Re: ambiguous overload

From:

onkar <onkar.n.m@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 6 Jan 2008 22:07:20 -0800 (PST)

Message-ID:

<a21174f2-a51d-43e0-ae68-ac11ab654101@e23g2000prf.googlegroups.com>

On Jan 7, 11:02 am, Ian Collins <ian-n...@hotmail.com> wrote:

onkar wrote:

#include<iostream>
using namespace std;
class Integer{
        int i;
        public:
                Integer(int ii):i(ii){}
                const Integer operator+(const Integer& rv){
                        cout<<"1-operator+"<<endl;
                        return Integer(i+rv.i);
                }
                Integer operator+=(Integer rv){
                        i+=rv.i;
                        cout<<"2-operator+="<<endl;
                        return *this;
                }
                friend Integer& operator+(Integer,Integer);

                void display(){
                        cout<<"3-display()// i="<<i<<endl;
                }
};
Integer& operator+(Integer rv,Integer rs ){
                        cout<<"2-operator+="<<endl;
        rv.i+=rs.i;
        return rv;

You shouldn't return a reference to a local variable!

What should I do to prevent this ??

Stick to one operator+. Why have two?

--
Ian Collins.

#include<iostream>
using namespace std;
class Integer{
        int i;
        public:
                Integer(int ii):i(ii){}
                /* const Integer operator+(const Integer& rv){
                        cout<<"1-operator+"<<endl;
                        return Integer(i+rv.i);
                } */
                Integer operator+=(Integer rv){
                        i+=rv.i;
                        cout<<"2-operator+="<<endl;
                        return *this;
                }
                friend Integer& operator+(Integer,Integer);

                void display(){
                        cout<<"3-display()// i="<<i<<endl;
                }
};
Integer& operator+(Integer rv,Integer rs ){
        cout<<"4-operator+"<<endl;
        rv.i+=rs.i;
        return rv;
}
int main(void){
         cout<<"buit-in types"<<endl;
        int i=1,j=2,k=3;
        k+=i+j;
        cout<<"user defined types:"<<endl;
        Integer ii(1),jj(2),kk(3);
        kk+=ii+jj;
        Integer d(1),b(2);
        d=2+b;
        d.display();
        return 0;
}

How to prevent this warning ??

g++ -g -Wall -o test test.cpp
test.cpp: In function 'Integer& operator+(Integer, Integer)':
test.cpp:22: warning: reference to local variable 'rv' returned

Note: If I remove & in
Integer& operator+(Integer rv,Integer rs )

g++ -g -Wall -o test test.cpp
test.cpp: In function 'Integer operator+(Integer, Integer)':
test.cpp:22: error: new declaration 'Integer operator+(Integer,
Integer)'
test.cpp:16: error: ambiguates old declaration 'Integer& operator+
(Integer, Integer)'
make: *** [test] Error 1

?? deadlocklike situation ?? :(