How do I assign an alias to a function name in C++?

There are different approaches:

  • With C++11 with non-template non-overloaded functions you can simply use:

    const auto& new_fn_name = old_fn_name;
    
  • If this function has multiple overloads you should use static_cast:

    const auto& new_fn_name = static_cast<OVERLOADED_FN_TYPE>(old_fn_name);
    

    Example: there are two overloads of function std::stoi

    int stoi (const string&, size_t*, int);
    int stoi (const wstring&, size_t*, int);
    

    If you want to make an alias to the first version you should use the following:

    const auto& new_fn_name = static_cast<int(*)(const string&, size_t*, int)>(std::stoi);
    

    Note: there is no way to make an alias to overloaded function such that all its overloaded versions work, so you should always specify which exact function overload you want.

  • With C++14 you can go even further with constexpr template variables. That allows you to alias templated functions:

    template<typename T>
    constexpr void old_function(/* args */);
    
    template<typename T>
    constexpr auto alias_to_old = old_function<T>;
    
  • Moreover, starting with C++11 you have a function called std::mem_fn that allows to alias member functions. See the following example:

    struct A {
       void f(int i) {
          std::cout << "Argument: " << i << '\n';
       }
    };
    
    
    A a;
    
    auto greet = std::mem_fn(&A::f); // alias to member function
    // prints "Argument: 5"
    greet(a, 5); // you should provide an object each time you use this alias
    
    // if you want to bind an object permanently use `std::bind`
    greet_a = std::bind(greet, a, std::placeholders::_1);
    greet_a(3); // equivalent to greet(a, 3) => a.f(3);
    

You can create a function pointer or a function reference:

void fn()
{
}

//...

void (*p)() = fn;//function pointer
void (&r)() = fn;//function reference

typedef int (*printf_alias)(const char*, ...);
printf_alias holler = std::printf;

Should do you fine.

Tags:

C++

Alias