#16366 [Opn->Csd]: bit shifting error

ID: 16366 Updated by: vrana@php.net Reported By: adam at adeptsoftware dot com -Status: Open +Status: Closed Bug Type: Documentation problem Operating System: WinXP PHP Version: 4.1.2 New Comment: This bug has been fixed in the documentation's XML sources. Since the online and downloadable versions of the documentation need some time to get updated, we would like to ask you to be a bit patient. Thank you for the report, and for helping us make our documentation better. Previous Comments: ------------------------------------------------------------------------ [2002-04-01 22:43:53] jason@php.net This is not really a bug, this is the behavior of a 32 bit system in any language. Run "perl -e 'print 11>>34'" or write a C program which does the same. Since this behavior is common and exists in other languages, the best we could do is document it. -Jason ------------------------------------------------------------------------ [2002-03-31 17:53:05] adam at adeptsoftware dot com Ahh.. It still should produce zero though. ------------------------------------------------------------------------ [2002-03-31 15:32:23] msopacua at idg dot nl Actually - the echo(11>>34) issue, is somewhat expected behavior. What happens, is that it returns 11>>2 (34 - 32) - BUT only on a 32-bit system. I just checked at an AIX 64-bit system, and there echo(11>>34) gives 0 And anything above 64-bit is than equal to $int>>($shift % 64). Maybe it should be added to the bitwise operators documentation. <?php print("32 bits test\n"); $int=11; for ($shift=31;$shift<35;$shift++) { print("$shift: "); $check=$int>>$shift; print($check); print("\n\n"); } print("64 bits test\n"); for($shift=63;$shift<67;$shift++) { print("$shift: "); $check=$int>>$shift; print($check); print("\n"); } ?> On a 64-bit system produces: $ php -f test.php 32 bits test 31: 0 32: 0 33: 0 34: 0 64 bits test 63: 0 64: 11 65: 5 66: 2 On a 32-bit system produces: 32 bits test 31: 0 32: 11 33: 5 34: 2 64 bits test 63: 0 64: 11 65: 5 66: 2 ------------------------------------------------------------------------ [2002-03-31 13:42:14] adam at adeptsoftware dot com Just a reminder of the original issue: echo (11>>34) produces "2" This is not a documentation problem, unless you want to write that shifting greater than 32 has incorrect results. ------------------------------------------------------------------------ [2002-03-31 13:39:23] daniel@php.net are you sure? there is already a bunch of reports on "floating-point bugs" in PHP. That's why I didn't reopen it. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/16366 -- Edit this bug report at http://bugs.php.net/?id=16366&edit=1