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From: Jonathan Nieder <jrnieder@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, sandals@crustytoothpaste.net,
	steadmon@google.com, peff@peff.net, congdanhqx@gmail.com,
	phillip.wood123@gmail.com, emilyshaffer@google.com,
	sluongng@gmail.com, jonathantanmy@google.com,
	Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 01/11] maintenance: create basic maintenance runner
Date: Wed, 12 Aug 2020 15:50:54 -0700	[thread overview]
Message-ID: <20200812225054.GB104953@google.com> (raw)
In-Reply-To: <xmqqsgcr4ixo.fsf@gitster.c.googlers.com>

Junio C Hamano wrote:
> Jonathan Nieder <jrnieder@gmail.com> writes:

>>> +static int maintenance_run(struct maintenance_opts *opts)
>>> +{
>>> +	return maintenance_task_gc(opts);
>>> +}
>>> +
>>> +int cmd_maintenance(int argc, const char **argv, const char *prefix)
>>> +{
>>> +	static struct maintenance_opts opts;
>>> +	static struct option builtin_maintenance_options[] = {
>>> +		OPT_BOOL(0, "auto", &opts.auto_flag,
>>> +			 N_("run tasks based on the state of the repository")),
>>> +		OPT_END()
>>> +	};
>>
>> optional: these could be local instead of static
>
> Do we have preference?  I think it is more common in our codebase to
> have these non-static but I do not think we've chosen which is more
> preferable with technical reasoning behind it.  As the top-level
> function in any callchain, cmd_foo() does not have multiple instances
> running at the same time, or it does not have to be prepared to be
> called twice, so they can afford to be static, but is there any upside
> for them to be static?

Code size, execution time:

- benefit of static: can rely on automatic zero-initialization of
  pages instead of spending cycles and text size on explicit
  zero-initialization

- benefit of local: avoids wasting address space in bss when the
  function isn't called

Neither of those seems important enough to care about. :)

Maintainability:

- benefit of static: address is determined at compile time, so can build
  using C89 compilers that require struct initializers to be constant
  (but Git already cannot be built with such compilers)

- benefit of local: less likely to accidentally move the static var into
  a function that needs to be reentrant

- benefit of local: allows readers and reviewers to build the habit of
  seeing non-const "static" declarations within a function as the
  unusual case.  When a "static" is declared in a function body, this
  means we are caching something or have some other performance reason
  to sacrifice reentrancy

It's mostly that last aspect (saving readers from having to think
about it) that motivates my suggestion above.

Older Git code used static more because it was needed when building
using C89 compilers.

Thanks,
Jonathan

  reply	other threads:[~2020-08-12 22:51 UTC|newest]

Thread overview: 91+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-06 15:48 [PATCH 00/11] Maintenance I: Command, gc and commit-graph tasks Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 01/11] maintenance: create basic maintenance runner Derrick Stolee via GitGitGadget
2020-08-07 22:16   ` Martin Ågren
2020-08-12 21:03   ` Jonathan Nieder
2020-08-12 22:07     ` Junio C Hamano
2020-08-12 22:50       ` Jonathan Nieder [this message]
2020-08-14  1:05     ` Derrick Stolee
2020-08-06 15:48 ` [PATCH 02/11] maintenance: add --quiet option Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 03/11] maintenance: replace run_auto_gc() Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 04/11] maintenance: initialize task array Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 05/11] maintenance: add commit-graph task Derrick Stolee via GitGitGadget
2020-08-07 22:29   ` Martin Ågren
2020-08-12 13:30     ` Derrick Stolee
2020-08-14 12:23       ` Martin Ågren
2020-08-06 15:48 ` [PATCH 06/11] maintenance: add --task option Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 07/11] maintenance: take a lock on the objects directory Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 08/11] maintenance: create maintenance.<task>.enabled config Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 09/11] maintenance: use pointers to check --auto Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 10/11] maintenance: add auto condition for commit-graph task Derrick Stolee via GitGitGadget
2020-08-06 15:48 ` [PATCH 11/11] maintenance: add trace2 regions for task execution Derrick Stolee via GitGitGadget
2020-08-18 14:22 ` [PATCH v2 00/11] Maintenance I: Command, gc and commit-graph tasks Derrick Stolee via GitGitGadget
2020-08-18 14:22   ` [PATCH v2 01/11] maintenance: create basic maintenance runner Derrick Stolee via GitGitGadget
2020-08-18 14:22   ` [PATCH v2 02/11] maintenance: add --quiet option Derrick Stolee via GitGitGadget
2020-08-18 14:23   ` [PATCH v2 03/11] maintenance: replace run_auto_gc() Derrick Stolee via GitGitGadget
2020-08-18 14:23   ` [PATCH v2 04/11] maintenance: initialize task array Derrick Stolee via GitGitGadget
2020-08-18 23:46     ` Jonathan Tan
2020-08-18 14:23   ` [PATCH v2 05/11] maintenance: add commit-graph task Derrick Stolee via GitGitGadget
2020-08-18 23:51     ` Jonathan Tan
2020-08-19 15:04       ` Derrick Stolee
2020-08-19 17:43         ` Jonathan Tan
2020-08-18 14:23   ` [PATCH v2 06/11] maintenance: add --task option Derrick Stolee via GitGitGadget
2020-08-19  0:00     ` Jonathan Tan
2020-08-19  0:36       ` Junio C Hamano
2020-08-19 15:09         ` Derrick Stolee
2020-08-19 17:35           ` Jonathan Tan
2020-08-18 14:23   ` [PATCH v2 07/11] maintenance: take a lock on the objects directory Derrick Stolee via GitGitGadget
2020-08-19  0:04     ` Jonathan Tan
2020-08-19 15:10       ` Derrick Stolee
2020-08-18 14:23   ` [PATCH v2 08/11] maintenance: create maintenance.<task>.enabled config Derrick Stolee via GitGitGadget
2020-08-18 14:23   ` [PATCH v2 09/11] maintenance: use pointers to check --auto Derrick Stolee via GitGitGadget
2020-08-18 14:23   ` [PATCH v2 10/11] maintenance: add auto condition for commit-graph task Derrick Stolee via GitGitGadget
2020-08-19  0:09     ` Jonathan Tan
2020-08-19 15:15       ` Derrick Stolee
2020-08-18 14:23   ` [PATCH v2 11/11] maintenance: add trace2 regions for task execution Derrick Stolee via GitGitGadget
2020-08-19  0:11     ` Jonathan Tan
2020-08-18 20:18   ` [PATCH v2 00/11] Maintenance I: Command, gc and commit-graph tasks Junio C Hamano
2020-08-19 14:51     ` Derrick Stolee
2020-08-25 18:33   ` [PATCH v3 " Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 01/11] maintenance: create basic maintenance runner Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 02/11] maintenance: add --quiet option Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 03/11] maintenance: replace run_auto_gc() Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 04/11] maintenance: initialize task array Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 05/11] maintenance: add commit-graph task Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 06/11] maintenance: add --task option Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 07/11] maintenance: take a lock on the objects directory Derrick Stolee via GitGitGadget
2020-08-26 23:02       ` Jonathan Tan
2020-08-25 18:33     ` [PATCH v3 08/11] maintenance: create maintenance.<task>.enabled config Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 09/11] maintenance: use pointers to check --auto Derrick Stolee via GitGitGadget
2020-08-25 18:33     ` [PATCH v3 10/11] maintenance: add auto condition for commit-graph task Derrick Stolee via GitGitGadget
2020-08-26 23:02       ` Jonathan Tan
2020-08-26 23:56         ` Junio C Hamano
2020-08-25 18:33     ` [PATCH v3 11/11] maintenance: add trace2 regions for task execution Derrick Stolee via GitGitGadget
2020-09-04 13:09     ` [PATCH v4 00/11] Maintenance I: Command, gc and commit-graph tasks Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 01/11] maintenance: create basic maintenance runner Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 02/11] maintenance: add --quiet option Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 03/11] maintenance: replace run_auto_gc() Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 04/11] maintenance: initialize task array Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 05/11] maintenance: add commit-graph task Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 06/11] maintenance: add --task option Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 07/11] maintenance: take a lock on the objects directory Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 08/11] maintenance: create maintenance.<task>.enabled config Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 09/11] maintenance: use pointers to check --auto Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 10/11] maintenance: add auto condition for commit-graph task Derrick Stolee via GitGitGadget
2020-09-04 13:09       ` [PATCH v4 11/11] maintenance: add trace2 regions for task execution Derrick Stolee via GitGitGadget
2020-09-17 18:11       ` [PATCH v5 00/11] Maintenance I: Command, gc and commit-graph tasks Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 01/11] maintenance: create basic maintenance runner Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 02/11] maintenance: add --quiet option Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 03/11] maintenance: replace run_auto_gc() Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 04/11] maintenance: initialize task array Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 05/11] maintenance: add commit-graph task Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 06/11] maintenance: add --task option Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 07/11] maintenance: take a lock on the objects directory Derrick Stolee via GitGitGadget
2020-09-21 13:36           ` Ævar Arnfjörð Bjarmason
2020-09-21 13:43             ` Derrick Stolee
2020-09-21 19:29               ` Junio C Hamano
2020-09-17 18:11         ` [PATCH v5 08/11] maintenance: create maintenance.<task>.enabled config Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 09/11] maintenance: use pointers to check --auto Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 10/11] maintenance: add auto condition for commit-graph task Derrick Stolee via GitGitGadget
2020-09-17 18:11         ` [PATCH v5 11/11] maintenance: add trace2 regions for task execution Derrick Stolee via GitGitGadget
2020-09-17 18:35         ` [PATCH v5 00/11] Maintenance I: Command, gc and commit-graph tasks Junio C Hamano
2020-09-18 13:14           ` Johannes Schindelin

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