Description:
------------
Using `abs(pad_size) < 0' to catch the LONG_MIN case invokes undefined behavior in 
C.  gcc simply assumes abs(pad_size) must be non-negative and discards the check.

Test script:
---------------
<?php
// This is for 64-bit systems.
$input = array(12, 10, 9);
$input = array_pad($input, -9223372036854775808, 0);
var_dump($input);
?>

Expected result:
----------------
Warning: array_pad(): You may only pad up to 1048576 elements at a time in t.php 
on line 3
bool(false)

Actual result:
--------------
array(3) {
  [0]=>
  int(12)
  [1]=>
  int(10)
  [2]=>
  int(9)
}