Edit report at http://bugs.php.net/bug.php?id=54334&edit=1
ID: 54334
Comment by: for-bugs at hnw dot jp
Reported by: for-bugs at hnw dot jp
Summary: The behavior for rounding to small precision was
changed and is against RFC
Status: Open
Type: Bug
Package: Math related
Operating System: Intel Linux and Intel MacOSX
PHP Version: 5.3.6
Block user comment: N
Private report: N
New Comment:
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.
Previous Comments:
------------------------------------------------------------------------
[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 http://bugs.php.net/bug.php?id=54334&edit=1
