Edit report at https://bugs.php.net/bug.php?id=54334&edit=1
ID: 54334
Updated by: yohg...@php.net
Reported by: for-bugs at hnw dot jp
Summary: The behavior for rounding to small precision was
changed and is against RFC
-Status: Open
+Status: Closed
Type: Bug
Package: Math related
Operating System: Intel Linux and Intel MacOSX
PHP Version: 5.3.6
-Assigned To:
+Assigned To: yohgaki
Block user comment: N
Private report: N
New Comment:
Thank you for your bug report. This issue has already been fixed
in the latest released version of PHP, which you can download at
http://www.php.net/downloads.php
It seems this is fixed. Tested by 5.5.1-dev/5.4.16
Previous Comments:
------------------------------------------------------------------------
[2011-04-03 16:14:51] for-bugs at hnw dot jp
I found another example.
<?php
var_dump(round(0.499999999999999));
PHP 5.3.0-5.3.3 returns float(0). However, PHP 5.3.4-5.3.6 returns float(1). Of
cource, this number 0.499999999999999 is different from 0.5 within IEEE754
double precision.
It seems to be BC break.
------------------------------------------------------------------------
[2011-03-21 12:21:56] for-bugs at hnw dot jp
Description:
------------
The behavior of function round() was changed with revision 301991. So when a
small number is rounded to small precision, round() of PHP5.3.4-5.3.6 returns
different value from PHP5.3.0-5.3.3. Additionally, the current behavior is
different from referred RFC(*1). I suppose it is not intended change.
For example, test script returns "float(4.0E-60)" for PHP 5.3.0-5.3.3 and PHP
5.2.17. However, PHP 5.3.4-5.3.6 shows "float(3.0E-60)".
This behavior changing was affected with revision 301991(*2) for fixing Bug
#52550(*3). However, I think this fix was useless.
Bug #52550 reports probability for integer overflow/underflow. However, the C
function php_intlog10abs() returns integer between -324 and 308 because of
property for IEEE754 64bit floating point numbers, so overflow/underflow never
occur for this part.
*1 http://wiki.php.net/rfc/rounding
*2
http://svn.php.net/viewvc/php/php-src/branches/PHP_5_3/ext/standard/math.c?r1=301991&r2=301990&pathrev=301991
*3 http://bugs.php.net/bug.php?id=52550
Test script:
---------------
<?php
var_dump(round(3.5e-60, 60));
Expected result:
----------------
float(4.0E-60)
Actual result:
--------------
float(3.0E-60)
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=54334&edit=1
