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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r9-9594] libstdc++: Replace incorrect static assertion in std::reduce [PR95833] Date: Fri, 18 Jun 2021 20:57:30 +0000 (GMT) [thread overview] Message-ID: <20210618205730.832B63893C4A@sourceware.org> (raw) https://gcc.gnu.org/g:ae17634d5fce496a50477eb0199f1eda8249622f commit r9-9594-gae17634d5fce496a50477eb0199f1eda8249622f Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Jun 18 14:46:58 2021 +0100 libstdc++: Replace incorrect static assertion in std::reduce [PR95833] The standard does not require the iterator's value type to be convertible to the result type, it only requires that the result of dereferencing the iterator can be passed to the binary function. libstdc++-v3/ChangeLog: PR libstdc++/95833 * include/std/numeric (reduce(Iter, Iter, T, BinaryOp)): Replace incorrect static_assert with ones matching the 'Mandates' conditions in the standard. * testsuite/26_numerics/reduce/95833.cc: New test. (cherry picked from commit 0532452dcd17910dfd3d2b0df50dfe3ef1194bf7) Diff: --- libstdc++-v3/include/std/numeric | 6 ++++-- libstdc++-v3/testsuite/26_numerics/reduce/95833.cc | 16 ++++++++++++++++ 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric index 7f80d06cfbc..25fdfaf735f 100644 --- a/libstdc++-v3/include/std/numeric +++ b/libstdc++-v3/include/std/numeric @@ -261,9 +261,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION reduce(_InputIterator __first, _InputIterator __last, _Tp __init, _BinaryOperation __binary_op) { - using value_type = typename iterator_traits<_InputIterator>::value_type; + using __ref = typename iterator_traits<_InputIterator>::reference; + static_assert(is_invocable_r_v<_Tp, _BinaryOperation&, _Tp&, __ref>); + static_assert(is_invocable_r_v<_Tp, _BinaryOperation&, __ref, _Tp&>); static_assert(is_invocable_r_v<_Tp, _BinaryOperation&, _Tp&, _Tp&>); - static_assert(is_convertible_v<value_type, _Tp>); + static_assert(is_invocable_r_v<_Tp, _BinaryOperation&, __ref, __ref>); if constexpr (__is_random_access_iter<_InputIterator>::value) { while ((__last - __first) >= 4) diff --git a/libstdc++-v3/testsuite/26_numerics/reduce/95833.cc b/libstdc++-v3/testsuite/26_numerics/reduce/95833.cc new file mode 100644 index 00000000000..cf4644f53c9 --- /dev/null +++ b/libstdc++-v3/testsuite/26_numerics/reduce/95833.cc @@ -0,0 +1,16 @@ +// { dg-do compile { target c++17 } } +// PR libstdc++/95833 - Incorrect static_assert in std::reduce overload + +#include <numeric> + +struct A { }; +struct B { }; + +struct binop +{ + template<typename T, typename U> + A operator()(T&&, U&&) const { return A{}; } +}; + +B b; +A a = std::reduce(&b, &b + 1, A{}, binop{});
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