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From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Enzo Matsumiya <ematsumiya@suse.de>, git@vger.kernel.org
Subject: Re: [PATCH v2] pager: fix crash when pager program doesn't exist
Date: Sun, 21 Nov 2021 18:10:08 -0800	[thread overview]
Message-ID: <xmqqfsrplz3z.fsf@gitster.g> (raw)
In-Reply-To: <YZqSBlvzz2KgOMnJ@coredump.intra.peff.net> (Jeff King's message of "Sun, 21 Nov 2021 13:37:58 -0500")

Jeff King <peff@peff.net> writes:

> We'd usually leave of "Reviewed-by" until the reviewer has had a chance
> to see _this_ version of the patch. I.e., usually it would not be added
> by the submitter, but by the maintainer (unless you are resending
> verbatim a patch that already got review).
>
>> diff --git a/run-command.c b/run-command.c
>> index f329391154ae..a7bf81025afb 100644
>> --- a/run-command.c
>> +++ b/run-command.c
>> @@ -19,6 +19,7 @@ void child_process_clear(struct child_process *child)
>>  {
>>  	strvec_clear(&child->args);
>>  	strvec_clear(&child->env_array);
>> +	child_process_init(child);
>>  }
>
> And naturally I agree that the patch itself looks good. :)

Well, not to me X-<.  This is way too aggressive a change to be made
lightly without auditing the current users of run_command API.

It is rather common for us to reuse "struct child_process" in a code
path, e.g. builtin/worktree.c::add_worktree() prepares a single
instance of such a struct, sets cp.git_cmd to true, and runs either
"update-ref" or "symbolic-ref" to update "HEAD".  After successful
invocation of such a git subcommand, it then runs "git reset --hard",
with this piece of code:

	cp.git_cmd = 1;

	if (!is_branch)
		strvec_pushl(&cp.args, "update-ref", "HEAD",
			     oid_to_hex(&commit->object.oid), NULL);
	else {
		strvec_pushl(&cp.args, "symbolic-ref", "HEAD",
			     symref.buf, NULL);
		if (opts->quiet)
			strvec_push(&cp.args, "--quiet");
	}

	cp.env = child_env.v;
	ret = run_command(&cp);
	if (ret)
		goto done;

	if (opts->checkout) {
		cp.argv = NULL;
		strvec_clear(&cp.args);
		strvec_pushl(&cp.args, "reset", "--hard", "--no-recurse-submodules", NULL);
		if (opts->quiet)
			strvec_push(&cp.args, "--quiet");
		cp.env = child_env.v;
		ret = run_command(&cp);
		if (ret)
			goto done;
	}

Now, we could argue that this existing caller is too lazy to assume
that cp.git_cmd bit will be retained after run_command()
successfully finishes and can reuse the structure without setting
the bit again, and it should be more defensive.  And "successful
run_command() clears the child process so that you'll get a clean
slate" may even be a better API in the longer term.

But then a change like this one that changes the world order to make
it a better place is also responsible to ensure that the callers are
already following the new world order.

When merged to 'seen', this literally destroys tons of tests (the
first and easiest one to observe may be t0002).

Thanks.




  reply	other threads:[~2021-11-22  2:10 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-20 19:40 [PATCH v2] pager: fix crash when pager program doesn't exist Enzo Matsumiya
2021-11-21 18:37 ` Jeff King
2021-11-22  2:10   ` Junio C Hamano [this message]
2021-11-22  4:35     ` Jeff King
2021-11-22 14:52       ` Enzo Matsumiya
2021-11-22 17:05         ` Junio C Hamano
2021-11-23 16:40           ` Enzo Matsumiya
2021-11-24  1:55             ` Ævar Arnfjörð Bjarmason
2021-11-24 15:51               ` Jeff King
2021-11-22 16:04       ` [PATCH 0/5] run-command API: get rid of "argv" Ævar Arnfjörð Bjarmason
2021-11-22 16:04         ` [PATCH 1/5] archive-tar: use our own cmd.buf in error message Ævar Arnfjörð Bjarmason
2021-11-22 21:04           ` Junio C Hamano
2021-11-22 16:04         ` [PATCH 2/5] upload-archive: use regular "struct child_process" pattern Ævar Arnfjörð Bjarmason
2021-11-22 17:02           ` Jeff King
2021-11-22 20:53           ` Ævar Arnfjörð Bjarmason
2021-11-22 21:10             ` Jeff King
2021-11-22 21:36               ` Ævar Arnfjörð Bjarmason
2021-11-22 16:04         ` [PATCH 3/5] run-command API users: use strvec_pushv(), not argv assignment Ævar Arnfjörð Bjarmason
2021-11-22 21:19           ` Junio C Hamano
2021-11-22 21:30             ` Ævar Arnfjörð Bjarmason
2021-11-22 16:04         ` [PATCH 4/5] run-command API users: use strvec_pushl(), not argv construction Ævar Arnfjörð Bjarmason
2021-11-22 16:04         ` [PATCH 5/5] run-command API: remove "argv" member, always use "args" Ævar Arnfjörð Bjarmason
2021-11-22 17:32           ` Jeff King
2021-11-22 18:19             ` Ævar Arnfjörð Bjarmason
2021-11-22 18:47               ` Jeff King
2021-11-22 17:52         ` [PATCH 0/5] run-command API: get rid of "argv" Jeff King
2021-11-22 18:11           ` Junio C Hamano
2021-11-22 18:33             ` Ævar Arnfjörð Bjarmason
2021-11-22 18:49               ` Jeff King
2021-11-22 18:26           ` Ævar Arnfjörð Bjarmason
2021-11-23 12:06         ` [PATCH v2 0/9] run-command API: get rid of "argv" and "env" Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 1/9] worktree: remove redundant NULL-ing of "cp.argv Ævar Arnfjörð Bjarmason
2021-11-23 15:26             ` Eric Sunshine
2021-11-24  1:54               ` Junio C Hamano
2021-11-24  6:00                 ` Eric Sunshine
2021-11-24  6:12                   ` Eric Sunshine
2021-11-24  5:44               ` Eric Sunshine
2021-11-23 12:06           ` [PATCH v2 2/9] upload-archive: use regular "struct child_process" pattern Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 3/9] run-command API users: use strvec_pushv(), not argv assignment Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 4/9] run-command tests: " Ævar Arnfjörð Bjarmason
2021-11-24  1:33             ` Eric Sunshine
2021-11-23 12:06           ` [PATCH v2 5/9] run-command API users: use strvec_pushl(), not argv construction Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 6/9] run-command API users: use strvec_push(), " Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 7/9] run-command API: remove "argv" member, always use "args" Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 8/9] difftool: use "env_array" to simplify memory management Ævar Arnfjörð Bjarmason
2021-11-23 12:06           ` [PATCH v2 9/9] run-command API: remove "env" member, always use "env_array" Ævar Arnfjörð Bjarmason
2021-11-25 22:52           ` [PATCH v3 0/9] run-command API: get rid of "argv" and "env" Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 1/9] worktree: stop being overly intimate with run_command() internals Ævar Arnfjörð Bjarmason
2021-11-26  9:48               ` Eric Sunshine
2021-11-25 22:52             ` [PATCH v3 2/9] upload-archive: use regular "struct child_process" pattern Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 3/9] run-command API users: use strvec_pushv(), not argv assignment Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 4/9] run-command tests: " Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 5/9] run-command API users: use strvec_pushl(), not argv construction Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 6/9] run-command API users: use strvec_push(), " Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 7/9] run-command API: remove "argv" member, always use "args" Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 8/9] difftool: use "env_array" to simplify memory management Ævar Arnfjörð Bjarmason
2021-11-25 22:52             ` [PATCH v3 9/9] run-command API: remove "env" member, always use "env_array" Ævar Arnfjörð Bjarmason
2021-11-22 15:31     ` [PATCH v2] pager: fix crash when pager program doesn't exist Enzo Matsumiya
2021-11-22 16:22       ` Ævar Arnfjörð Bjarmason
2021-11-22 16:46         ` Enzo Matsumiya
2021-11-22 17:10           ` Ævar Arnfjörð Bjarmason
2021-11-22 17:41             ` Jeff King
2021-11-22 18:00             ` Junio C Hamano
2021-11-22 18:26               ` Jeff King
2021-11-22 17:55           ` Junio C Hamano
2021-11-22 18:19             ` Junio C Hamano
2021-11-22 18:37               ` Jeff King
2021-11-22 20:39                 ` Junio C Hamano
2021-11-22 17:08         ` Junio C Hamano
2021-11-22 18:35           ` Ævar Arnfjörð Bjarmason
2021-11-22 16:30       ` Jeff King

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