c - libevent API: understanding the pointer parameters or return values -

for following libevent api:

void event_set(struct event *ev, int fd, short event, void (*cb)(int, short, void *), void *arg)  event_add(struct event *ev, const struct timeval *timeout);   struct event* event_new (struct event_base *, evutil_socket_t, short, event_callback_fn, void)    

i want know:

1) pointer parameter ev in second function event_add, function event_add makes local copy of ev structure or not?

for example, if like:

  code snippet 1:       struct event ev;      event_set(&ev, ..para list 1...);    // event 1       event_add(&ev, ...);      event_set(&ev, ..para list 2...);    // event 2      event_add(&ev, ...); 

event 1 different event 2 because parameter list 1 different parameter list 2. if event_add makes local copy, no problem, if event_add doesn't make local copy, these 2 event_add add event 2?

besides, if have main function:

   void func(){      struct event ev;      event_set(&ev, ...);      event_add(&ev, ...)    }     int main(){       func();       event_base_dispatch(base);    } 

after func() called, execution returns main(). since ev local variable inside func(). if event_add(&ev,...) doesn't make local copy, ev find , there problem. can call event_add() on local event structure?

i want add many timer events(use evtimer_set) time time, , adding happens in callback functions. can't define global variabbles timeout events in advance, if event_add() can't called on local variables, there solutions this?

2) event_new returns structure pointer, want know structure, in stack/heap memory or static memory?

my special case::

        in main.c                 int main(){                     struct event_base *base;                     struct event pcap_ev;                     .....                     // here file descriptor pcapfd                     event_set(&pcap_ev, pcapfd, ev_read|ev_persist, on_capture, pcap_handle);                     event_base_set(base, &pcap_ev);                     event_add(&pcap_ev, null);                     .....                     event_base_dispatch(base);                }           on_capture callback function:                 void *on_capture(int pcapfd, short op, void *arg)                 {                  pcap_t *handle;                  handle = (pcap_t *)arg;                  fqueue_t* pkt_queue;                   pkt_queue = init_fqueue();                  pcap_dispatch(handle, -1, collect_pkt, pkt_queue);  // function put cached packets pkt_queue                  process_pcap(pkt_queue);                 }            sub-routine process_pcap():                  void process_pcap(pkt_queue);{                       (pkt in pkt_queue){      // here pseudo code                            insert(table, pkt);     // here insert pkt table                             struct event pkt_ev;                            evtimer_set(&pkt_ev, timer_cb, null);  // want call timer_cb after timeout                            event_base_set(base, &pkt_ev);                            event_add(&pkt_ev, timeout);                                            }                 }           callback function timer_cb():                  timer_cb(...){                      if(...)  delete(table, pkt);                      .......                 } 

i'm afraid timer_cb() won't called because pkt_ev local variable.

you must use different struct event instance each event want know about. can call event_add() on local struct event variable if variable has lifetime spans across calls event loop api until removed event_del().

the allocation functions default heap, can substitute own allocation routines in place event_set_mem_functions().