From 9733463d2b141a166bfa2f55ec316066ab0f71b6 Mon Sep 17 00:00:00 2001
From: Steven Fackler <sfackler@gmail.com>
Date: Sat, 23 Sep 2017 21:19:01 -0700
Subject: [PATCH] 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
---
 src/liballoc/vec_deque.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs
index 6836fbb7c4d..6d64e9e303f 100644
--- a/src/liballoc/vec_deque.rs
+++ b/src/liballoc/vec_deque.rs
@@ -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);