CODEWITHSUNDEEP
c++classobjectintoperator-overloading
Mohammad Noman
Mohammad Noman

Reputation: 73

operator overloading and function overloading producing ambiguous compiler error

In the given code, I am not able to understand why the compiler is producing errors when the function is called. It is passing object of test class which has its data member of a test2 class

class Test2 {
    int y;
};

class Test {
    int x;
    Test2 t2;
public:
    operator Test2 () {return t2;}
    operator int () {return x;}
};

void fun (int x) { 
    cout << "fun(int) called";
}

void fun (Test2 t) {
    cout << "fun(Test 2) called";
}

int main() {
    Test t;
    fun(t);
    return 0;
}

Upvotes: 0

Views: 41

Answers (2)

P.W
P.W

Reputation: 26800

The call fun(t); is ambiguous because both overloads of fun are eligible for it.

This is again because t is a Test object which can be converted to both Test2 and int.

Marking either one of the conversion operators as explicit will resolve this issue.

See Demo here.

Upvotes: 0

lubgr
lubgr

Reputation: 38267

I am not able to understand why the compiler is producing errors when the function is called

How is the compiler supposed to figure out which function to call? You have two function in the overload set associated with the name func, and two operators that allow for implicit conversions to types that equally well match both function parameters of this overload set.

The situation is identical to

void f(long);
void f(short);

f(42); // Error: both conversions int -> log and int -> short possible

You can fix it by e.g.

fun(static_cast<Test2>(t)); // be explicit on the calling side

or by marking one (or both) of the conversion operators as explicit

explicit operator Test2 () {return t2;}

which disables implicit conversions to Test2 and requires an explicit cast as shown before.

Upvotes: 1

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