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

[demerphq <demerphq@gmail.com>]

On 28 February 2018 at 08:49, Jeff King <peff@peff.net> wrote:
> On Wed, Feb 28, 2018 at 07:42:51AM +0000, Eric Wong wrote:
>
>> > > >  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;
> };

FWIW, this doesn't need to use CORE::die like that unless you have
code that overrides die() or CORE::GLOBAL::die, which would be pretty
unusual.

die() within $SIG{__DIE__} is special cased not to trigger $SIG{__DIE__} again.

Of course it doesn't hurt, but it might make a perl hacker do a double
take why you are doing it. Maybe add a comment like

# using CORE::die to armor against overridden die()

cheers,
Yves