#27258 [Asn->Csd]: gmp_powm: fix for bug #27172 breaks large (> 31 bit on i386) modulos

ID: 27258 Updated by: iliaa@php.net Reported By: oscar at the-rileys dot net -Status: Assigned +Status: Closed Bug Type: Math related Operating System: NetBSD 1.6 PHP Version: 4CVS,5CVS Assigned To: iliaa New Comment: 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. Previous Comments: ------------------------------------------------------------------------ [2004-02-15 01:17:52] oscar at the-rileys dot net I neglected to mention that this is vs. CVS snapshot 200402142230. The original bugfix that caused the problem was submitted on 2/8/04. ------------------------------------------------------------------------ [2004-02-15 01:14:04] oscar at the-rileys dot net Description: ------------ The fix for bug #27172 (possible floating-point exception in gmp_powm) breaks the function with modulos longer than 31 bits. This is because the modulo argument is converted (destructively) to a long before it is fetched as a GMP number. The problem is rectified by moving the block that checks for a zero modulo to a point after the argument is fetched for use in the function. I have posted a diff here: http://oscar.the-rileys.net/php5-gpm_powm-patch.diff I have tested this on my own server, and it appears to fix the problem with at least 1024-bit modulos and still guards against 0 modulos - test for yourself to be sure, of course, Reproduce code: --------------- This is the example code from the documentation page for gpm_powm: <?php    $pow1 = gmp_powm("2", "31", "2147483649");    echo gmp_strval($pow1) . "\n"; ?> Expected result: ---------------- The number 2147483648 should be output. Actual result: -------------- The number 1 is output. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27258&edit=1