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Auto merge of #44802 - sfackler:vecdeque-oob, r=Gankro
Fix capacity comparison in reserve

You can otherwise end up in a situation where you don't actually resize
but still call into handle_cap_increase which then corrupts head/tail.

Closes #44800

Not totally sure the right way to write a test for this - there are some debug asserts the old bad behavior will hit but we don't build the stdlib with debug assertions by default.

r? @gankro
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bors committed Sep 27, 2017
2 parents d4da744 + 81bac74 commit f71b37b
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Showing 2 changed files with 26 additions and 1 deletion.
2 changes: 1 addition & 1 deletion src/liballoc/vec_deque.rs
Expand Up @@ -558,7 +558,7 @@ impl<T> VecDeque<T> {
.and_then(|needed_cap| needed_cap.checked_next_power_of_two())
.expect("capacity overflow");

if new_cap > self.capacity() {
if new_cap > old_cap {
self.buf.reserve_exact(used_cap, new_cap - used_cap);
unsafe {
self.handle_cap_increase(old_cap);
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25 changes: 25 additions & 0 deletions src/test/run-pass-valgrind/issue-44800.rs
@@ -0,0 +1,25 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![feature(global_allocator, alloc_system, allocator_api)]
extern crate alloc_system;

use std::collections::VecDeque;
use alloc_system::System;

#[global_allocator]
static ALLOCATOR: System = System;

fn main() {
let mut deque = VecDeque::with_capacity(32);
deque.push_front(0);
deque.reserve(31);
deque.push_back(0);
}

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