[Bug c/28823] New: sizeof not handled by pre-processor in #if statement

["gmalkin at convergedaccess dot com" <gcc-bugzilla at gcc dot gnu dot org>]

The following code:

#define EMS_SYSTEM_NUM 12
#define EMS_INET_NUM   12
#define EMS_SUBSYS_NUM  2

typedef struct _ercb {
    struct _ercb *ercb_next;
    struct _ercb *ercb_prev;
    short         ercb_did;
    short         ercb_pad;
} ems_rcb_t;

typedef struct {
    ems_rcb_t  *era_rcbp;
    unsigned    era_ecount;   /* event count */
    unsigned    era_bcount;   /* byte count */
} ems_era_elem_t;

static ems_era_elem_t  ems_system[EMS_SYSTEM_NUM];
static ems_era_elem_t  ems_inet[EMS_INET_NUM];
static ems_era_elem_t *ems_erm[] = {ems_system, ems_inet};

#if (sizeof(ems_erm) / sizeof(ems_era_elem_t *) != EMS_SUBSYS_NUM)
#error "EMS registration matrix not up to date"
#endif

main()
{
}

Compiled with the following command:

gcc -c testcase.c

Produces the following error:

testcase.c:22:12: error: missing binary operator before token "("

Where line 22 is the #if and the second ( is the 12th character.  The problem
appears to be that the #if is parsing the line before the sizeof() is resolved
to its manifest constant.  This causes the parser to treat "sizeof" as a term
and therefore to want a binary operator prior to the next term (in this case,
the open paren).  The fix is to resolve the sizeof first.  I tried creating a
#define for the sizeof() and replacing the defined value in the #if, but that
produced exactly the same error.


-- 
           Summary: sizeof not handled by pre-processor in #if statement
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gmalkin at convergedaccess dot com
 GCC build triplet: 4.1.1 20060525 (Red Hat 4.1.1-1)
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28823