C++ Logo


Advanced search

Re: [std-proposals] Making contiguous objects

From: Breno Guimarães <brenorg_at_[hidden]>
Date: Sun, 12 Mar 2023 14:59:17 -0300
> It's much easier to call `.release()` on a properly managed RAII
return object, than it is to remember to call `delete[]` (or whatever) on a
non-RAII return value.

I agree, and that functionality can be created on top of the proposed
function by calling make_contiguous_objects (or new_..) and
destroy_contiguous object.
But that would be an extension to the raw functionality. I mean, if we find
the raw functionality to have unfixable problems, there is no point in
discussing the RAII version.

>And now I'm confused: Is this make_contiguous_*objects* or make_contiguous_
*storage*? Because most library users will need the latter, not the former.

It's "_objects". I don't agree most library users would need the latter. At
least it's not in the use cases I looked at.
Some might want to defer the initialization of some arrays, but then they
use it like `std::make_contiguous_objects<Metadata,
ElementAlignedStorage>(nElements, nElements)`
And manually do part of the work.
But make_contiguous objects would give the buffer size calculation
(including alignment) and the exception-safe creation of the metadata array.

> If you construct objects, then you need the manager to remember how many
of each type of object to destroy (not just the total number of bytes,
which the C++ runtime remembers for us for free anyway).

That is why the API returns a tuple of spans. That is the object that
remembers how many and which type.

Best Regards,
Breno G.

On Sun, Mar 12, 2023 at 2:46 PM Ville Voutilainen <
ville.voutilainen_at_[hidden]> wrote:

> On Sun, 12 Mar 2023 at 19:42, Arthur O'Dwyer via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
> > And now I'm confused: Is this make_contiguous_objects or
> make_contiguous_storage? Because most library users will need the latter,
> not the former.
> Why on earth would this be the latter? An allocator can already be
> used for getting storage.

Received on 2023-03-12 17:59:28