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re PR libstdc++/47913 ([C++0x] improve ratio_add to overflow less often) 

2011-03-02  Marc Glisse  <marc.glisse@normalesup.org>

	PR libstdc++/47913
	* include/std/ratio (ratio_add): Avoid denominator overflow.
	* testsuite/20_util/ratio/operations/47913.cc: New.

From-SVN: r170616
This commit is contained in:
Marc Glisse 2011-03-02 14:57:57 +00:00 committed by Paolo Carlini
parent 34161e98f7
commit 8fddbce4ab
3 changed files with 58 additions and 6 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2011-03-02 Marc Glisse <marc.glisse@normalesup.org>
PR libstdc++/47913
* include/std/ratio (ratio_add): Avoid denominator overflow.
* testsuite/20_util/ratio/operations/47913.cc: New.
2011-02-28 Benjamin Kosnik <bkoz@redhat.com>
* testsuite/20_util/hash/chi2_quality.cc: Use C++0x mode on simulators.

16
libstdc++-v3/include/std/ratio
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@ -177,15 +177,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct ratio_add
{
private:
static const intmax_t __gcd =
static constexpr intmax_t __gcd =
__static_gcd<_R1::den, _R2::den>::value;
static constexpr intmax_t __n = __safe_add<
__safe_multiply<_R1::num, (_R2::den / __gcd)>::value,
__safe_multiply<_R2::num, (_R1::den / __gcd)>::value>::value;
// The new numerator may have common factors with the denominator,
// but they have to also be factors of __gcd.
static constexpr intmax_t __gcd2 = __static_gcd<__n, __gcd>::value;
public:
typedef ratio<
__safe_add<
__safe_multiply<_R1::num, (_R2::den / __gcd)>::value,
__safe_multiply<_R2::num, (_R1::den / __gcd)>::value>::value,
__safe_multiply<_R1::den, (_R2::den / __gcd)>::value> type;
typedef ratio<__n / __gcd2,
__safe_multiply<_R1::den / __gcd2, _R2::den / __gcd>::value> type;
static constexpr intmax_t num = type::num;
static constexpr intmax_t den = type::den;

42
libstdc++-v3/testsuite/20_util/ratio/operations/47913.cc Normal file
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@ -0,0 +1,42 @@
// { dg-options "-std=gnu++0x" }
// { dg-require-cstdint "" }
// Copyright (C) 2011 Free Software Foundation
//
// 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/>.
#include <ratio>
#include <testsuite_hooks.h>
// libstdc++/47913
void test01()
{
bool test __attribute__((unused)) = true;
using namespace std;
const intmax_t m = (intmax_t)1 << (4 * sizeof(intmax_t) - 1);
typedef ratio_add<ratio<1, (m - 1) * (m - 2)>,
ratio<1, (m - 3) * (m - 2)> > ra_type;
VERIFY( ra_type::num == 2 );
VERIFY( ra_type::den == (m - 1) * (m - 3) );
}
int main()
{
test01();
return 0;
}