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Date: Sat, 22 Nov 2003 20:45:50 +0100
Reply-To: Marcus Boerger <helly@php.net>
Message-ID: <9349135392.20031122204550@marcus-boerger.de>
To: Andi Gutmans <andi@zend.com>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] Using do_alloca() instead of emalloc()
From: helly@php.net (Marcus Boerger)

Hello Andi,

Thursday, November 20, 2003, 10:48:57 AM, you wrote:

> Hey,

> I've been taking a look at the __autoload problem. During that time I saw 
> that lots of places in the code (especially reflection API) use 
> zend_str_tolower_dup().
> In most of these cases it would be much more efficient to use 
> do_alloca()/free_alloca() because that usually uses alloca() which 
> allocates on the stack.

Well Zeev and  you  told us to never it :-)

> Simplified example from reflection API code:

> lcname = zend_str_tolower_dup(name_str, name_len);

> if (zend_hash_find(&ce->properties_info, lcname, name_len + 1, (void **) 
> &property_info) == FAILURE) {
> 	efree(lcname);
> 	/* Error message */
> 	return;
> }

> efree(lcname);

> This should really be:

> lcname = do_alloca(name_len+1);
> zend_str_tolower_copy(lcname, name_str, name_len+1);

> if (zend_hash_find(&ce->properties_info, lcname, name_len + 1, (void **) 
> &property_info) == FAILURE) {
> 	free_alloca(lcname);
> 	/* Error message */
> 	return;
> }

> free_alloca(lcname);

> There are two times where you really shouldn't use do_alloca/free_alloca:
> a) If you're in code which requires a regular malloc() don't use them (the
> fallback is emalloc()).
> b) Only use them in functions which are about to return. They shouldn't be
> used in places like the main zend_execute loop because it would just make 
> the stack grow more and more (in almost all cases where 
> zend_str_tolower_dup() is being used, do_alloca/free_alloca are applicable).

> I need to go away for the weekend now but it be cool if people here would 
> at least take care of this in their code (such as reflection API code).

> Thanks,

> Andi




-- 
Best regards,
 Marcus                            mailto:helly@php.net