From: osolo at wndtabs dot com
Operating system: Linux
PHP version: 4.4.0
PHP Bug Type: *Math Functions
Bug description: Accuracy of round() function affected by compiler
optimizations
Description:
------------
The round() function will return inconsistent results when PHP is compiled
under certain Linux distro/CPU/compiler combinations.
For example, if when compiling PHP on Gentoo 1.12.0_pre6/cc 3.4.4/Pentium
4, we get:
round(0.245,2) => 0.24
Instead of the expected 0.25.
I've traced the problem to the PHP_ROUND_WITH_FUZZ macro in
ext/standard/math.c. This macro starts out as:
#define PHP_ROUND_WITH_FUZZ(val, places) { \
double tmp_val=val, f = pow(10.0, (double) places); \
...
Changing the first line to:
volatile double tmp_val=val; double f = pow(10.0, (double) places); \
I suspect the problem is that the optimizer is keeping tmp_val in a
floating point register that has a difference precision than a C double.
Declaring it volatile keeps it in the variable and makes things more
consisntant.
--
Edit bug report at http://bugs.php.net/?id=34599&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=34599&r=trysnapshot4
Try a CVS snapshot (php5.0):
http://bugs.php.net/fix.php?id=34599&r=trysnapshot50
Try a CVS snapshot (php5.1):
http://bugs.php.net/fix.php?id=34599&r=trysnapshot51
Fixed in CVS: http://bugs.php.net/fix.php?id=34599&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=34599&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=34599&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=34599&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=34599&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=34599&r=support
Expected behavior: http://bugs.php.net/fix.php?id=34599&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=34599&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=34599&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=34599&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=34599&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=34599&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=34599&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=34599&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=34599&r=float
No Zend Extensions: http://bugs.php.net/fix.php?id=34599&r=nozend
MySQL Configuration Error: http://bugs.php.net/fix.php?id=34599&r=mysqlcfg
