From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "Andrzej Hunt" <andrzej@ahunt.org>,
git@vger.kernel.org, "Junio C Hamano" <gitster@pobox.com>,
"Lénaïc Huard" <lenaic@lhuard.fr>,
"Derrick Stolee" <dstolee@microsoft.com>,
"Felipe Contreras" <felipe.contreras@gmail.com>,
"SZEDER Gábor" <szeder.dev@gmail.com>,
"Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
"Eric Sunshine" <sunshine@sunshineco.com>,
"Elijah Newren" <newren@gmail.com>
Subject: Re: [PATCH v2 2/4] SANITIZE tests: fix memory leaks in t13*config*, add to whitelist
Date: Wed, 1 Sep 2021 03:53:51 -0400 [thread overview]
Message-ID: <YS8xj9XtKqEEy/Bb@coredump.intra.peff.net> (raw)
In-Reply-To: <87y28hwylq.fsf@evledraar.gmail.com>
On Tue, Aug 31, 2021 at 02:47:01PM +0200, Ævar Arnfjörð Bjarmason wrote:
> > That works, but now "util" is not available for all the _other_ uses for
> > which it was intended. And if we're not using it for those other uses,
> > then why does it need to exist at all? If we are only using it to hold
> > the allocated string pointer, then shouldn't it be "char *to_free"?
>
> Because having it be "char *" doesn't cover the common case of
> e.g. getting an already allocated "struct something *" which contains
> your string, setting the "string" in "struct string_list_item" to some
> string in that struct, and the "util" to the struct itself, as we now
> own it and want to free() it later in its entirety.
OK. I buy that storing a void pointer makes it more flexible. I'm not
altogether convinced this pattern is especially common, but it's not any
harder to work with than a "need_to_free" flag, so there's no reason not
to do that (and to be fair, I didn't look around for possible uses of
the pattern; it's just not one I think of as common off the top of my
head).
> That and the even more common case I mentioned upthread of wanting to
> ferry around the truncated version of some char *, but still wanting to
> account for the original for an eventual free().
>
> But yes, if you want to account for freeing that data *and* have util
> set to something else you'll need to have e.g. your own wrapper struct
> and your own string_list_clear_func() callback.
But stuffing it into the util field of string_list really feels like a
stretch, and something that would make existing string_list use painful.
There are tons of cases where util points to some totally unrelated (in
terms of memory ownership) item. I'd venture to say most cases where
string_list_clear() is called without free_util would count here.
> > I don't think most interfaces take a string_list_item now, so wouldn't
> > they similarly need to be changed? Though the point is that all of these
> > degrade to a regular C-string, so when you are just passing the value
> > (and not ownership), you would just dereference at that point.
>
> Sure, just like things would need to be changed to handle your proposed
> "struct def_string".
>
> By piggy-backing on an already used struct in our codebase we can get a
> lot of that memory management pretty much for free without much
> churn.
>
> If you squint and pretend that "struct string_list_item" isn't called
> something to do with that particular collections API (but it would make
> use of it) then we've already set up most of the scaffolding and
> management for this.
It's that squinting that bothers me. Sure, it's _kinda_ similar. And I
don't have any problem with some kind of struct that says "this is a
string, and when you are done with it, this is how you free it". And I
don't have any problem with building the "dup" version of string_list
with that struct as a primitive. But it seems to me to be orthogonal
from the "util" pointer of a string_list, which is about creating a
mapping from the string to some other thing (which may or may not
contain the string, and may or may not be owned).
TBH, I have always found the "util" field of string_list a bit ugly (and
really most of string_list). I think most cases would be better off with
a different data structure (a set or a hash table), but we didn't have
convenient versions of those for a long time. I don't mind seeing
conversions of string_list to other data structures. But that seems to
be working against using string_list's string struct in more places.
-Peff
next prev parent reply other threads:[~2021-09-01 7:53 UTC|newest]
Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 14:38 UNLEAK(), leak checking in the default tests etc Ævar Arnfjörð Bjarmason
2021-06-09 17:44 ` Andrzej Hunt
2021-06-09 20:36 ` Felipe Contreras
2021-06-10 10:46 ` Jeff King
2021-06-10 10:56 ` Ævar Arnfjörð Bjarmason
2021-06-10 13:38 ` Jeff King
2021-06-10 15:32 ` Andrzej Hunt
2021-06-10 16:36 ` Jeff King
2021-06-11 15:44 ` Andrzej Hunt
2021-06-10 19:01 ` SZEDER Gábor
2021-07-14 0:11 ` [PATCH 0/4] add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-07-14 0:11 ` [PATCH 1/4] tests: " Ævar Arnfjörð Bjarmason
2021-07-14 3:23 ` Đoàn Trần Công Danh
2021-07-14 0:11 ` [PATCH 2/4] SANITIZE tests: fix memory leaks in t13*config*, add to whitelist Ævar Arnfjörð Bjarmason
2021-07-14 0:11 ` [PATCH 3/4] SANITIZE tests: fix memory leaks in t5701*, " Ævar Arnfjörð Bjarmason
2021-07-14 0:11 ` [PATCH 4/4] SANITIZE tests: fix leak in mailmap.c Ævar Arnfjörð Bjarmason
2021-07-14 2:19 ` Eric Sunshine
2021-07-14 17:23 ` [PATCH v2 0/4] add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-07-14 17:23 ` [PATCH v2 1/4] tests: " Ævar Arnfjörð Bjarmason
2021-07-14 18:42 ` Andrzej Hunt
2021-07-14 22:39 ` Ævar Arnfjörð Bjarmason
2021-07-15 21:14 ` Jeff King
2021-07-15 21:06 ` Jeff King
2021-07-16 14:46 ` Ævar Arnfjörð Bjarmason
2021-07-16 18:09 ` Jeff King
2021-07-16 18:45 ` Jeff King
2021-07-16 18:56 ` Ævar Arnfjörð Bjarmason
2021-07-16 19:22 ` Jeff King
2021-07-14 17:23 ` [PATCH v2 2/4] SANITIZE tests: fix memory leaks in t13*config*, add to whitelist Ævar Arnfjörð Bjarmason
2021-07-14 18:57 ` Andrzej Hunt
2021-07-14 22:56 ` Ævar Arnfjörð Bjarmason
2021-07-15 21:42 ` Jeff King
2021-07-16 5:18 ` Andrzej Hunt
2021-07-16 21:20 ` Jeff King
2021-07-16 7:46 ` Ævar Arnfjörð Bjarmason
2021-07-16 21:16 ` Jeff King
2021-08-31 12:47 ` Ævar Arnfjörð Bjarmason
2021-09-01 7:53 ` Jeff King [this message]
2021-09-01 11:45 ` Ævar Arnfjörð Bjarmason
2021-07-14 17:23 ` [PATCH v2 3/4] SANITIZE tests: fix memory leaks in t5701*, " Ævar Arnfjörð Bjarmason
2021-07-15 17:37 ` Andrzej Hunt
2021-07-15 21:43 ` Jeff King
2021-08-31 13:46 ` [PATCH] protocol-caps.c: fix memory leak in send_info() Ævar Arnfjörð Bjarmason
2021-08-31 15:32 ` Bruno Albuquerque
2021-08-31 18:15 ` Junio C Hamano
[not found] ` <CAPeR6H69a_HMwWnpHzssaCm_ow=ic7AnzMdZVQJQ2ECRDaWzaA@mail.gmail.com>
2021-08-31 20:08 ` Ævar Arnfjörð Bjarmason
2021-07-14 17:23 ` [PATCH v2 4/4] SANITIZE tests: fix leak in mailmap.c Ævar Arnfjörð Bjarmason
2021-08-31 13:42 ` [PATCH] mailmap.c: fix a memory leak in free_mailap_{info,entry}() Ævar Arnfjörð Bjarmason
2021-08-31 16:22 ` Eric Sunshine
2021-08-31 19:38 ` Jeff King
2021-08-31 19:46 ` Junio C Hamano
2021-07-15 17:37 ` [PATCH v2 0/4] add a test mode for SANITIZE=leak, run it in CI Andrzej Hunt
2021-08-31 13:35 ` [PATCH v3 0/8] " Ævar Arnfjörð Bjarmason
2021-09-01 9:56 ` Jeff King
2021-09-01 10:42 ` Jeff King
2021-09-02 12:25 ` Ævar Arnfjörð Bjarmason
2021-09-03 11:13 ` Jeff King
2021-09-07 15:33 ` [PATCH v4 0/3] " Ævar Arnfjörð Bjarmason
2021-09-07 15:33 ` [PATCH v4 1/3] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-09-07 15:33 ` [PATCH v4 2/3] CI: refactor "if" to "case" statement Ævar Arnfjörð Bjarmason
2021-09-07 15:33 ` [PATCH v4 3/3] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-09-07 16:29 ` Eric Sunshine
2021-09-07 16:51 ` Jeff King
2021-09-07 16:44 ` [PATCH v4 0/3] " Jeff King
2021-09-07 18:22 ` Junio C Hamano
2021-09-07 21:30 ` [PATCH v5 " Ævar Arnfjörð Bjarmason
2021-09-07 21:30 ` [PATCH v5 1/3] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-09-07 21:30 ` [PATCH v5 2/3] CI: refactor "if" to "case" statement Ævar Arnfjörð Bjarmason
2021-09-07 21:30 ` [PATCH v5 3/3] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-09-08 4:46 ` Eric Sunshine
2021-09-16 3:56 ` [PATCH] fixup! " Carlo Marcelo Arenas Belón
2021-09-16 6:14 ` Ævar Arnfjörð Bjarmason
2021-09-08 11:02 ` [PATCH v5 0/3] " Junio C Hamano
2021-09-08 12:03 ` Ævar Arnfjörð Bjarmason
2021-09-09 23:10 ` Emily Shaffer
2021-09-16 10:48 ` [PATCH v6 0/2] " Ævar Arnfjörð Bjarmason
2021-09-16 10:48 ` [PATCH v6 1/2] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-09-16 10:48 ` [PATCH v6 2/2] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-09-19 8:03 ` [PATCH v7 0/2] " Ævar Arnfjörð Bjarmason
2021-09-19 8:03 ` [PATCH v7 1/2] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-09-19 8:03 ` [PATCH v7 2/2] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-09-22 11:17 ` [PATCH] fixup! " Carlo Marcelo Arenas Belón
2021-09-23 1:50 ` Ævar Arnfjörð Bjarmason
2021-09-23 9:20 ` [PATCH v8 0/2] " Ævar Arnfjörð Bjarmason
2021-09-23 9:20 ` [PATCH v8 1/2] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-09-23 9:20 ` [PATCH v8 2/2] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-11-03 22:44 ` Re* " Junio C Hamano
2021-11-03 23:57 ` Junio C Hamano
2021-11-04 10:06 ` Ævar Arnfjörð Bjarmason
2021-11-16 18:31 ` [PATCH] t0006: date_mode can leak .strftime_fmt member Ævar Arnfjörð Bjarmason
2021-11-16 19:04 ` Junio C Hamano
2021-11-16 19:31 ` Jeff King
2022-02-02 21:03 ` [PATCH 0/5] date.[ch] API: split from cache.h, add API docs, stop leaking memory Ævar Arnfjörð Bjarmason
2022-02-02 21:03 ` [PATCH 1/5] cache.h: remove always unused show_date_human() declaration Ævar Arnfjörð Bjarmason
2022-02-02 21:03 ` [PATCH 2/5] date API: create a date.h, split from cache.h Ævar Arnfjörð Bjarmason
2022-02-02 21:19 ` Ævar Arnfjörð Bjarmason
2022-02-15 3:04 ` Junio C Hamano
2022-02-02 21:03 ` [PATCH 3/5] date API: provide and use a DATE_MODE_INIT Ævar Arnfjörð Bjarmason
2022-02-02 21:03 ` [PATCH 4/5] date API: add basic API docs Ævar Arnfjörð Bjarmason
2022-02-15 2:14 ` Junio C Hamano
2022-02-02 21:03 ` [PATCH 5/5] date API: add and use a date_mode_release() Ævar Arnfjörð Bjarmason
2022-02-15 0:28 ` Junio C Hamano
2022-02-04 23:53 ` [PATCH v2 0/5] date.[ch] API: split from cache.h, add API docs, stop leaking memory Ævar Arnfjörð Bjarmason
2022-02-04 23:53 ` [PATCH v2 1/5] cache.h: remove always unused show_date_human() declaration Ævar Arnfjörð Bjarmason
2022-02-04 23:53 ` [PATCH v2 2/5] date API: create a date.h, split from cache.h Ævar Arnfjörð Bjarmason
2022-02-04 23:53 ` [PATCH v2 3/5] date API: provide and use a DATE_MODE_INIT Ævar Arnfjörð Bjarmason
2022-02-04 23:53 ` [PATCH v2 4/5] date API: add basic API docs Ævar Arnfjörð Bjarmason
2022-02-04 23:53 ` [PATCH v2 5/5] date API: add and use a date_mode_release() Ævar Arnfjörð Bjarmason
2022-02-14 17:25 ` [PATCH v2 0/5] date.[ch] API: split from cache.h, add API docs, stop leaking memory Ævar Arnfjörð Bjarmason
2022-02-14 19:52 ` Junio C Hamano
2022-02-16 8:14 ` [PATCH v3 " Ævar Arnfjörð Bjarmason
2022-02-16 8:14 ` [PATCH v3 1/5] cache.h: remove always unused show_date_human() declaration Ævar Arnfjörð Bjarmason
2022-02-16 8:14 ` [PATCH v3 2/5] date API: create a date.h, split from cache.h Ævar Arnfjörð Bjarmason
2022-02-16 8:14 ` [PATCH v3 3/5] date API: provide and use a DATE_MODE_INIT Ævar Arnfjörð Bjarmason
2022-02-16 8:14 ` [PATCH v3 4/5] date API: add basic API docs Ævar Arnfjörð Bjarmason
2022-02-16 8:14 ` [PATCH v3 5/5] date API: add and use a date_mode_release() Ævar Arnfjörð Bjarmason
2022-02-16 17:45 ` [PATCH v3 0/5] date.[ch] API: split from cache.h, add API docs, stop leaking memory Junio C Hamano
[not found] ` <cover-v3-0.8-00000000000-20210831T132607Z-avarab@gmail.com>
2021-08-31 13:35 ` [PATCH v3 1/8] Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 2/8] CI: refactor "if" to "case" statement Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 3/8] tests: add a test mode for SANITIZE=leak, run it in CI Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 4/8] tests: annotate t000*.sh with TEST_PASSES_SANITIZE_LEAK=true Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 5/8] tests: annotate t001*.sh " Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 6/8] tests: annotate t002*.sh " Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 7/8] tests: annotate select t0*.sh " Ævar Arnfjörð Bjarmason
2021-08-31 13:35 ` [PATCH v3 8/8] tests: annotate select t*.sh " Ævar Arnfjörð Bjarmason
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