From: php at codewhore dot org
Operating system: Linux 2.4
PHP version: 4.3.1
PHP Bug Type: Filesystem function related
Bug description: Certain combinations of fseek() and fwrite() produce unexpected
results
In PHP:
<?php
$fp = fopen('./foo', 'w+');
fwrite($fp, 'quxbar', 6);
fseek($fp, 3, SEEK_SET);
fread($fp, 1);
fseek($fp, 4, SEEK_SET);
fwrite($fp, '!', 1);
fseek($fp, 0, SEEK_SET);
$buf = fread($fp, 4095);
echo "$buf\n";
?>
In C:
#include <stdio.h>
int main()
{
static char buf[4096];
FILE *f = fopen("./foo", "w+");
fwrite("quxbar", 6, 1, f);
fseek(f, 3, SEEK_SET);
fread(&buf, 1, 1, f);
fseek(f, 4, SEEK_SET);
fwrite("!", 1, 1, f);
fseek(f, 0, SEEK_SET);
fread(&buf, 4095, 1, f);
printf("%s\n", buf);
return 0;
}
The PHP version outputs 'quxbar!.
The C version outputs 'quxb!r'.
In fact, for any PHP code of the structure:
<?php
fseek($fp, $x, SEEK_SET);
fread($fp, $n);
fseek($fp, $y, SEEK_SET);
fwrite($fp, '!', 1);
?>
the data from the fwrite always gets written to the end of the stream when
$x < $y and $n is exactly 1. I can reproduce this with different whence
parameters, but it seems to only happen with a seek followed by a
single-byte read.
--
Edit bug report at http://bugs.php.net/?id=22362&edit=1
--
Try a CVS snapshot: http://bugs.php.net/fix.php?id=22362&r=trysnapshot
Fixed in CVS: http://bugs.php.net/fix.php?id=22362&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=22362&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=22362&r=needtrace
Try newer version: http://bugs.php.net/fix.php?id=22362&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=22362&r=support
Expected behavior: http://bugs.php.net/fix.php?id=22362&r=notwrong
Not enough info: http://bugs.php.net/fix.php?id=22362&r=notenoughinfo
Submitted twice: http://bugs.php.net/fix.php?id=22362&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=22362&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=22362&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=22362&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=22362&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=22362&r=gnused
