How to fix error refactoring decltype inside template

Question

edit Possibly can\'t be done, see Clean implementation of function template taking function pointer although answer 1 there has a C macro work-around https://stacko

Answer 1

You cannot use decltype with a type as the goal is to obtain the type of a variable. But in decltype(&D), D is a type.

I would rather pass throught a template function:

template
class unique_gptr : public std::unique_ptr {
    public: unique_gptr(T* t) : std::unique_ptr(t, F) { };
};

template 
unique_gptr make_unique_gptr(T pointer, D deleter)
{
    return unique_gptr(pointer);
}

auto ptr = make_unique(new int(2), ::free_int);