diff options
| -rw-r--r-- | library/std/src/sys/pal/windows/thread_local_key.rs | 35 |
1 files changed, 13 insertions, 22 deletions
diff --git a/library/std/src/sys/pal/windows/thread_local_key.rs b/library/std/src/sys/pal/windows/thread_local_key.rs index 5eee4a9667b..1d9cb316a45 100644 --- a/library/std/src/sys/pal/windows/thread_local_key.rs +++ b/library/std/src/sys/pal/windows/thread_local_key.rs @@ -1,7 +1,7 @@ use crate::cell::UnsafeCell; use crate::ptr; use crate::sync::atomic::{ - AtomicBool, AtomicPtr, AtomicU32, + AtomicPtr, AtomicU32, Ordering::{AcqRel, Acquire, Relaxed, Release}, }; use crate::sys::c; @@ -9,10 +9,6 @@ use crate::sys::c; #[cfg(test)] mod tests; -/// An optimization hint. The compiler is often smart enough to know if an atomic -/// is never set and can remove dead code based on that fact. -static HAS_DTORS: AtomicBool = AtomicBool::new(false); - // Using a per-thread list avoids the problems in synchronizing global state. #[thread_local] #[cfg(target_thread_local)] @@ -24,12 +20,11 @@ static DESTRUCTORS: crate::cell::RefCell<Vec<(*mut u8, unsafe extern "C" fn(*mut #[inline(never)] #[cfg(target_thread_local)] pub unsafe fn register_keyless_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) { + dtors_used(); match DESTRUCTORS.try_borrow_mut() { Ok(mut dtors) => dtors.push((t, dtor)), Err(_) => rtabort!("global allocator may not use TLS"), } - - HAS_DTORS.store(true, Relaxed); } #[inline(never)] // See comment above @@ -130,6 +125,7 @@ impl StaticKey { #[cold] unsafe fn init(&'static self) -> Key { if self.dtor.is_some() { + dtors_used(); let mut pending = c::FALSE; let r = c::InitOnceBeginInitialize(self.once.get(), 0, &mut pending, ptr::null_mut()); assert_eq!(r, c::TRUE); @@ -215,7 +211,6 @@ unsafe fn register_dtor(key: &'static StaticKey) { Err(new) => head = new, } } - HAS_DTORS.store(true, Release); } // ------------------------------------------------------------------------- @@ -281,17 +276,16 @@ unsafe fn register_dtor(key: &'static StaticKey) { // the address of the symbol to ensure it sticks around. #[link_section = ".CRT$XLB"] -#[allow(dead_code, unused_variables)] -#[used] // we don't want LLVM eliminating this symbol for any reason, and -// when the symbol makes it to the linker the linker will take over pub static p_thread_callback: unsafe extern "system" fn(c::LPVOID, c::DWORD, c::LPVOID) = on_tls_callback; -#[allow(dead_code, unused_variables)] -unsafe extern "system" fn on_tls_callback(h: c::LPVOID, dwReason: c::DWORD, pv: c::LPVOID) { - if !HAS_DTORS.load(Acquire) { - return; - } +fn dtors_used() { + // we don't want LLVM eliminating p_thread_callback when destructors are used. + // when the symbol makes it to the linker the linker will take over + unsafe { crate::intrinsics::volatile_load(&p_thread_callback) }; +} + +unsafe extern "system" fn on_tls_callback(_h: c::LPVOID, dwReason: c::DWORD, _pv: c::LPVOID) { if dwReason == c::DLL_THREAD_DETACH || dwReason == c::DLL_PROCESS_DETACH { #[cfg(not(target_thread_local))] run_dtors(); @@ -301,19 +295,16 @@ unsafe extern "system" fn on_tls_callback(h: c::LPVOID, dwReason: c::DWORD, pv: // See comments above for what this is doing. Note that we don't need this // trickery on GNU windows, just on MSVC. - reference_tls_used(); - #[cfg(target_env = "msvc")] - unsafe fn reference_tls_used() { + #[cfg(all(target_env = "msvc", not(target_thread_local)))] + { extern "C" { static _tls_used: u8; } crate::intrinsics::volatile_load(&_tls_used); } - #[cfg(not(target_env = "msvc"))] - unsafe fn reference_tls_used() {} } -#[allow(dead_code)] // actually called below +#[cfg(not(target_thread_local))] unsafe fn run_dtors() { for _ in 0..5 { let mut any_run = false; |