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Subject: Re: [PHP-DEV] Evaluation of constructor arguments if there's no constructor
From: rowan.collins@gmail.com (Rowan Collins)

Julien Pauli wrote (on 14/08/2014):
> On Thu, Aug 14, 2014 at 8:26 AM, Tjerk Meesters
> <tjerk.meesters@gmail.com> wrote:
>> Hi internals,
>>
>> I was sifting through the bucket o’ bugs and found these two related issues:
>> https://bugs.php.net/bug.php?id=67829
>> https://bugs.php.net/bug.php?id=54162 (closed)
>>
>> They concern the behaviour of the engine when a class defines no constructor or if the class to be instantiated doesn’t exist, which can be seen here: http://3v4l.org/jOQY0
>>
>> This is obviously a design decision, but doesn’t seem to have a mention in the documentation nor the spec (I couldn’t find it under the ‘new’ operator).
>>
>> I can add a paragraph in the documentation for it; the question is whether it should also be added to the spec, seeing how HHVM and PHP behave differently in this respect? It could be added as implementation dependent behaviour I suppose?
> This is a known behavior which is part of the VM.
> It is designed at http://lxr.php.net/xref/PHP_5_5/Zend/zend_vm_def.h#3383
>
> I guess its an optimisation that prevents the compiler from compiling
> a ZEND_DO_FCALL for constructors, which optimizes a bit the VM path
> for object construction.
> Dmitry should have more informations.
>
> I'm +1 for a documentation or spec mention.
>
>
> Julien.Pauli
>

When it came up on StackOverflow chat, it was cheekily dubbed "Rasmus 
evaluation", because nobody could find any theory matching that 
particular optimisation: 
https://chat.stackoverflow.com/transcript/11/2013/9/28/14-17

I'm still not entirely sure it's a good idea, and can't imagine how 
anyone would rely on it (if you have a look at that trasnscript, you'll 
find some fun attempts at finding an esoteric use). Is it really that 
big an optimisation that it's worth such surprising behaviour?

-- 
Rowan Collins
[IMSoP]