This reenables epoll_pwait2() use, i.e. undoes the effect of
39f756d3ae.
Instead of just reverting that, this PR will change things so that we
strictly rely on glibc's new epoll_pwait2() wrapper (which was added
earlier this year), and drop our own manual fallback syscall wrapper.
That should nicely side-step any issues with correct syscall wrapping
definitions (which on some arch seem not to be easy, given the sigset_t
size final argument), by making this a glibc problem, not ours.
Given that the only benefit this delivers are time-outs more granular
than msec, it shouldn't really matter that we'll miss out on support
for this on systems with older glibcs.
The ifdef pattern is the same for all syscalls, so most of the time, if one is
not defined, all others will too. So let's reduce the noise a bit and emit one
warning in case the support for the architecture is fully missing. (Current
template was copied over from before when we added numbers for each syscall by
hand and stopped making sense when we started generating the header from a
table that is expected to have all syscall numbers.)
If the file was always generated on the fly, the header would be pointless.
But since we distribute it, it should be there. C.f.
a0e150b2f4.
This was forgotten in 35b42e5600.
Getting the numbers right for all architectures has proven to be a
constant chore. Let's autogenerate the header from the tables that
were imported in one of the previous commits.
Fixes#18074. (Hopefully. I cannot verify this on all architectures.)
To update the lists, or to update the header after template changes:
ninja -C build update-syscall-tables update-syscall-header
Note: the generated file is saved in git. Initially I wanted to only
store the tables in git, and generate the header during each build.
Generation is quick enough, but the header is used in many many
places (wherever missing_syscall.h is included, directly or indirectly),
which means that we would need to declare the dependency in meson, so
the header would be generated early enough. This turned out to be very
noisy. Storing the generated header in version control avoids the hassle.
