Comment by kstenerud

I think you may have misread the code:

    while (howmany != 0) {
        val = random();
        if( val is odd) {
          out[index] =  val;
          index += 1;
        }
        howmany--;
    }

vs

    while (howmany != 0) {
        val = random();
        out[index] = val;
        index += (val bitand 1);
        howmany--;
    }

Both of these store a list of odd numbers in out[], with "index" containing the resulting count of how many numbers are in out[]. Both will have an "index" (count) value of 0 if all inputs were even, and neither attempts to access out[index-1].