Bug #51396 [Com]: Math is Unreliable

Edit report at http://bugs.php.net/bug.php?id=51396&edit=1 ID: 51396 Comment by: john dot smith dot 1964 at gmail dot com Reported by: codeslinger at compsalot dot com Summary: Math is Unreliable Status: Feedback Type: Bug Package: Math related Operating System: any PHP Version: Irrelevant New Comment: The folk at Mandriva saw the same problem, figured it out and submitted a patch to PHP. I'm confused, because we're certainly still seeing the problem: https://qa.mandriva.com/show_bug.cgi?id=37171 "In PHP on Mandriva 2008, some float to string conversions return "0.0:" !! In critical software, this can lead to major loss of data or inconsistant results." Previous Comments: ------------------------------------------------------------------------ [2010-04-13 03:36:47] john dot smith dot 1964 at gmail dot com I am seeing this bug consistently on standard Windows builds such as 5.2.4 and 5.2.13. Our Server is: Windows NT 5.2 build 3790 Sample code is simple: <? echo round(1451,2); ?> On 5.2.4 it will result in "1450.:0" every time. On 5.2.4, other such *funny* values are 1701,1821,1951,2091,2101,2111,2121,2341,2351... On 5.2.13,the numbers 1700 and 1900 consistently return "colon-ized" results. This is a especially problematic, because 1700 and 1900 occur more frequently in our eCommerce app! This issue is a real problem for us. It has been touched on (but not solved) in at least Bugs 46376, 47716, 47304 and 47418. ------------------------------------------------------------------------ [2010-03-27 14:19:44] johannes@php.net You are mentioned this version information: php -v PHP 5.2.4-2ubuntu5.10 with Suhosin-Patch 0.9.6.2 (cli) (built: Jan 6 2010 22:01:14) Copyright (c) 1997-2007 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies with Xdebug v2.0.3, Copyright (c) 2002-2007, by Derick Rethans with Zend Debugger v5.2.15, Copyright (c) 1999-2008, by Zend Technologies This version is very different from the versions we provide. a) Ubuntu adds some custom patches b) Suhosin does major changes to the engine c) Xdebug as well as Zend Debugger do changes to our executor unit. All these components aren't supported here. ------------------------------------------------------------------------ [2010-03-27 12:50:58] codeslinger at compsalot dot com One further note, in the repro above, it has to be exactly 16 nines. by adding or removing a 9, it does not fail. Also, as far as I know, all of the failures have been on 32bit Intel cpu's. This probably will not fail on a 64bit cpu. ------------------------------------------------------------------------ [2010-03-27 12:22:12] codeslinger at compsalot dot com well, it's hard to prove a negative. but I have run a bunch of tests on the Linux snapshot and it appears to be working fine. A VERY BIG THANKYOU I did not find any windows snapshots, the latest is 5.2.13 from Feb 24. based on the symptoms, my initial assumption was that this was caused by some kind of array corruption, this turned out to be wrong. the actual repro can be boiled down to one line... :-) echo (string) (double) -0.09999999999999999; With the caveat that there are other values which also trigger this. ------------------------------------------------------------------------ [2010-03-26 21:37:12] pajoye@php.net Please try using this snapshot: http://snaps.php.net/php5.2-latest.tar.gz For Windows: http://windows.php.net/snapshots/ ------------------------------------------------------------------------ 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/bug.php?id=51396 -- Edit this bug report at http://bugs.php.net/bug.php?id=51396&edit=1