Re: [boost] static_vector using aligned_storage

Subject: Re: [boost] static_vector using aligned_storage
From: Nevin Liber (nevin_at_[hidden])
Date: 2012-12-18 02:15:35

On 17 December 2012 22:45, Adam Wulkiewicz <adam.wulkiewicz_at_[hidden]>wrote:

> I assumed that in the allocated memory the hybrid_vector stores only
> elements exceeding the static storage. In this case it would store
> them in two different places - static storage and allocated one.

I hope not.  One of the properties of vector is that the space is
contiguous.  If the current storage (whether embedded or allocated)
capacity is exceeded, allocate new space, move-if-noexcept or copy the
elements from the old space to the new space (say, via
std::move_if_noexcept), then deallocate the old space if and only if it was
originally allocated.

> It would work, if after the static storage overflow and the first
> allocation, elements were moved to the newly allocated memory. I don't
> know however if this isn't too big penalty.
>

It isn't any different than the normal "penalty" for vector.

> Yes I understand this. My question is regarding the case when data()
> returns Alloc::pointer (I believe this is the case in MS
> implementation).
>

Sounds like a bug.  The standard is quite clear that data() returns a T*,
not Alloc::pointer.
-- 
 Nevin ":-)" Liber  <mailto:nevin_at_[hidden]>  [phone]