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From: Ben Gardiner <BenGardiner@nanometrics.ca>
To: Andrew Haley <aph@redhat.com>
Cc: GCJ <java@gcc.gnu.org>
Subject: Re: libSegFault.so and gcj
Date: Fri, 15 May 2009 20:23:00 -0000	[thread overview]
Message-ID: <4A0DCF4D.1030506@nanometrics.ca> (raw)
In-Reply-To: <4A0C40E7.6080907@redhat.com>

Andrew Haley wrote:
>> I reason from this that the segfaults are likely stack overflows. Could
>> anyone confirm this?
>>     
> That's quite possible.  Do you not have a debugger?
>
> Clearly if it really is a stack overflow then you're not going to be
> able to call the null pointer handler.  There is a way around this,
> though.  If you use the -fstack-check option gcc generates a probe
> at the start of every method that writes a zero some 12kbytes below
> the stack pointer.  This will give you enough stack space for the
> catch_segv handler to run.
David Daney wrote:
> Usually if you die with a SIGSEGV, it is due to stack overflow.
> Probably for one reason or another you are getting a fault during the
> NullPointerException processing which causes the signal handler to be
> reentered recursively.  This goes on until the stack overflows and the
> kernel then kills the process.  If you could attach a debugger to the
> process, that might shed some light on exactly what is happening.
> Assuming that it is not normal for your application to take
> NullPointerExceptions it shouldn't be too tedious.
Andrew and David, thank you for your insights and for the speed with 
which they were provided.

About the debugger; I agree it would be the easiest way to figure out 
what's going on here. Since I don't know how to reproduce the problem I 
was hoping to get some information from our devices in the field if and 
when they die of a segmentation fault.

Would it be possible -- and if so, are there any significant drawbacks 
-- to store the previous handler in INIT_SEGV and register it when 
catch_segv is entered, then re-register catch_segv on the way out? Would 
this allow the segv signal to be passed up to libSegFault.so's handler 
when it would have otherwise resulted in a recursive dead-end?

,Ben Gardiner

 

  parent reply	other threads:[~2009-05-15 20:23 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-14 15:28 Ben Gardiner
2009-05-14 16:04 ` Andrew Haley
2009-05-15  9:17   ` Andrew Haley
2009-05-15 20:23   ` Ben Gardiner [this message]
2009-05-15 20:49     ` David Daney
2009-05-14 16:10 ` David Daney

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