84 lines
3.4 KiB
C
84 lines
3.4 KiB
C
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/* Provide tzset for systems that don't have it or for which it's broken.
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Copyright (C) 2001-2003, 2005-2007, 2009-2020 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>. */
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/* written by Jim Meyering */
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#include <config.h>
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/* Specification. */
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#include <time.h>
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#include "localtime-buffer.h"
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/* This is a wrapper for tzset, for systems on which tzset may clobber
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the static buffer used for localtime's result.
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Work around the bug in some systems whereby tzset clobbers the
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static buffer that localtime uses for its return value. The
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tzset function from Solaris 2.5, 2.5.1, and 2.6 has this problem. */
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void
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tzset (void)
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#undef tzset
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{
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#if TZSET_CLOBBERS_LOCALTIME
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/* Save and restore the contents of the buffer used for localtime's
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result around the call to tzset. */
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struct tm save = *localtime_buffer_addr;
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#endif
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#if defined _WIN32 && ! defined __CYGWIN__
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/* Rectify the value of the environment variable TZ.
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There are four possible kinds of such values:
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- Traditional US time zone names, e.g. "PST8PDT". Syntax: see
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<https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset>
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- Time zone names based on geography, that contain one or more
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slashes, e.g. "Europe/Moscow".
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- Time zone names based on geography, without slashes, e.g.
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"Singapore".
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- Time zone names that contain explicit DST rules. Syntax: see
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<https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
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The Microsoft CRT understands only the first kind. It produces incorrect
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results if the value of TZ is of the other kinds.
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But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value
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of the second kind for most geographies, or of the first kind in a few
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other geographies. If it is of the second kind, neutralize it. For the
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Microsoft CRT, an absent or empty TZ means the time zone that the user
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has set in the Windows Control Panel.
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If the value of TZ is of the third or fourth kind -- Cygwin programs
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understand these syntaxes as well --, it does not matter whether we
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neutralize it or not, since these values occur only when a Cygwin user
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has set TZ explicitly; this case is 1. rare and 2. under the user's
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responsibility. */
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const char *tz = getenv ("TZ");
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if (tz != NULL && strchr (tz, '/') != NULL)
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_putenv ("TZ=");
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/* On native Windows, tzset() is deprecated. Use _tzset() instead. See
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<https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/posix-tzset>
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<https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset> */
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_tzset ();
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#elif HAVE_TZSET
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tzset ();
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#else
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/* Do nothing. Avoid infinite recursion. */
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#endif
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#if TZSET_CLOBBERS_LOCALTIME
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*localtime_buffer_addr = save;
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#endif
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}
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