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Finished documenting all unsafe op inside unsafe fn

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This commit is contained in:
Alexis Bourget 2020-07-11 00:15:24 +02:00
parent 8c9cb06c2e
commit a83b79ec31
1 changed files with 17 additions and 5 deletions
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22
library/std/src/thread/local.rs
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@ -539,20 +539,28 @@ pub mod os {
} }
pub unsafe fn get(&'static self, init: fn() -> T) -> Option<&'static T> { pub unsafe fn get(&'static self, init: fn() -> T) -> Option<&'static T> {
let ptr = self.os.get() as *mut Value<T>; // SAFETY: No mutable references are ever handed out meaning getting
// the value is ok.
let ptr = unsafe { self.os.get() as *mut Value<T> };
if ptr as usize > 1 { if ptr as usize > 1 {
if let Some(ref value) = (*ptr).inner.get() { // SAFETY: the check ensured the pointer is safe (its destructor
// is not running) + it is coming from a trusted source (self).
if let Some(ref value) = unsafe { (*ptr).inner.get() } {
return Some(value); return Some(value);
} }
} }
self.try_initialize(init) // SAFETY: At this point we are sure we have no value and so
// initializing (or trying to) is safe.
unsafe { self.try_initialize(init) }
} }
// `try_initialize` is only called once per os thread local variable, // `try_initialize` is only called once per os thread local variable,
// except in corner cases where thread_local dtors reference other // except in corner cases where thread_local dtors reference other
// thread_local's, or it is being recursively initialized. // thread_local's, or it is being recursively initialized.
unsafe fn try_initialize(&'static self, init: fn() -> T) -> Option<&'static T> { unsafe fn try_initialize(&'static self, init: fn() -> T) -> Option<&'static T> {
let ptr = self.os.get() as *mut Value<T>; // SAFETY: No mutable references are ever handed out meaning getting
// the value is ok.
let ptr = unsafe { self.os.get() as *mut Value<T> };
if ptr as usize == 1 { if ptr as usize == 1 {
// destructor is running // destructor is running
return None; return None;
@ -563,7 +571,11 @@ pub mod os {
// local copy, so do that now. // local copy, so do that now.
let ptr: Box<Value<T>> = box Value { inner: LazyKeyInner::new(), key: self }; let ptr: Box<Value<T>> = box Value { inner: LazyKeyInner::new(), key: self };
let ptr = Box::into_raw(ptr); let ptr = Box::into_raw(ptr);
self.os.set(ptr as *mut u8); // SAFETY: At this point we are sure there is no value inside
// ptr so setting it will not affect anyone else.
unsafe {
self.os.set(ptr as *mut u8);
}
ptr ptr
} else { } else {
// recursive initialization // recursive initialization