Re: [Problem] test_must_fail makes possibly questionable assumptions about exit_code.

From: Jeff King <peff@peff.net>
Date: Feb 28, 2018, 07:49 UTC
Message-ID: <20180228074918.GA32127@sigill.intra.peff.net>
In-Reply-To: <20180228074251.GA11673@dcvr>

On Wed, Feb 28, 2018 at 07:42:51AM +0000, Eric Wong wrote:

Show 28 quoted lines

> > > >  a) We could override the meaning of die() in Git.pm.  This feels
> > > >     ugly but if it works, it would be a very small patch.
> > > 
> > > Unlikely to work since I think we use eval {} to trap exceptions
> > > from die.
> > > 
> > > >  b) We could forbid use of die() and use some git_die() instead (but
> > > >     with a better name) for our own error handling.
> > > 
> > > Call sites may be dual-use: "die" can either be caught by an
> > > eval or used to show an error message to the user.
> 
> <snip>
> 
> > > >  d) We could wrap each command in an eval {...} block to convert the
> > > >     result from die() to exit 128.
> > > 
> > > I prefer option d)
> > 
> > FWIW, I agree with all of that. You can do (d) without an enclosing eval
> > block by just hooking the __DIE__ handler, like:
> > 
> > $SIG{__DIE__} = sub {
> >   print STDERR "fatal: @_\n";
> >   exit 128;
> > };
> 
> Looks like it has the same problems I pointed out with a) and b).

You're right. I cut down my example too much and dropped the necessary eval magic. Try this:

-- >8 --
SIG{__DIE__} = sub {
  CORE::die @_ if $^S || !defined($^S);
  print STDERR "fatal: @_";
  exit 128;
};

eval {
  die "inside eval";
};
print "eval status: $@" if $@;

die "outside eval"; -- 8< --

Running that should produce:

$ perl foo.pl; echo $? eval status: inside eval at foo.pl line 8. fatal: outside eval at foo.pl line 12. 128

It may be getting a little too black-magic, though. Embedding in an eval is at least straightforward, if a bit more invasive.

-Peff