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From: Jakub Jelinek <jakub@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc(refs/vendors/redhat/heads/gcc-8-branch)] libstdc++: Fix division by zero in std::sample Date: Fri, 23 Apr 2021 10:51:06 +0000 (GMT) [thread overview] Message-ID: <20210423105106.43F153AC5C07@sourceware.org> (raw) https://gcc.gnu.org/g:652f5ba6faaba8c9b8cff1383aee65e808572fcf commit 652f5ba6faaba8c9b8cff1383aee65e808572fcf Author: Patrick Palka <ppalka@redhat.com> 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<typename _Gen::result_type, _USize>; + 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 +// <http://www.gnu.org/licenses/>. + +// { dg-options "-std=gnu++17" } +// { dg-do run { target c++17 } } +// { dg-require-cstdint "" } + +#include <algorithm> +#include <random> +#include <testsuite_hooks.h> +#include <testsuite_iterators.h> + +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<const int, forward_iterator_wrapper> pop(&in, &in); + int out; + test_container<int, output_iterator_wrapper> samp(&out, &out + 1); + + auto it = sample(pop.begin(), pop.end(), samp.begin(), 1, rng); + VERIFY( it.ptr == &out ); +} + +int +main() +{ + test01(); +}
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