Bug #54334 [Opn->Csd]: The behavior for rounding to small precision was changed and is against RFC

Edit report at https://bugs.php.net/bug.php?id=54334&edit=1 ID: 54334 Updated by: yohgaki@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) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=54334&edit=1