diff options
Diffstat (limited to 'library/std/src')
| -rw-r--r-- | library/std/src/thread/local.rs | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs index 1f5f26e3e14..c2c7ab91898 100644 --- a/library/std/src/thread/local.rs +++ b/library/std/src/thread/local.rs @@ -162,6 +162,7 @@ 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(target_env = "msvc"), inline)] // see comments below unsafe fn __getit() -> $crate::option::Option<&'static $t> { const _REQUIRE_UNSTABLE: () = $crate::thread::require_unstable_const_init_thread_local(); @@ -260,6 +261,29 @@ macro_rules! __thread_local_inner { #[inline] fn __init() -> $t { $init } + // When reading this function you might ask "why is this inlined + // everywhere other than MSVC?", 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 MSVC 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. + // + // Because of this we never inline on MVSC, but we do inline on + // other platforms (where external references to thread locals + // across DLLs are supported). A better fix for this would be to + // inline this function on MSVC, but only for "statically linked" + // components. For example if two separately compiled rlibs end up + // getting linked into a DLL then it's fine to inline this function + // across that boundary. It's only not fine to inline this function + // across a DLL boundary. Unfortunately rustc doesn't currently have + // this sort of logic available in an attribute, and it's not clear + // that rustc is even equipped to answer this (it's more of a Cargo + // question kinda). This means that, unfortunately, MSVC gets the + // pessimistic path for now where it's never inlined. + // + // The issue of "should enable on MSVC sometimes" is #84933 + #[cfg_attr(not(target_env = "msvc"), inline)] unsafe fn __getit() -> $crate::option::Option<&'static $t> { #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] static __KEY: $crate::thread::__StaticLocalKeyInner<$t> = |