Re: Yet Another Container: DynamicArray

From: Gavin Lambert (boost_at_[hidden])
Date: 2020-01-29 11:53:48

At 19:02 29/01/2020, Glen Fernandes wrote:
 >You shouldn't expect that. For any unique_ptr<T, D> you can only
 >expect that .get() gives you a D::pointer. For default_delete<T> 

 >this might be T*.  But it always depends on the Deleter.

That seems like a significantly more annoying interface than 
std::shared_ptr uses.

shared_ptr can hold fancy pointers too, but it happens explicitly 
via using fancy<T> rather than plain T, so the explicit 
indirection on usage is obvious too.

Having that be an implementation detail of the deleter changing 
the effective "type" of the first template argument (which is what 
people think of as the type of the pointer, even if the standard 
disagrees) seems quite annoying.

Maybe we should have a type-erased unique ownership pointer as 
well.  I know the reason why we didn't was to avoid heap 
allocation or wasted storage for the common case, but there ought 
to be some happy middle ground.

 >The correct way to get a raw pointer from any
 >potentially-fancy-pointer x is:   to_address(x)
 >
 >This can be boost::to_address (C++03 or higher), or
 >std::to_address (C++20 or higher)

Hmm.  This is news to me; I don't think I've read about it 
anywhere in conjunction with unique_ptr.  Perhaps since it doesn't 
actually exist yet (most compilers are still mostly C++17).

But eg. 
<https://en.cppreference.com/w/cpp/memory/unique_ptr>https://en.cppreference.com/w/cpp/memory/unique_ptr 
appears entirely mute on the topic.  (There's a passing reference 
to fancy pointers but even that doesn't talk about it.)