double boost::bind cause compile-time error

Question

The following code give compile error caused by line 17:

#include <boost/bind.hpp>
#include <boost/function.hpp>

void func()
{}

class A{
public:

    template <typename T>
    static void foo(T const& arg){}

    template <typename T>
    void bar(T const& arg){
        boost::bind(&A::foo<T>, arg);  //OK
        boost::function<T> functor1 = boost::bind(func); //OK
        boost::function<T> functor2 = boost::bind(&A::foo<T>, arg); //ERROR, LINE 17
    }
};

int main()
{
    A obj1;
    obj1.bar(func);
}

The question is, what the protoype of functor2 in line 17 should be?
If I really want to keep the functor2's prototype to be "boost::function<void()>, how to make the boost::bind return such a type?

The compilation error is:usr/include/boost/bind/bind.hpp:253: error: invalid initialization of reference of type 'void (&)()' from expression of type 'void (*)()'
What does it mean?

Answer 1

foo(T const& arg) takes a reference argument. In order to pass a reference argument through boost::bind, you need to wrap it with boost::ref.

boost::function<T> functor2 = boost::bind(&A::foo<T>, boost::ref(arg));