Ferenc Gerlits created MINIFICPP-2254:
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Summary: Simplify template used by log_format_string to make
VS2022 understand it
Key: MINIFICPP-2254
URL: https://issues.apache.org/jira/browse/MINIFICPP-2254
Project: Apache NiFi MiNiFi C++
Issue Type: Bug
Reporter: Ferenc Gerlits
Assignee: Ferenc Gerlits
The {{map_args}} class template used by the {{log_format_string}} class
template in Logger.h uses some tricky template magic so that we can call the
logger both with invocable objects and plain value objects.
This template magic compiled fine in VS2019, as well as VS2022 up to version
19.35. However, since version 19.36, it no longer compiles.
{code:java}
#include <concepts>
#include <type_traits>
template<typename... Funcs>struct overloaded : Funcs... {
using Funcs::operator()...;
};
// deduction guide. doesn't hurt, but doesn't help either
//template<typename... Funcs>//overloaded(Funcs...) -> overloaded<Funcs...>;
const auto inline map_args = overloaded {
[](std::invocable<> auto&& f) { return
std::invoke(std::forward<decltype(f)>(f)); }, // works in 19.35, fails in 19.36
// [](auto&& f) requires(std::is_invocable_v<decltype(f)>) { return
std::invoke(std::forward<decltype(f)>(f)); }, // this works in both
[](auto&& value) { return std::forward<decltype(value)>(value); }
};
int main() {
return map_args(int());
}
{code}
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