[Bug middle-end/48269] Incorrect fortify warning for a packed struct member

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48269

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-24 10:43:29 UTC ---
  D.83064_56 = in_int_3(D)->strong_source;
  D.83065_57 = D.83064_56->_vptr.KisPacketSource;
  D.83086_59 = MEM[(int (*__vtbl_ptr_type) (void) *)D.83065_57 + 92B];
  D.73136 = OBJ_TYPE_REF(D.83086_59;D.83064_56->23) (D.83064_56); [return slot
optimization]
  D.83087_61 = std::basic_string<char>::c_str (&D.73136);
  D.83088_63 = &MEM[(struct drone_source_packet *)dpkt_1 + 12B].interface_str;
  __s_143 = (char * restrict) D.83088_63;
  D.85546_145 = 16;
  __builtin___snprintf_chk (__s_143, 16, 1, D.85546_145, "%s", D.83087_61);
  std::basic_string<char>::~basic_string (&D.73136);
  D.83064_65 = in_int_3(D)->strong_source;
  D.83065_66 = D.83064_65->_vptr.KisPacketSource;
  D.83090_68 = MEM[(int (*__vtbl_ptr_type) (void) *)D.83065_66 + 96B];
  D.73137 = OBJ_TYPE_REF(D.83090_68;D.83064_65->24) (D.83064_65); [return slot
optimization]
  D.83091_70 = std::basic_string<char>::c_str (&D.73137);
  D.83092_72 = &MEM[(struct drone_source_packet *)dpkt_1 + 12B].type_str;
  __s_147 = (char * restrict) D.83092_72;
  D.85552_149 = 9;
  __builtin___snprintf_chk (__s_147, 16, 1, D.85552_149, "%s", D.83091_70);


so for some reason we compute the object size of *D.38092_72 as 9.  We
allocated
dpkt_1 as

  dpkt_1 = malloc (89);

which looks like enough.

C testcase:

typedef struct {
    unsigned int sentinel;
    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;
}