diff mbox series

[16/59] Improve performance in 2 BC

Message ID	20250105055750.1668721-17-eggert@cs.ucla.edu (mailing list archive)
State	New
Headers	DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2BD1B3858C54 From: Paul Eggert <eggert@cs.ucla.edu> To: libc-alpha@sourceware.org Cc: Paul Eggert <eggert@cs.ucla.edu> Subject: [PATCH 16/59] Improve performance in 2 BC Date: Sat, 4 Jan 2025 21:56:51 -0800 Message-ID: <20250105055750.1668721-17-eggert@cs.ucla.edu> In-Reply-To: <01207110-bd60-46ae-9c08-fb39c2011067@cs.ucla.edu> References: <01207110-bd60-46ae-9c08-fb39c2011067@cs.ucla.edu> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: list Errors-To: libc-alpha-bounces~patchwork=sourceware.org@sourceware.org
Series	time: sync mktime from Gnulib \| [00/59] time: sync mktime from Gnulib [01/59] Split intprops.h into two [02/59] Support stdckdint.h internally if older GCC [03/59] Fix mishandling of default DST rule [04/59] Don't worry about !TZDEFAULT [05/59] Support static_assert in pre-C23 C [06/59] Sync mktime.c from Gnulib 2024-10-04 [07/59] Document mktime out-of-range + tm_isdst [08/59] Push tzset lock into callers of time functions [09/59] Omit parse_offset unnecessary tz == '\0' [10/59] Don’t assume TZif bloat is likely [11/59] tzset no longer calls ftello [12/59] Check TZif files more carefully [13/59] Remove alignment assumption from __tzfile_read [14/59] Treat oddball UTC offset strings as zero [15/59] Simplify __tz_compute [16/59] Improve performance in 2 BC [17/59] Don’t mishandle years < 1970 in compute_change [18/59] Match RFC 9636 names [19/59] Trivial tzset_internal speedup [20/59] Fix obscure bug when stdoffset == dstoffset [21/59] Document assumption that NO_DST == 0 [22/59] __use_tzfile is boolean [23/59] Minor tzfile.c clarity improvements [24/59] Stop using zic's -y option [25/59] Fix mishandling of default DST rule [26/59] Simplify treatment of missing and empty TZ [27/59] TZ="" always means UTC sans leap seconds [28/59] Prefer "UTC" for UTC [29/59] Simplify setting tz_rules to UTC [30/59] Update tzname etc. even if TZ is unchanged [31/59] "POSIX TZ" -> "proleptic TZ" [32/59] Reject invalid TZ strings in TZif files [33/59] Reject TZif files containing '\0' in TZ string [34/59] mktime should not consult 'daylight' [35/59] Remove __use_tzfile [36/59] Remove arbitrary limit on TZ, TZDIR lengths [37/59] Tighten setuid TZif file name check [38/59] Avoid a malloc in __tzfile_read [39/59] Free earlier in __tzfile_read [40/59] Improve __tzfile_read TZ="" comment [41/59] Refactor enum tz_rule_type [42/59] __offtime now returns struct tm [43/59] Fix overflow checking in offtime [44/59] Handle TZif time type 0 correctly [45/59] Remove invalid tzset tests from tst-bz29951.c [46/59] tzset, not localtime, now parses TZif TZ spec [47/59] Minor compute_change widening tweak [48/59] Minor SECSPERDAY widening tweak [49/59] Remove leap-second goto from __tzfile_compute [50/59] Remove use_last label from __tzfile_compute [51/59] Refactor ‘if’ in __tzfile_compute [52/59] Refactor localtime ‘if’ in __tzfile_compute [53/59] Refactor post-transition-table ‘if’ [54/59] Refactor __tzfile_compute to avoid two gotos [55/59] Refactor __tzfile_compute index local [56/59] mktime: prefer bool to int [57/59] mktime: port __mktime64 locking to Gnulib [58/59] mktime: improve tm_isdst heuristic [59/59] time: test DST adjustment for DST-less zones

Checks

Context	Check	Description
redhat-pt-bot/TryBot-apply_patch	success	Patch applied to master at the time it was sent

Commit Message

Paul Eggert Jan. 5, 2025, 5:56 a.m. UTC

  * time/tzset.c: Include <limits.h>, for INT_MIN.
(parse_rule): Initialize computed_for to INT_MIN, not -1, as
INT_MIN is otherwise impossible after adding 1900.
(compute_change): Simplify accordingly.
---
 time/tzset.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff mbox series

Patch

diff --git a/time/tzset.c b/time/tzset.c
index bd3509307e..e869fbf3fd 100644
--- a/time/tzset.c
+++ b/time/tzset.c
@@ -16,6 +16,7 @@ 
    <https://www.gnu.org/licenses/>.  */
 
 #include <ctype.h>
+#include <limits.h>
 #include <stdbool.h>
 #include <stdckdint.h>
 #include <stddef.h>
@@ -55,7 +56,8 @@  typedef struct
     /* We cache the computed time of change for a
        given year so we don't have to recompute it.  */
     __time64_t change;	/* When to change to this zone.  */
-    int computed_for;	/* Year above is computed for.  */
+    int computed_for;	/* Year that CHANGE is computed for.
+			   If INT_MIN, CHANGE is unspecified.  */
   } tz_rule;
 
 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
@@ -339,7 +341,7 @@  parse_rule (const char **tzp, int whichrule)
     secs = 2 * 60 * 60;
 
   tzr->secs = secs;
-  tzr->computed_for = -1;
+  tzr->computed_for = INT_MIN;
   *tzp = tz;
   return true;
 }
@@ -444,8 +446,7 @@  compute_change (tz_rule *rule, int year)
 {
   __time64_t t;
 
-  if (year != -1 && rule->computed_for == year)
-    /* Operations on times in 2 BC will be slower.  Oh well.  */
+  if (rule->computed_for == year)
     return;
 
   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */