Re: [Discuss-gnuradio] Weird malloc/free crash in pm_remez.cc

[Tom Rondeau]

On Mon, Nov 25, 2013 at 10:12 PM, Mark Cottrell
<address@hidden> wrote:
> On Mon, Nov 25, 2013 at 3:03 PM, Josh Myer <address@hidden> wrote:
>>
>> Hi all,
>>
>> I’ve got an annoying crash in the current head of gnuradio.  It’s
>> reproducible with the GRC file up at:
>>
>> http://www.joshisanerd.com/am_demod_crash.grc
>>
>> Does this crash for anyone else?  If nobody else can repro, this is
>> probably something that’s hosed in my environment.  Until someone else can
>> confirm this, it’s probably not worth looking into for anyone else.
>>
>> For me, the crash is at pm_remez.cc:698, the free(Grid) call in the error
>> handler.  (It’s coming from an error code of -2, which is probably due to my
>> putting in totally insane parameters or some such.)
>>
>> The odd thing is that it doesn’t look like it should be crashing in this
>> code path.  The pointer it’s freeing is totally fine when I step through
>> with gdb: the same as the malloc’d value, and no intervening free() calls,
>> yet it’s still crashing when it gets free()’d.  When I move the free(Grid)
>> line around, the crash follows it.  It doesn’t look like anything else is
>> getting screwed up, so I don’t know what to make of this.
>>
>> (FWIW, my goal is to poke around at decoding RDS.  I’ve removed a lot of
>> stuff to get down to this minimal program that shows the problem.  I’ve
>> gotten the AM demod stuff sorta working in ipython, and am now trying to
>> port it back to gnuradio… pointers on anything that’s clearly wrong with my
>> design there would be appreciated.)
>> —
>> /jbm
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>
>
> I was able to reproduce your problem with the linked grc file. I'm running
> gnuradio 3.7.2git-171-g362b0fb6 in debian jessie, and I have absolutely no
> idea what would be causing it, sorry.  At least now it seems as though it
> isn't isolated to a problem with your environment.
>
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You set the audio passband in the AM Demod to 0, which is what's
causing the problem. That's a bogus passband value, though it
shouldn't be causing a memory crash. We'll have to protect against
this instead of just letting it crash.

Thanks for the report.

Tom