Using clock nanosleep leads to more accurate sleep times on platforms
where it is supported.
To enable using clock_nanosleep this makes `sleep_until` platform
specific. That unfortunatly requires identical placeholder
implementations for the other platforms (windows/mac/wasm etc).
we will land platform specific implementations for those later. See the
`sleep_until` tracking issue.
This requires an accessors for the Instant type. As that accessor is only
used on the platforms that have clock_nanosleep it is marked as allow_unused.
32bit time_t targets do not use clock_nanosleep atm, they instead rely
on the same placeholder as the other platforms. We could make them
use clock_nanosleep too in the future using `__clock_nanosleep_time64`.
__clock_nanosleep_time64 is documented at:
https://www.gnu.org/software/libc/manual/html_node/64_002dbit-time-symbol-handling.html
Before making thread_local accept statements inside the const block,
this test would fail to compile as follows:
error: no rules expected the token `let`
--> library/std/tests/thread.rs:26:13
|
26 | let value = 1;
| ^^^ no rules expected this token in macro call
|
note: while trying to match meta-variable `$init:expr`
--> library/std/src/thread/local.rs:189:69
|
189 | ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = const { $init:expr }; $($rest:tt)*) => (
| ^^^^^^^^^^
