Date: Sat, 3 Feb 2024 20:25:16 +0100
To: cygwin@cygwin.com
Subject: Re: Restore SEM_FAILCRITICALERRORS [was: Aren't Windows System Error
 popups meant to be disabled in Cygwin?]
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Mail-Followup-To: cygwin@cygwin.com, David Allsopp <david@tarides.com>
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From: Corinna Vinschen via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Corinna Vinschen <corinna-cygwin@cygwin.com>
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On Feb  3 13:39, Corinna Vinschen via Cygwin wrote:
> On Feb  2 19:51, Corinna Vinschen via Cygwin wrote:
> > On Feb  2 18:22, Corinna Vinschen via Cygwin wrote:
> > > On Feb  2 14:56, David Allsopp via Cygwin wrote:
> > > > On Fri, 2 Feb 2024 at 14:18, Corinna Vinschen via Cygwin wrote:
> > > > > Is it actually a safe bet that the error mode set by SetThreadErrorMode
> > > > > is then propagated as process error mode to the child process?
> > > > >
> > > > > I have to ask that because Microsoft conveniently forgot to document
> > > > > this scenario in the MSDN docs.
> > > > 
> > > > :o) Never knowingly clear, are they! It would seem to be the intent of
> > > > SetThreadErrorMode that it would behave that way but who knows.
> > > > 
> > > > Happy to set up a quick experiment to check that it does work (i.e.
> > > > [...]
> > > Wanna try this?
> > [...]
> > However, it occured to me that this won't work at all.
> > [...]
> 
> Sorry to say that, but SetThreadErrorMode/CreateProcess don't do what we
> want them to do.  I just tested this myself with a modified Cygwin DLL
> (code below) and it turns out that the child process error mode is
> the same as the parent's process error mode.  Changing the thread
> error mode from the Cygwin default 3 (aka SEM_FAILCRITICALERRORS |
> SEM_NOGPFAULTERRORBOX) to 0 doesn't have any effect.
> [...etc.]

MSYS2 has introduced the environment variable option CYGWIN=winjitdebug.
I backported this patch now.  So default is back to propagating Cygwin's
error mode and if you want to reset the error mode of a non-Cygwin child
process back to OS default, just set the option, for instance, like
this:

  $ CYGWIN=winjitdebug env <your-non-Cygwin.exe>

This patch will be in Cygwin 3.5.1.  For the time being, it will be
available in the next test release cygwin-3.6.0-0.28.g918c3eda4176 as
well.


HTH,
Corinna

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