diff options
Diffstat (limited to 'library/std/src/sys_common/thread_local_dtor.rs')
-rw-r--r-- | library/std/src/sys_common/thread_local_dtor.rs | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/library/std/src/sys_common/thread_local_dtor.rs b/library/std/src/sys_common/thread_local_dtor.rs new file mode 100644 index 000000000..1d13a7171 --- /dev/null +++ b/library/std/src/sys_common/thread_local_dtor.rs @@ -0,0 +1,49 @@ +//! Thread-local destructor +//! +//! Besides thread-local "keys" (pointer-sized non-addressable thread-local store +//! with an associated destructor), many platforms also provide thread-local +//! destructors that are not associated with any particular data. These are +//! often more efficient. +//! +//! This module provides a fallback implementation for that interface, based +//! on the less efficient thread-local "keys". Each platform provides +//! a `thread_local_dtor` module which will either re-export the fallback, +//! or implement something more efficient. + +#![unstable(feature = "thread_local_internals", issue = "none")] +#![allow(dead_code)] + +use crate::ptr; +use crate::sys_common::thread_local_key::StaticKey; + +pub unsafe fn register_dtor_fallback(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) { + // The fallback implementation uses a vanilla OS-based TLS key to track + // the list of destructors that need to be run for this thread. The key + // then has its own destructor which runs all the other destructors. + // + // The destructor for DTORS is a little special in that it has a `while` + // loop to continuously drain the list of registered destructors. It + // *should* be the case that this loop always terminates because we + // provide the guarantee that a TLS key cannot be set after it is + // flagged for destruction. + + static DTORS: StaticKey = StaticKey::new(Some(run_dtors)); + type List = Vec<(*mut u8, unsafe extern "C" fn(*mut u8))>; + if DTORS.get().is_null() { + let v: Box<List> = box Vec::new(); + DTORS.set(Box::into_raw(v) as *mut u8); + } + let list: &mut List = &mut *(DTORS.get() as *mut List); + list.push((t, dtor)); + + unsafe extern "C" fn run_dtors(mut ptr: *mut u8) { + while !ptr.is_null() { + let list: Box<List> = Box::from_raw(ptr as *mut List); + for (ptr, dtor) in list.into_iter() { + dtor(ptr); + } + ptr = DTORS.get(); + DTORS.set(ptr::null_mut()); + } + } +} |