Re: Is t7006-pager.sh racy?

From: Jeff King <peff@peff.net>
Date: Oct 28, 2021, 22:10 UTC
Message-ID: <YXsfvU+faPH6m/m/@coredump.intra.peff.net>
In-Reply-To: <20211028195527.GA2574@szeder.dev>

On Thu, Oct 28, 2021 at 09:55:27PM +0200, SZEDER Gábor wrote:

Show 14 quoted lines

> > 
> > My usual test for an intentional SIGPIPE is "yes". So something like:
> > 
> >   git -p \
> >     -c core.pager='exit 0' \
> >     -c alias.yes='!yes' \
> >     yes
> > 
> > will reliably trigger SIGPIPE from yes, which git.c will then translate
> > into an exit code of 141.
> 
> Oh, that's clever.  Alas it's not applicable to our tests, because
> 'yes' is not portable; 8648732e29 (t/test-lib.sh: provide a shell
> implementation of the 'yes' utility, 2009-08-28).

True, though it would be easy enough to do:

  git -c alias.yes='!while true; do echo y; done' yes

> > So something like "git log --stdin" works, but you have to contort
> > yourself a bit to make it race-free:
> [...]
> Ugh.  I think this would work reliably, but...  ugh :)

Yes. :)

Show 6 quoted lines

> I wonder whether we could do this as a new pair of 'test-tool'
> helpers, one to run the pager through the usual pager-invoking
> machinery and to generate a lot of output, the other to be used as the
> early-exiting pager, with a pipe between the two to ensure that the
> SIGPIPE does happen.  Well, essentially the same that you outlined
> above but in C instead of shell, which I somehow find less "ugh".

Maybe, though now we may be diverging from how git.c uses the pager. As gross as what I wrote is, it is testing the code we want to test, I think. I am not sure that the alias vs builtin thing is worth caring about anyway, though, in which case the alias.yes thing above would be fine.

-Peff