, but at least is consistent in what it does now ;)

Bootstrapped and tested on x86_64-unknonw-linux-gnu, applied to trunk.

Richard.

2011-03-24  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48269
	* tree-object-size.c (addr_object_size): Do not double-account
	for MEM_REF offsets.

	* gcc.dg/builtin-object-size-10.c: New testcase.

Index: gcc/tree-object-size.c
===================================================================
*** gcc/tree-object-size.c	(revision 171384)
--- gcc/tree-object-size.c	(working copy)
*************** addr_object_size (struct object_size_inf
*** 348,355 ****
  	  tree bytes2 = compute_object_offset (TREE_OPERAND (ptr, 0), pt_var);
  	  if (bytes2 != error_mark_node)
  	    {
- 	      bytes2 = size_binop (PLUS_EXPR, bytes2,
- 				   TREE_OPERAND (pt_var, 1));
  	      if (TREE_CODE (bytes2) == INTEGER_CST
  		  && tree_int_cst_lt (pt_var_size, bytes2))
  		bytes2 = size_zero_node;
--- 348,353 ----
Index: gcc/testsuite/gcc.dg/builtin-object-size-10.c
===================================================================
*** gcc/testsuite/gcc.dg/builtin-object-size-10.c	(revision 0)
--- gcc/testsuite/gcc.dg/builtin-object-size-10.c	(revision 0)
***************
*** 0 ****
--- 1,26 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -fdump-tree-objsz-details" } */
+ 
+ typedef struct {
+     char sentinel[4];
+     char data[0];
+ } drone_packet;
+ typedef struct {
+     char type_str[16];
+     char channel_hop;
+ } drone_source_packet;
+ drone_packet *
+ foo(char *x)
+ {
+   drone_packet *dpkt = __builtin_malloc(sizeof(drone_packet)
+ 					+ sizeof(drone_source_packet));
+   drone_source_packet *spkt = (drone_source_packet *) dpkt->data;
+   __builtin___snprintf_chk (spkt->type_str, 16,
+ 			    1, __builtin_object_size (spkt->type_str, 1),
+ 			    "%s", x);
+   return dpkt;
+ }
+ 
+ /* { dg-final { scan-tree-dump "maximum object size 21" "objsz" } } */
+ /* { dg-final { scan-tree-dump "maximum subobject size 16" "objsz" } } */
+ /* { dg-final { cleanup-tree-dump "objsz" } } */