[Bug c++/47942] New: Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[Bug c++/47942] New: Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[skagget77 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

           Summary: Not possible to initialize a shared_ptr with a class
                    defined in function scope, inheriting from a global
                    scope base class
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: skagget77@gmail.com


Here's some code reproducing the problem:

#include <memory>

struct Base {
    virtual ~Base() {}
};

typedef std::tr1::shared_ptr<Base> BasePtr;

BasePtr GetImpl() {
    struct InlineImpl : Base{
    };

    return BasePtr(new InlineImpl);
}

int main() {
   BasePtr ptr = GetImpl();
}

The result is:

In function 'BasePtr GetImpl()':
Line 13: error: no matching function for call to
'std::tr1::shared_ptr<Base>::shared_ptr(GetImpl()::InlineImpl*)'

If I change from shared_ptr<Base> to Base* it works as expected. It also works
as expected if I do return Base(reinterpret_cast<Base*>(new InlineImpl)).

Best regards,

Johan Andersson

[Bug c++/47942] Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[skagget77 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

--- Comment #1 from Johan Andersson <skagget77 at gmail dot com> 2011-03-01 13:28:26 UTC ---
I might add that this bug is also present in gcc (Debian 4.4.5-11) 4.4.5.

[Bug c++/47942] Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-01 13:37:25 UTC ---
1) GCC 4.1.2 is ancient and unmaintained
2) your example code doesn't compile (should #include <tr1/memory>)
3) in C++03 you cannot use a type without linkage as a template argument
4) You should not use reinterpret_cast, static_cast is correct


Your options are either to use C++0x mode (classes without linkage can be used
as template arguments in C++0x) or to upcast the pointer

[Bug c++/47942] Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-01 13:45:26 UTC ---
(In reply to comment #2)
> Your options are either to use C++0x mode (classes without linkage can be used
> as template arguments in C++0x) or to upcast the pointer

It seems that the change to allow local types as template args (see
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm for the
proposal) was implemented in GCC 4.5, so you can't rely on that in 4.4

So the best option is:

    return BasePtr(static_cast<Base*>(new InlineImpl));

[Bug c++/47942] Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[skagget77 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

--- Comment #4 from Johan Andersson <skagget77 at gmail dot com> 2011-03-01 13:58:00 UTC ---
Thanks for the quick reply and advice to use static_cast, the reinterpret_cast
was a temporary memory lapse!

The old GCC version was because I used a web-interface to verify the problem.
I'm normally on Windows and Visual C++.

(In reply to comment #3)
> (In reply to comment #2)
> > Your options are either to use C++0x mode (classes without linkage can be used
> > as template arguments in C++0x) or to upcast the pointer
> 
> It seems that the change to allow local types as template args (see
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2657.htm for the
> proposal) was implemented in GCC 4.5, so you can't rely on that in 4.4
> 
> So the best option is:
> 
>     return BasePtr(static_cast<Base*>(new InlineImpl));

[Bug c++/47942] Not possible to initialize a shared_ptr with a class defined in function scope, inheriting from a global scope base class

[pluto at agmk dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47942

Pawel Sikora <pluto at agmk dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pluto at agmk dot net

--- Comment #5 from Pawel Sikora <pluto at agmk dot net> 2011-06-05 15:25:07 UTC ---
*** Bug 49291 has been marked as a duplicate of this bug. ***