Re: [PATCH 3/3] pager: properly log pager exit code when signalled

From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Vincent Lefevre <vincent@vinc17.net>,
	Chris Torek <chris.torek@gmail.com>,
	Denton Liu <liu.denton@gmail.com>,
	"Jeff Hostetler" <jeffhost@microsoft.com>
Subject: Re: [PATCH 3/3] pager: properly log pager exit code when signalled
Date: Mon, 01 Feb 2021 20:21:20 +0100	[thread overview]
Message-ID: <8735yffvbj.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <xmqqft2fmzk6.fsf@gitster.c.googlers.com>

On Mon, Feb 01 2021, Junio C Hamano wrote:

> Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:
>
>> When git invokes a pager that exits with non-zero the common case is
>> that we'll already return the correct SIGPIPE failure from git itself,
>> but the exit code logged in trace2 has always been incorrectly
>> reported[1]. Fix that and log the correct exit code in the logs.
>>
>> Since this gives us something to test outside of our recently-added
>> tests needing a !MINGW prerequisite, let's refactor the test to run on
>> MINGW and actually check for SIGPIPE outside of MINGW.
>>
>> The wait_or_whine() is only called with a true "in_signal" from from
>> finish_command_in_signal(), which in turn is only used in pager.c.
>>
>> I'm not quite sure about that BUG() case. Can we have a true in_signal
>> and not have a true WIFEXITED(status)? I haven't been able to think of
>> a test case for it.
>>
>> 1. The incorrect logging of the exit code in was seemingly copy/pasted
>>    into finish_command_in_signal() in ee4512ed481 (trace2: create new
>>    combined trace facility, 2019-02-22)
>>
>> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
>> ---
>>  run-command.c    |  8 +++++--
>>  t/t7006-pager.sh | 61 +++++++++++++++++++++++++++++++++++++++++-------
>>  2 files changed, 58 insertions(+), 11 deletions(-)
>>
>> diff --git a/run-command.c b/run-command.c
>> index ea4d0fb4b15..10e1c96c2bd 100644
>> --- a/run-command.c
>> +++ b/run-command.c
>> @@ -551,8 +551,12 @@ static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
>>  
>>  	while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
>>  		;	/* nothing */
>> -	if (in_signal)
>> -		return 0;
>> +	if (in_signal && WIFEXITED(status))
>> +		return WEXITSTATUS(status);
>> +	if (in_signal) {
>> +		BUG("was not expecting waitpid() status %d", status);
>> +		return -1;
>> +	}
>
> Doesn't BUG die, never to return control back to us?  How about
> "warning()" or "error()"?

Maybe I shouldn't do that, but I'm doing it reflexively because SunCC
will yell at me otherwise. See 56f56ac50b9 (style: do not "break" in
switch() after "return", 2020-12-16).

Maybe I should just deal with its complaints, or add an "/* unreachable
*/" comment there...