Overloading a virtual function - c++

Question

I am trying to overload a virtual function, like this:
#include<iostream>
#include<string>
using std::cout;
using std::endl;
using std::string;
class Base{
public:
virtual void show(int x){
cout << "Showing int as Base: " << x << endl;
}
};
class Derived : public Base{
public:
using Base::show;
virtual void show(string s){
cout << "Showing string as Derived: " << s << endl;
}
};
int main(){
Derived x;
Base& ref = x;
ref.show(3);
ref.show(string("hi")/*in case the compiler refuses to implicitly convert const char* to std::string*/);
}
However, GCC complains error: cannot convert 'std::string' {aka 'std::__cxx11::basic_string<char>'} to 'int', and says note: initializing argument 1 of 'virtual void Base::show(int)'
It seems like gcc just ignored the Derived's overload of show.
I suspect that overloading together with polymorphism is just a BIT too much to handle for the compiler, since that would require storing the type information in the vtable as well, which MAY be not possible.
But then, what should I do to mimic this behaviour?
This worked:
#include<iostream>
#include<string>
#include<any>
using std::cout;
using std::endl;
using std::string;
using std::any;
using std::any_cast;
class Base{
public:
virtual void show(int x){
cout << "Showing int as Base: " << x << endl;
}
virtual void show(any x) = 0;
};
class Derived : public Base{
public:
using Base::show;
virtual void show(any s) override{
if(s.type() != typeid(std::string)){
if(s.type() != typeid(int)){
throw "SOME_ERROR_INDICATING_INVALID_FUNCTION_CALL";
}
Base::show(any_cast<int>(s));
return;
}
cout << "Showing string as Derived: " << any_cast<string>(s) << endl;
}
};
int main(){
Derived x;
Base& ref = x;
ref.show(3);
ref.show(string("hi")/*invokes show(any) override */);
}
but it seems really stupid. Is there any other workaround?
EDIT: adding virtual void show(string x)=0; to base is NOT desireable. This is just a MRE, and in the real program I have lots of derived classes, and I don't want to add a pure virtual function in Base for each of those customizations.

Answer 1

The problem is that you're calling show through a reference to a base object while passing a std::string as an argument but the base class doesn't have any such method so this call can't succeed.
To solve this you can add a declaration for virtual void show(string s) =0; inside the base class.
class Base{
public:
virtual void show(int x){
cout << "Showing int as Base: " << x << endl;
}
//added this declaration for making it pure virtual
virtual void show(string s)=0;
};