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Small refactoring to make this code more clear

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This hairy conditional doesn't need to be so. It _does_ need to be a
thin pointer, otherwise, it will fail to compile, so let's pull that out
into a temporary for future readers of the source.

Also, after a discussion with @pnkfelix and @gankro, we don't need these
null checks anymore, as zero-on-drop has been gone for a while now.
This commit is contained in:
Steve Klabnik 2015-12-28 15:28:46 -05:00
parent 27a1834ce5
commit 2cff12e0d6
2 changed files with 11 additions and 8 deletions
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9
src/liballoc/arc.rs
View File

@ -554,9 +554,9 @@ impl<T: ?Sized> Drop for Arc<T> {
// This structure has #[unsafe_no_drop_flag], so this drop glue may run
// more than once (but it is guaranteed to be zeroed after the first if
// it's run more than once)
let ptr = *self._ptr;
// if ptr.is_null() { return }
if ptr as *mut u8 as usize == 0 || ptr as *mut u8 as usize == mem::POST_DROP_USIZE {
let thin = *self._ptr as *const ();
if thin as usize == mem::POST_DROP_USIZE {
return;
}
@ -709,9 +709,10 @@ impl<T: ?Sized> Drop for Weak<T> {
/// ```
fn drop(&mut self) {
let ptr = *self._ptr;
let thin = ptr as *const ();
// see comments above for why this check is here
if ptr as *mut u8 as usize == 0 || ptr as *mut u8 as usize == mem::POST_DROP_USIZE {
if thin as usize == mem::POST_DROP_USIZE {
return;
}

10
src/liballoc/rc.rs
View File

@ -449,8 +449,9 @@ impl<T: ?Sized> Drop for Rc<T> {
fn drop(&mut self) {
unsafe {
let ptr = *self._ptr;
if !(*(&ptr as *const _ as *const *const ())).is_null() &&
ptr as *const () as usize != mem::POST_DROP_USIZE {
let thin = ptr as *const ();
if thin as usize != mem::POST_DROP_USIZE {
self.dec_strong();
if self.strong() == 0 {
// destroy the contained object
@ -782,8 +783,9 @@ impl<T: ?Sized> Drop for Weak<T> {
fn drop(&mut self) {
unsafe {
let ptr = *self._ptr;
if !(*(&ptr as *const _ as *const *const ())).is_null() &&
ptr as *const () as usize != mem::POST_DROP_USIZE {
let thin = ptr as *const ();
if thin as usize != mem::POST_DROP_USIZE {
self.dec_weak();
// the weak count starts at 1, and will only go to zero if all
// the strong pointers have disappeared.