x = (x++) in gcc

Question

Possible Duplicate:
Undefined Behavior and Sequence Points

I wrote the following code and [to my surprise] it printed: xx: 1 zz: 0

I would have expected both xx and zz to print as 0. This is tried with gcc 4.2, 4.4 and 4.7 on linux and darwin. Upon some research, I find that x=x++ is undefined behavior but I would expect (x++) to be executed first and return 0. Can someone shed light into this strange compiler behavior?

#include <iostream>
using namespace std;

int frwd(int aa) { return aa; }

int main() {
  int xx = 0;
  xx = (xx++);
  cout << "xx:" << xx << endl;

  int zz = 0;
  zz = frwd(zz++);
  cout << "zz:" << zz << endl;
}

Complete explanation at: [Undefined Behavior and Sequence Points](http://stackoverflow.com/questions/4176328/undefined-behavior-and-sequence-points) — Carl Norum, Jul 27 '12 at 06:18

score 1 · Answer 1 · answered Jul 27 '12 at 06:17

1

Undefined behaviour is undefined. Anything could happen. Your question is a duplicate many times over.

answered Jul 27 '12 at 06:17

Carl Norum

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Unless Jon Skeet answers it, then it becomes a million rep question :p – Matthias Jul 27 '12 at 06:20

x = (x++) in gcc

1 Answers1