Subject: Re: [boost] question about C++11 guidelines
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-05-04 02:06:39
Le 03/05/12 11:15, loic.actarus.joly_at_[hidden] a écrit :
> ---- Message d'origine ----
> >De : "Robert Ramey"<ramey_at_[hidden]>
> >À : boost_at_[hidden]
> >Objet : Re: [boost] question about C++11 guidelines
> >Date : 03/05/2012 08:30:06 CEST
> >Eric Niebler wrote:
> > > Say I'm rewriting an existing Boost library and targeting C++11
> > > users. I plan to ship C++03 and C++11 versions of my library
> > > side-by-side, so back-compat isn't an issue for the new code. Is
> > > there a reason to prefer using Boost's versions of utilities like
> > > enable_if, type traits, integral constant wrappers (e.g. mpl::int_),
> > > tuples, etc., over the now-standard ones?
> > >
> > > I'm leaning toward using std:: where I can, and falling back on
> > > Boost's versions only when there is a compelling reason.
> > Isn't easier to just use the boost versions knowing that they
> > will be implemented in the most efficient/appropriate way
> > for the compiler in question?
> From what I understood, std::make_shared is more efficiently implemented on
> some platforms that boost::make_shared, so I would not assume that boost
> version is better than the version provided by the compiler.
> From a boost user point of view, I have another issue with boost
> compatibility with C++11, that is not used by either proposal:
> - If types such as boost::shared_ptr and boost::tuple are used in the
> library boost.sampleLib, whenever I want to interface boost.sampleLib with
> other code that was written without boost, and makes use of std::shared_ptr
> or std::tuple, I have troubles, and need to convert/copy objects
Yes, this is an issue that merits a better solution.
> - If types such as std::shared_ptr and std::tuple are used in the library
> boost.sampleLib, whenever I want to interface boost.sampleLib with other
> code that was written with boost, and makes use of boost::shared_ptr or
> boost::tuple, I have troubles, and need to convert/copy objects
> The more I think of it, the more I believe the right solution is not to have
> two different types, but making sure that on a platform where
> std::shared_ptr exists, boost::shared_ptr is defined as an alias to
> std::shared_ptr, and just the same for all C++11 types that were first
> developped with boost.
> Frankly, I have been using boost on VC10 that contains std::shared_ptr for
> quite some time now, and I can say it is quite a pain, there are many subtle
> compilation problems that all come down to the fact that there are
> duplicated types with the same name in the same program.
> For instance:
> struct A
> A(int i);
> A(std::vector<int> const&v);
> using boost::make_shared;
> std::vector<int> v;
> boost::shared_ptr<A> p1 = make_shared<A> (3); // Works
> boost::shared_ptr<A> p1 = make_shared<A> (v); // Does not work, there is no
> conversion from std::shared_ptr to boost::shared_ptr
Where std::make_shared is used here?
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk