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CMake: Unconditionally use 64-bit time_t on 32-bit glibc platforms

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The GNU C library has support for 64-bit time_t on all architectures,
but default to 32-bit time_t on some 32-bit architectures (x86 and
ARM) unless the _TIME_BITS feature test macro is defined:

https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html

Debian already does this when building packages. Most other platforms
that Wireshark can build on have 64-bit time_t already on all architectures;
one exception is FreeBSD on i386 (but not 32-bit ARM):

https://man.freebsd.org/cgi/man.cgi?arch

FreeBSD is dropping support for i386 for Release 15; Release 14 has an
EOL of Nov 2028. So at some point we could consider requiring 64-bit
time_t.

Ping #11744
This commit is contained in:
John Thacker 2025-05-13 10:59:13 -04:00
parent 3afd82ad01
commit 9c27acd7a5
1 changed files with 28 additions and 0 deletions
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28
ConfigureChecks.cmake
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@ -153,6 +153,34 @@ check_struct_has_member("struct tm" tm_gmtoff time.h HAVE_STRUC
include(CheckTypeSize)
check_type_size("ssize_t" SSIZE_T)
# Unconditionally force use of 64-bit time_t on 32-bit platforms with glibc.
check_symbol_exists(__GLIBC__ "time.h" HAVE___GLIBC__)
if(HAVE___GLIBC__ AND CMAKE_SIZEOF_VOID_P EQUAL 4)
# _TIME_BITS=64 requires _FILE_OFFSET_BITS=64, which we should have
# already ensured is set by FindLFS, but this doesn't hurt
check_symbol_exists(_FILE_OFFSET_BITS "time.h" HAVE__FILE_OFFSET_BITS)
if (NOT HAVE__FILE_OFFSET_BITS)
list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_FILE_OFFSET_BITS=64)
endif()
check_symbol_exists(_TIME_BITS "time.h" HAVE__TIME_BITS)
if (NOT HAVE__TIME_BITS)
list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_TIME_BITS=64)
endif()
endif()
# Do we want to eventually just fail for non Y2038 compliant hosts (or all
# less than 64-bit time_t hosts, if we don't want to consider theoretical
# cases like unsigned 32 bit time_t?)
# The only way to truly test this is to compile a program, especially
# due to multiple architectures.
#check_type_size("time_t" TIME_T_SIZE)
#if(TIME_T_SIZE_64 EQUAL 0)
# message("multiple architectures with possibly different time_t sizes.")
#elseif(TIME_T_SIZE_64 LESS 8)
# message(FATAL_ERROR "time_t is less than 64-bit")
#endif()
#
# Check if the libc vsnprintf() conforms to C99. If this fails we may
# need to fall-back on GLib I/O.