As far as I see from the sources of ext/sysvshm, it's not needed to do arithmetic (bit) OR (|) of "perm" with IPC_CREAT (and IPC_EXCL). The extension will do it for you. It tries to attach to the memory segment and if the try did not succeed it tries to attach but with flags set to user_flag | IPC_CREAT | IPC_EXCL.
The exact code (shm_flag is the third param to the function) :
if ((shm_id = shmget(shm_key, 0, 0)) < 0) {
if (shm_size < sizeof(sysvshm_chunk_head)) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%x: memorysize too small", shm_key);
efree(shm_list_ptr);
RETURN_FALSE;
}
if ((shm_id = shmget(shm_key, shm_size, shm_flag | IPC_CREAT | IPC_EXCL)) < 0) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "failed for key 0x%x: %s", shm_key, strerror(errno));
efree(shm_list_ptr);
RETURN_FALSE;
}
}
