Re: [Libevent-users] Re: Infinite loop in libevent-1.4.14b-stable

[Daniel Janzon <janzon@xxxxxxxxx>]

Hi Nick,

On Fri, Mar 2, 2012 at 9:00 PM, Nick Mathewson <nickm@xxxxxxxxxxxxx> wrote:
> On Fri, Mar 2, 2012 at 10:00 AM, Daniel Janzon <janzon@xxxxxxxxx> wrote:
>> I found a similar report in the mailing list archive, where it was
>> concluded that this can happen when event_set is called after
>> event_add. In this case, however, the only place in the code where
>> event_set is called, is on the line before even_add.
>
> That isn't a guarantee unless you're *certain* that the memory that
> you're calling event_set() on is not a currently added event.

Quite true! I guess it must be that that's happening although I can't find
any error in the code.

> Libevent 2.0's debug-mode feature would catch this case, if you have a
> chance to build against 2.0 some time and turn on debug mode.
>
> As a fail-safe mode, you can stop using event_set() and write your own
> (forward-compatible!) event_new() and event_free(), so you don't need
> to worry about accidentally re-assigning an event.

Thereby trading an infinite loop for a memory leak. Not a bad deal :)

> Alternatively, if the memory that you're calling event_set() on has a
> known initial state (for example, you're getting it from calloc()),
> you could check its ev_flags values before you call  event_set on it;
> that might turn up the problem.

I reuse the event objects millions of times. I guess memsetting them
to zero before event_set may smoke out the bug. I'll try that.

Regards,
Daniel
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