From: Junio C Hamano <gitster@pobox.com>
To: "Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] config.c: fix potential number truncation in git_parse_signed()
Date: Wed, 06 Jul 2016 12:33:52 -0700 [thread overview]
Message-ID: <xmqqa8husgrj.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20160702131333.8418-1-pclouds@gmail.com> ("Nguyễn Thái Ngọc Duy"'s message of "Sat, 2 Jul 2016 15:13:33 +0200")
Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:
> clang -Wabsolute-value on IA-32 architecture complains that "absolute
> value function 'labs' given an argument of type 'intmax_t' (aka 'long
> long') but has parameter of type 'long' which may cause truncation of
> value". Very unlikely for this code though. Nevertheless, add an
> explicit check for truncation to shut clang up and error out.
Thanks. It however makes me wonder if it is a better approach to
avoid downcasting intmax_t to long by using imaxabs()?
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> config.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/config.c b/config.c
> index d7ce34b..880bd4a 100644
> --- a/config.c
> +++ b/config.c
> @@ -503,6 +503,7 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
> intmax_t val;
> uintmax_t uval;
> uintmax_t factor = 1;
> + long int lival;
>
> errno = 0;
> val = strtoimax(value, &end, 0);
> @@ -512,9 +513,14 @@ static int git_parse_signed(const char *value, intmax_t *ret, intmax_t max)
> errno = EINVAL;
> return 0;
> }
> - uval = labs(val);
> + lival = (long int)val;
> + if (lival != val) {
> + errno = ERANGE;
> + return 0;
> + }
> + uval = labs(lival);
> uval *= factor;
> - if (uval > max || labs(val) > uval) {
> + if (uval > max || labs(lival) > uval) {
> errno = ERANGE;
> return 0;
> }
next prev parent reply other threads:[~2016-07-06 19:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-02 13:13 [PATCH] config.c: fix potential number truncation in git_parse_signed() Nguyễn Thái Ngọc Duy
2016-07-06 19:33 ` Junio C Hamano [this message]
2016-07-08 16:01 ` Duy Nguyen
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