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# year2038.m4 serial 8
dnl Copyright (C) 2017-2022 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl Attempt to ensure that 'time_t' can go past the year 2038 and that
dnl the functions 'time', 'stat', etc. work with post-2038 timestamps.
m4_ifdef([AC_SYS_YEAR2038], [
AC_DEFUN([gl_YEAR2038_EARLY])
AC_DEFUN([gl_YEAR2038], [AC_SYS_YEAR2038])
AC_DEFUN([gl_YEAR2038_BODY], [_AC_SYS_YEAR2038])
], [
AC_DEFUN([gl_YEAR2038_EARLY],
[
AC_REQUIRE([AC_CANONICAL_HOST])
case "$host_os" in
mingw*)
AC_DEFINE([__MINGW_USE_VC2005_COMPAT], [1],
[For 64-bit time_t on 32-bit mingw.])
;;
esac
])
# gl_YEAR2038_TEST_INCLUDES
# -------------------------
AC_DEFUN([gl_YEAR2038_TEST_INCLUDES],
[[
#include <time.h>
/* Check that time_t can represent 2**32 - 1 correctly. */
#define LARGE_TIME_T \\
((time_t) (((time_t) 1 << 30) - 1 + 3 * ((time_t) 1 << 30)))
int verify_time_t_range[(LARGE_TIME_T / 65537 == 65535
&& LARGE_TIME_T % 65537 == 0)
? 1 : -1];
]])
# gl_YEAR2038_BODY(REQUIRE-YEAR2038-SAFE)
-----------------------------------------
AC_DEFUN([gl_YEAR2038_BODY],
[
AC_ARG_ENABLE([year2038],
[ --disable-year2038 omit support for timestamps past the year 2038])
AS_IF([test "$enable_year2038" != no],
[
dnl On many systems, time_t is already a 64-bit type.
dnl On those systems where time_t is still 32-bit, it requires kernel
dnl and libc support to make it 64-bit. For glibc 2.34 and later on Linux,
dnl defining _TIME_BITS=64 and _FILE_OFFSET_BITS=64 is needed on x86 and ARM.
dnl
dnl On native Windows, the system include files define types __time32_t
dnl and __time64_t. By default, time_t is an alias of
dnl - __time32_t on 32-bit mingw,
dnl - __time64_t on 64-bit mingw and on MSVC (since MSVC 8).
dnl But when compiling with -D__MINGW_USE_VC2005_COMPAT, time_t is an
dnl alias of __time64_t.
dnl And when compiling with -D_USE_32BIT_TIME_T, time_t is an alias of
dnl __time32_t.
AC_CACHE_CHECK([for time_t past the year 2038], [gl_cv_type_time_t_y2038],
[AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([gl_YEAR2038_TEST_INCLUDES])],
[gl_cv_type_time_t_y2038=yes], [gl_cv_type_time_t_y2038=no])
])
if test "$gl_cv_type_time_t_y2038" = no; then
AC_CACHE_CHECK([for 64-bit time_t with _TIME_BITS=64],
[gl_cv_type_time_t_bits_macro],
[AC_COMPILE_IFELSE(
[AC_LANG_SOURCE([[#define _TIME_BITS 64
#define _FILE_OFFSET_BITS 64
]gl_YEAR2038_TEST_INCLUDES])],
[gl_cv_type_time_t_bits_macro=yes],
[gl_cv_type_time_t_bits_macro=no])
])
if test "$gl_cv_type_time_t_bits_macro" = yes; then
AC_DEFINE([_TIME_BITS], [64],
[Number of bits in a timestamp, on hosts where this is settable.])
dnl AC_SYS_LARGFILE also defines this; it's OK if we do too.
AC_DEFINE([_FILE_OFFSET_BITS], [64],
[Number of bits in a file offset, on hosts where this is settable.])
gl_cv_type_time_t_y2038=yes
fi
fi
if test $gl_cv_type_time_t_y2038 = no; then
AC_COMPILE_IFELSE(
[AC_LANG_SOURCE(
[[#ifdef _USE_32BIT_TIME_T
int ok;
#else
error fail
#endif
]])],
[AC_MSG_FAILURE(
[The 'time_t' type stops working after January 2038.
Remove _USE_32BIT_TIME_T from the compiler flags.])],
[# If not cross-compiling and $1 says we should check,
# and 'touch' works with a large timestamp, then evidently wider time_t
# is desired and supported, so fail and ask the builder to fix the
# problem. Otherwise, just warn the builder.
m4_ifval([$1],
[if test $cross_compiling = no \
&& TZ=UTC0 touch -t 210602070628.15 conftest.time 2>/dev/null; then
case `TZ=UTC0 LC_ALL=C ls -l conftest.time 2>/dev/null` in
*'Feb 7 2106'* | *'Feb 7 17:10'*)
AC_MSG_FAILURE(
[The 'time_t' type stops working after January 2038,
and your system appears to support a wider 'time_t'.
Try configuring with 'CC="${CC} -m64"'.
To build with a 32-bit time_t anyway (not recommended),
configure with '--disable-year2038'.]);;
esac
rm -f conftest.time
fi])
if test "$gl_warned_about_y2038" != yes; then
AC_MSG_WARN(
[The 'time_t' type stops working after January 2038,
and this package needs a wider 'time_t' type
if there is any way to access timestamps after that.
Configure with 'CC="${CC} -m64"' perhaps?])
gl_warned_about_y2038=yes
fi
])
fi])
])
AC_DEFUN([gl_YEAR2038],
[
gl_YEAR2038_BODY([require-year2038-safe])
])
]) # m4_ifndef AC_SYS_YEAR2038
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