From: Bernhard Voelker <mail@bernhard-voelker.de>
To: Paul Eggert <eggert@cs.ucla.edu>, Eli Zaretskii <eliz@gnu.org>
Cc: emacs-orgmode@gnu.org, manikulin@gmail.com,
Gnulib bugs <bug-gnulib@gnu.org>,
54764@debbugs.gnu.org
Subject: Re: bug#54764: encode-time: make DST and TIMEZONE fields of the list argument optional ones
Date: Sat, 23 Apr 2022 16:35:41 +0200 [thread overview]
Message-ID: <199c2d68-7057-ca0e-477c-645ca39f1709@bernhard-voelker.de> (raw)
In-Reply-To: <9e4781b2-2ffa-b1ce-09b4-ead82cad9038@cs.ucla.edu>
On 4/20/22 20:19, Paul Eggert wrote:
> diff --git a/lib/gettime-res.c b/lib/gettime-res.c
> index 611f83ad27..bb4d0b191d 100644
> --- a/lib/gettime-res.c
> +++ b/lib/gettime-res.c
> @@ -53,6 +53,8 @@ gettime_res (void)
>
> long int hz = TIMESPEC_HZ;
> long int r = hz * res.tv_sec + res.tv_nsec;
> + struct timespec earlier;
> + earlier.tv_nsec = -1;
>
> /* On some platforms, clock_getres (CLOCK_REALTIME, ...) yields a
> too-large resolution, under the mistaken theory that it should
> @@ -61,9 +63,22 @@ gettime_res (void)
> resolution. Work around the problem with high probability by
> trying clock_gettime several times and observing the resulting
> bounds on resolution. */
> - for (int i = 0; 1 < r && i < 32; i++)
> + int nsamples = 32;
> + for (int i = 0; 1 < r && i < nsamples; i++)
> {
> - struct timespec now = current_timespec ();
> + /* If successive timestamps disagree the clock resolution must
> + be small, so exit the inner loop to check this sample.
> + Otherwise, arrange for the outer loop to exit but continue
> + the inner-loop search for a differing timestamp sample. */
> + struct timespec now;
> + for (;; i = nsamples)
> + {
> + now = current_timespec ();
> + if (earlier.tv_nsec != now.tv_nsec || earlier.tv_sec != now.tv_sec)
> + break;
> + }
> + earlier = now;
> +
> r = gcd (r, now.tv_nsec ? now.tv_nsec : hz);
> }
lib/gettime-res.c: In function 'gettime_res':
lib/gettime-res.c:77:46: error: 'earlier.tv_sec' may be used uninitialized in this function \
[-Werror=maybe-uninitialized]
77 | if (earlier.tv_nsec != now.tv_nsec || earlier.tv_sec != now.tv_sec)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We know that earlier.tv_sec is set when tv_nsec is set, but the compiler does not,
obviously. Considering the nested loops, I'd say initializing tv_sec doesn't
harm performance-wise.
Have a nice day,
Berny
next prev parent reply other threads:[~2022-04-23 15:00 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 12:37 bug#54764: encode-time: make DST and TIMEZONE fields of the list argument optional ones Max Nikulin
2022-04-09 7:52 ` Paul Eggert
2022-04-10 3:57 ` Max Nikulin
2022-04-13 14:40 ` Max Nikulin
2022-04-13 18:35 ` Paul Eggert
2022-04-14 13:19 ` Max Nikulin
2022-04-14 22:46 ` Paul Eggert
2022-04-15 2:14 ` Tim Cross
2022-04-15 17:23 ` Max Nikulin
2022-04-16 19:23 ` Paul Eggert
2022-04-21 16:59 ` Max Nikulin
2022-04-19 2:02 ` Paul Eggert
2022-04-19 5:50 ` Eli Zaretskii
2022-04-19 22:22 ` Paul Eggert
2022-04-20 7:23 ` Eli Zaretskii
2022-04-20 18:19 ` Paul Eggert
2022-04-20 18:41 ` Eli Zaretskii
2022-04-20 19:01 ` Paul Eggert
2022-04-20 19:14 ` Eli Zaretskii
2022-04-20 19:23 ` Paul Eggert
2022-04-20 19:30 ` Eli Zaretskii
2022-04-21 0:11 ` Paul Eggert
2022-04-21 6:44 ` Eli Zaretskii
2022-04-21 23:56 ` Paul Eggert
2022-04-22 5:01 ` Eli Zaretskii
2022-04-23 14:35 ` Bernhard Voelker [this message]
2022-04-20 15:07 ` Max Nikulin
2022-04-20 18:29 ` Paul Eggert
2022-04-25 15:30 ` Max Nikulin
2022-04-25 15:37 ` Paul Eggert
2022-04-25 19:49 ` Paul Eggert
2022-04-30 11:22 ` Max Nikulin
2022-05-01 2:32 ` Paul Eggert
2022-05-01 17:15 ` Max Nikulin
2022-04-13 15:12 ` Max Nikulin
2022-04-16 16:26 ` Max Nikulin
2022-04-17 1:58 ` Paul Eggert
2022-04-20 16:56 ` Max Nikulin
2022-04-20 19:17 ` Paul Eggert
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