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Date: Tue, 12 May 2009 11:53:38 +0100
Message-ID: <af54caaf0905120353n798c2f67y50af257d524b95f5@mail.gmail.com>
To: Dmitry Stogov <dmitry@zend.com>
Cc: Stanislav Malyshev <stas@zend.com>, Guilherme Blanco <guilhermeblanco@gmail.com>, 
	Marcus Boerger <helly@php.net>, Timm Friebe <thekid@thekid.de>, internals@lists.php.net
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Subject: Re: [PHP-DEV] Method call improvements
From: paul.biggar@gmail.com (Paul Biggar)

On Tue, May 12, 2009 at 9:43 AM, Dmitry Stogov <dmitry@zend.com> wrote:
>> Apologies, I'm not familiar with run-time inheritence in PHP. My
>> understanding was that when a classes source code is compiled, its
>> parent classes must be known. When is this not the case?
>
> The parent class may be defined in other file that is loaded at runtime
> using include() statement. It's very usual case. So the PHP first loads the
> include file and then declares child class at runtime.

>> Must it be known for the class' first instantiation?
>
> Of course. :)


On Tue, May 12, 2009 at 7:25 AM, Dmitry Stogov <dmitry@zend.com> wrote:
> The real things is even worse as during compilation of a class it's parent
> class doesn't have to be known. So construction of VMTs becomes a bit
> problematic. BTW we could think in this way...


OK, so I dont understand this exactly. Is it correct to say that if a
class uses inheritance its compilation will be deferred until its
first instantiation? Or is it compiled when it is seen, and its parent
backpatched in later. When is later?

But I think its fair to say that it has static inheritance - that is,
its full inheritance chain is known before it can be instantiated, and
it can never be changed after that.





>> In the worst case, it _might_ be cheaper to build it at instantiation
>> time, but I would have to look up how expensive that is in a more
>> static language to be sure. Certainly, it is currently so expensive
>> that almost anything else would be better (including the OP's patch).
>
> I don't see how run-time VMT contraction may help, because calls to virtual
> method must know VMT offset at compile-time.

Right. Construction is fine. Their use is not. I don't know what I was
thinking.



So it looks like the best way forwards is still the OP's patch?



Thanks,
Paul



-- 
Paul Biggar
paul.biggar@gmail.com