问C中的共享内存，shmdt的问题，它抛出无效参数

EN

 typedef struct {
int id;     //Client ID
int size;   //Memory Size
int mem;    //ID obtained from shmid
int  buf;   //shared memory var
} Segm;

 Segm segms[10];
int count_s = 0;

     int * buffer; /* shared buffer */
        /* we declared to zone to share */
       buffer =  shmat (mem, (char *)0, 0);
       if (buffer == NULL) {
          fprintf (stderr, "Error reserve shared memory \n");
          return -1; 
       }
        segms[count_s].mem = mem;
        segms[count_s].buf = *buffer;

  int mem = segms[i].mem;

 /* detach from the segment: */
    if (shmdt(&segms[i].buf) == -1) {
              perror("[SHMservice] Error: shmdt");
              result = -2;
    }

   shmctl (mem, IPC_RMID, (struct shmid_ds *)NULL);