#45953 [Opn->Bgs]: Sign-Bit Manipulating is buggy

ID: 45953 Updated by: mattwil@php.net Reported By: ben at umingo dot de -Status: Open +Status: Bogus Bug Type: Output Control Operating System: Windows XP 32Bit PHP Version: 5.2.6 New Comment: Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php What's happening is that when the script is parsed and compiled, 0x81234567 actually becomes a float/double type since, as you mention, it's too big for 32-bit signed range and the intended behavior is to keep it positive (as it would be on platforms with 64-bit longs) and not restrict it to integer type only. The bitwise operators like | only operate on integers, and it converts a float/double to int first, which results in "overflow" to a negative number that you're seeing. Typecasting to (int) will also force the overflow (same internal conversion used by bitwise operators), and give the result you expect (on 32-bit platform anyway). Example: <?php var_dump(0x81234567); var_dump(0x81234567 | 0x81234567); var_dump((int) 0x81234567); Output: float(2166572391) int(-2128394905) int(-2128394905) Previous Comments: ------------------------------------------------------------------------ [2008-08-30 10:23:30] ben at umingo dot de Description: ------------ Problem is with sign bit. If i have 0x81234567 then first bit is set to 1 (sign bit). I would expect that number to be negative, as all integers are signed 32 bit integers. If i echo that number, it is positive! If i compute something with this number, it turns negative! I have a standard PHP 5.2.6 Version and did not modify anything at it. Reproduce code: --------------- <? //sign bit is not handled correctly //a | a is expected to be a ... //WORKS NOT echo "with sign bit <br>"; echo (0x81234567 | 0x81234567); //result is negative echo "<br>"; echo (0x81234567 );//result is positive echo "<br>without sign bit <br>"; //WORKS echo (0x71234567 | 0x71234567); echo "<br>"; echo (0x71234567 ); ?> Expected result: ---------------- with sign bit -2128394905 -2128394905 without sign bit 1898136935 1898136935 Actual result: -------------- with sign bit -2128394905 2166572391 without sign bit 1898136935 1898136935 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=45953&edit=1