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Date: Tue, 21 Feb 2006 18:09:13 -0500
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To: Nuno Lopes <nlopess@php.net>
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Subject: Re: [PHP-DEV] recover from a segfault
From: ilia@prohost.org (Ilia Alshanetsky)

Nuno Lopes wrote:
> In the last days I've exchanged some e-mails with PCRE's author because 
> of one more bug that appeared in our database about segfaults in PCRE 
> (related to stack overflows).
> PCRE can consume a lot of stack, because of backtracking (thus 
> segfaulting PHP). Yesterday I've discovered that when using the 
> setrlimit() function, most segfaults can be avoided 
> (http://mega.ist.utl.pt/~ncpl/php_pcre_stack_limits.txt)  :)

This sounds like an interesting idea, I think we need to consider it 
doing for PHP in general rather then jut when PCRE is being used. The 
only thing is that rather then setting the stack to infinity, perhaps a 
small value can be used ;-)

> I've done a little program for fun to show myself how to catch the 
> SIGSEGV signals and print a nice message. 
> (http://mega.ist.utl.pt/~ncpl/break-stack.html)
> 
> So, catching the signal is easy. What about recovery? Doesn't anyone has 
> experience in this area? Can this be done? (and in most 
> SAPIs/architectures?)
> 

After SEGV or any memory problem has happened the situation is 
undefined. Another words you cannot reliably continue the operation of 
the program. Which is why termination and dumping of core is the lesser 
of all evils in this case.

Ilia