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

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> On Sat, Jan 05, 2013 at 09:03:16AM -0500, Jeff King wrote:
> ...
> The downside is that callers of run_command can no longer
> differentiate between a signal received directly by the
> sub-process, and one propagated. However, no caller
> currently cares, and since we already optimize out some
> calls to the shell under the hood, that distinction is not
> something that should be relied upon by callers.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---

Very nicely explained.  Thanks.

>  Documentation/technical/api-run-command.txt | 6 ++----
>  editor.c                                    | 2 +-
>  run-command.c                               | 2 +-
>  3 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/technical/api-run-command.txt b/Documentation/technical/api-run-command.txt
> index f18b4f4..5d7d7f2 100644
> --- a/Documentation/technical/api-run-command.txt
> +++ b/Documentation/technical/api-run-command.txt
> @@ -55,10 +55,8 @@ The functions above do the following:
>    non-zero.
>  
>  . If the program terminated due to a signal, then the return value is the
> -  signal number - 128, ie. it is negative and so indicates an unusual
> -  condition; a diagnostic is printed. This return value can be passed to
> -  exit(2), which will report the same code to the parent process that a
> -  POSIX shell's $? would report for a program that died from the signal.
> +  signal number + 128, ie. the same value that a POSIX shell's $? would
> +  report.  A diagnostic is printed.
>  
>  
>  `start_async`::
> diff --git a/editor.c b/editor.c
> index 065a7ab..27bdecd 100644
> --- a/editor.c
> +++ b/editor.c
> @@ -51,7 +51,7 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
>  		sigchain_push(SIGINT, SIG_IGN);
>  		sigchain_push(SIGQUIT, SIG_IGN);
>  		ret = finish_command(&p);
> -		sig = ret + 128;
> +		sig = ret - 128;
>  		sigchain_pop(SIGINT);
>  		sigchain_pop(SIGQUIT);
>  		if (sig == SIGINT || sig == SIGQUIT)
> diff --git a/run-command.c b/run-command.c
> index 757f263..cfb7274 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -249,7 +249,7 @@ static int wait_or_whine(pid_t pid, const char *argv0)
>  		 * mimics the exit code that a POSIX shell would report for
>  		 * a program that died from this signal.
>  		 */
> -		code -= 128;
> +		code += 128;
>  	} else if (WIFEXITED(status)) {
>  		code = WEXITSTATUS(status);
>  		/*