Re: [PATCH] pager: exit without error on SIGPIPE

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 1, 2021, 20:55 UTC
Message-ID: <xmqq8s87ld8y.fsf@gitster.c.googlers.com>
In-Reply-To: <87wnvrefbv.fsf@evledraar.gmail.com>

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

Show 28 quoted lines

>> Would it be the matter of propagating the exit status of the pager
>> noticed by wait_or_white() down thru finish_command_in_signal() and
>> wait_for_pager(1) to here, so
>>
>>  - If we know pager exited with non-zero status, we would report,
>>    perhaps with warning(_("..."));
>>
>>  - If we notice we got a SIGPIPE, we ignore it---it is nothing of
>>    interest to the end-user;
>>
>>  - Otherwise we do not do anything differently.
>>
>> would be sufficient?  Implementors of "git -p" may know that "git"
>> happens to implement its paging by piping its output to an external
>> pager, but the end-users do not care.  Implementors may say they are
>> giving 'q' to their pager "less", but to the end-users, who report
>> "I ran 'git log' and after reading a pageful, I told it to 'q'uit",
>> the distinction does not have any importance.
>>
>> Or are there more to it, in that the exit status we get from the
>> pager, combined with the kind of signal we are getting, is not
>> sufficient for us to tell what is going on?
>
> It is, I just wonder if ignoring the exit code is a practical issue as
> long as we're not clobbering SIGPIPE, particularly with my trace2
> logging patch in this thread.
>
> But yeah, we could patch git to handle this in the general case....

Sorry, but now you lost me.

I was merely wondering if Denton's patch can become a small update on top of these, if we just made sure that the exit code of the pager noticed by wait_or_whine() is reported to the code where Denton makes the decision to say "let's not re-raise but simply exit with 0 return as what we got is SIGPIPE". I guess we could even make git exit with the pager's return code in that case, as the end-user observable result would be similar to "git log | less" where 'less' may be segfaulting or exiting cleanly.

IOW, something like this on top of your three-patch series?

 pager.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git c/pager.c w/pager.c
index 3d37dd7ada..73bc5fc0e4 100644
--- c/pager.c
+++ w/pager.c
@@ -28,8 +28,14 @@ static void wait_for_pager_atexit(void)
 
 static void wait_for_pager_signal(int signo)
 {
+	int status;
+
 	close_pager_fds();
-	finish_command_in_signal(&pager_process);
+	status = finish_command_in_signal(&pager_process);
+
+	if (signo == SIGPIPE)
+		exit(status);
+
 	sigchain_pop(signo);
 	raise(signo);
 }