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From: Jeff King <peff@peff.net>
To: Patrick Steinhardt <ps@pks.im>
Cc: git@vger.kernel.org, "Junio C Hamano" <gitster@pobox.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Eric Sunshine" <sunshine@sunshineco.com>
Subject: Re: [PATCH v2 2/3] config: unify code paths to get global config paths
Date: Fri, 9 Apr 2021 11:21:16 -0400
Message-ID: <YHBw7D/fEUdCckc8@coredump.intra.peff.net> (raw)
In-Reply-To: <dddc85bcf54e9b19f1612cf2a5be928dcb2bad7d.1617975637.git.ps@pks.im>

On Fri, Apr 09, 2021 at 03:43:25PM +0200, Patrick Steinhardt wrote:

> There's two callsites which assemble global config paths, once in the
> config loading code and once in the git-config(1) builtin. We're about
> to implement a way to override global config paths via an environment
> variable which would require us to adjust both sites.
> 
> Unify both code paths into a single `git_global_config()` function which
> returns both paths for `~/.gitconfig` and the XDG config file. This will
> make the subsequent patch which introduces the new envvar easier to
> implement.

Seems like a good step forward. There is one minor issue with the
implementation, though.

> diff --git a/builtin/config.c b/builtin/config.c
> index 02ed0b3fe7..604a0973a5 100644
> --- a/builtin/config.c
> +++ b/builtin/config.c
> @@ -671,9 +671,9 @@ int cmd_config(int argc, const char **argv, const char *prefix)
>  	}
>  
>  	if (use_global_config) {
> -		char *user_config = expand_user_path("~/.gitconfig", 0);
> -		char *xdg_config = xdg_config_home("config");
> +		const char *user_config, *xdg_config;
>  
> +		git_global_config(&user_config, &xdg_config);

The pointer out-parameters make sense here, since we need to return two
values. I notice they became const, so the function will hold on to
ownership of the memory.

> @@ -688,10 +688,8 @@ int cmd_config(int argc, const char **argv, const char *prefix)
>  		if (access_or_warn(user_config, R_OK, 0) &&
>  		    xdg_config && !access_or_warn(xdg_config, R_OK, 0)) {
>  			given_config_source.file = xdg_config;
> -			free(user_config);
>  		} else {
>  			given_config_source.file = user_config;
> -			free(xdg_config);
>  		}

...which is why we drop these free() calls. So far so good.

> +void git_global_config(const char **user, const char **xdg)
> +{
> +	static const char *user_config, *xdg_config;
> +
> +	if (!user_config) {
> +		user_config = expand_user_path("~/.gitconfig", 0);
> +		xdg_config = xdg_config_home("config");
> +	}
> +
> +	*user = user_config;
> +	*xdg = xdg_config;
> +}

And here in the implementation we hold on to the static values forever.

I think your "did we initialize already" check isn't robust, though.
expand_user_path() can return NULL, in which case every call would
trigger a re-initialization (even leaking xdg_config if it was set in
the last round).

So I think you'd need a separate "static int initialized" variable.

That said, I wonder if we should just pass ownership of the memory to
the caller. It is a minor inconvenience that they will have to free()
the result, but we're already doing that. And it removes any possibility
of thread unsafety.

I guess it doesn't match git_system_config() as well, then. But arguably
it should also just pass ownership (it also has only a handful of
callers, and freeing the result would not be a big deal).

I'm OK with either solution, though.

-Peff

  reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08 14:17 [PATCH] config: Introduce GIT_CONFIG_NOGLOBAL Patrick Steinhardt
2021-04-08 16:44 ` Eric Sunshine
2021-04-08 17:25 ` Junio C Hamano
2021-04-08 23:18   ` Jeff King
2021-04-08 23:43     ` Junio C Hamano
2021-04-09  0:25       ` Jeff King
2021-04-08 23:34   ` Ævar Arnfjörð Bjarmason
2021-04-08 23:39   ` Ævar Arnfjörð Bjarmason
2021-04-08 23:30 ` Ævar Arnfjörð Bjarmason
2021-04-08 23:56   ` Junio C Hamano
2021-04-09 13:43 ` [PATCH v2 0/3] config: allow overriding global/system config Patrick Steinhardt
2021-04-09 13:43   ` [PATCH v2 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-09 15:13     ` Jeff King
2021-04-09 13:43   ` [PATCH v2 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-09 15:21     ` Jeff King [this message]
2021-04-09 13:43   ` [PATCH v2 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-09 15:38     ` Jeff King
2021-04-12 14:04       ` Patrick Steinhardt
2021-04-09 22:18     ` Junio C Hamano
2021-04-09 15:41   ` [PATCH v2 0/3] config: allow overriding global/system config Jeff King
2021-04-12 14:46   ` [PATCH v3 " Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-12 14:46     ` [PATCH v3 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-12 17:04       ` Junio C Hamano
2021-04-13  7:11     ` [PATCH v4 0/3] config: allow overriding global/system config Patrick Steinhardt
2021-04-13  7:11       ` [PATCH v4 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-13  7:25         ` Jeff King
2021-04-16 21:14         ` SZEDER Gábor
2021-04-17  8:44           ` Jeff King
2021-04-17 21:37             ` Junio C Hamano
2021-04-18  5:39               ` Jeff King
2021-04-19 11:03                 ` Patrick Steinhardt
2021-04-23  9:27                   ` Jeff King
2021-04-13  7:11       ` [PATCH v4 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-13  7:11       ` [PATCH v4 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-13  7:33         ` Jeff King
2021-04-13  7:54           ` Patrick Steinhardt
2021-04-13  7:33       ` [PATCH v4 0/3] config: allow overriding global/system config Jeff King
2021-04-13 17:49       ` Junio C Hamano
2021-04-14  5:37         ` Patrick Steinhardt
2021-04-19 12:31       ` [PATCH v5 " Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 1/3] config: rename `git_etc_config()` Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 2/3] config: unify code paths to get global config paths Patrick Steinhardt
2021-04-19 12:31         ` [PATCH v5 3/3] config: allow overriding of global and system configuration Patrick Steinhardt
2021-04-21 20:46           ` SZEDER Gábor
2021-04-21 21:06             ` SZEDER Gábor
2021-04-22  5:36               ` Patrick Steinhardt
2021-04-23  5:47             ` [PATCH] t1300: fix unset of GIT_CONFIG_NOSYSTEM leaking into subsequent tests Patrick Steinhardt
2021-04-19 21:55         ` [PATCH v5 0/3] config: allow overriding global/system config Junio C Hamano
2021-04-23  9:32         ` Jeff King
2021-04-12 14:46 ` [PATCH v3] config: allow overriding of global and system configuration Patrick Steinhardt

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