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Date: Wed, 2 Jul 2025 12:34:06 +0200
To: cygwin AT cygwin DOT com
Subject: Re: setpgid non-compliance with POSIX?
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From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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On Jun 30 12:07, Jeremy Drake via Cygwin wrote:
> On Mon, 30 Jun 2025, Corinna Vinschen via Cygwin wrote:
> 
> > On Jun 28 12:32, Jeremy Drake via Cygwin wrote:
> > > I was looking at setpgid yesterday, and it seems deficient with respect to
> > > the errors required to be returned by the POSIX docs in
> > > https://pubs.opengroup.org/onlinepubs/9799919799/functions/setpgid.html
> > >
> > > Basically, it seems that setpgid allows any arbitrary positive integer to
> > > be set as pgid, rather than restricting to setting it to either the
> > > process's pid or to an existing pgid in the same session (sid).
> >
> > Yeah, error checking in setpgid is a bit on the lacking side.  With only
> > minor changes, the function is basically 25 years old :}
> 
> The POSIX docs metioned that an old BSD allowed setting arbitrary pgid
> 
> > Off the top of my head I don't know how to check the pgid already exists.
> > Do you?
> 
> I think it'd have to iterate all processes and check pgid and sid members
> of pinfo until it found a match.

I'd suggest not to follow up on this for now.  We didn't have any
problems with this so far.  If you like you can create a testcase as a
known failure, but a real fix of this without OS support is a lot of
work with a questionable gain.


Corinna

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