#43487 [Opn->Asn]: Wrong conversion of float to string

ID: 43487 Updated by: jani@php.net Reported By: jm at wo dot cz -Status: Open +Status: Assigned Bug Type: Strings related Operating System: Linux PHP Version: 5.2.5 -Assigned To: +Assigned To: dmitry New Comment: Dmitry, can you check this out? There's a patch too. :) Previous Comments: ------------------------------------------------------------------------ [2008-02-11 17:49:44] oeriksson at mandriva dot com Here's a shorter URL that hopefully won't wrap: http://n1.nux.se/php-5.2.5-use-volatile-to-force-float-store.patch ------------------------------------------------------------------------ [2008-02-01 12:07:10] oeriksson at mandriva dot com Pascal Rigaux at Mandriva has a patch for this, please review it. http://svn.mandriva.com/cgi-bin/viewvc.cgi/packages/cooker/php/current/SOURCES/php-5.2.5-use-volatile-to-force-float-store.patch?revision=161099&view=markup ------------------------------------------------------------------------ [2008-01-31 15:42:55] oeriksson at mandriva dot com Update; taken from our bugzilla: "as peroyvind found, the miscompilation is inside Zend/zend_strtod.c, and -no-ftree-vrp workaround the bug." ------------------------------------------------------------------------ [2008-01-30 19:41:18] oeriksson at mandriva dot com I think I found the problem. On Mandriva Linux Cooker we are using: gcc (GCC) 4.2.2 20071128 (prerelease) (4.2.2-2mdv2008.1) glibc-2.7-1mdv2008.1 If I change the optimization from -O2 to -O0 (-O+zero) the bug goes away on x86_32. ------------------------------------------------------------------------ [2008-01-28 21:30:37] jm at wo dot cz The CVS snapshot makes no difference, still getting the same incorrect strings. [jm@st5mag ~]$ php -n -r '$f=array(1E-4, 1E-5, 1E-6, 1E-7, 1E-8); foreach ($f as $fval) echo $fval, "\n";' 0.0001 1.0E-5 :.0E-7 :.0E-8 1.0E-8 [jm@st5mag ~]$ php -v PHP 5.2.6-dev (cli) (built: Jan 28 2008 16:13:46) Copyright (c) 1997-2008 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies Previous poster suggested a CPU-related issue. I have encountered this issue on the following CPUs: vendor_id : AuthenticAMD cpu family : 15 model : 5 model name : AMD Opteron(tm) Processor 248 stepping : 8 cpu MHz : 2205.074 vendor_id : GenuineIntel cpu family : 6 model : 13 model name : Intel(R) Pentium(R) M processor 1.80GHz stepping : 6 cpu MHz : 1800.000 vendor_id : AuthenticAMD cpu family : 15 model : 37 model name : AMD Opteron(tm) Processor 252 stepping : 1 cpu MHz : 2606.078 ------------------------------------------------------------------------ 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/43487 -- Edit this bug report at http://bugs.php.net/?id=43487&edit=1