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author | Jonathan Wakely <jwakely@redhat.com> | 2018-10-18 22:41:01 +0100 |
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committer | Jonathan Wakely <redi@gcc.gnu.org> | 2018-10-18 22:41:01 +0100 |
commit | 4f9f5a0c05dbea06b650fed849798c44e52abd55 (patch) | |
tree | 078c926ac642e2eeae3a59eeafaa768fc3bc9dbf | |
parent | 9a34d8e8a878afb66784729f6e9afddb8a02b9b0 (diff) | |
download | gcc-4f9f5a0c05dbea06b650fed849798c44e52abd55.zip gcc-4f9f5a0c05dbea06b650fed849798c44e52abd55.tar.gz gcc-4f9f5a0c05dbea06b650fed849798c44e52abd55.tar.bz2 |
PR libstdc++/87641 correctly initialize accumulator in valarray::sum()
Use the value of the first element as the initial value of the
__valarray_sum accumulator. Value-initialization might not create the
additive identity for the value type.
PR libstdc++/87641
* include/bits/valarray_array.h (__valarray_sum): Use first element
to initialize accumulator instead of value-initializing it.
* testsuite/26_numerics/valarray/87641.cc: New test.
From-SVN: r265291
-rw-r--r-- | libstdc++-v3/ChangeLog | 10 | ||||
-rw-r--r-- | libstdc++-v3/include/bits/valarray_array.h | 9 | ||||
-rw-r--r-- | libstdc++-v3/testsuite/26_numerics/valarray/87641.cc | 75 |
3 files changed, 89 insertions, 5 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index ef5e247..4024fc9 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,13 @@ +2018-10-18 Jonathan Wakely <jwakely@redhat.com> + + Backport from mainline + 2018-10-18 Jonathan Wakely <jwakely@redhat.com> + + PR libstdc++/87641 + * include/bits/valarray_array.h (__valarray_sum): Use first element + to initialize accumulator instead of value-initializing it. + * testsuite/26_numerics/valarray/87641.cc: New test. + 2018-10-15 Jonathan Wakely <jwakely@redhat.com> * testsuite/22_locale/numpunct/members/char/3.cc: Adjust test to diff --git a/libstdc++-v3/include/bits/valarray_array.h b/libstdc++-v3/include/bits/valarray_array.h index 4df1181..1f8f1b7 100644 --- a/libstdc++-v3/include/bits/valarray_array.h +++ b/libstdc++-v3/include/bits/valarray_array.h @@ -341,17 +341,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } // - // Compute the sum of elements in range [__f, __l) + // Compute the sum of elements in range [__f, __l) which must not be empty. // This is a naive algorithm. It suffers from cancelling. - // In the future try to specialize - // for _Tp = float, double, long double using a more accurate - // algorithm. + // In the future try to specialize for _Tp = float, double, long double + // using a more accurate algorithm. // template<typename _Tp> inline _Tp __valarray_sum(const _Tp* __f, const _Tp* __l) { - _Tp __r = _Tp(); + _Tp __r = *__f++; while (__f != __l) __r += *__f++; return __r; diff --git a/libstdc++-v3/testsuite/26_numerics/valarray/87641.cc b/libstdc++-v3/testsuite/26_numerics/valarray/87641.cc new file mode 100644 index 0000000..eae5440 --- /dev/null +++ b/libstdc++-v3/testsuite/26_numerics/valarray/87641.cc @@ -0,0 +1,75 @@ +// Copyright (C) 2018 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/>. + +#include <valarray> +#include <testsuite_hooks.h> + +void +test01() +{ + // PR libstdc++/87641 + std::valarray<int> v1(3); + v1[0] = 1; + v1[1] = 2; + v1[2] = 3; + std::valarray< std::valarray<int> > v2(v1, 3); + std::valarray<int> v3 = v2.sum(); + VERIFY( v3.size() == v1.size() ); + VERIFY( v3[0] == 3 ); + VERIFY( v3[1] == 6 ); + VERIFY( v3[2] == 9 ); +} + +struct X +{ + X() : val(1) { } + + X& operator+=(const X& x) { val += x.val; return *this; } + bool operator==(const X& x) { return val == x.val; } + + int val; +}; + +void +test02() +{ + std::valarray<X> v1(1); + VERIFY( v1.sum() == v1[0] ); + + std::valarray<X> v2(2); + VERIFY( v2.sum().val == 2 ); +} + +struct Y +{ + X& operator+=(const Y&) { throw 1; } +}; + +void +test03() +{ + std::valarray<Y> v1(1); + (void) v1.sum(); // no addition performed for a single element +} + +int +main() +{ + test01(); + test02(); + test03(); +} |