I'm developing a graphical user interface software using PhAB.

I made some simple program. 
It's function is like this:  button click -> just call PtHold() 

on_button_click()
{
   PtHold();
}
It works well.


But I changed it like this: button click -> send it to server -> receive ACK from server -> call PtHold()

regist_receive(&receive_from_server);

on_button_click()
{
   send_to_server();
}

receive_from_server()
{
   PtHold();
}

In this case program causes memory fault every time. (SIGSEGV)
It is same for PtRelease() too.

I have no idea about the reason. It is so weird.
Anybody can explain about this phenomenon?