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Date:	Sat, 18 Jul 2009 11:45:40 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject:	Re: fun? with libsigsegv
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On Jul 18 00:20, Christopher Faylor wrote:
> On Fri, Jul 17, 2009 at 10:55:13PM +0000, Eric Blake wrote:
> >Eric Blake <ebb9 <at> byu.net> writes:
> >>Of course, given the code, that meant I wasn't using libsigsegv like I
> >>thought I was.  So, with my typo corrected, I'm (unfortunately) still
> >>seeing libsigsegv interference:
> >>
> >>$ ./foo fclose -1, errno 9 Aborted (core dumped)
> >
> >Even more depressing - this looks like a regression.  The same STC,
> >compiled with libsigsegv under cygwin 1.5, works in that environment.
> >
> >And I'm not sure what to do in gdb to try and get more useful
> >information:
> 
> AFAICT, the libsigsegv handler is overriding the "myfault" stuff in
> Cygwin and is causing a fault for something that should be ignored.  The
> "fault" in this case is coming from our old friend
> verifyable_object_isvalid.  We expect faults there and they are supposed
> to be ignored.
> 
> The regression from 1.5 is because this didn't cause a fault in 1.5 so
> it looks like something changed in newlib.
> 
> Looking at libsigsegv's code, I don't think it is being smart enough
> about Cygwin.
> 
> It isn't clear to me why sigaltstack is needed here since I don't see
> anything special happening with the stack.  It looks like you could
> modify libsigsegv to just avoid trying to do anything with the signal
> stack and you could use Cygwin's signal handlers directly.

As Eric mentioned already, the next gawk version comes with libsigsegv
as part of the package.  IIUC, it's not behaving correctly, so I guess
I should rather build the next gawk version with --disable-libsigsegv,
right?  I just don't know what other effect this has on gawk.  I'll
ask the maintainer.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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