On Oct 1, 2014, at 4:34 PM, Argyrios Kyrtzidis <[email protected]> wrote:
> + John
>
> John, could you advice here ?
>
>> On Oct 1, 2014, at 4:20 PM, Marshall Clow <[email protected]> wrote:
>>
>> On Oct 1, 2014, at 3:36 PM, Marshall Clow <[email protected]> wrote:
>>>
>>> Richard Smith pointed out that destroying a pointer to an objective-C class
>>> might require an ARC call, and so the compiler needs to see the type to
>>> figure out if it is_destructible.
>>>
>>> Note that is_destructible<ObjCForwardClass**>::value is true, so it’s just
>>> pointers to objective-C objects, not pointers in general.
>>
>> Richard also pointed me to:
>> http://clang.llvm.org/docs/AutomaticReferenceCounting.html#retainable-object-pointers
>>
>> So, while I agree with Argyrios that this changed the behavior of
>> is_trivially_destructible for forward-declared objective-C classes,
>> I am now convinced that the old behavior was incorrect, and the new behavior
>> is “better”.
>>
>> One could argue that a forward-declared objective-C class is not a complete
>> type, since the compiler doesn’t know how to destroy it, and if so, then
>> is_destructible is not required to give any answer at all ("T shall be a
>> complete type”).
Pointers to forward-declared Objective-C classes are still complete types.
They should be both destructible and (outside of ARC) non-trivially
destructible.
I assume the problem here is ObjC property syntax, which usually looks like
“foo.prop” where foo has ObjC pointer type. Type-checking a property access
really does require the type to be complete. However, pseudo-destructor calls
are not property accesses, and should not require the pointee type to be
complete.
Does that answer your question?
John.
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