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Diffstat (limited to '')
| -rw-r--r-- | m4/year2038.m4 | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/m4/year2038.m4 b/m4/year2038.m4 new file mode 100644 index 0000000..06db589 --- /dev/null +++ b/m4/year2038.m4 @@ -0,0 +1,124 @@ +# 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]) +]) |