Subject: Re: [boost] make_shared_array
From: Peter Dimov (lists_at_[hidden])
Date: 2012-11-02 20:20:12
Nathan Crookston wrote:
> On Fri, Nov 2, 2012 at 11:47 AM, Peter Dimov <lists_at_[hidden]> wrote:
> > Voila:
> > https://svn.boost.org/trac/boost/changeset/81149
> Very slick. Compiler errors for using operator* on a shared_ptr<T>
> are a little circuitous, but not too bad. . . though once everyone has
> a compiler-implemented static_assert such errors will be nicer.
I think that it's possible to remove op* completely in C++11 by using a
defaulted template parameter, as in
template<class R = sp_dereference<T>::type> R operator* () const;
with sp_dereference<T> not having ::type. But this means even more
#ifdefs, and it's already much too #ifdef-y for my taste, so...
> I assume that, using the aliasing constructor, I'll be able to write
> something like the following:
> shared_ptr<int> a1(new int);
> shared_ptr<int> a2(a1, &a1);
> a1.reset();//a2 is still okay after this line.
I see no reason for you to not be able to. :-)
> Should shared_ptr<T> be constructable from shared_array<T>?
At the moment I'm inclined to leave shared_array as is, purely as a legacy,
and focus on shared_ptr<T> as the spiffy new way forward.
> It seems like the following syntax is possible (my toy code seemed to
> shared_ptr<B> sp1 = make_shared<B>(<B ctor args>);//1
> shared_ptr<B> sp2 = make_shared<B>(number_of_B);//2: Default
> shared_ptr<B> sp3 = make_shared<B>(number_of_B, <B ctor args>);//3:
> All initialized to this.
> shared_ptr<int> sp4 = make_shared<int>(number_of_ints);//4:
> shared_ptr<int> sp4 = make_shared<int>(number_of_ints, 5);//5: all
> initialized to 5
Glen just proposed the same syntax, and I like it, although I prefer
shared_ptr<int> sp4a = make_shared<int>(number_of_ints);//4a:
initialized to 0
shared_ptr<int> sp4b = make_shared_noinit<int>(number_of_ints);//4b:
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