Re: Bug: Failure if stdin is closed.

From: Dale Worley <worley@c-66-31-108-177.hsd1.ma.comcast.net>
Date: Jul 11, 2013, 17:21 UTC
Message-ID: <201307111721.r6BHLiXD013670@freeze.ariadne.com>
In-Reply-To: <87r4f52jjf.fsf@linux-k42r.v.cablecom.net>

> From: Thomas Rast <trast@inf.ethz.ch>

> May I ask why you need this, and to what extent this problem cannot be
> solved by instead redirecting from/to /dev/null?

The situation in which the problem arose is described here:

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> worley@alum.mit.edu (Dale R. Worley) writes:
> 
> > (The original problem and the discussion that ensued is on the
> > git-users mailing list:
> > https://groups.google.com/forum/#!topic/git-users/lNQ7Cn35EqA)

It involves invoking git from Apache. I haven't read up on the details because I didn't need to in order to debug the problem.

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> Closing 2 usually has even funkier consequences if the program proceeds
> to open some other file, it ends up as fd 2, and it then dies with an
> error.  In that sense it might be saner to simply die whenever open()
> gives an FD in the 0..2 range (and we weren't explicitly trying to
> reopen one of them).

True... But fd 2 may be needed under many unpredictable circumstances. In regard to fd 0, we can predict that standard input (per se) will not be needed, so it's anti-robust to require that it be open for the code to function at all.

> However, does it fully fix the issue you describe?  What if you then run
> 'git checkout -F -' to read the message from stdin?

Obviously, if the git command explicitly requires use of standard-input, then standard-input needs to be open.

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> > However, when looking at the code, I noticed that few of the functions
> > have comments describing what they do, and none describe their input
> > and output values.  In particular, there are no comments specifying
> > what the error return values are.  This is appalling for a supposedly
> > professional-quality project!
> 
> You are touching on a sore point of the git code base.  Some
> contributors have made a point of adding comments where appropriate, so
> we're improving, but round tuits are in short supply as always.  If you
> can supply such tuits, they would be appreciated.

I will try to put my money where my mouth is.

Dale