asked on

AIX 4.2 shared memory

I'm using AIX 4.2 and in the midst of porting over a working C program written originally in SunOS. I managed to compile in AIX but encounter runtime error. I'm using the dbx debugger at the moment

These are the error messages

key = 1342742594
shmsz = 56736
shmid = 118786

initing real-time prices shm tables ....
addr(SHM_stkcodetbl_ptr) = 805306368
initing Stock Code Hash Table Shm....
addr(SHM_stknametbl_ptr) = 1073741824
initing Stock Name Hash Table Shm....
addr(SHM_stkmkt_ptr) = -1879048192
initing Stock Market Shm....
addr(SHM_stkcommon_ptr) = -1610612736
initing Stock Common Shm....
addr(SHM_timestamp_ptr) = 4294967295d
addr(SHM_timestamp_ptr) = 4294967295ld
addr(SHM_timestamp_ptr) = -1
addr(SHM_timestamp_ptr) = -1
initing Timestamp Shm....

(dbx) where
memset() at 0xd001ccc4
init_timestamp_shm(), line 306 in "initshm.c"
init_main_shmtbl(), line 767 in "initshm.c"
init_sun_shmtbl(), line 430 in "mainshm.c"
init_shmtbl_MODE(mode = 2), line 614 in "fep.c"
main(argc = 3, argv = 0x2ff22ce8), line 332 in "fep.c"

Segmentation fault in memset at 0xd001ccc4
0xd001ccc4 (memset+0x444) 98860000 stb r4,0x0(r6)

(dbx) print *SHM_timestamp_ptr
(timestamp = "ÿ", sysdate = "", vernum = "")

(dbx) print SHM_timestamp_ptr
0xffffffff

(dbx) print *SHM_ent_dptr
(stock_code = "ÿ", newsID = "", news_subject = "", stkpar_value = "", desc = "",
announce_date = 0, EX_date = 0, toSCANS_date = 0, lodge_date = 0, pay_date = 0,
entitl_percent = "", entitl_sen = "", entitl_numerator = 0, entitl_denom = 0, e
ntitl_type = "", entitl_indicator = '\0', entitl_remark = "", dissem_date = -934
803275, dissem_time = 2050998400)

(dbx) print SHM_ent_dptr
0xffffffff

HEADER file
-----------
typedef struct {
char timestamp [ TIMESTAMP_LEN +1 ];
char sysdate [ SYSTEMDATE_LEN +1 ];
char vernum [ VERNUM_LEN +1 ];

} TIMESTAMP_FEP;

typedef struct {
char stock_code [ STKCODE_LEN +1];
int key;
int next;
} HASH_ENTRY;

typedef struct {
char stock_code[ STKCODE_LEN +1];
char newsID[ NEWSID_LEN +1];
char news_subject [ TEXT_LEN +1];
char stkpar_value [ STKPAR_LEN+1];
char desc[ ENTT_DESC_LEN +1];
int announce_date ;
int EX_date ;
int toSCANS_date ;
int lodge_date ;
int pay_date ;
char entitl_percent [ ENTT_PERCENT_LEN+1];
char entitl_sen[ ENTT_SEN_LEN+1];
int entitl_numerator;
int entitl_denom;
char entitl_type [ ENTT_TYPE_LEN +1];
char entitl_indicator;
char entitl_remark [ ENTT_REM_LEN +1];
int dissem_date ;
int dissem_time ;

} ENTITL;

SOURCE CODE (partly):
---------------------
extern TIMESTAMP_FEP *SHM_timestamp_ptr;
extern HASH_ENTRY *SHM_ent_hptr;
extern ENTITL *SHM_ent_dptr;

int
init_timestamp_shm ()
{
TIMESTAMP_FEP *tmp_timestamp_ptr;

unsigned int timestamp_addr;
unsigned long ltimestamp_addr;

timestamp_addr = (unsigned int)SHM_timestamp_ptr;
ltimestamp_addr = (unsigned long)SHM_timestamp_ptr;

tmp_timestamp_ptr = SHM_timestamp_ptr; /* don't clobber original pointe
r */
fprintf(stderr,"addr(SHM_timestamp_ptr) = %ud \n", SHM_timestamp_ptr);
fprintf(stderr,"addr(SHM_timestamp_ptr) = %uld \n", SHM_timestamp_ptr);

fprintf(stderr,"addr(SHM_timestamp_ptr) = %d \n", timestamp_addr);
fprintf(stderr,"addr(SHM_timestamp_ptr) = %ld \n", ltimestamp_addr);

#ifdef DEBUG
fprintf(stderr, "initing Timestamp Shm....\n");
#endif
/*memset ( tmp_timestamp_ptr, MyNULL, sizeof ( TIMESTAMP_FEP ));*/
memset ( tmp_timestamp_ptr->timestamp, MyNULL, sizeof ( tmp_timestamp_ptr->tim /* ERROR indicated by debugger */
estamp ));
memset ( tmp_timestamp_ptr->sysdate, MyNULL, sizeof ( tmp_timestamp_ptr->sysda
te ));
memset ( tmp_timestamp_ptr->vernum, MyNULL, sizeof ( tmp_timestamp_ptr->vernum
));

return (0);

} /* -- init_timestamp_shm () -- */

int
init_entt_shm ( )
{
HASH_ENTRY *tmp_hash_ptr;
ENTITL *tmp_entt_ptr;
int i;

tmp_hash_ptr = SHM_ent_hptr;
tmp_entt_ptr = SHM_ent_dptr;

#ifdef DEBUG
fprintf(stderr, "initing Entitlement Shm....\n");
#endif
/*memset ( tmp_hash_ptr, MyNULL, MAX_ENT_HASH_ENTRIES * sizeof (HASH_ENTRY));*
/
memset ( tmp_hash_ptr->stock_code, MyNULL, MAX_ENT_HASH_ENTRIES * sizeof (tmp_
hash_ptr->stock_code));
tmp_hash_ptr->key = 0;
tmp_hash_ptr->next = 0;
for ( i = 0; i < MAX_ENT_HASH_ENTRIES; i++) {
tmp_hash_ptr [i].next = DEAD;
tmp_hash_ptr [i].key = DEAD;
}/* for */

/*
* Init Entitlement Data Shm
*/
/*memset ( tmp_entt_ptr, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( ENTITL));*/
memset ( tmp_entt_ptr->stock_code, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_
entt_ptr->stock_code));
memset ( tmp_entt_ptr->newsID, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_entt
_ptr->newsID));
/*memset ( tmp_entt_ptr, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( ENTITL));*/
memset ( tmp_entt_ptr->stock_code, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_
entt_ptr->stock_code));
memset ( tmp_entt_ptr->newsID, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_entt
_ptr->newsID));
memset ( tmp_entt_ptr->news_subject, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tm
p_entt_ptr->news_subject));
memset ( tmp_entt_ptr->stkpar_value, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tm
p_entt_ptr->stkpar_value));
memset ( tmp_entt_ptr->desc, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_entt_p
tr->desc));
tmp_entt_ptr->announce_date = 0;
tmp_entt_ptr->EX_date = 0;
tmp_entt_ptr->toSCANS_date = 0;
tmp_entt_ptr->lodge_date = 0;
tmp_entt_ptr->pay_date = 0;
memset ( tmp_entt_ptr->entitl_percent, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof(
tmp_entt_ptr->entitl_percent));
memset ( tmp_entt_ptr->entitl_sen, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp_
entt_ptr->entitl_sen));
tmp_entt_ptr->entitl_numerator = 0;
tmp_entt_ptr->entitl_denom = 0;
memset ( tmp_entt_ptr->entitl_type, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( tmp
_entt_ptr->entitl_type));
tmp_entt_ptr->entitl_indicator = NULL;
memset ( tmp_entt_ptr->entitl_remark, MyNULL, MAX_ENT_DATA_ENTRIES * sizeof( t
mp_entt_ptr->entitl_remark));
tmp_entt_ptr->dissem_date = 0;
tmp_entt_ptr->dissem_time = 0;

return (0);

} /* -- init_entt_shm () -- */

---------------------------------------------

What is wrong with that statement? Is it because the shared memory allocated is not enough? I was told that I don't have to allocate shared memory in AIX. However, all the shared memory segments appear when I issued the "ipcs -m" command. Could it be that I'm accessing the wrong segment of the shared memory? It stops midway into initialising the shared memory.

Pls help me out.

aditya070797

Hmm..
0xffffffff seems like a lot of junk.. Looks like your SHM_time_stamp_ptr is hosed from the start... check
if your variables are defined properly first. memset tries to 'set ' the contents of the memory location pointed to by the pointer, to
the value provided.. if the pointer points to junk, it will sigabrt..
--Aditya Vedula.

ASKER CERTIFIED SOLUTION

jos010697

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derick042497

ASKER

Attached is the code using shmat(). It ran fine until it reaches the code below (remarked). Is it alright to typecast a shared memory pointer to a structure pointer?

CODE:
----
int
attach_oddlots_shm ( )
{
key_t key;
int shmid;
/*long shmsz;*/
size_t shmsz;

key = (key_t) ODD_LOTS_SHMKEY;
shmsz = MAX_COUNTERS * sizeof ( ODD_LOTS );

if ( ( shmid = shmget (key, shmsz, IPC_CREAT | 0644 )) == -1 ) {
perror ("shmget ODD_LOTS");
printf ("errno :%d", errno);
return (-1);
}

/* Error 0xffffffff appears right after the statement below */
if (( SHM_oddlots_ptr
= (ODD_LOTS*) shmat ( shmid,(char*)0,0)) == NULL) {
perror ("shmat ODD_LOTS");
return (-1);
}
return (0);
}

STRUCTURE:
---------
typedef struct {
char stock_code[ STKCODE_LEN +1 ];
char delivery_basis;
char total_volume [ ODDLOT_TOTALVOL_LEN +1];
char total_value [ ODDLOT_TOTALVALUE_LEN+1];
int stk_refcode;
char buyin_price [ ODDLOT_BUYINPRICE_LEN+1];
int buyin_qty;
char odd_lot_stat;
char buy_price [ ODDLOT_BUYPRICE_LEN+1];
int buy_qty;
char sell_price [ ODDLOT_SELLPRICE_LEN+1];
int sell_qty;
char lastdone_price [ ODDLOT_LASTDONEPRICE_LEN+1];
int lastdone_qty;
} ODD_LOTS;

}