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Bug #41328 Weird results from floor after compiling with pentium4 optimizations
Submitted: 2007-05-08 17:26 UTC Modified: 2007-05-16 01:00 UTC
From: rgonzalez at gnt dot cc Assigned:
Status: No Feedback Package: *Math Functions
PHP Version: 5.2.2 OS: Linux Slackware 10.2
Private report: No CVE-ID: None
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 [2007-05-08 17:26 UTC] rgonzalez at gnt dot cc
Description:
------------
I compiled PHP 5.2.2 with CFLAGS="-O2 -march=pentium4
-mcpu=pentium4", as usual (I've done so with all the 5.x.x series, and the
proc is a Pentium 4, of course) and a customer complained about weird
results in one of his scripts. I isolated the problem to be related to the
floor function. The problem was that it returned weird results. Sample
script:

<?php

$nt = 100;
$promrow2['uni_gifts'] = 1;
$promrow2['unidades'] = 10;
$calc_cnt=floor(($nt*$promrow2['uni_gifts'])/$promrow2['unidades']);

print $calc_cnt;

?>

printed :.0000000001

I needed to cast (int)floor to get the right result. I recompiled with CFLAGS="-O2 -march=i686 -mcpu=i686" and the problem was solved. I've compiled 5.2.2 with nocona optimizations without problems in other machines.

Software:

PHP 5.2.2
GCC 3.2.2


Reproduce code:
---------------
<?php

$nt = 100;
$promrow2['uni_gifts'] = 1;
$promrow2['unidades'] = 10;
$calc_cnt=floor(($nt*$promrow2['uni_gifts'])/$promrow2['unidades']);

print $calc_cnt;

?>


Expected result:
----------------
10

Actual result:
--------------
:.0000000001

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History

AllCommentsChangesGit/SVN commitsRelated reports
 [2007-05-08 17:44 UTC] tony2001@php.net
Try newer GCC first.
 [2007-05-16 01:00 UTC] php-bugs at lists dot php dot net
No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
 
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