c++ unary increment operator

[MSDousti]

Hi,
I'm confused with C++'s unary increment operator(++).
Consider the following code:

//////////////////////////////////////////////////////////////////////
#include <iostream>
using namespace std;

int main()
{
int a=2;
a= (a==2 ? a+=100:0) + (a>3 ? a+=200:1000) + a++;
cout << a << endl;
return 0;
}
//////////////////////////////////////////////////////////////////////

I have run this code both on linux (using g++) and windows (VS.NET).
Surprisingly, the resaults were incompatible!
g++ answers: 507
VS answers: 707

Can anyone help?

 

[Mike Wahler]

Hi,
I'm confused with C++'s unary increment operator(++).
Consider the following code:

//////////////////////////////////////////////////////////////////////
#include <iostream>
using namespace std;

int main()
{
int a=2;
a= (a==2 ? a+=100:0) + (a>3 ? a+=200:1000) + a++;
cout << a << endl;
return 0;
}
//////////////////////////////////////////////////////////////////////

I have run this code both on linux (using g++) and windows (VS.NET).
Surprisingly, the resaults were incompatible!
g++ answers: 507
VS answers: 707

The language does not specify the order in which the
expressions:

(a==2 ? a+=100:0)
(a>3 ? a+=200:1000)
a++

.... are evaluated.

Can anyone help?

Break the code down to where you have sufficient control
over evaluation order. Look up 'sequence points'. I can't
tell you what you need here, since you don't say which result
you want.

-Mike