https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95833
Bug ID: 95833
Summary: Incorrect static_assert in std::reduce overload taking
a binary functor
Product: gcc
Version: 10.0
URL: https://stackoverflow.com/q/62499765
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: eugns.p at gmail dot com
Target Milestone: ---
Created attachment 48773
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48773&action=edit
Preprocessed code for minimal example
The std::reduce overload that takes a binary functor
template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
_Tp reduce(_InputIterator, _InputIterator, _Tp, _BinaryOperation);
(defined here:
https://github.com/gcc-mirror/gcc/blob/releases/gcc-10/libstdc%2B%2B-v3/include/std/numeric#L236)
contains an incorrect static assertion:
static_assert(is_convertible_v<value_type, _Tp>);
There is no such requirement in the standard. This static assert causes a
compilation failure of the following minimal example:
#include <iostream>
#include <array>
#include <numeric>
#include <cstring>
struct StringLength {
auto operator()(const char* l, std::size_t r) const {
return std::strlen(l) + r;
}
auto operator()(std::size_t l, const char* r) const {
return l + std::strlen(r);
}
auto operator()(const char* l, const char* r) const {
return std::strlen(l) + std::strlen(r);
}
auto operator()(std::size_t l, std::size_t r) const {
return l + r;
}
};
int main() {
std::array<const char*, 3> arr{"A", "B", "C"};
std::cout << std::reduce(arr.begin(), arr.end(), std::size_t{},
StringLength{});
}
https://godbolt.org/z/Av3iY9
