[PD-dev] Segfault without messages

[Hans-Christoph Steiner]

Please post this to the bug tracker.  Its under the Help menu, its  
called "report bug".  Or search puredata.info for "bug tracker".

.hc

On Oct 23, 2010, at 8:05 PM, Brian Neltner wrote:

> Thanks Claude for your help.
>
> I will personally just be switching to mavg instead of history for now
> since I need to be confident it will work. Is there someone I can  
> notify
> who maintains the history external who would be interested in knowing
> about the bug?
>
> Brian
>
> On Sun, 2010-10-24 at 00:38 +0100, Claude Heiland-Allen wrote:
>> On 24/10/10 00:22, Brian Neltner wrote:
>>> Thanks for the info Claude,
>>>
>>> Here is what gdb eventually spit out.
>>>
>>> I read the documentation page, but I'm afraid I don't really see  
>>> what I
>>> should do from that. Is it trying to do a trace with #0 being the
>>> immediate call that crashed, while #1 is what called #0 and #2  
>>> called #1
>>> and so on? If so, it seems that maxlib history is what is causing  
>>> the
>>> problem.
>>
>> Yes, in the absence of symbol information from 'history.pd_linux', I
>> would guess that it is these lines that are the problem:
>>
>> http://pure-data.svn.sourceforge.net/viewvc/pure-data/branches/pd-extended/0.42/externals/maxlib/history.c?revision=13589&view=markup#l155
>>
>> 155 	 if(++x->x_inpointer > MAX_ARG)
>> 156 	{
>> 157 	x->x_inpointer = 0;
>> 158 	}
>>
>> Possibly it should be >= instead of >, otherwise the code might end  
>> up
>> reading/writing past the end of the 0-indexed arrays of size MAX_ARG,
>> causing all kinds of memory corruption and random crashes, but I  
>> don't
>> suggest making the change without checking whether it is correct -  
>> the
>> code doesn't have any comments indicating the data invariants.
>>
>>> Sorry, I wish I knew more about programming...
>>> Brian
>>>
>>> On Sat, 2010-10-23 at 21:13 +0100, Claude Heiland-Allen wrote:
>>>> On 23/10/10 20:36, Brian Neltner wrote:
>>>>> I have attached the offending script.
>>>>
>>>> Seems quite simple, but I don't have pd-extended and miss the  
>>>> required
>>>> libraries to test.
>>>>
>>>>> pd gui; pd process exited
>>>>> Segmentation Fault
>>>>>
>>>>> Not very useful...
>>>>
>>>> You could try 'gdb' or 'valgrind' to get more useful output.
>>>>
>>>> $ gdb --args pd-extended blah blah
>>>>> run
>>>> Segmentation Fault
>>>>> bt
>>>> (tells you where the error is, hopefully)
>>>>> quit
>>>> $
>>>>
>>>> See also:
>>>>
>>>> http://puredata.info/docs/developer/DebuggingPdExternals
>>>>
>>>>
>>>> Claude
>>>
>>
>>
>> Claude
>
>
>
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