diff mbox series

[15/59] Simplify __tz_compute

Message ID	20250105055750.1668721-16-eggert@cs.ucla.edu (mailing list archive)
State	New
Headers	DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 8A7503858D3C From: Paul Eggert <eggert@cs.ucla.edu> To: libc-alpha@sourceware.org Cc: Paul Eggert <eggert@cs.ucla.edu> Subject: [PATCH 15/59] Simplify __tz_compute Date: Sat, 4 Jan 2025 21:56:50 -0800 Message-ID: <20250105055750.1668721-16-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 (__tz_compute): Omit last arg USE_LOCALTIME,
since this function should be called only when using localtime.
All callers changed.  Clarify isdst computation.
---
 time/tzfile.c |  2 +-
 time/tzset.c  | 35 ++++++++++++-----------------------
 time/tzset.h  |  2 +-
 3 files changed, 14 insertions(+), 25 deletions(-)

diff mbox series

Patch

diff --git a/time/tzfile.c b/time/tzfile.c
index 7125f5a8e3..5a7514e466 100644
--- a/time/tzfile.c
+++ b/time/tzfile.c
@@ -636,7 +636,7 @@  __tzfile_compute (__time64_t timer, int use_localtime,
 	    goto use_last;
 
 	  /* Use the rules from the TZ string to compute the change.  */
-	  __tz_compute (timer, tp, 1);
+	  __tz_compute (timer, tp);
 
 	  goto leap;
 	}
diff --git a/time/tzset.c b/time/tzset.c
index 6783067053..bd3509307e 100644
--- a/time/tzset.c
+++ b/time/tzset.c
@@ -525,32 +525,21 @@  compute_change (tz_rule *rule, int year)
 }
 
 
-/* Figure out the correct timezone for TM and set `__tzname',
-   `__timezone', and `__daylight' accordingly.  */
+/* Figure out the correct local timezone for TM.  */
 void
-__tz_compute (__time64_t timer, struct tm *tm, int use_localtime)
+__tz_compute (__time64_t timer, struct tm *tm)
 {
   compute_change (&tz_rules[0], 1900 + tm->tm_year);
   compute_change (&tz_rules[1], 1900 + tm->tm_year);
 
-  if (use_localtime)
-    {
-      int isdst;
-
-      /* We have to distinguish between northern and southern
-	 hemisphere.  For the latter the daylight saving time
-	 ends in the next year.  */
-      if (__builtin_expect (tz_rules[0].change
-			    > tz_rules[1].change, 0))
-	isdst = (timer < tz_rules[1].change
-		 || timer >= tz_rules[0].change);
-      else
-	isdst = (timer >= tz_rules[0].change
-		 && timer < tz_rules[1].change);
-      tm->tm_isdst = isdst;
-      tm->tm_zone = __tzname[isdst];
-      tm->tm_gmtoff = tz_rules[isdst].offset;
-    }
+  /* Distinguish between northern and southern hemisphere.
+     For the latter the daylight saving time ends in the next year.  */
+  bool isdst = (__glibc_likely (tz_rules[0].change <= tz_rules[1].change)
+		? tz_rules[0].change <= timer && timer < tz_rules[1].change
+		: ! (tz_rules[1].change <= timer && timer < tz_rules[0].change));
+  tm->tm_isdst = isdst;
+  tm->tm_zone = __tzname[isdst];
+  tm->tm_gmtoff = tz_rules[isdst].offset;
 }
 
 /* Reinterpret the TZ environment variable and set `tzname'.  */
@@ -599,8 +588,8 @@  __tz_convert (__time64_t timer, int use_localtime, struct tm *tp)
     {
       if (! __offtime (timer, 0, tp))
 	tp = NULL;
-      else
-	__tz_compute (timer, tp, use_localtime);
+      else if (use_localtime)
+	__tz_compute (timer, tp);
       leap_correction = 0;
       leap_extra_sec = false;
     }
diff --git a/time/tzset.h b/time/tzset.h
index d2d5853f0b..8c87ad6a24 100644
--- a/time/tzset.h
+++ b/time/tzset.h
@@ -15,7 +15,7 @@  extern void __tzfile_compute (__time64_t timer, int use_localtime,
 			      int *leap_correct, bool *leap_hit,
 			      struct tm *tp) attribute_hidden;
 extern void __tzset_parse_tz (const char *tz) attribute_hidden;
-extern void __tz_compute (__time64_t timer, struct tm *tm, int use_localtime)
+extern void __tz_compute (__time64_t timer, struct tm *tm)
   __THROW attribute_hidden;
 
 __libc_lock_define (extern, __tzset_lock attribute_hidden);