From: Stefan Beller <sbeller@google.com>
To: Andrey Okoshkin <a.okoshkin@samsung.com>
Cc: "git@vger.kernel.org" <git@vger.kernel.org>,
vmiklos@frugalware.org, Jeff King <peff@peff.net>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH] merge-recursive: check GIT_MERGE_VERBOSITY only once
Date: Tue, 24 Oct 2017 09:28:31 -0700 [thread overview]
Message-ID: <CAGZ79kaSZG9WriqX0SLbTnEDRr-4YdFRuK17+9wnxyrftfnMmg@mail.gmail.com> (raw)
In-Reply-To: <3aed764b-388c-d163-08fc-32b294c6b9d3@samsung.com>
On Tue, Oct 24, 2017 at 8:27 AM, Andrey Okoshkin <a.okoshkin@samsung.com> wrote:
> Add check of 'GIT_MERGE_VERBOSITY' environment variable only once in
> init_merge_options().
> Consequential call of getenv() may return NULL pointer and strtol() crashes.
> However the stored pointer to the obtained getenv() result may be invalidated
> by some other getenv() call from another thread as getenv() is not thread-safe.
But do we have other threads running at the time?
Inspecting the four callsites:
* sequencer.c:
The prior lines to hold the index lock suggests we're not in a threaded
environment
* builtin/merge-recursive.c:
In cmd_merge_recursive and we're fiddling with argv/argc, which
suggests we in a main function, not having threads around
* builtin/am.c: fall_back_threeway called by am_run.
(am is not threaded)
* builtin/merge:
In try_merge_strategy called from the main function, also index locking
* builtin/checkout.c:
merge_working_tree also locks the index.
So I think this function is never called from within a threaded environment
in git.
>
> Signed-off-by: Andrey Okoshkin <a.okoshkin@samsung.com>
> ---
> merge-recursive.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/merge-recursive.c b/merge-recursive.c
> index 1494ffdb8..eaac98145 100644
> --- a/merge-recursive.c
> +++ b/merge-recursive.c
> @@ -2163,6 +2163,7 @@ static void merge_recursive_config(struct merge_options *o)
>
> void init_merge_options(struct merge_options *o)
> {
> + const char *merge_verbosity = getenv("GIT_MERGE_VERBOSITY");
Despite not being in a threaded environment, I wonder if we want to
minimize the time between calling getenv and the use of the result,
i.e. declare merge_verbosity here, but assign it later, just before the
condition?
(The compiler may shuffle stuff around anyway, so this is a
moot suggestion; It gears mostly towards making the code more
readable/maintainable when presenting this part of the code
to the user.)
With or without this change:
Reviewed-by: Stefan Beller <sbeller@google.com>
> memset(o, 0, sizeof(struct merge_options));
> o->verbosity = 2;
> o->buffer_output = 1;
> @@ -2171,9 +2172,8 @@ void init_merge_options(struct merge_options *o)
> o->renormalize = 0;
> o->detect_rename = 1;
> merge_recursive_config(o);
> - if (getenv("GIT_MERGE_VERBOSITY"))
> - o->verbosity =
> - strtol(getenv("GIT_MERGE_VERBOSITY"), NULL, 10);
> + if (merge_verbosity)
> + o->verbosity = strtol(merge_verbosity, NULL, 10);
> if (o->verbosity >= 5)
> o->buffer_output = 0;
> strbuf_init(&o->obuf, 0);
> --
> 2.14.3
next prev parent reply other threads:[~2017-10-24 16:28 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20171024152727epcas2p4fb7dcf147e44aadf7733098151d469a5@epcas2p4.samsung.com>
2017-10-24 15:27 ` [PATCH] merge-recursive: check GIT_MERGE_VERBOSITY only once Andrey Okoshkin
2017-10-24 16:28 ` Stefan Beller [this message]
2017-10-24 16:45 ` Eric Sunshine
2017-10-24 17:11 ` Martin Ågren
2017-10-24 19:52 ` Jeff King
2017-10-25 1:48 ` Junio C Hamano
2017-10-25 4:07 ` Eric Sunshine
2017-10-25 7:27 ` Jeff King
2017-10-25 11:39 ` [PATCH v2] " Andrey Okoshkin
2017-10-25 11:53 ` Eric Sunshine
2017-10-25 12:27 ` Andrey Okoshkin
2017-10-25 13:03 ` [PATCH v3] " Andrey Okoshkin
2017-10-27 17:29 ` Stefan Beller
2017-10-30 7:42 ` [PATCH v4] " Andrey Okoshkin
2017-10-31 1:42 ` Junio C Hamano
2017-10-31 2:26 ` Junio C Hamano
2017-10-31 7:13 ` Andrey Okoshkin
2017-10-31 7:20 ` Junio C Hamano
2017-10-31 9:09 ` [PATCH v5] " Andrey Okoshkin
2017-10-25 11:13 ` [PATCH] " Andrey Okoshkin
2017-10-25 10:49 ` Andrey Okoshkin
2017-10-25 10:49 ` Andrey Okoshkin
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