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auto merge of #6461 : thestinger/rust/fix_priority_queue, r=pcwalton

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uninit() would result in potentially running a destructor on arbitrary
memory if the Ord implementation throws
This commit is contained in:
bors 2013-05-13 21:31:42 -07:00
commit 3aa1122ec2
1 changed files with 4 additions and 56 deletions
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60
src/libstd/priority_queue.rs
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@ -12,14 +12,7 @@
use core::old_iter::BaseIter;
use core::util::{replace, swap};
#[abi = "rust-intrinsic"]
extern "rust-intrinsic" {
fn move_val_init<T>(dst: &mut T, src: T);
fn init<T>() -> T;
#[cfg(not(stage0))]
fn uninit<T>() -> T;
}
use core::unstable::intrinsics::{init, move_val_init};
pub struct PriorityQueue<T> {
priv data: ~[T],
@ -141,33 +134,13 @@ pub impl <T:Ord> PriorityQueue<T> {
// The implementations of siftup and siftdown use unsafe blocks in
// order to move an element out of the vector (leaving behind a
// junk element), shift along the others and move it back into the
// zeroed element), shift along the others and move it back into the
// vector over the junk element. This reduces the constant factor
// compared to using swaps, which involves twice as many moves.
#[cfg(not(stage0))]
priv fn siftup(&mut self, start: uint, mut pos: uint) {
unsafe {
let new = *ptr::to_unsafe_ptr(&self.data[pos]);
while pos > start {
let parent = (pos - 1) >> 1;
if new > self.data[parent] {
let x = replace(&mut self.data[parent], uninit());
move_val_init(&mut self.data[pos], x);
pos = parent;
loop
}
break
}
move_val_init(&mut self.data[pos], new);
}
}
#[cfg(stage0)]
priv fn siftup(&mut self, start: uint, mut pos: uint) {
unsafe {
let new = *ptr::to_unsafe_ptr(&self.data[pos]);
let new = replace(&mut self.data[pos], init());
while pos > start {
let parent = (pos - 1) >> 1;
@ -183,35 +156,10 @@ pub impl <T:Ord> PriorityQueue<T> {
}
}
#[cfg(not(stage0))]
priv fn siftdown_range(&mut self, mut pos: uint, end: uint) {
unsafe {
let start = pos;
let new = *ptr::to_unsafe_ptr(&self.data[pos]);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
if right < end && !(self.data[child] > self.data[right]) {
child = right;
}
let x = replace(&mut self.data[child], uninit());
move_val_init(&mut self.data[pos], x);
pos = child;
child = 2 * pos + 1;
}
move_val_init(&mut self.data[pos], new);
self.siftup(start, pos);
}
}
#[cfg(stage0)]
priv fn siftdown_range(&mut self, mut pos: uint, end: uint) {
unsafe {
let start = pos;
let new = *ptr::to_unsafe_ptr(&self.data[pos]);
let new = replace(&mut self.data[pos], init());
let mut child = 2 * pos + 1;
while child < end {