Xcode - Control reaches end of non-void function operator error

Hello guys im using Xcode on Yosemite OS, when i try to use these operators i got error Control reaches end of non-void function,could someone tell me how to fix it?

`A& A::operator= (A& src)`
{

    delete[] b_;

    i_ = src.i_;
    b_ = new B[i_];
    for(int i = 0; i < i_; i++)
        b_[i].set(src.b_[i].get());

} `//Here appear this error>> Control reaches end of non-void function`


    std::ostream& operator<< (std::ostream& str, const A& a)
 {
     str << a.i_ << ":";
        for(int i = 0; i < a.i_; ++i)
            str << " " << a.b_[i].get();``
        return str << std::endl;

}

std::istream& operator>> (std::istream& str, A &a)
{
    int i;
    str >> i;

    A* b = new A(i);
    a = *b;

} //Here appear this error>> Control reaches end of non-void function