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nth_element fix [58800]

From: Christopher Jefferson <chris at bubblescope dot net>
To: "libstdc++" <libstdc++ at gcc dot gnu dot org>, gcc-patches at gcc dot gnu dot org
Date: Sat, 19 Oct 2013 22:02:57 +0100
Subject: nth_element fix [58800]
Authentication-results: sourceware.org; auth=none

A previous fix to a performance problem in std::sort unfortunately has
lead to a crashing bug in std::nth_element.

The following minimal patch fixes the problem (there are a couple of
different ways of fixing it, this is the shortest and safest).

2013-09-19 Chris Jefferson <chris@bubblescope.net>

PR libstdc++/58800
* include/bits/stl_algo.h (__unguarded_partition_pivot) : Change
__last - 2 to __last - 1, so we correctly work on arrays of length 4.
* testsuite/25_algorithms/nth_element/58800.cc : New

Attachment: nth_element1.patch
Description: Binary data

Follow-Ups:
- Re: nth_element fix [58800]
  - From: Paolo Carlini

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