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Bug #10002 sprintf() and floating point
Submitted: 2001-03-26 14:13 UTC Modified: 2002-10-14 22:48 UTC
From: bmr at comtime dot com Assigned: hholzgra (profile)
Status: Closed Package: Strings related
PHP Version: 4.1.1 OS: Debian
Private report: No CVE-ID: None
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From: bmr at comtime dot com
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 [2001-03-26 14:13 UTC] bmr at comtime dot com 
<?php
printf('%.2f',0.09999999999999999167332731531132594682276248931884765625);
?>
produces '0.0:' instead of '0.10'

I'm really curious as to why PHP just doesn't use libc's sprintf().

./configure --with-oracle=/usr/local/oracle/product/8.1.7 \
  --with-oci8=/usr/local/oracle/product/8.1.7 --enable-force-cgi-redirect \
  --enable-track-vars --with-posix --enable-sockets --enable-sigchild \
  --with-gd=/usr/local

gcc version 2.95.2 19991024 (release)


This is not exactly a fix...
--- ext/standard/formatted_print.c      Mon Mar 26 14:01:31 2001
+++ ext/standard/formatted_print.c-fixed        Mon Mar 26 14:02:26 2001
@@ -92,7 +92,7 @@
                while (p1 < &cvt_buf[NDIG])
                        *p++ = *p1++;
        } else if (arg > 0) {
-               while ((fj = arg * 10) < 1) {
+               while ((fj = arg * 10.0) < 0.9999999) {
                        arg = fj;
                        r2--;
                }

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 [2001-03-26 17:19 UTC] derick@php.net 
This bug is in 4.0.5RC2 too, just confirmed it
 [2001-03-27 08:32 UTC] zeev@php.net 
I can't reproduce it under RH 6.2.  Generally the fix isn't supposed to do anything (since arg is a double, 10 should be converted to a double automatically), but the fix can't hurt anything so if it works around a compiler bug, it's fine.

PHP cannot use sprintf() because sprintf() works with C types with predefined types for the arguments, whether PHP has its own types, and autoconverts arguments to match the format string.
 [2001-03-27 12:30 UTC] derick@php.net 
Patch applied, but it's still a strange thing.
 [2002-01-09 16:36 UTC] pgerzson at freestart dot hu 
I'm sorry to say that I experienced similar misbehaviour
with  PHP 4.0.6 and 4.1.1, too. 

I'm pulling aggregated statistics from database and display
it. I'm currently working on minimize a test case, please wait. Till then, visit this link:

http://213.134.22.60/~gerzson/sprintf.php

this is a very simple test script with a show_source() and 
phpinfo(). I think this bug should be reopened.
 [2002-01-09 16:43 UTC] gerzson@php.net 
I'd like to reopen it. Visit the page: 

http://213.134.22.60/~gerzson/sprintf.php
 [2002-01-15 12:33 UTC] pgerzson at freestart dot hu 
I played with ini settings (to be frank remove the
php.ini), and now examples work fine.
 [2002-01-22 07:46 UTC] martin at humany dot com 
I cant reproduce this bug under PHP 4.1.1 neither in Windows XP or Linux 2.4.
I tried the original example aswell as the additional examples from http://213.134.22.60/~gerzson/sprintf.php

(abstract from phpinfo()):

System Linux www3 2.4.17 #4 SMP Sat Dec 22 19:40:48 CET 2001 i686 unknown 
Build Date Jan 13 2002 
Configure Command  './configure' '--with-apache=../apache_1.3.22' '--with-mysql=/usr/local' '--with-gd=/usr/local' '--with-jpeg-dir=/usr' '--enable-ftp' '--enable-bcmath' '--with-ming' '--with-mcrypt' '--with-mhash' '--with-xml' '--with-imap' '--with-pdflib' '--with-curl' '--with-png-dir=/usr' '--with-zlib' '--with-freetype-dir=/usr/local/include/freetype2' '--enable-gd-native-ttf' '--disable-posix-threads' '--enable-memory-limit=yes' '--enable-track-vars' '--enable-trans-sid' '--enable-debug=no' '--enable-inline-optimization'
 [2002-06-17 06:59 UTC] hholzgra@php.net 
locale-dependant, does not work for locales where decimal_point is != '.' right now
 [2002-10-14 22:48 UTC] iliaa@php.net 
This bug has been fixed in CVS.

In case this was a PHP problem, snapshots of the sources are packaged
every three hours; this change will be in the next snapshot. You can
grab the snapshot at http://snaps.php.net/.
 
In case this was a documentation problem, the fix will show up soon at
http://www.php.net/manual/.

In case this was a PHP.net website problem, the change will show
up on the PHP.net site and on the mirror sites in short time.
 
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