Hoisting the dynamic type out of a loop (a.k.a. doing Java the C++ way)

Question

I was discussing the merits of \"modern\" languages compared to C++ with some friends recently, when the following came up (I think inspired by Java):

Does any C++ c

Answer 1

It has been pointed out to me that GCC has an extension, called "bound member functions", that does indeed allow you to store the actual function pointer. Demo:

struct Foo
{
    virtual ~Foo() { }
    virtual int f(int, int) = 0;
};

void f(Foo & x)
{
    using gcc_func_type = int (*)(Foo *, int, int);

    gcc_func_type fp = (gcc_func_type)(x.*&Foo::f);  // !

    for ( /* ... */ )
    {
        int result = fp(&x, 10, 20);   // no virtual dispatch!
    }
}

The syntax requires that you go through a pointer-to-member indirection (i.e. you cannot just write (x.f)), and the cast must be a C-style cast. The resulting function pointer has the type of a pointer to a free function, with the instance argument taken as the first parameter.