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[2003-04-03 13:33 UTC] a dot eibach at gmx dot net
Hi.
What is illegal code? Code with the intention to break something. But sometimes it's even a bad mistake causing this (inheriting a wrong class or deriving from an illegal class or...)
The following stuff is really ILLEGAL code. YOU SHOULD NEVER PROGRAM LIKE THIS. ;) But Apache shouldn't GPF, too. The Apache people warped me over here because they said that this is no Apache issue. May they be right.
As you can see...
The code is *very* narrowed down. It's definitely not _that_ simple IRL.
Main class is 'db_entry'. Class 'contact' is derived from employer, which is derived itself from db_entry.
Now we get ILLEGAL. We create a new 'contact' member object by directly (!!!) instantiating contact from the db_entry constructor. (Of course, we should instantiate 'employer', because contact is created inside too. But we want the crash, don't we :))
Crazy thing is that PHP doesn't complain about anything if this is done with *existing* 'contact()' constructor.
If this is missing or disabled ('//' part), Apache crashes.
OS: Win98 SE
Apache: 1.3.27
PHP: 4.3.1 (stable)
--script--
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 FINAL//EN">
<HTML>
<HEAD>
</HEAD>
<BODY BGCOLOR="#FFFFFF" LINK="#990000" VLINK="#003366" TEXT="#000000"
TOPMARGIN=16 LEFTMARGIN=10 MARGINWIDTH=10 MARGINHEIGHT=16>
<font face="Arial">
<?php
class employer extends db_entry
{
var $contactman;
function employer() /* constructor */
{
$this->contactman = new contact();
}
}
class contact extends employer
{
// function contact() // this is the constructor and it's MISSING!!!
// { // --> crash
// }
}
class db_entry
{
var $ct_entry;
function db_entry()
{
/* generate indirect member object by illegally
instantiating an object TWO hierarchy steps below!!! */
$this->ct_entry = new contact();
// -> crash!
}
}
$newentr = new db_entry();
echo "OK";
?>
</font>
</BODY>
</HTML>
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Last updated: Wed Apr 24 12:01:29 2024 UTC |
It's not so crazy. You've just got some endless recursion there, which is why it doesn't happen when you uncomment the contact constructor. When the contact object is instantiated, the employer constructor is called in the absence of a contact constructor. Since a new contact object is instanitated in the employer constructor, you get recursion, as the employer constructor is effectively calling itself. You'll eventually run out of memory or something similarly strange will happen, hence the segfault. You'll get the same results if you do "function foo() { return foo(); } foo();" I don't imagine this will be fixed. It's not PHP's fault is somebody codes an endless recursion loop. J