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| author | Thom Chiovoloni <thom@shift.click> | 2022-09-03 00:28:03 -0700 |
|---|---|---|
| committer | Thom Chiovoloni <thom@shift.click> | 2022-11-22 02:09:47 -0800 |
| commit | 3099dfdd9fc1a331eb9c53200b310fa1a06e1573 (patch) | |
| tree | 77d5a5435e9ba2a652bf194f1a102bd2fbcf831d /library/std/src/thread/local.rs | |
| parent | 911cbf8e46f0f3b044c87fc5cbca922878db757b (diff) | |
| download | rust-3099dfdd9fc1a331eb9c53200b310fa1a06e1573.tar.gz rust-3099dfdd9fc1a331eb9c53200b310fa1a06e1573.zip | |
Forbid inlining `thread_local!`'s `__getit` function on Windows
Diffstat (limited to 'library/std/src/thread/local.rs')
| -rw-r--r-- | library/std/src/thread/local.rs | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs index 5d267891bb0..154b608c0dc 100644 --- a/library/std/src/thread/local.rs +++ b/library/std/src/thread/local.rs @@ -181,7 +181,8 @@ macro_rules! thread_local { macro_rules! __thread_local_inner { // used to generate the `LocalKey` value for const-initialized thread locals (@key $t:ty, const $init:expr) => {{ - #[cfg_attr(not(windows), inline)] // see comments below + #[cfg_attr(not(all(windows, target_thread_local)), inline)] // see comments below + #[cfg_attr(all(windows, target_thread_local), inline(never))] #[deny(unsafe_op_in_unsafe_fn)] unsafe fn __getit( _init: $crate::option::Option<&mut $crate::option::Option<$t>>, @@ -294,12 +295,17 @@ macro_rules! __thread_local_inner { fn __init() -> $t { $init } // When reading this function you might ask "why is this inlined - // everywhere other than Windows?", and that's a very reasonable - // question to ask. The short story is that it segfaults rustc if - // this function is inlined. The longer story is that Windows looks - // to not support `extern` references to thread locals across DLL - // boundaries. This appears to at least not be supported in the ABI - // that LLVM implements. + // everywhere other than Windows?", and "why must it not be inlined + // on Windows?" and these are very reasonable questions to ask. + // + // The short story is that Windows doesn't support referencing + // `#[thread_local]` across DLL boundaries. The slightly longer + // story is that each module (dll or exe) has its own separate set + // of static thread locals, so if you try and reference a + // `#[thread_local]` that comes from `crate1.dll` from within one of + // `crate2.dll`'s functions, then it might give you a completely + // different thread local than what you asked for (or it might just + // crash). // // Because of this we never inline on Windows, but we do inline on // other platforms (where external references to thread locals @@ -314,8 +320,9 @@ macro_rules! __thread_local_inner { // Cargo question kinda). This means that, unfortunately, Windows // gets the pessimistic path for now where it's never inlined. // - // The issue of "should enable on Windows sometimes" is #84933 - #[cfg_attr(not(windows), inline)] + // The issue of "should improve things on Windows" is #84933 + #[cfg_attr(not(all(windows, target_thread_local)), inline)] + #[cfg_attr(all(windows, target_thread_local), inline(never))] unsafe fn __getit( init: $crate::option::Option<&mut $crate::option::Option<$t>>, ) -> $crate::option::Option<&'static $t> { |