Use time64 implementation by Michael G Schwern to extend allowed date/time range

The main benefit of this is to allow date/time values outside of the 32bit time_t
range which is very important on 32bit platforms. But there are also some other
issues that will be fixed with this, for example on macOS, mktime() will not work
for dates < 1902 despite time_t being 64bit.

In the same run this commit will also use a reentrant version of gmtime64_r that
should help in multithreaded scenarios.

Original code taken from: https://github.com/evalEmpire/y2038

1 files changed, 27 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index 8394997..5f99d95 100644
--- a/configure.ac
+++ b/configure.ac
@@ -56,7 +56,7 @@ AC_TYPE_UINT32_T
 AC_TYPE_UINT8_T
 
 # Checks for library functions.
-AC_CHECK_FUNCS([asprintf strcasecmp strdup strerror strndup stpcpy vasprintf])
+AC_CHECK_FUNCS([asprintf strcasecmp strdup strerror strndup stpcpy vasprintf gmtime_r localtime_r timegm])
 
 # Checking endianness
 AC_C_BIGENDIAN([AC_DEFINE([__BIG_ENDIAN__], [1], [big endian])],
@@ -78,6 +78,32 @@ case ${host_os} in
 esac
 AM_CONDITIONAL(WIN32, test x$win32 = xtrue)
 
+# Check if struct tm has a tm_gmtoff member
+AC_CACHE_CHECK(for tm_gmtoff in struct tm, ac_cv_struct_tm_gmtoff,
+        AC_TRY_COMPILE([
+                #include <time.h>
+        ], [
+                struct tm tm;
+                tm.tm_gmtoff = 1;
+        ], ac_cv_struct_tm_gmtoff=yes, ac_cv_struct_tm_gmtoff=no))
+
+if (test "$ac_cv_struct_tm_gmtoff" = "yes"); then
+        AC_DEFINE(HAVE_TM_TM_GMTOFF, 1, [Define if struct tm has a tm_gmtoff member])
+fi
+
+# Check if struct tm has a tm_zone member
+AC_CACHE_CHECK(for tm_zone in struct tm, ac_cv_struct_tm_zone,
+        AC_TRY_COMPILE([
+                #include <time.h>
+        ], [
+                struct tm tm;
+                tm.tm_zone = 1;
+        ], ac_cv_struct_tm_zone=yes, ac_cv_struct_tm_zone=no))
+
+if (test "$ac_cv_struct_tm_zone" = "yes"); then
+        AC_DEFINE(HAVE_TM_TM_ZONE, 1, [Define if struct tm has a tm_zone member])
+fi
+
 # Cython Python Bindings
 AC_ARG_WITH([cython],
             [AS_HELP_STRING([--without-cython],