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+# year2038.m4 serial 7
+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.
+
+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])
+])