Question

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Could anyone explain these undefined behaviors (i = i++ + ++i , i = i++, etc…)

Why this code is generating 8 as a result ?

#include <iostream> 
using namespace  std ;
void myFunction(int i)
{
    i = i + 2 + ++i;
    cout<<i<<endl;
}

void main () 
{
    int i = 2;
    myFunction(i);
    cin>> i;
}

I think the result should be 7 not 8…I am using Visual Studio 2008

Answer 1

The order of evaluation of terms on the right hand side of this expression

i = i + 2 + ++i;

is undefined. i.e. they can occur in any order. In this case the compiler has chosen to increment i first (++i, third term), before evaluating i (first term), which results in 3 + 2 + 3.