[fpc-pascal] Linux IPC (SHM) : Getting Strange Value for shm_nattch (# of attachements)

[Tom__G]

Hi,

I try to get number of processes attached to a specific shared memory
segment.
So I read the shmctl record to retrieve this into shared memory :

type TShmid_ds = record
  shm_perm: TIPC_Perm; Permissions
  shm_segsz: cint; Segment size
  shm_atime: time_t; Last access time
  shm_dtime: time_t; Last detach time
  shm_ctime: time_t; Create time
  shm_cpid: ipc_pid_t; Creator PID
  shm_lpid: ipc_pid_t; Last operation PID
  shm_nattch: Word; Number of attachments  <--<< !
  shm_npages: Word; Number of pages
  shm_pages: Pointer; ?
  attaches: pointer; ?
end; 

I just created a simple function that I added to example found here : 
http://www.freepascal.org/docs-html/rtl/ipc/shmctl.html
http://www.freepascal.org/docs-html/rtl/ipc/shmctl.html 

...
Function Get_Nb_Proc(ID : longint) : word;
Var
  data : TSHMid_ds;
  shmctl_result : integer;
begin
  
  shmctl_result := shmctl (shmid,IPC_STAT, at data);
    
  writeln ('shmctl_result :', inttostr(shmctl_result));

  If shmctl_result=-1 then
  begin
    writeln ('Error : shmctl :',fpgeterrno);
    halt(1);
  end
  else
    Get_Nb_Proc:=data.shm_nattch;
end;
...

I tested and attached 1, 2 or 3 max processes to the segment. But I always
get strange high value while 'ipcs -m' shows me correct number of
attachements :

tom at debian:~/TESTS$ ipcs -m
------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0x53030001 24379392   tom        666        100        2

tom at debian:~/TESTS$ ./shmtool1
Shared memory -1 exists. Opening as client
shmctl_result :0
Number of Processes Attached to Shared Memory Segment 24379392 : 40920 
<--<< !
Press to Close

Does anyone know what happens ?
Thanks
Tom

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