From 0f5e30d16004334cac1a25dbeefc0cfb886a404d Mon Sep 17 00:00:00 2001 From: Ulrik Sverdrup Date: Sat, 7 Nov 2015 18:09:20 +0100 Subject: [PATCH] sort: Guard the fast path by length check The right part must not be empty. --- src/libcollections/slice.rs | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/libcollections/slice.rs b/src/libcollections/slice.rs index cb3f39e0cac4b..9ea3389e81cc4 100644 --- a/src/libcollections/slice.rs +++ b/src/libcollections/slice.rs @@ -1066,10 +1066,12 @@ fn merge_sort(v: &mut [T], mut compare: F) where F: FnMut(&T, &T) -> Order let mut out = buf_tmp.offset(start as isize); let out_end = buf_tmp.offset(right_end_idx as isize); - // if left[last] <= right[0], they are already in order: + // If left[last] <= right[0], they are already in order: // fast-forward the left side (the right side is handled // in the loop). - if compare(&*right.offset(-1), &*right) != Greater { + // If `right` is not empty then left is not empty, and + // the offsets are in bounds. + if right != right_end && compare(&*right.offset(-1), &*right) != Greater { let elems = (right_start as usize - left as usize) / mem::size_of::(); ptr::copy_nonoverlapping(&*left, out, elems); out = out.offset(elems as isize);