1 /* Work around platform bugs in localtime. 2 Copyright (C) 2017-2021 Free Software Foundation, Inc. 3 4 This file is free software: you can redistribute it and/or modify 5 it under the terms of the GNU Lesser General Public License as 6 published by the Free Software Foundation; either version 2.1 of the 7 License, or (at your option) any later version. 8 9 This file is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public License 15 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 16 17 #include <config.h> 18 19 /* Specification. */ 20 #include <time.h> 21 22 #include <stdlib.h> 23 #include <string.h> 24 25 #undef localtime 26 27 struct tm * 28 rpl_localtime (const time_t *tp) /* */ 29 { 30 #if defined _WIN32 && ! defined __CYGWIN__ 31 /* Rectify the value of the environment variable TZ. 32 There are four possible kinds of such values: 33 - Traditional US time zone names, e.g. "PST8PDT". Syntax: see 34 <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset> 35 - Time zone names based on geography, that contain one or more 36 slashes, e.g. "Europe/Moscow". 37 - Time zone names based on geography, without slashes, e.g. 38 "Singapore". 39 - Time zone names that contain explicit DST rules. Syntax: see 40 <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03> 41 The Microsoft CRT understands only the first kind. It produces incorrect 42 results if the value of TZ is of the other kinds. 43 But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value 44 of the second kind for most geographies, or of the first kind in a few 45 other geographies. If it is of the second kind, neutralize it. For the 46 Microsoft CRT, an absent or empty TZ means the time zone that the user 47 has set in the Windows Control Panel. 48 If the value of TZ is of the third or fourth kind -- Cygwin programs 49 understand these syntaxes as well --, it does not matter whether we 50 neutralize it or not, since these values occur only when a Cygwin user 51 has set TZ explicitly; this case is 1. rare and 2. under the user's 52 responsibility. */ 53 const char *tz = getenv ("TZ"); 54 if (tz != NULL && strchr (tz, '/') != NULL) 55 _putenv ("TZ="); 56 #endif 57 58 return localtime (tp); 59 }