Improve ZEND_NEW RC inference

[iluuu1994]

ZEND_NEW returns RC1 if the instanciated class has no constructor.

[bwoebi]

That's only true for create_object == NULL and the handler being zend_std_get_constructor, I think. For anything else we cannot do such guarantees (extension code...).

[iluuu1994]

@bwoebi I forgot about create_object. I wasn't aware of the get_constructor handler... Do you think it's enough to check zend_class_entry.default_object_handlers? It may theoretically differ from zend_object.handlers at runtime. If not, I suppose we must restrict this to user classes. Same goes for write_property in #13237.

It's worth noting that we already make some assumptions here. E.g. we're assuming that assigning to a declared, untyped property does not throw, even though an overwritten write_property might.

php-src/Zend/Optimizer/zend_inference.c

Lines 5092 to 5093 in e2c3c48

	return !(prop_info->flags & ZEND_ACC_PUBLIC)
	&& prop_info->ce != op_array->scope;

[bwoebi]

I think it should be good enough to check default_object_handlers. Yes, at runtime it may change theoretically, but at that point I think it should be the extensions responsibility to be a good citizen and either notify at minit-time by changing these.

But be aware that this is Optimizer code of which one does not necessarily see the effects when developing extensions...

[bwoebi]

E.g. we're assuming that assigning to a declared, untyped property does not throw, even though an overwritten write_property might.

:-/

I think that's not a great check. I just checked the code of the extension I maintain (dd-trace-php), we do throw on < PHP 8 in the write handler to emulate a readonly. We don't do further validity checks in our code, but as long as we don't have proper virtual properties, I guess extensions will use it to validate.

[dstogov]

I don't object. Just select a good enough condition.

Does this cause any improvements in the JIT generated code?

[dstogov]

The last line is not necessary. If create_object is NULL then ce->default_object_handlers->get_constructor == zend_std_get_constructor is true.

[iluuu1994]

As discussed in the other issue, the default handlers may be changed without specifying create_object. create_object may still be used to swap the handlers. Support for this could be dropped in the future, essentially making zend_object->handlers and implementation detail, i.e. a cached pointer to object->ce->default_object_handlers to avoid a pointer indirection.