modulus operator returns incorrect results on 64 bit linux

Bug #47422	modulus operator returns incorrect results on 64 bit linux
Submitted:	2009-02-17 12:36 UTC	Modified:	2009-02-17 14:22 UTC
From:	d_kelsey at uk dot ibm dot com	Assigned:
Status:	Closed	Package:	Scripting Engine problem
PHP Version:	5.2CVS-2009-02-17 (CVS)	OS:	Linux 64Bit
Private report:	No	CVE-ID:	None

[2009-02-17 12:36 UTC] d_kelsey at uk dot ibm dot com

Description:
------------
on a 64bit system the following 
var_dump(1%4294967295);
should return 1, but returns 0. 
The problem is in the 
ZEND_API int mod_function(...) in zend_operators.c

A call is made to abs which expects a 32bit int and returns a 32bit int, but 4294967295 is > 32 bits in size so the abs call returns an incorrect value.

A proposed fix is to change the line
"if (abs(op2->value.lval) == 1) {"
to
"if (op2->value.lval == 1 || op2->value.lval == -1) {"

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports

[2009-02-17 14:22 UTC] mattwil@php.net

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

Thanks. Actually, just -1 needs to be checked there anyway, since only when doing LONG_MIN % -1 (in PHP, "(-PHP_INT_MAX - 1) % -1;") would there be a crash/error (which that's there to catch of course).