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Mail Archives: cygwin/2018/10/04/05:18:21

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Subject: Re: An increment to Jon Turney's stackdump2backtrace script
To: cygwin AT cygwin DOT com
References: <af84c3ce-364e-e058-ac39-ef2713e06cda AT maxrnd DOT com> <8541aec5-b9f1-c9c4-bdc6-2f5940d10bc2 AT dronecode DOT org DOT uk>
From: Mark Geisert <mark AT maxrnd DOT com>
Message-ID: <8ff3264e-eb21-25f7-6a45-76b7309738f7@maxrnd.com>
Date: Thu, 4 Oct 2018 02:18:02 -0700
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In-Reply-To: <8541aec5-b9f1-c9c4-bdc6-2f5940d10bc2@dronecode.org.uk>

Jon Turney wrote:
> On 01/10/2018 10:20, Mark Geisert wrote:
>> For those Cygwin developers who tend to attract stackdump files...
>>
>> ..mark (who defines an alias 'bt' to launch the script because he can't get
>> gdb out of his head)
>
> Nice. Thanks.
>
>> OTHERS=`ldd $IMG1 | awk '{print $3}' | sort -r | tr '\\n' ' '`
>
> One thing you should be aware of here is that you are assuming that the other
> DLLs (i) have the same base address locally and on the system where the
> stackdump was generated [an assumption which rebase will tend to invalidate],
> and (ii) don't get relocated.

True.  It's geared toward my workflow which only deals with stuff I've built on 
my own machine and debugging/fixing pretty soon after causing the stackdump. 
Any update to any of the files involved risks invalidating the stackdump.

> (The executable and cygwin1.dll don't suffer from this problem, as they have
> fixed addresses in the process memory layout used by cygwin)
>
> For this reason, stackdumps are a weak tool for debugging crashes in other
> DLLs.  There were some patches posted to add DLL load addresses to the
> stackdump, not sure what happened to them...

Huh.  I'll see if I can find them in the cygwin-patches archive.

> It would perhaps be better to write a minidump, which captures that information
> (and more...)

Are you alluding specifically to Windows minidump or just generally a small 
information dump?

On a related topic, I noticed dumper.exe in winsup/utils and played around with 
it.  I'm unsure if it captures everything one would want in a corefile.  I'm 
also unsure if there could even be a PE/COFF corefile and what it would contain.
Cheers,

..mark

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