1 /* Provide tzset for systems that don't have it or for which it's broken.
2
3 Copyright (C) 2001-2003, 2005-2007, 2009-2021 Free Software Foundation, Inc.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation; either version 2, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
17
18 /* written by Jim Meyering */
19
20 #include <config.h>
21
22 /* Specification. */
23 #include <time.h>
24
25 #include <stdlib.h>
26 #include <string.h>
27
28 void
rpl_tzset(void)29 rpl_tzset (void)
30 #undef tzset
31 {
32 #if defined _WIN32 && ! defined __CYGWIN__
33 /* Rectify the value of the environment variable TZ.
34 There are four possible kinds of such values:
35 - Traditional US time zone names, e.g. "PST8PDT". Syntax: see
36 <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset>
37 - Time zone names based on geography, that contain one or more
38 slashes, e.g. "Europe/Moscow".
39 - Time zone names based on geography, without slashes, e.g.
40 "Singapore".
41 - Time zone names that contain explicit DST rules. Syntax: see
42 <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
43 The Microsoft CRT understands only the first kind. It produces incorrect
44 results if the value of TZ is of the other kinds.
45 But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value
46 of the second kind for most geographies, or of the first kind in a few
47 other geographies. If it is of the second kind, neutralize it. For the
48 Microsoft CRT, an absent or empty TZ means the time zone that the user
49 has set in the Windows Control Panel.
50 If the value of TZ is of the third or fourth kind -- Cygwin programs
51 understand these syntaxes as well --, it does not matter whether we
52 neutralize it or not, since these values occur only when a Cygwin user
53 has set TZ explicitly; this case is 1. rare and 2. under the user's
54 responsibility. */
55 const char *tz = getenv ("TZ");
56 if (tz != NULL && strchr (tz, '/') != NULL)
57 _putenv ("TZ=");
58
59 /* On native Windows, tzset() is deprecated. Use _tzset() instead. See
60 <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/posix-tzset>
61 <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset> */
62 _tzset ();
63 #else
64 tzset ();
65 #endif
66 }
67