Re: [boost] question about C++11 guidelines

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?

Best,
Vicente