https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93421
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:4d039cb9a1d0ffc6910fe09b726c3561b64527dc commit r11-5022-g4d039cb9a1d0ffc6910fe09b726c3561b64527dc Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Sep 24 17:35:52 2020 +0100 libstdc++: Use custom timespec in system calls [PR 93421] On 32-bit targets where userspace has switched to 64-bit time_t, we cannot pass struct timespec to SYS_futex or SYS_clock_gettime, because the userspace definition of struct timespec will not match what the kernel expects. We use the existence of the SYS_futex_time64 or SYS_clock_gettime_time64 macros to imply that userspace *might* have switched to the new timespec definition. This is a conservative assumption. It's possible that the new syscall numbers are defined in the libc headers but that timespec hasn't been updated yet (as is the case for glibc currently). But using the alternative struct with two longs is still OK, it's just redundant if userspace timespec still uses a 32-bit time_t. We also check that SYS_futex_time64 != SYS_futex so that we don't try to use a 32-bit tv_sec on modern targets that only support the 64-bit system calls and define the old macro to the same value as the new one. We could possibly check #ifdef __USE_TIME_BITS64 to see whether userspace has actually been updated, but it's not clear if user code is meant to inspect that or if it's only for libc internal use. libstdc++-v3/ChangeLog: PR libstdc++/93421 * src/c++11/chrono.cc [_GLIBCXX_USE_CLOCK_GETTIME_SYSCALL] (syscall_timespec): Define a type suitable for SYS_clock_gettime calls. (system_clock::now(), steady_clock::now()): Use syscall_timespec instead of timespec. * src/c++11/futex.cc (syscall_timespec): Define a type suitable for SYS_futex and SYS_clock_gettime calls. (relative_timespec): Use syscall_timespec instead of timespec. (__atomic_futex_unsigned_base::_M_futex_wait_until): Likewise. (__atomic_futex_unsigned_base::_M_futex_wait_until_steady): Likewise.
