Re: [PATCH] run-command: encode signal death as a positive integer

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jan 5, 2013, 22:19 UTC
Message-ID: <20130105221909.GA3247@elie.Belkin>
In-Reply-To: <20130105144949.GA24479@sigill.intra.peff.net>

Hi,

Jeff King wrote:

> When a sub-command dies due to a signal, we encode the
> signal number into the numeric exit status as "signal -
> 128".

[...]

> So we have a negative value inside the code, but once it
> passes across an exit() barrier, it looks positive (and any
> code we receive from a sub-shell will have the positive
> form).

[...]

> Unfortunately, this means that when the "use_shell" option
> is set, we need to be on the lookout for _both_ forms.

[...]

>             for the callers that do care, we can make life
> slightly easier by just using the consistent positive form.

Makes perfect sense.

>  Documentation/technical/api-run-command.txt | 6 ++----
>  editor.c                                    | 2 +-
>  run-command.c                               | 2 +-
>  3 files changed, 4 insertions(+), 6 deletions(-)

t/test-terminal.perl imitates the same logic. It doesn't check for anything other than whether the exit status is 0, but maybe it would be worth squashing in the below as a futureproofing measure nonetheless.

Aside from the launch_editor bugfix, the only observable effects of the above patch I can find are some changed error messages:

	error: external filter cat failed -126
	-> error: external filter cat failed 130

	warning: svnrdump, returned -126
	-> warning: svnrdump, returned 130

Those messages are equally senseless before and after the patch, so
for what it's worth,
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>

Thanks.

diff --git i/t/test-terminal.perl w/t/test-terminal.perl
index 10172aee..1fb373f2 100755
--- i/t/test-terminal.perl
+++ w/t/test-terminal.perl
@@ -31,7 +31,7 @@ sub finish_child {
 	} elsif ($? & 127) {
 		my $code = $? & 127;
 		warn "died of signal $code";
-		return $code - 128;
+		return $code + 128;
 	} else {
 		return $? >> 8;
 	}