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Don’t mark flow_ref::deref_mut as unsafe.

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See discussion in https://github.com/servo/servo/pull/7237
This commit is contained in:
Simon Sapin 2015-08-18 19:37:15 +02:00
parent 649250130b
commit 21d69314d4
10 changed files with 53 additions and 72 deletions
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14
components/layout/flow_ref.rs
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@ -8,7 +8,6 @@
//! be superfluous. This design is largely duplicating logic of Arc<T> and
//! Weak<T>; please see comments there for details.
#![allow(unsafe_code)]
use flow::Flow;
use std::sync::{Arc, Weak};
@ -16,9 +15,14 @@ use std::sync::{Arc, Weak};
pub type FlowRef = Arc<Flow>;
pub type WeakFlowRef = Weak<Flow>;
// FIXME(https://github.com/servo/servo/issues/6503) This introduces unsound mutable aliasing.
// Try to replace it with Arc::get_mut (which checks that the reference count is 1).
pub unsafe fn deref_mut<'a>(r: &'a mut FlowRef) -> &'a mut Flow {
/// WARNING: This should only be used when there is no aliasing:
/// when the traversal ensures that no other threads accesses the same flow at the same time.
/// See https://github.com/servo/servo/issues/6503
/// Use Arc::get_mut instead when possible (e.g. on an Arc that was just created).
#[allow(unsafe_code)]
pub fn deref_mut<'a>(r: &'a mut FlowRef) -> &'a mut Flow {
let ptr: *const Flow = &**r;
&mut *(ptr as *mut Flow)
unsafe {
&mut *(ptr as *mut Flow)
}
}