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From: Eric Sunshine <sunshine@sunshineco.com>
To: Andrzej Hunt <andrzej@ahunt.org>
Cc: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	Git List <git@vger.kernel.org>,
	Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH v4 3/8] for-each-repo: run subcommands on configured repos
Date: Mon, 3 May 2021 13:01:42 -0400	[thread overview]
Message-ID: <CAPig+cToeuq7S1176ze7kX9krjK1rGMOM-JDznF_Fr_qV09qWw@mail.gmail.com> (raw)
In-Reply-To: <cda4f200-2400-e915-e995-36eea2a27c11@ahunt.org>

I'm not Stolee and hadn't even looked at this code before, but I'll
jump in with a couple comments...

On Mon, May 3, 2021 at 12:11 PM Andrzej Hunt <andrzej@ahunt.org> wrote:
> On 15/10/2020 19:21, Derrick Stolee via GitGitGadget wrote:
> > +static int run_command_on_repo(const char *path,
> > +                            void *cbdata)
> > +{
> > +     int i;
> > +     struct child_process child = CHILD_PROCESS_INIT;
> > +     struct strvec *args = (struct strvec *)cbdata;
>
> I was curious there's a strong reason for declaring args as void *
> followed by this cast? The most obvious answer seems to be that this
> probably evolved from a callback - and we could simplify it now?

Agreed, the `void*` cbdata doesn't make sense here.

> > +     strvec_pushl(&child.args, "-C", path, NULL);
> > +
> > +     for (i = 0; i < args->nr; i++)
> > +             strvec_push(&child.args, args->v[i]);
>
> So here we're copying all of args - and I don't see any way of avoiding
> it since we're adding it to child's arg list.

... (dot dot dot)

> > +int cmd_for_each_repo(int argc, const char **argv, const char *prefix)
> > +{
> > +     struct strvec args = STRVEC_INIT;
> > +     for (i = 0; i < argc; i++)
> > +             strvec_push(&args, argv[i]);
>
> But why do we have to copy all of argv 1:1 into args here, only to later
> pass it to run_command_on_repo() which, as described above, copies the
> entire input again? I suspect this was done to comply with
> run_command_on_repo()'s API (which takes strvec) - does that seem
> plausible, or did I miss something?
>
> Which brings me to the real reason for my questions: I noticed we "leak"
> args (this leak is of no significance since it happens in cmd_*, but
> LSAN still complains, and I'm trying to get tests running leak-free). My
> initial inclination was to strvec_clear() or UNLEAK() args - but if we
> can avoid creating args in the first place we also wouldn't need to
> clear it later.
>
> My current proposal is therefore to completely remove args and pass
> argc+argv into run_command_on_repo() - but I wanted to be sure that I
> didn't miss some important reason to stick with the current approach.

An alternative to all this copying would be to take advantage of
child_process.argv which is owned by the caller, thus does not get
freed automatically by run_command(). This would allow you to re-use
the same argument vector for all calls. And you don't need
run_command_on_repo() at all. Something like this in
cmd_for_each_repo(), untested and typed directly in email:

    struct child_process child = CHILD_PROCESS_INIT;

    for (i = 0; !result && i < values->nr; i++) {
        const char *d = chdir(values->items[i].string);
        if (chdir(d))
            die_errno(_("cannot chdir to '%s'"), d);
        child.git_cmd = 1;
        child.argv = argv;
        result = run_command(&child);
    }

This assumes that argv[] is correctly NULL-terminated after
parse_options() -- I didn't check, but expect it to be so. If not,
it's easy enough to copy argv[] into `args` once and then
strvec_clear(&args) at the end of the function.

The one downside is that trace output wouldn't be as helpful (I think)
because you wouldn't see an explicit "-C <dir>", but I suppose the
tracing machinery can be invoked manually to address this.

  reply	other threads:[~2021-05-03 17:10 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-04 15:41 [PATCH 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-09-08 13:07   ` Đoàn Trần Công Danh
2020-09-09 12:14     ` Derrick Stolee
2020-09-04 15:42 ` [PATCH 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 5/7] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-09-08  6:29   ` SZEDER Gábor
2020-09-08 12:43     ` Derrick Stolee
2020-09-08 19:31     ` Junio C Hamano
2020-09-04 15:42 ` [PATCH 6/7] maintenance: recommended schedule in register/start Derrick Stolee via GitGitGadget
2020-09-04 15:42 ` [PATCH 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-09-11 17:49 ` [PATCH v2 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-09-17 14:05     ` Đoàn Trần Công Danh
2020-09-11 17:49   ` [PATCH v2 5/7] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-09-11 17:49   ` [PATCH v2 6/7] maintenance: recommended schedule in register/start Derrick Stolee via GitGitGadget
2020-09-29 19:48     ` Martin Ågren
2020-09-30 20:11       ` Derrick Stolee
2020-10-01 20:38         ` Derrick Stolee
2020-10-02  0:38           ` Đoàn Trần Công Danh
2020-10-02  1:55             ` Derrick Stolee
2020-10-05 13:16               ` Đoàn Trần Công Danh
2020-10-05 18:17                 ` Derrick Stolee
2020-09-11 17:49   ` [PATCH v2 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-10-05 12:57   ` [PATCH v3 0/7] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 1/7] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 2/7] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 3/7] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 4/7] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 5/7] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-10-05 12:57     ` [PATCH v3 6/7] maintenance: use default schedule if not configured Derrick Stolee via GitGitGadget
2020-10-05 19:57       ` Martin Ågren
2020-10-08 13:32         ` Derrick Stolee
2020-10-05 12:57     ` [PATCH v3 7/7] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget
2020-10-15 17:21     ` [PATCH v4 0/8] Maintenance III: Background maintenance Derrick Stolee via GitGitGadget
2020-10-15 17:21       ` [PATCH v4 1/8] maintenance: optionally skip --auto process Derrick Stolee via GitGitGadget
2020-10-15 17:21       ` [PATCH v4 2/8] maintenance: add --schedule option and config Derrick Stolee via GitGitGadget
2021-02-09 14:06         ` Ævar Arnfjörð Bjarmason
2021-02-09 16:54           ` Derrick Stolee
2021-05-10 12:16             ` Ævar Arnfjörð Bjarmason
2021-05-10 18:42               ` Junio C Hamano
2020-10-15 17:21       ` [PATCH v4 3/8] for-each-repo: run subcommands on configured repos Derrick Stolee via GitGitGadget
2021-05-03 16:10         ` Andrzej Hunt
2021-05-03 17:01           ` Eric Sunshine [this message]
2021-05-03 19:26             ` Eric Sunshine
2021-05-03 19:43           ` Derrick Stolee
2020-10-15 17:22       ` [PATCH v4 4/8] maintenance: add [un]register subcommands Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 5/8] maintenance: add start/stop subcommands Derrick Stolee via GitGitGadget
2020-12-09 18:51         ` Josh Steadmon
2020-12-09 19:16           ` Josh Steadmon
2020-12-09 21:59             ` Derrick Stolee
2020-12-10  0:13             ` Junio C Hamano
2020-12-10  1:52               ` Derrick Stolee
2020-12-10  6:54                 ` Junio C Hamano
2020-10-15 17:22       ` [PATCH v4 6/8] maintenance: create maintenance.strategy config Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 7/8] maintenance: use 'incremental' strategy by default Derrick Stolee via GitGitGadget
2020-10-15 17:22       ` [PATCH v4 8/8] maintenance: add troubleshooting guide to docs Derrick Stolee via GitGitGadget

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