How does this snippet not cause SIGSEGV or similar

Question

I've came across this interesting snippet. I said no way it could work (without crashing). Shockingly, it runs "ok" both on Linux (compiled with gcc) and on OSX (llvm). Even more disturbingly, Valgrind doesn't find anything wrong!!!

What gives?

int main(void) {
  int a[3];
  2[a] = 1;
}

Did you have a logical reason for expecting a crash, besides "omg I haven't seen anything like that before" ? — M.M, May 12 '14 at 13:36

score 5 · Answer 1 · answered May 12 '14 at 13:20

5

In short and simple, the compiler translates anything in the form x[y] to *(x + y). So 2[a] translates to *(2 + a) which is the same as *(a + 2) from a[2].

answered May 12 '14 at 13:20

Eregrith

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`x[y] == *(x + y) == *(y + x) == y[x]` – May 12 '14 at 13:22
That's what I said. You could even write `x[y] <=> *(x + y) <=> *(y + x) <=> y[x]` – Eregrith May 12 '14 at 13:23

How does this snippet not cause SIGSEGV or similar

1 Answers1