#42510 [Opn]: unpack('V') sign-extends result on x86-64

ID: 42510 User updated by: jr-php2 at quo dot to Reported By: jr-php2 at quo dot to Status: Open Bug Type: Strings related Operating System: Linux x86-64 PHP Version: 5.2.4 New Comment: Digging deeper, it looks like 'V' and 'N' used to work as documented until bug #38770 was "fixed in CVS". Isn't #38770 a bogus report, though? Since 'N' is documented as being unsigned, isn't the user wrong to expect it to return a negative result? Previous Comments: ------------------------------------------------------------------------ [2007-09-01 20:33:57] jr-php2 at quo dot to Okay, looking at the unpack() code, it appears that: - 'l' and 'L' are both treated as signed, even though 'l' is documented as signed and 'L' is documented as unsigned. - 'N' and 'V' are treated as signed, even though both are documented as unsigned. So who's right here, the code or the documentation? ------------------------------------------------------------------------ [2007-09-01 17:26:12] jr-php2 at quo dot to Sorry, I mixed up the expected and actual results. It should say: Expected result: ---------------- unpack = 3368601800 ip2long = 3368601800 Actual result: -------------- unpack = -926365496 ip2long = 3368601800 ------------------------------------------------------------------------ [2007-09-01 17:22:10] jr-php2 at quo dot to Description: ------------ On x86-64, unpack('V') sign-extends from 32-bit to 64-bit. In other words, it can return a negative number. Since 'V' specifies an *unsigned* 32-bit value, this is incorrect; the upper 32 bits of the 64-bit result should always be zero. This behavior makes unpack() inconsistent with other functions like ip2long() and crc32() which never return negative numbers on 64-bit PHP. Reproduce code: --------------- $u = unpack('Vresult', chr(200).chr(200).chr(200).chr(200)); echo "unpack = ", $u['result'], "\n"; echo "ip2long = ", ip2long('200.200.200.200'), "\n"; Expected result: ---------------- unpack = -926365496 ip2long = 3368601800 Actual result: -------------- unpack = 3368601800 ip2long = 3368601800 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=42510&edit=1