Julien Pauli wrote (on 14/08/2014):
On Thu, Aug 14, 2014 at 8:26 AM, Tjerk Meesters
<tjerk.meest...@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]
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