Re: [Libevent-users] Re: help with debugging

[Mihai Draghicioiu <mihai.draghicioiu@xxxxxxxxx>]

My app is not using threads by itself. If there are any extra threads,
they are made by libevent internally, as far as i know.
See my other reply, i think i've figured the crash out. To answer your
question, it seems a DNS timeout triggers the crash.

On Sat, Sep 18, 2010 at 8:17 PM, Mark Ellzey <mthomas@xxxxxxxxxx> wrote:
> On Fri, Sep 17, 2010 at 10:29:08AM -0400, Nick Mathewson wrote:
>> On Fri, Sep 17, 2010 at 5:22 AM, Mihai Draghicioiu
>> <mihai.draghicioiu@xxxxxxxxx> wrote:
>> [...]
>> > Core was generated by `/home/mihai/frogmod-justice/frogserv'.
>> > Program terminated with signal 11, Segmentation fault.
>> > [New process 14829]
>> > #0 ?evhttp_request_get_input_buffer (req=0x99d90f8) at http.c:3014
>> > 3014 ? ?{
>> > (gdb) up
>> > #1 ?0x08091a0e in _bufferevent_run_eventcb (bufev=0x20, what=0) at
>> > bufferevent.c:264
>> > 264 ? ? ? ? ? ? ? ? ? ? bufev->errorcb(bufev, what, bufev->cbarg);
>> > Current language: ?auto; currently c
>> > (gdb)
>> > #2 ?0x080928cd in bufferevent_connect_getaddrinfo_cb (result=-4,
>> > ai=0x99e3100, arg=0x99d90f8) at bufferevent_sock.c:444
>> > 444 ? ? ? ? ? ? ? ? ? ? _bufferevent_run_eventcb(bev, BEV_EVENT_ERROR);
>> > (gdb) list 434
>>
>> This might or might not be for real. ÂIt could just be that by the
>> time the debugger is invoked, the memory that used to have 'bufev' has
>> already in _bufferevent_run_eventcb() has become an unused ("dead")
>> variable, and so the compiler has decided it can be overwritten by
>> something else. ÂYou could toss in an "assert(bufev != 0x20)" there if
>> you want to be sure , but I wouldn't expect it to trigger.
>>
>
> In my experience seeing a stacktrace like that is very reminiciant of a
> threading issue. If your application is threaded, your backtrace looks
> like garbage, it probably *is* garbage.
>
> Mihai, I did look at your code; compiled and ran it in a VM. What
> exactly triggers the crash? Please contact me off-list.
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