From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1888) id 96E7B39B7012; Wed, 21 Apr 2021 12:08:18 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 96E7B39B7012 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Patrick Palka To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r8-10856] libstdc++: Fix division by zero in std::sample X-Act-Checkin: gcc X-Git-Author: Patrick Palka X-Git-Refname: refs/heads/releases/gcc-8 X-Git-Oldrev: a34c19926b87f9cadd5ea84f5c5b93ae76b14558 X-Git-Newrev: 378b238923e6b19ab941d2b350f1db873d131940 Message-Id: <20210421120818.96E7B39B7012@sourceware.org> Date: Wed, 21 Apr 2021 12:08:18 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Apr 2021 12:08:18 -0000 https://gcc.gnu.org/g:378b238923e6b19ab941d2b350f1db873d131940 commit r8-10856-g378b238923e6b19ab941d2b350f1db873d131940 Author: Patrick Palka Date: Mon Sep 21 20:48:23 2020 -0400 libstdc++: Fix division by zero in std::sample This fixes a division by zero in the selection-sampling std::__sample overload when the input range is empty (and hence __unsampled_sz is 0). libstdc++-v3/ChangeLog: * include/bits/stl_algo.h (__sample): Exit early when the input range is empty. * testsuite/25_algorithms/sample/3.cc: New test. (cherry picked from commit 813ad9c4dd5a779f12ad2abf710c6e75a3117ef0) Diff: --- libstdc++-v3/include/bits/stl_algo.h | 3 ++ libstdc++-v3/testsuite/25_algorithms/sample/3.cc | 50 ++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h index 753ebb7a09c..5c3d29bee5f 100644 --- a/libstdc++-v3/include/bits/stl_algo.h +++ b/libstdc++-v3/include/bits/stl_algo.h @@ -5754,6 +5754,9 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO using _Gen = remove_reference_t<_UniformRandomBitGenerator>; using __uc_type = common_type_t; + if (__first == __last) + return __out; + __distrib_type __d{}; _Size __unsampled_sz = std::distance(__first, __last); __n = std::min(__n, __unsampled_sz); diff --git a/libstdc++-v3/testsuite/25_algorithms/sample/3.cc b/libstdc++-v3/testsuite/25_algorithms/sample/3.cc new file mode 100644 index 00000000000..e89c40e27ee --- /dev/null +++ b/libstdc++-v3/testsuite/25_algorithms/sample/3.cc @@ -0,0 +1,50 @@ +// Copyright (C) 2020 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++17" } +// { dg-do run { target c++17 } } +// { dg-require-cstdint "" } + +#include +#include +#include +#include + +std::mt19937 rng; + +using std::sample; +using __gnu_test::test_container; +using __gnu_test::output_iterator_wrapper; +using __gnu_test::forward_iterator_wrapper; + +void +test01() +{ + const int in = 0; + test_container pop(&in, &in); + int out; + test_container samp(&out, &out + 1); + + auto it = sample(pop.begin(), pop.end(), samp.begin(), 1, rng); + VERIFY( it.ptr == &out ); +} + +int +main() +{ + test01(); +}