From: Jeff King <peff@peff.net>
To: "Martin Ågren" <martin.agren@gmail.com>
Cc: git@vger.kernel.org, "brian m . carlson" <sandals@crustytoothpaste.net>
Subject: Re: [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format`
Date: Wed, 23 Jan 2019 00:57:05 -0500 [thread overview]
Message-ID: <20190123055704.GA19601@sigill.intra.peff.net> (raw)
In-Reply-To: <f8b021033b887923662eb9fa63f6df1677ebbbb5.1548186510.git.martin.agren@gmail.com>
On Tue, Jan 22, 2019 at 10:45:48PM +0100, Martin Ågren wrote:
> Call `clear_...()` at the start of `read_...()` instead of just zeroing
> the struct, since we sometimes enter the function multiple times. This
> means that it is important to initialize the struct before calling
> `read_...()`, so document that.
This part is a little counter-intuitive to me. Is anybody ever going to
pass in anything except a struct initialized to REPOSITORY_FORMAT_INIT?
If so, might it be kinder for read_...() to not assume anything about
the incoming struct, and initialize it from scratch? I.e., not to use
clear() but just do the initialization step?
A caller which calls read_() multiple times would presumably have an
intervening clear (either their own, or the one done on an error return
from the read function).
Other than that minor nit, I like the overall shape of this.
One interesting tidbit:
> +/*
> + * Always use this to initialize a `struct repository_format`
> + * to a well-defined, default state before calling
> + * `read_repository()`.
> + */
> +#define REPOSITORY_FORMAT_INIT \
> +{ \
> + .version = -1, \
> + .is_bare = -1, \
> + .hash_algo = GIT_HASH_SHA1, \
> + .unknown_extensions = STRING_LIST_INIT_DUP, \
> +}
> [...]
> + struct repository_format candidate = REPOSITORY_FORMAT_INIT;
This uses designated initializers, which is a C99-ism, but one we've
used previously and feel confident in. But...
> +void clear_repository_format(struct repository_format *format)
> +{
> + string_list_clear(&format->unknown_extensions, 0);
> + free(format->work_tree);
> + free(format->partial_clone);
> + *format = (struct repository_format)REPOSITORY_FORMAT_INIT;
> +}
...this uses that expression not as an initializer, but as a compound
literal. That's also C99, but AFAIK it's the first usage in our code
base. I don't know if it will cause problems or not.
The "old" way to do it is:
struct repository_format foo = REPOSITORY_FORMAT_INIT;
memcpy(format, &foo, sizeof(foo));
Given how simple it is to fix if it turns out to be a problem, I'm OK
including it as a weather balloon.
-Peff
next prev parent reply other threads:[~2019-01-23 5:57 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 7:25 [PATCH 0/3] setup: add `clear_repository_format()` Martin Ågren
2018-12-18 7:25 ` [PATCH 1/3] setup: drop return value from `read_repository_format()` Martin Ågren
2018-12-19 15:27 ` Jeff King
2018-12-19 21:42 ` Martin Ågren
2018-12-20 0:17 ` brian m. carlson
2018-12-20 2:52 ` Jeff King
2018-12-20 3:45 ` brian m. carlson
2018-12-20 14:53 ` Jeff King
2018-12-18 7:25 ` [PATCH 2/3] setup: do not use invalid `repository_format` Martin Ågren
2018-12-19 0:18 ` brian m. carlson
2018-12-19 21:43 ` Martin Ågren
2018-12-19 15:38 ` Jeff King
2018-12-19 21:46 ` Martin Ågren
2018-12-19 23:17 ` Jeff King
2018-12-20 0:21 ` brian m. carlson
2018-12-18 7:25 ` [PATCH 3/3] setup: add `clear_repository_format()` Martin Ågren
2018-12-19 15:48 ` Jeff King
2018-12-19 21:49 ` Martin Ågren
2019-01-14 18:34 ` [PATCH v2 0/3] " Martin Ågren
2019-01-14 18:34 ` [PATCH v2 1/3] setup: free old value before setting `work_tree` Martin Ågren
2019-01-14 18:34 ` [PATCH v2 2/3] setup: do not use invalid `repository_format` Martin Ågren
2019-01-15 19:31 ` Jeff King
2019-01-17 6:31 ` Martin Ågren
2019-01-22 7:07 ` Jeff King
2019-01-22 13:34 ` Martin Ågren
2019-01-22 21:45 ` [PATCH v3 0/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-01-22 21:45 ` [PATCH v3 1/2] setup: free old value before setting `work_tree` Martin Ågren
2019-01-22 21:45 ` [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-01-23 5:57 ` Jeff King [this message]
2019-01-24 0:14 ` brian m. carlson
2019-01-25 19:25 ` Martin Ågren
2019-01-25 19:24 ` Martin Ågren
2019-01-25 19:51 ` Jeff King
2019-02-25 19:21 ` Martin Ågren
2019-02-26 17:46 ` Jeff King
2019-02-28 20:36 ` [PATCH v4 0/2] " Martin Ågren
2019-02-28 20:36 ` [PATCH v4 1/2] setup: free old value before setting `work_tree` Martin Ågren
2019-02-28 20:36 ` [PATCH v4 2/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-03-06 4:56 ` [PATCH v4 0/2] " Jeff King
2019-01-14 18:34 ` [PATCH v2 3/3] setup: add `clear_repository_format()` Martin Ågren
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