[LLVMdev] Uninitialized variable - question

[Jakub Staszak]

Hello,

I was wondering about the case below. I tried to find any information in C standard, but I found nothing.
In this case, variable "i" is uninitialized, but it is the _same_ value passed as an argument, so only of "a" or "b" should be printed.

What I found is that with -O2:
LLVM (trunk) prints both "a" and "b"
GCC (4.2) prints both "a" and "b"
GCC (trunk) prints "b" only.

As I said, I don't know what standard says here.


#include <stdio.h>

void f(int i) __attribute__((noinline));
void g(int i) __attribute__((noinline));

void f(int i) {
  if (i) printf("a\n");
}

void g(int i) {
  if (!i) printf("b\n");
}

int main() {
  int i;
  f(i);
  g(i);
}


- Kuba