Re: [PATCH 3/6] Facilitate debugging Git executables in tests with gdb

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 27, 2015, 16:34 UTC
Message-ID: <xmqqr3kge0d3.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <alpine.DEB.1.00.1510271036100.31610@s15462909.onlinehome-server.info>

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

Show 20 quoted lines

>> Most TEST_ environment variables that git respects are under
>> GIT_TEST_* --- e.g., GIT_TEST_OPTS.  Should this match that pattern
>> as well, for easier debugging with commands like 'env | grep GIT_'?
>
> I dunno. This variable is most useful when inserted into the shell scripts
> in t/ themselves, not when specified via the command line. For example, if
> you have something like
>
> 	test_expect_success '123' '
> 		...
> 		# This Git call somehow fails and I have no clue why
> 		git push remote HEAD
> 		...
> 	'
>
> then prefixing the `git push` command with `TEST_GDB_GIT=1` lets you use
> `gdb` when running the test with the `-i` and `-v` flags.
>
> Please note that `TEST_GDB_GIT` is already a major step up from my initial
> `DDD`.

Yeah, that was my first reaction when I saw this patch. Instead of having to munge that line to "gdb -whatever-args git", you can do a single-shot debugging in a convenient way. And quite honestly, because nobody sane will run:

     $ cd t && TEST_GDB_GIT=1 sh ./t1234-frotz.sh

and can drive all the "git" running under gdb at the same time, I think what you showed would be the _only_ practical use case. I would have thought that TEST_GDB_GIT was way too long (and so is GIT_TEST_GDB) and was about to suggest using something short and sweet, even shorter than DDD, that you can easily add and remove.

It can be called GDB=1, perhaps?

I agree with all other points Jonathan made in his review, including "Neat." part ;-)

Thanks.