[backport from gcc-4.7/trunk <mikpe@it.uu.se>]

gcc/

2011-05-19  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48985
	* tree-object-size.c (addr_object_size): If the pointed-to
	variable is a decl use DECL_SIZE_UNIT instead of TYPE_SIZE_UNIT.

gcc/testsuite/

2011-05-19  Richard Guenther  <rguenther@suse.de>

	PR testsuite/49063
	* gcc.dg/builtin-object-size-11.c: Use -std=gnu89.

2011-05-19  Richard Guenther  <rguenther@suse.de>

	PR middle-end/48985
	* gcc.dg/builtin-object-size-11.c: New testcase.

--- gcc-4.6.0/gcc/testsuite/gcc.dg/builtin-object-size-11.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.0/gcc/testsuite/gcc.dg/builtin-object-size-11.c	2011-05-19 22:30:59.000000000 +0200
@@ -0,0 +1,21 @@
+/* PR48985 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu89" } */
+
+extern void abort (void);
+
+struct s {
+    int i;
+    char c[];
+} s = { 1, "01234" };
+
+__SIZE_TYPE__ f (void) { return __builtin_object_size (&s.c, 0); }
+
+int
+main()
+{
+  if (f() != sizeof ("01234"))
+    abort ();
+
+  return 0;
+}
--- gcc-4.6.0/gcc/tree-object-size.c.~1~	2011-03-17 14:22:26.000000000 +0100
+++ gcc-4.6.0/gcc/tree-object-size.c	2011-05-19 22:29:11.000000000 +0200
@@ -205,6 +205,12 @@ addr_object_size (struct object_size_inf
 	pt_var_size = size_int (sz);
     }
   else if (pt_var
+	   && DECL_P (pt_var)
+	   && host_integerp (DECL_SIZE_UNIT (pt_var), 1)
+	   && (unsigned HOST_WIDE_INT)
+	        tree_low_cst (DECL_SIZE_UNIT (pt_var), 1) < offset_limit)
+    pt_var_size = DECL_SIZE_UNIT (pt_var);
+  else if (pt_var
 	   && (SSA_VAR_P (pt_var) || TREE_CODE (pt_var) == STRING_CST)
 	   && TYPE_SIZE_UNIT (TREE_TYPE (pt_var))
 	   && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (pt_var)), 1)