On Fri, 23 Jan 2026 at 17:08:32 +0530, Ujjwal Sarswat wrote:
When running the test suite on 32-bit architectures that use 64-bit time_t
(e.g., modern armhf/i386 for Y2038 compliance), test_server_simple_timeouts
fails with OSError: [Errno 22] Invalid argument.
i386 does not use 64-bit time_t by default, at least on Debian: this was
agreed on as a way to avoid regressing legacy binary-only software
(mostly games!), which is the main use-case for i386 in the 2020s, and
would break if we changed the ABI of time_t. As far as I'm aware, both
Debian and Ubuntu have followed the same policy on this.
This is a special exception for i386 (possibly also hurd-i386, I'm not
sure about the non-Linux ports). Other 32-bit architectures, such as
armel, armhf and various -ports architectures, have done the ABI break
and now use 64-bit time_t.
Ubuntu doesn't compile most packages for i386, so in practice this
subtlety probably doesn't matter on Ubuntu, but it does matter on
Debian.
Individual packages can force 64-bit time_t by adding -D_TIME_BITS=64 to
their CPPFLAGS, but this must only be done if the package maintainer
knows that it does not alter the library's external ABI. For example
libsdl3 does this, as can be seen in the
https://buildd.debian.org/status/fetch.php?pkg=libsdl3&arch=i386&ver=3.4.0%2Bds-1&stamp=1767281138&raw=0
build log, because libsdl3 is careful not to use OS-defined types like
time_t or struct stat in its ABI.
Proposed Fix: Change the packing format from "ll" to "qq" (long long). This
forces 8-byte integers on all platforms, ensuring the structure is always 16 bytes when time_t is
64-bit.
This would fix armhf, but might be wrong on i386, so it should be tested
on both armhf and i386 before applying this change. It might be
necessary to generate the correct format string dynamically, based on
properties of the architecture.
You mentioned that m2.time_t_bits() exists, so that could be used as a
way to select the correct format.
Strictly speaking, neither "ll" nor "qq" is guaranteed to be of a
specific size in bits: "ll" with no special prefix is equivalent to
"@ll", meaning two C `long` objects, whatever that means on the current
platform, and similarly "qq" or "@qq" is two C `long long` objects
(although in practice `long long` has a length of 64 bits on all Debian
architectures). The format string for a pair of 64-bit integers,
specifically, would be "=qq".
smcv
