Changes in README

Changes in README http://nxr.netbsd.org/rss/src/lib/libc/time/README en Copyright 2005 Java Release 2025c - 2025-12-10 14:42:37 -0800 Briefly: Several code changes for compatibility with FreeBSD. Changes to code An unset TZ is no longer invalid when /etc/localtime is missing, and is abbreviated "UTC" not "-00". This reverts to 2024b behavior. (Problem and patch reported by Dag-Erling Smørgrav.) New function offtime_r, short for fixed-offset localtime_rz. It is defined if STD_INSPIRED is defined. (Patch from Dag-Erling Smørgrav.) tzset etc. are now more cautious about questionable TZ settings. Privileged programs now reject TZ settings that start with '/', unless they are TZDEFAULT (default "/etc/localtime") or start with TZDIR then '/' (default "/usr/share/zoneinfo/"). Unprivileged programs now require files to be regular files and reject relative names containing ".." directory components; formerly, only privileged programs did those two things. These changes were inspired by similar behavior in FreeBSD. On NetBSD, unprivileged programs now use O_REGULAR to check whether a TZ setting starting with '/' names a regular file, avoiding a minor security race still present elsewhere. TZ strings taken from tzalloc arguments are now treated with no less caution than TZ strings taken from the environment, as the old undocumented behavior would have been hard to explain. tzset etc. no longer use the 'access' system call to check access; instead they now use the system calls issetugid, getauxval, getresuid/getresgid, and geteuid/getegid/getuid/getgid (whichever first works) to test whether a program is privileged. Compile with -DHAVE_SYS_AUXV_H=[01] to enable or disable <sys/auxv.h> which (if it defines AT_SECURE) enables getauxval, and compile with -DHAVE_ISSETUGID=[01], -DHAVE_GETRESUID=[01], and -DHAVE_GETEUID=[01] to enable or disable the other calls' use. The new CFLAGS option -DTZ_CHANGE_INTERVAL=N makes tzset etc. check for TZif file changes if the in-memory data are N seconds old or more, and are derived from the TZ environment variable. This is intended for platforms that want tzset etc. to reflect changes to whatever file TZ selects (including changes to /etc/localtime if TZ is unset). If N is negative (the default) these checks are omitted; this is the traditional behavior. The new CFLAGS options -DHAVE_STRUCT_STAT_ST_CTIM=0 and -DHAVE_STRUCT_TIMESPEC=0 port to non-POSIX.1-2008 platforms that lack st_ctim and struct timespec, respectively. tzset etc. now treat ' ' like '_' in time zone abbreviations, just as they treat other invalid bytes. This continues the transition begun in release 96k, which removed spaces in tzdata because the spaces break time string parsers. The new CFLAGS option -DTHREAD_PREFER_SINGLE causes tzcode in single-threaded processes to avoid locks, as FreeBSD does. This can save time in single-threaded apps. The threadedness testing costs CPU time and energy in multi-threaded apps. New options -DHAVE___ISTHREADED and -DHAVE_SYS_SINGLE_THREADED_H can help configure how to test for single-threadedness. The new CFLAGS option -DTHREAD_RWLOCK uses read-write locks, as macOS does, instead of mutexes. This saves real time when TZ is rarely changing and many threads call tzcode simultaneously. It costs more CPU time and energy. The new CFLAGS option -TTHREAD_TM_MULTI causes localtime to return a pointer to thread-specific memory, as FreeBSD does, instead of to the same memory in all threads. This supports unportable programs that incorrectly use localtime instead of localtime_r. This option affects gmtime and offtime similarly to localtime. Because the corresponding storage is freed on thread exit, this option is incompatible with POSIX.1-2024 and earlier. It also costs CPU time and memory. tzfree now preserves errno, consistently with POSIX.1-2024 'free'. tzcode now uses mempcpy if available, guessing its availability. Compile with -DHAVE_MEMPCPY=1 or 0 to override the guess. tzcode now uses strnlen to improve asymptotic performance a bit. Compile with -DHAVE_STRNLEN=0 if your platform lacks it. tzcode now hand-declares unistd.h-provided symbols like getopt if HAVE_UNISTD_H=0, not if HAVE_POSIX_DECLS=0. tzset etc. now have an experimental OPENAT_TZDIR option; see Makefile and localtime.c for details. On platforms like GNU/Hurd that do not define PATH_MAX, exceedingly long TZ strings no longer fail merely because they exceed an arbitrary file name length limit imposed by tzcode. zic has new options inspired by FreeBSD. '-D' skips creation of output ancestor directories, '-m MODE' sets output files' mode, and '-u OWNER[:GROUP]' sets output files' owner and group. zic now uses the fdopen function, which was standardized by POSIX.1-1988 and is now safe to use in portable code. This replaces its use of the older umask function, which complicated maintenance. /src/lib/libc/time/README - 1.18 Thu Dec 18 17:45:29 UTC 2025 christos Import tzcode 2023d: localtime.c no longer mishandles TZif files that contain a single transition into a DST regime. Previously, it incorrectly assumed DST was in effect before the transition too. (Thanks to Alois Treindl for debugging help.) localtime.c's timeoff no longer collides with OpenBSD 7.4. The C code now uses _Generic only if __STDC_VERSION__ says the compiler is C11 or later. tzselect now optionally reads zonenow.tab, to simplify when configuring only for timestamps dated from now on. tzselect no longer creates temporary files. tzselect no longer mishandles the following: Spaces and most other special characters in BUGEMAIL, PACKAGE, TZDIR, and VERSION. TZ strings when using mawk 1.4.3, which mishandles regular expressions of the form /X{2,}/. ISO 6709 coordinates when using an awk that lacks the GNU extension of newlines in -v option-arguments. Non UTF-8 locales when using an iconv command that lacks the GNU //TRANSLIT extension. zic no longer mishandles data for Palestine after the year 2075. Previously, it incorrectly omitted post-2075 transitions that are predicted for just before and just after Ramadan. (Thanks to Ken Murchison for debugging help.) zic now works again on Linux 2.6.16 and 2.6.17 (2006). /src/lib/libc/time/README - 1.17 Sat Dec 23 20:48:38 UTC 2023 christos Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility, and we were "slim" already) Support for zic's long-obsolete '-y YEARISTYPE' option has been removed and, with it, so has support for the TYPE field in Rule lines, which is now reserved for compatibility with earlier zic. These features were previously deprecated in release 2015f. (Thanks to Tim Parenti.) zic now defaults to '-b slim' instead of to '-b fat'. zic's new '-l -' and '-p -' options uninstall any existing localtime and posixrules files, respectively. The undocumented and ineffective tzsetwall function has been removed. /src/lib/libc/time/README - 1.16 Fri Oct 09 18:38:48 UTC 2020 christos merge 2019a Changes to code zic now has an -r option to limit the time range of output data. For example, 'zic -r @1000000000' limits the output data to timestamps starting 1000000000 seconds after the Epoch. This helps shrink output size and can be useful for applications not needing the full timestamp history, such as TZDIST truncation; see Internet RFC 8536 section 5.1. (Inspired by a feature request from Christopher Wong, helped along by bug reports from Wong and from Tim Parenti.) Changes to documentation Mention Internet RFC 8536 (February 2019), which documents TZif. tz-link.html now cites tzdata-meta <https://tzdata-meta.timtimeonline.com/>. /src/lib/libc/time/README - 1.15 Thu Apr 04 18:18:31 UTC 2019 christos Update to 2018f: Changes to code zic now always generates TZif files where time type 0 is used for timestamps before the first transition. This simplifies the reading of TZif files and should not affect behavior of existing TZif readers because the same set of time types is used; only their internal indexes may have changed. This affects only the legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and EET, which previously used nonzero types for these timestamps. Because of the type 0 change, zic no longer outputs a dummy transition at time -2**59 (before the Big Bang), as clients should no longer need this to handle historical timestamps correctly. This reverts a change introduced in 2013d and shrinks most TZif files by a few bytes. zic now supports negative time-of-day in Rule and Leap lines, e.g., "Rule X min max - Apr lastSun -6:00 1:00 -" means the transition occurs at 18:00 on the Saturday before the last Sunday in April. This behavior was documented in 2018a but the code did not entirely match the documentation. localtime.c no longer requires at least one time type in TZif files that lack transitions or have a POSIX-style TZ string. This future-proofs the code against possible future extensions to the format that would allow TZif files with POSIX-style TZ strings and without transitions or time types. A read-access subscript error in localtime.c has been fixed. It could occur only in TZif files with timecnt == 0, something that does not happen in practice now but could happen in future versions. localtime.c no longer ignores TZif POSIX-style TZ strings that specify only standard time. Instead, these TZ strings now override the default time type for timestamps after the last transition (or for all time stamps if there are no transitions), just as DST strings specifying DST have always done. leapseconds.awk now outputs "#updated" and "#expires" comments, and supports leap seconds at the ends of months other than June and December. (Inspired by suggestions from Chris Woodbury.) Changes to documentation New restrictions: A Rule name must start with a character that is neither an ASCII digit nor "-" nor "+", and an unquoted name should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~". The latter restriction makes room for future extensions (a possibility noted by Tom Lane). tzfile.5 now documents what time types apply before the first and after the last transition, if any. Documentation now uses the spelling "timezone" for a TZ setting that determines timestamp history, and "time zone" for a geographic region currently sharing the same standard time. The name "TZif" is now used for the tz binary data format. tz-link.htm now mentions the A0 TimeZone Migration utilities. (Thanks to Aldrin Martoq for the link.) /src/lib/libc/time/README - 1.14 Fri Oct 19 23:05:35 UTC 2018 christos branches: 1.13.2; 1.13.4; Merge tzcode2018c [ changelog with changes to tzdata sections removed ] Release 2018c - 2018-01-22 23:00:44 -0800 Changes to build procedure The build procedure now works around mawk 1.3.3's lack of support for character class expressions. (Problem reported by Ohyama.) Release 2018b - 2018-01-17 23:24:48 -0800 Changes to build procedure The distribution now contains the file 'pacificnew' again. This file was inadvertantly omitted in the 2018a distribution. (Problem reported by Matias Fonzo.) Release 2018a - 2018-01-12 22:29:21 -0800 Changes to build procedure The default installation locations have been changed to mostly match Debian circa 2017, instead of being designed as an add-on to 4.3BSD circa 1986. This affects the Makefile macros TOPDIR, TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR, USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor locations more precisely. (This responds to suggestions from Brian Inglis and from Steve Summit.) The default installation procedure no longer creates the backward-compatibility link US/Pacific-New, which causes confusion during user setup (e.g., see Debian bug 815200). Use 'make BACKWARD="backward pacificnew"' to create the link anyway, for now. Eventually we plan to remove the link entirely. tzdata.zi now contains a version-number comment. (Suggested by Tom Lane.) The Makefile now quotes values like BACKWARD more carefully when passing them to the shell. (Problem reported by Zefram.) Builders no longer need to specify -DHAVE_SNPRINTF on platforms that have snprintf and use pre-C99 compilers. (Problem reported by Jon Skeet.) Changes to code zic has a new option -t FILE that specifies the location of the file that determines local time when TZ is unset. The default for this location can be configured via the new TZDEFAULT makefile macro, which defaults to /etc/localtime. Diagnostics and commentary now distinguish UT from UTC more carefully; see theory.html for more information about UT vs UTC. zic has been ported to GCC 8's -Wstringop-truncation option. (Problem reported by Martin Sebor.) Changes to documentation and commentary The zic man page now documents the longstanding behavior that times and years can be out of the usual range, with negative times counting backwards from midnight and with year 0 preceding year 1. (Problem reported by Michael Deckers.) The theory.html file now mentions the POSIX limit of six chars per abbreviation, and lists alphabetic abbreviations used. The files tz-art.htm and tz-link.htm have been renamed to tz-art.html and tz-link.html, respectively, for consistency with other file names and to simplify web server configuration. /src/lib/libc/time/README - 1.13 Thu Jan 25 22:48:42 UTC 2018 christos merge 2017a /src/lib/libc/time/README - 1.12 Sat Mar 11 18:23:14 UTC 2017 christos branches: 1.11.2; merge tzcode2016g /src/lib/libc/time/README - 1.11 Fri Oct 07 15:29:42 UTC 2016 christos branches: 1.10.2; Sync with 2016b /src/lib/libc/time/README - 1.10 Tue Mar 15 15:16:01 UTC 2016 christos Sync with tzcode2014h /src/lib/libc/time/README - 1.9 Tue Oct 07 21:51:03 UTC 2014 christos branches: 1.8.4; update from tzcode 2013e to tzcode2013i i: The compile-time flag NOSOLAR has been removed, as nowadays the benefit of slightly shrinking runtime table size is outweighed by the cost of disallowing potential future updates that exceed old limits. h: Fix localtime overflow bugs with 32-bit unsigned time_t. zdump no longer assumes sscanf returns maximal values on overflow. g: 'zic' now runs on platforms that lack both hard links and symlinks. (Thanks to Theo Veenker for reporting the problem, for MinGW.) Also, fix some bugs on platforms that lack hard links but have symlinks. 'zic -v' again warns that Asia/Tehran has no POSIX environment variable to predict the far future, fixing a bug introduced in 2013e. f: The types of the global variables 'timezone' and 'altzone' (if present) have been changed back to 'long'. This is required for 'timezone' by POSIX, and for 'altzone' by common practice, e.g., Solaris 11. These variables were originally 'long' in the tz code, but were mistakenly changed to 'time_t' in 1987; nobody reported the incompatibility until now. The difference matters on x32, where 'long' is 32 bits and 'time_t' is 64. (Thanks to Elliott Hughes.) /src/lib/libc/time/README - 1.8 Thu Dec 26 18:34:28 UTC 2013 christos branches: 1.7.2; merge 2012e /src/lib/libc/time/README - 1.7 Thu Aug 09 00:38:25 UTC 2012 christos branches: 1.6.6; Import tzcode2009k. - now understands 64bit time_t and 64bit data in timezone files. - localtime(), gmtime(), asctime() and ctime() may now fail with a NULL result if time_t cannot be represented by struct tm. /src/lib/libc/time/README - 1.6 Thu Dec 31 22:49:15 UTC 2009 mlelstv Merge tzcode2002b. /src/lib/libc/time/README - 1.5 Tue Jan 29 00:40:33 UTC 2002 kleink branches: 1.4.12; sync with tzcode1998b /src/lib/libc/time/README - 1.4 Thu Jan 22 07:17:19 UTC 1998 jtc sync with tzcode1998a /src/lib/libc/time/README - 1.3 Thu Jan 22 07:06:56 UTC 1998 jtc RCS Id Police. /src/lib/libc/time/README - 1.2 Fri Jan 09 04:11:55 UTC 1998 perry branches: 1.1.1; Initial revision /src/lib/libc/time/README - 1.1 Fri Mar 10 07:08:14 UTC 1995 jtc import tzcode2009k /src/lib/libc/time/README - 1.1.1.7 Sun Oct 25 16:20:16 UTC 2009 mlelstv Import tzcode2002b. /src/lib/libc/time/README - 1.1.1.6 Tue Jan 29 00:30:29 UTC 2002 kleink