--- /dev/null
+@node Avoiding the year 2038 problem
+@section Avoiding the year 2038 problem
+
+The ``year 2038 problem'' denotes unpredictable behaviour of programs
+that will likely occur in the year 2038, for programs that use a 32-bit
+@samp{time_t} type. See @url{https://en.wikipedia.org/wiki/Year_2038_problem}
+for details.
+
+The gnulib module @samp{year2038} attempts to avoid this problem, by
+ensuring that @code{time_t} is a 64-bit type.
--- /dev/null
+# year2038.m4 serial 1
+dnl Copyright (C) 2017 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' is a 64-bit type
+dnl and that the functions time(), stat(), etc. return 64-bit times.
+
+AC_DEFUN([gl_YEAR2038_EARLY],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ case "$host_os" in
+ mingw*)
+ AC_DEFINE([__MINGW_USE_VC2005_COMPAT], [1],
+ [For 64-bit time_t on 32-bit mingw.])
+ ;;
+ esac
+])
+
+AC_DEFUN([gl_YEAR2038],
+[
+ AC_REQUIRE([AC_CANONICAL_HOST])
+ case "$host_os" in
+ mingw*)
+ 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 64-bit time_t], [gl_cv_type_time_t_64],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[#include <time.h>
+ int verify_time_t_size[sizeof (time_t) >= 8 ? 1 : -1];
+ ]],
+ [[]])],
+ [gl_cv_type_time_t_64=yes], [gl_cv_type_time_t_64=no])
+ ])
+ if test $gl_cv_type_time_t_64 = no; then
+ dnl Just bail out if 'time_t' is not 64-bit, and let the user fix the
+ dnl problem.
+ AC_EGREP_CPP([booboo], [
+ #ifdef _USE_32BIT_TIME_T
+ booboo
+ #endif
+ ],
+ [AC_MSG_FAILURE([This package requires a 64-bit 'time_t' type. Remove _USE_32BIT_TIME_T from the compiler flags.])],
+ [AC_MSG_FAILURE([This package requires a 64-bit 'time_t' type. Your system include files surely provide a way to make 'time_t' an alias of '__time64_t'.])])
+ fi
+ ;;
+ *)
+ 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 on Linux/x86, this
+ dnl is work in progress; see
+ dnl <https://sourceware.org/glibc/wiki/Y2038ProofnessDesign>.
+ ;;
+ esac
+])