shmat () возвращает другой "shmaddr" для того же " shmkey"

Вот моя установка...

/* Bounded Buffer item structure */

struct item {

    int  id;  /* string index value */

    char str[80];  /* string value */

};



/* Structure for the shared memory region */

typedef struct {

    int    debug;           /* debug flag */

    int    in;              /* index of next empty slot */    

    int    out;             /* index of next full slot  */

    char   MUTEXname[32];   /* name of the MUTEX semaphore */

    char   EMPTYname[32];   /* name of the EMPTY semaphore */

    char   FULLname[32];    /* name of the FULL semaphore  */

    struct item buff[BUFFSIZE];  /* circular buffer for producer/consumer items*/

    char   strarray[MAX_STRINGS][80]; /* shared array of strings for consumers */

} shr_mem_t;



/* Values for obtaining a shmid key via ftok() */

#define KEYPATH "."

#define KEYPROJ 4520

Main: (развилит () процессы "производитель" и "потребитель")

/* Use ftok() to get a value for a key to identify a shared memory segment */

shm_key = ftok(KEYPATH, KEYPROJ);



/* Create the shared memory segment */

shmid = shmget(shm_key, sizeof(shr_mem_t), IPC_CREAT | IPC_EXCL | 0660);



/* Attach shared memory segment to the parent process */

shmptr = shmat(shmid, NULL, 0);

Продюсер:

/* Use ftok() to get value for the key to identify the shared memory segment */

shm_key = ftok(KEYPATH, KEYPROJ);



/* Get the ID of the existing shared memory segment */

shmid = shmget(shm_key, sizeof(shr_mem_t), 0660);



/* Attach the shared memory segment */

shmptr = shmat(shmid, NULL, 0);

Потребитель:

/* Use ftok() to get value for the key to identify the shared memory segment */

shm_key = ftok(KEYPATH, KEYPROJ);



/* Get the ID of the existing shared memory segment */

shmid = shmget(shm_key, sizeof(shr_mem_t), 0660);   



/* Attach the shared memory segment */

shmptr = shmat(shmid, NULL, 0);

Проверка ошибок: (для краткости...)

if (shmid == -1) {

    perror("shmget failed in __________");

    exit(1);

} else {

    sprintf(errString, "<*> __________ shared memory id: %i ", shmid);

    perror(errString);

}



if(shmptr == (void *)(-1)) {

    perror("shmat failed in __________");

    exit(1);

} else {

    sprintf(errString, "<*> __________ attaching to shared memory address: %p ", shmptr);

    perror(errString);

}

Вывод:

<*> Main creating shared memory id: 101376 : No such file or directory

<*> Main attaching to shared memory address: 16000 : No such file or directory

Creating the producer and consumer processes...

<*> Producer located shared memory id: 101376 : Successful

<*> Consumer located shared memory id: 101376 : Successful

<*> Producer attaching to shared memory address: 10000 : Successful

<*> Consumer attaching to shared memory address: 10000 : Successful

Что происходит с адресом общей памяти? Как Main и Prod/Cons процессы получают разные shmaddr, когда они присоединяются, когда у них один и тот же shmid?

Заранее спасибо,

Z@K!