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Auto merge of #43931 - eddyb:const-local-key, r=alexcrichton

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Make the LocalKey facade of thread_local! inlineable cross-crate.

Fixes (almost*) #25088 by changing the `LocalKey` `static` `thread_local!` generates to a `const`.
This can be done because a `LocalKey` value holds no actual TLS data, only function pointers to get at said data, and it could even be made `Copy` without any negative consequences.
The recent stabilization of rvalue promotion to `'static` allows doing this without changing the API.
r? @alexcrichton

*almost because we can't yet inline `__getit` because it breaks on MSVC, see https://github.com/rust-lang/rust/pull/43931#issuecomment-323534214
This commit is contained in:
bors
2017-09-07 06:52:05 +00:00
parent a6a9d4c5fd 4e2be14986
commit d7d75eff30
2 changed files with 14 additions and 4 deletions
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16
src/libstd/thread/local.rs
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@@ -159,8 +159,9 @@ macro_rules! thread_local {
#[allow_internal_unstable]
#[allow_internal_unsafe]
macro_rules! __thread_local_inner {
($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
$(#[$attr])* $vis static $name: $crate::thread::LocalKey<$t> = {
(@key $(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
{
#[inline]
fn __init() -> $t { $init }
unsafe fn __getit() -> $crate::option::Option<
@@ -182,7 +183,16 @@ macro_rules! __thread_local_inner {
unsafe {
$crate::thread::LocalKey::new(__getit, __init)
}
};
}
};
($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
#[cfg(stage0)]
$(#[$attr])* $vis static $name: $crate::thread::LocalKey<$t> =
__thread_local_inner!(@key $(#[$attr])* $vis $name, $t, $init);
#[cfg(not(stage0))]
$(#[$attr])* $vis const $name: $crate::thread::LocalKey<$t> =
__thread_local_inner!(@key $(#[$attr])* $vis $name, $t, $init);
}
}