https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95968
Bug ID: 95968
Summary: error: 'args#0' is not a constant expression
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: zakeria433 at gmail dot com
Target Milestone: ---
Hi,
command: g++ test_class.cpp -Wall -Wextra -std=c++20
System: Debian 10
The following code is rejected by Gcc 10.1. However, if I replace test_class's
constructor with constexpr instead of consteval, it does compile on gcc.
// Example program
#include <tuple>
#include <type_traits>
// #include <concepts>
template<typename T, typename ... Pack>
requires(std::is_floating_point<T>::value)
class test_class
{
public:
const T first_param;
const std::tuple <Pack...> pack;
consteval test_class(T first_param_, Pack... pack_) :
first_param(first_param_),
pack(pack_...)
{
}
consteval auto test_func()
{
//auto p = first_param;
auto x = std::apply([/*p*/](const auto ... args) {return
test_class(1.0, args...);}, pack);
return x;
}
};
int main()
{
constexpr auto var1 = test_class(4.0);
//constexpr auto var2 = test_class(5.0);
constexpr auto var3 = test_class(12.0, var1).test_func();
//static_assert(vart3.first_param == 12, "assert fail");
}
error: ‘args#0’ is not a constant expression
22 | auto x = std::apply([/*p*/](const auto ... args) {return
test_class(1.0, args...);}, pack);
|
^~~~~~~~~~~~~~~~~~~~~~~~
Live demo:
https://godbolt.org/z/oWWFaP
