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libstdc++: Fix divide by zero in default template argument

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libstdc++-v3/ChangeLog:

	* include/bits/random.h (__detail::_Mod): Avoid divide by zero.
	* testsuite/26_numerics/random/linear_congruential_engine/operators/call.cc:
	New test.
This commit is contained in:
Jonathan Wakely 2020-10-08 00:34:56 +01:00
parent 23f75da95f
commit 6ae17a3b68
2 changed files with 28 additions and 1 deletions
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2
libstdc++-v3/include/bits/random.h
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@ -109,7 +109,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp, _Tp __m, _Tp __a, _Tp __c,
bool __big_enough = (!(__m & (__m - 1))
|| (_Tp(-1) - __c) / __a >= __m - 1),
bool __schrage_ok = __m % __a < __m / __a>
bool __schrage_ok = __a != 0 && __m % __a < __m / __a>
struct _Mod
{
typedef typename _Select_uint_least_t<std::__lg(__a)

27
libstdc++-v3/testsuite/26_numerics/random/linear_congruential_engine/operators/call.cc Normal file
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@ -0,0 +1,27 @@
// 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-do compile { target c++11 } }
#include <random>
unsigned
test01()
{
std::linear_congruential_engine<unsigned, 0, 0, 0> l;
return l(); // this used to result in divide by zero
}