1 files changed, 66 insertions, 0 deletions
diff --git a/src/gl/tzset.c b/src/gl/tzset.c
new file mode 100644
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--- /dev/null
+++ b/src/gl/tzset.c
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+/* Provide tzset for systems that don't have it or for which it's broken.
+
+   Copyright (C) 2001-2003, 2005-2007, 2009-2021 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <https://www.gnu.org/licenses/>.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+/* Specification.  */
+#include <time.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+void
+rpl_tzset (void)
+#undef tzset
+{
+#if defined _WIN32 && ! defined __CYGWIN__
+  /* Rectify the value of the environment variable TZ.
+     There are four possible kinds of such values:
+       - Traditional US time zone names, e.g. "PST8PDT".  Syntax: see
+         <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset>
+       - Time zone names based on geography, that contain one or more
+         slashes, e.g. "Europe/Moscow".
+       - Time zone names based on geography, without slashes, e.g.
+         "Singapore".
+       - Time zone names that contain explicit DST rules.  Syntax: see
+         <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
+     The Microsoft CRT understands only the first kind.  It produces incorrect
+     results if the value of TZ is of the other kinds.
+     But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value
+     of the second kind for most geographies, or of the first kind in a few
+     other geographies.  If it is of the second kind, neutralize it.  For the
+     Microsoft CRT, an absent or empty TZ means the time zone that the user
+     has set in the Windows Control Panel.
+     If the value of TZ is of the third or fourth kind -- Cygwin programs
+     understand these syntaxes as well --, it does not matter whether we
+     neutralize it or not, since these values occur only when a Cygwin user
+     has set TZ explicitly; this case is 1. rare and 2. under the user's
+     responsibility.  */
+  const char *tz = getenv ("TZ");
+  if (tz != NULL && strchr (tz, '/') != NULL)
+    _putenv ("TZ=");
+
+  /* On native Windows, tzset() is deprecated.  Use _tzset() instead.  See
+     <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/posix-tzset>
+     <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset>  */
+  _tzset ();
+#else
+  tzset ();
+#endif
+}