[Trilinos-Users] boost/std::shared_ptr interoperability

[Bartlett, Roscoe A.]

That should work.   However, the only issue is that if you convert from an RCP to a std::shared_ptr and then want to take that std::shared_ptr and convert back to an RCP (or visa versa), it would be nice if you got the original RCP and copy it instead of creating a new RCPNode object (and new reference count).  That is what the existing RCP <-> boost::shared_ptr converts do I believe.

-Ross

From: Simone Pezzuto [mailto:junki.gnu at gmail.com]
Sent: Thursday, January 30, 2014 10:47 AM
To: Bartlett, Roscoe A.
Cc: Wojciech Smigaj; trilinos-users at software.sandia.gov
Subject: Re: [Trilinos-Users] boost/std::shared_ptr interoperability

Some time ago, after digging on stackoverflow, I came up with this solution:

#include <Teuchos_RCP.hpp>
#include <Teuchos_RCPBoostSharedPtrConversions.hpp>
#include <boost/shared_ptr.hpp>
#include <iostream>
#include <cstdlib>

// It creates T1<T> from T2<T>, in such a way that the deleter
// of T1<T> it's just a lambda function that holds a reference of T2
template<template <typename T> class T1, template <typename T> class T2, typename T>
T1<T> convert_to (const T2<T>& ptr)
{
    return T1<T> (ptr.get(), [ptr](T*){});
}

int main(void)
{
    // boost -> {std, Teuchos}
    {
        boost::shared_ptr<int> b_ptr(new int(20));
        auto c_ptr = convert_to<std::shared_ptr>(b_ptr);
        auto t_ptr = Teuchos::rcp(b_ptr);
    }
    // RCP -> {boost, std}
    {
        Teuchos::RCP<int> t_ptr(new int(20));
        auto b_ptr = Teuchos::shared_pointer(t_ptr);
        auto c_ptr = convert_to<std::shared_ptr>(t_ptr);
    }
    // std -> {boost, Teuchos}
    {
        std::shared_ptr<int> c_ptr(new int(20));
        auto b_ptr = convert_to<boost::shared_ptr>(c_ptr);
        // RCP doesn't support lambda functions, while boost::shared_ptr does
        // because the deleter is templated
        // auto t_ptr = convert_to<Teuchos::RCP>(c_ptr); // Not working!
        // Not optimal workaround
        auto t_ptr = Teuchos::rcp(convert_to<boost::shared_ptr>(s_ptr));
    }

    return EXIT_SUCCESS;
}

Is fundamental to have consistent internal counters of each smart pointer. The "conversion" simply overloads
the deleter with a do-nothing function, but such that it takes as argument a reference of the other smart pointer,
so that its internal counter is increased.

Cheers,
 Simone

2014-01-30 Bartlett, Roscoe A. <bartlettra at ornl.gov<mailto:bartlettra at ornl.gov>>:
Nico and others,

You will want to copy the code for supporting the interoperability of Teuchos::RCP and boost::shared_ptr for use with std::shared_ptr I think.

I am currently on projects that don’t allow C++11 yet so you should expect  little support for C++11 at this point.  However, this might change in the next few months.  At that point, I will update a bunch of this software to optionally take advantage of C++11 features and to provide interoperability with std::shared_ptr.

-Ross

P.S. I remember being a grad student being able to use bleeding edge compilers and approaches.  Those were good days in many respects.

> -----Original Message-----
> From: trilinos-users-bounces at software.sandia.gov<mailto:trilinos-users-bounces at software.sandia.gov> [mailto:trilinos-users-<mailto:trilinos-users->
> bounces at software.sandia.gov<mailto:bounces at software.sandia.gov>] On Behalf Of Wojciech Smigaj
> Sent: Thursday, January 30, 2014 9:08 AM
> To: trilinos-users at software.sandia.gov<mailto:trilinos-users at software.sandia.gov>
> Subject: Re: [Trilinos-Users] boost/std::shared_ptr interoperability
>
> On 30/01/2014 13:12, Nico Schlömer wrote:
>  > Hi all,
>  >
>  > is there any better way for creating an RCP from a
> boost/std::shared_ptr than
>  >
>  >      Teuchos::rcp(myBoostPtr.get(), false))
>  >
>  > ?
>  >
>  > Cheers,
>  > Nico
>
> Hi Nico,
>
> yes, there are dedicated functions for doing this; see here:
>
> http://trilinos.sandia.gov/packages/docs/r11.0/packages/teuchos/doc/html/
> group__Teuchos__RCPBoostSharedPtrConversions__grp.html
>
> Best regards,
> Wojciech
> _______________________________________________
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> Trilinos-Users at software.sandia.gov<mailto:Trilinos-Users at software.sandia.gov>
> http://software.sandia.gov/mailman/listinfo/trilinos-users

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