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Subject: Re: 2.4-2.5 x64: bash crashes on backticks, gdb crashes on opening core dump
References: <56EE67C4.1070900@mail.mipt.ru>
Cc: Ivan Pozdeev <vano@mail.mipt.ru>
To: cygwin@cygwin.com
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From: Jon Turney <jon.turney@dronecode.org.uk>
Message-ID: <56F11625.7000904@dronecode.org.uk>
Date: Tue, 22 Mar 2016 09:53:41 +0000
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On 20/03/2016 09:05, Ivan Pozdeev wrote:
> gdb
> ---
> I managed to debug the gdb session with VisualGDB (trial).
> It turns out, the root cause is that the /bin/sh executable is x64, but
> the core file `sh.exe.core' - of the same executable - has i386 format!
> (objdump: <...>sh.exe.core:     file format elf32-i386)
>
> And gdb doesn't check that. Created ticket (incl. patch):
> https://sourceware.org/bugzilla/show_bug.cgi?id=19834
>
> Now I'm stumped. How can this be?! Does this mean `dumper' is faulty?
> If this was normal, gdb would likely be able to process the dumps.
>
> summary
> -------
> Writing this primarily to alert the community of these apparent critical
> bugs.
> Hints on where to look inside `dumper' would be more than welcome, too.

This is clearly a bug in dumper, which doesn't look like it's been 
ported to x86_64. See [1]

Ideally gdb wouldn't crash when presented with such an invalid core dump.

The strangeness which is a cygwin core dump doesn't appear to be 
documented anywhere but in the source code of dumper, but it is an elf 
file containing the memory image of the dumper process, with elf notes 
containing various Win32 API status structures.

[1] 
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=winsup/utils/dumper.cc;hb=HEAD#l628


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