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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> {
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 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);
}
}
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,
// except in corner cases where thread_local dtors reference other
// thread_local's, or it is being recursively initialized.
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 {
// destructor is running
return None;
@ -563,7 +571,11 @@ pub mod os {
// local copy, so do that now.
let ptr: Box<Value<T>> = box Value { inner: LazyKeyInner::new(), key: self };
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
} else {
// recursive initialization