Should I call evhttp_request_free to release resource in http server? - http

Question

I use libevent2.1.1 to write a simple http server, I think I should release evhttp_request with evhttp_request_free in http_server_callback. but when I run it, error happened. Please tell me why, and what I should do.
void http_server_callback (struct evhttp_request *req, void *arg)
{
evhttp_send_reply (req, HTTP_OK, "OK", NULL);
evhttp_request_free(req);
}
int http_server_run (void)
{
struct event_base *base;
struct evhttp *http;
struct evhttp_bound_socket *handle;
base = event_base_new ();
if (! base)
{
fprintf (stderr, "Couldn't create an event_base: exiting\n");
return 1;
}
http = evhttp_new (base);
if (! http)
{
fprintf (stderr, "couldn't create evhttp. Exiting.\n");
return 1;
}
evhttp_set_gencb (http, http_server_callback, NULL);
handle = evhttp_bind_socket_with_handle (http, "127.0.0.1", 8888);
if (! handle)
{
fprintf (stderr, "couldn't bind to port 8888. Exiting.\n");
return 1;
}
event_base_dispatch (base);
return 0;
}
int main (void)
{
WSADATA WSAData;
WSAStartup (0x101, &WSAData);
http_server_run();
return 0;
}
thanks in advance

Answer 1

the req will be freed in the callback function evhttp_send_done when server finishes writing. So it results in a double free.
the source code in libevent:
static void
evhttp_send_done(struct evhttp_connection *evcon, void *arg)
{
int need_close;
struct evhttp_request *req = TAILQ_FIRST(&evcon->requests);
TAILQ_REMOVE(&evcon->requests, req, next);
need_close =
(REQ_VERSION_BEFORE(req, 1, 1) &&
!evhttp_is_connection_keepalive(req->input_headers))||
evhttp_is_connection_close(req->flags, req->input_headers) ||
evhttp_is_connection_close(req->flags, req->output_headers);
EVUTIL_ASSERT(req->flags & EVHTTP_REQ_OWN_CONNECTION);
evhttp_request_free(req);
...
}