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Message-ID: <f486a2f2-cdb5-57e7-b57f-7b525379d092@gmail.com>
Date: Fri, 7 Oct 2022 17:08:51 +0200
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To: Yasuo Ohgaki <yohgaki@ohgaki.net>
Cc: PHP Internals List <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Preventing stack overflows
From: arnaud.lb@gmail.com (Arnaud Le Blanc)

On 07/10/2022 16:14, Yasuo Ohgaki wrote:
> The root cause that users cannot understand what happened is this:
> 
> $ php -n -r 'set_error_handler(function ($severity,$message, $filename, 
> $lineno) { throw new ErrorException($message, 0, $severity, $filename, 
> $lineno); });  function f() { f(); } f();'
> 
> Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to 
> allocate 262144 bytes) in Command line code on line 1
> 
> When a fatal error happens, PHP does not allow  a stack dump.  Very old 
> PHP allowed users to catch E_ERROR by user error handler, but it is 
> disabled to prevent users from shooting their own foot.
> I suppose allowing users to catch "only one" fatal error would solve 
> many issues as  well as infinite recursion.

Fatal errors definitely need improvements.

Stack overflows are even worth, as the process is terminated by the system:

     $ php test.php
     Segmentation fault

With the proposed change, an exception is throw before it happens:

     $ php test.php
     Fatal error: Uncaught Error: Maximum call stack size of 28672 bytes
     reached. Infinite recursion? in test.php:8
     Stack trace:
     #0 test.php(8): C->__destruct()
     #1 test.php(8): C->__destruct()
     #2 test.php(8): C->__destruct()
     ...
     #7 {main}
       thrown in test.php on line 8