callbacks question - c

Question

Basically im trying to make a dispatcher, but it fails because it's always "!event->callback_function", my code:
#include "event.h"
#include "memory.h"
#include "thread.h"
#include <stdio.h>
#include <time.h>
#include <assert.h>
bool running;
typedef struct Event {
event_callback_t cb;
time_t delay;
void* p;
struct Event* next;
} Event;
Event* g_events;
void _remove_event __P((Event**, Event *));
void event_dispatch_internal __P(());
void add_event_internal __P((Event**, Event *));
void
event_dispatch()
{
g_events = (Event *)MyMalloc(sizeof(*g_events));
create_thread((callback_t)event_dispatch_internal, (void *)NULL);
}
void
add_event_internal(Event** events, Event* event)
{
event->next = *events;
*events = event;
}
void
add_event(callback, param, delay)
event_callback_t callback;
void *param;
time_t delay;
{
Event* event;
event = (Event *)MyMalloc(sizeof(*event));
assert(0 != event);
event->delay = time(NULL) + delay;
event->p = param;
event->cb = callback;
add_event_internal(&g_events, event);
}
void
_remove_event(Event** events, Event* event)
{
event = *events;
*events = event->next;
}
void
event_dispatch_internal()
{
#ifdef _DEBUG
fprintf(stderr, "Events started\n");
#endif
while (true) {
Event* tmp;
for (tmp = g_events; tmp; tmp = tmp->next) {
if (time(NULL) >= tmp->delay) {
tmp->cb(tmp->p);
#ifdef _DEBUG
fprintf(stderr, "Executed event %p:%u\n", (void *)tmp, (unsigned int)tmp->delay);
#endif
_remove_event(&g_events, tmp);
}
}
}
}
it crashes but when i do it like that:
for (tmp = g_events; tmp; tmp = tmp->next) {
if (time(NULL) >= tmp->delay) {
if (!tmp->cb) {
tmp->cb(tmp->p);
#ifdef _DEBUG
fprintf(stderr, "Executed event %p:%u\n", (void *)tmp, (unsigned int)tmp->delay);
#endif
} else {
fprintf(stderr, "Couldnt execute event %p:%u\n", (void *)tmp, (unsigned int)tmp->delay);
}
}
}
it always gives "Couldn't execute event blabla"
while i call it like that:
void test_(void *);
void
test_(void *p)
{
fprintf(stderr, "test(): %d\n", *(int *)p);
}
int main()
{
int test;
test = 5;
event_dispatch();
add_event(test_, (void *)&test, 1);
do { } while (1);
return 0;
}
any help is apperciated

Answer 1

Your code doesn't make any sense. You fire off a thread, which then loops forever trying to walk the g_events list. However, at startup, that just has a single, uninitialised node in it, so anything could happen!
Furthermore (1), you have no synchronization between your threads, so even if you fix the above problem, you're likely to get into nasty race hazards when people try to add events.
Furthermore (2), both your threads are effectively in "busy-wait" loops, which will suck your CPU dry. You need to investigate a mechanism that causes your threads to sleep until something arrives, such as semaphores.