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Date: Mon, 19 Apr 2010 14:44:35 +0300
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Subject: Re: 1.7.5: cygwin programs throw STATUS_ACCESS_VIOLATION exceptions
From: Yuval Emek <yuval DOT emek AT gmail DOT com>
To: cygwin AT cygwin DOT com
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On Mon, Apr 19, 2010 at 09:32, Christopher Faylor
<cgf-use-the-mailinglist-please AT cygwin DOT com> wrote:
> On Mon, Apr 19, 2010 at 02:20:48AM +0100, Dave Korn wrote:
>>On 18/04/2010 23:09, Yuval Emek wrote:
>>
>>> The context of the file xterm.exe.stackdump is:
>>> Exception: STATUS_ACCESS_VIOLATION at eip=3D610202F7
>>> eax=3D00CE00F8 ebx=3D61229E44 ecx=3D7530783F edx=3D002D20F0 esi=3D00000=
000 edi=3D0022FA14
>>> ebp=3D61020A10 esp=3D0022C7E4 program=3DC:\cygwin\bin\xterm.exe, pid 46=
40, thread main
>>> cs=3D001B ds=3D0023 es=3D0023 fs=3D003B gs=3D0000 ss=3D0023
>>> Stack trace:
>>> Frame =A0 =A0 Function =A0Args
>>> End of stack trace
>>
>>$ addr2line --exe cygwin-1.7.5-1/winsup/cygwin/cygwin1.dbg
>>610202F7
>>/ext/build/netrel/src/cygwin-1.7.5-1/winsup/cygwin/dll_init.cc:78
>>
>> =A0 =A071 =A0/* Initialize an individual DLL */
>> =A0 =A072 =A0int
>> =A0 =A073 =A0dll::init ()
>> =A0 =A074 =A0{
>> =A0 =A075 =A0 =A0int ret =3D 1;
>> =A0 =A076
>> =A0 =A077 =A0 =A0/* Why didn't we just import this variable? */
>> =A0 =A078 =A0 =A0*(p.envptr) =3D __cygwin_environ;
>> =A0 =A079
>>
>> =A0Ah. =A0Hmm. =A0That certainly does look like it's nothing to do with =
the DEP or
>>anything else; either we're missing a null pointer check here, or there's=
 some
>>reason why that pointer's never supposed to be null at this point in the =
code
>>but somehow it is.
>
> p.envptr is supposed to be filled in by the call to _cygwin_crt0_common
> in cygwin_attach_dll. =A0It is supposed to be set to the address of the
> "environ" variable in the DLL. =A0It is not supposed to be NULL. =A0That
> assignment should actually not even be necessary but the fact that
> envptr may be NULL is a problem. =A0Of course, it could just be some
> non-NULL garbage too. =A0Running in gdb and getting a stack trace would be
> instructive.

Can you be more specific? (I have been using cygwin for a while, but I
never debugged it beforehand.)
I can install gdb using setup.exe . What should I do then in order to
obtain a stack trace?

Thanks,

    Yuval

>
> The handling of the environ pointer has always made my head hurt. =A0In
> retrospect, I wish I'd simplified it for 1.7.x.
>
> cgf
>
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