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Make FlowRef a newtype

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This creates a sharp distinction between `Arc<Flow>`s, which may be
owned by anyone, and `FlowRef`s, which may only be owned by the
traversal code. By checking the reference count, we ensure that a `Flow`
cannot be pointed to by `Arc`s and `FlowRef`s simultaneously.

This is not a complete fix for #6503, though it is a necessary start
(enforcing the no-aliasing rule of `FlowRef::deref_mut` will require far
more work).

Fixes #14014
This commit is contained in:
Michael Howell 2016-11-03 12:53:27 -07:00
parent 5b4cc9568d
commit 5f320bd2ca
10 changed files with 145 additions and 101 deletions
Download patch file Download diff file Expand all files Collapse all files

21
components/layout/flow_list.rs
View file

@ -3,8 +3,9 @@
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use flow::Flow;
use flow_ref::{self, FlowRef};
use flow_ref::FlowRef;
use std::collections::{LinkedList, linked_list};
use std::sync::Arc;
/// This needs to be reworked now that we have dynamically-sized types in Rust.
/// Until then, it's just a wrapper around LinkedList.
@ -31,6 +32,10 @@ impl FlowList {
self.flows.push_back(new_tail);
}
pub fn push_back_arc(&mut self, new_head: Arc<Flow>) {
self.flows.push_back(FlowRef::new(new_head));
}
pub fn back(&self) -> Option<&Flow> {
self.flows.back().map(|x| &**x)
}
@ -42,8 +47,12 @@ impl FlowList {
self.flows.push_front(new_head);
}
pub fn pop_front(&mut self) -> Option<FlowRef> {
self.flows.pop_front()
pub fn push_front_arc(&mut self, new_head: Arc<Flow>) {
self.flows.push_front(FlowRef::new(new_head));
}
pub fn pop_front_arc(&mut self) -> Option<Arc<Flow>> {
self.flows.pop_front().map(FlowRef::into_arc)
}
pub fn front(&self) -> Option<&Flow> {
@ -114,7 +123,7 @@ impl FlowList {
impl<'a> DoubleEndedIterator for MutFlowListIterator<'a> {
fn next_back(&mut self) -> Option<&'a mut Flow> {
self.it.next_back().map(flow_ref::deref_mut)
self.it.next_back().map(FlowRef::deref_mut)
}
}
@ -122,7 +131,7 @@ impl<'a> Iterator for MutFlowListIterator<'a> {
type Item = &'a mut Flow;
#[inline]
fn next(&mut self) -> Option<&'a mut Flow> {
self.it.next().map(flow_ref::deref_mut)
self.it.next().map(FlowRef::deref_mut)
}
#[inline]
@ -146,6 +155,6 @@ impl<'a> FlowListRandomAccessMut<'a> {
Some(next_flow) => self.cache.push((*next_flow).clone()),
}
}
flow_ref::deref_mut(&mut self.cache[index])
FlowRef::deref_mut(&mut self.cache[index])
}
}