C++ member function overloading with & (ampersand)

Question

How to pick the correct error() member function? Do I need to cast somehow?

using namespace std;

struct test
{
   int error();
   void error(int x);
   int fun();
};

int main() {
   auto f1 = &test::error; // how to pick the correct function?
   auto f2 = &test::fun; // works
}

Answer 1

Do I need to cast somehow?

Yes, you can use static_cast.

static_cast may also be used to disambiguate function overloads by performing a function-to-pointer conversion to specific type, as in

std::for_each(files.begin(), files.end(),
              static_cast<std::ostream&(*)(std::ostream&)>(std::flush));

So you can:

auto f1 = static_cast<int(test::*)()>(&test::error);
auto f2 = static_cast<void(test::*)(int)>(&test::error);