C - Undefined behaviour or proper output

Asked Jul 25 '12 at 05:51

Active Jul 25 '12 at 06:00

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

I've read about these sort of statements before, but this one is strange.

For this piece of code in C,

int main()
{
  int a=5,i;
  i = (++a)+(++a)+(++a);
  printf("%d",i);
  return 0;
}

what output should one expect ? Or does it result in undefined behaviour ?

edited May 23 '17 at 11:48

Community

asked Jul 25 '12 at 05:51

Cygnus

Short answer: Yes, it's undefined behavior. – Mysticial Jul 25 '12 at 05:53
OK. Can you give a short explanation for it too ?? :) – Cygnus Jul 25 '12 at 05:54
3

Here's another good read: [Undefined Behavior and Sequence Points](http://stackoverflow.com/questions/4176328/undefined-behavior-and-sequence-points) – Mysticial Jul 25 '12 at 05:55
Thanks for that link !! Wonderful explanation !! :) – Cygnus Jul 25 '12 at 05:56
@Cygnus: If it's undefined, the most you can explain is how the implementation of the compiler gives a certain result. – nhahtdh Jul 25 '12 at 05:56

0 Answers0