Problem with chaining operator<< and operator++

Question

I\'m learning C++ and I have this problem:

#include 
using namespace std;


class test
{
    public:
             


        

Answer 1

Let's examine how the line

cout << obj << ' ' << ++obj << endl;

is translated.

Step 1.

cout << obj

becomes

// A non-member function.
operator<<(cout, obj)

Step 2.

operator<<(cout, obj) << ' '

becomes

// Also a non-member function.
operator<<(operator<<(cout, obj), ' ')

Step 3.

operator<<(operator<<(cout, obj), ' ') << ++obj

becomes

// Also a non-member function.
operator<<(operator<<(operator<<(cout, obj), ' '), ++obj)

Step 4.

operator<<(operator<<(operator<<(cout, obj), ' '), ++obj) << endl;

becomes

// A member function.
operator<<(operator<<(operator<<(cout, obj), ' '), ++obj).operator<<(endl);

That's the entire line.

In such an expression there is no guarantee that operator<<(cout, obj) will be executed before ++obj. It appears that in your platform, ++obj is executed before operator<<(cout, obj) is executed. That explains the behavior.

Please note that the standard has changed. If you are able to use C++17, you will get the expected behavior.