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Re: make_shared and friends.

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On 27.04.2012 20:12, Jason McKesson wrote:
>
> Does the C++11 specification allow you to say that the `make_shared`
> template is a friend, and thus guarantee that it can access the
> appropriate private constructors of a class? Yes, there is syntax that
> would make `make_shared` a friend. But does the spec *require* that
> the constructors are called directly from `make_shared` itself, since
> it cannot transfer friendship to any subsidiary object types?


I don't think so.

But as a practical matter make your destructor protected (or private),
instead of the constructors.

If the private constructors imply factory functions, then by switching
to making the destructor non-public for the general case you reduce
the number of construction/destruction support functions from M class
specific factory functions, where M is the average number of
constructors, to 1 common destroy function, which you can make a
friend. And if you have make_shared as a single common factory
function (note that this can be a bit unsafe since it or its wrapper
will then have access to /all/ the constructors), then by doing the
switch you introduce just 1 more function. No matter the number of
such classes you create.


Cheers & hth.,

- Alf


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Thread

make_shared and friends. Jason McKesson <jmckesson@gmail.com> - 2012-04-27 11:12 -0700
  Re: make_shared and friends. Daniel Krügler<daniel.kruegler@googlemail.com> - 2012-04-27 11:47 -0700
    Re: make_shared and friends. Jason McKesson <jmckesson@gmail.com> - 2012-04-28 17:02 -0700
      Re: make_shared and friends. Daniel Krügler <daniel.kruegler@googlemail.com> - 2012-04-29 23:59 -0700
        Re: make_shared and friends. Jason McKesson <jmckesson@gmail.com> - 2012-05-01 11:29 -0700
          Re: make_shared and friends. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2012-05-02 11:11 -0700
          Re: make_shared and friends. Daniel Krügler <daniel.kruegler@googlemail.com> - 2012-05-02 11:12 -0700
  Re: make_shared and friends. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2012-04-28 17:00 -0700

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