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iphoneiosipadmemory-leaksgrand-central-dispatch
Udayakumar Rayala
Udayakumar Rayala

Reputation: 2284

Memory leaks when generating dispatch source timer events

We are using dispatch queues to generate timer events. Following is the code which does the task:

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
if (!timer) return self;
dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), interval * NSEC_PER_SEC, 5 * NSEC_PER_SEC);

dispatch_source_set_event_handler(timer, 
^{
    //Some work…
});

This works very well except that when we run the profiler, we see a lot of memory leaks from these methods:

We had made sure that timer is released using dispatch_release() method.

Can someone please let us know if there is any mistake we are doing in the code above? And also if you can point out any example of timer event generation, it would be helpful.

Upvotes: 1

Views: 4746

Answers (1)

Kazuki Sakamoto
Kazuki Sakamoto

Reputation: 14009

dispatch_source_set_timer(3) Mac OS X Manual Page

All timers will repeat indefinitely until dispatch_source_cancel() is called.

How do you call dispatch_source_cancel() and dispatch_release() for the timer?

Dispatch source timer example:

dispatch_source_t timer = dispatch_source_create(
    DISPATCH_SOURCE_TYPE_TIMER, 0, 0,
        dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0));

dispatch_source_set_timer(timer,
    dispatch_time(DISPATCH_TIME_NOW, 1ull * NSEC_PER_SEC),
        DISPATCH_TIME_FOREVER, 1ull * NSEC_PER_SEC);

dispatch_source_set_event_handler(timer, ^{
    NSLog(@"wakeup!");

    dispatch_source_cancel(timer);
});

dispatch_source_set_cancel_handler(timer, ^{
    NSLog(@"canceled");

    dispatch_release(timer);
});

dispatch_resume(timer);

Upvotes: 4

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