Using print() function in copy constructor C++ - c++

Question

The task is to create class, which counts the objects of its type, in every moment. Here is my code. The errors are:
1. the object has type qualifiers that are not compatible with the member function "counter::print";
2. return value type does not match the function type; - this was obwious really!
I corrected the errors and it gives me new one that I can't fix;
1. 'void counter::print(void)': cannot convert 'this' pointer from 'const counter' to 'counter &'
class counter {
private:
static int count;
public:
counter();
counter(const counter &from);
void print() const;
~counter();
};
counter::counter() {
++count;
}
counter::counter(const counter &from) {
++count;
cout << "Copy constructor:\t";
from.print(); // here is the error
}
void counter::print() const{
cout << "\t Number of objects = " << count << endl;
}
counter::~counter() {
--count;
cout << "Destructor:\t\t";
print();
}
int counter::count = 0;
counter f(counter x);
void main() {
counter c;
cout << "After constructing of c:";
c.print();
cout << "Calling f()" << endl;
f(c);
cout << "After calling f():";
c.print();
}
counter f(counter x) {
cout << "Argument inside f():\t";
x.print();
return x;
}

Answer 1

Firstly, change:
void print();
to:
void print() const;
because (a) it's a const method anyway and (b) you're trying to call it in a const context within your constructor.
For the second error here:
void f(counter x) {
cout << "Argument inside f():\t";
x.print();
return x; // 2 - nd error
}
it should be fairly obvious that you can't return a value from a void function. Either change it to:
counter f(counter x) {
cout << "Argument inside f():\t";
x.print();
return x;
}
or simply don't return anything:
void f(counter x) {
cout << "Argument inside f():\t";
x.print();
}

Answer 2

void print();
You have declared a non-const member function, which means it cannot be called by const instances.
from.print(); // 1 - st error
Here the type of from is const counter& which means it cannot call the print function. Instead make your print function const.
void print() const;
void counter::print() const { ... }
return x; // 2 - nd error
Why are you returning anything from a function with a void return type?