Re: [Boost-users] [signals] Compiler warnings with BOOST_ALL_DYN_LINK

25 Mar 2005

      ----- Original Message ----- 
From: "Klaus Nowikow" 
To: 
Sent: Thursday, March 24, 2005 11:23 AM
Subject: [Boost-users] [signals] Compiler warnings with BOOST_ALL_DYN_LINK
...
Hello,
I have a problem using Boost.Signals. With this test program:
<code>
// See the previous thread regarding
// "[regex] Unresolved external symbols under VC7.1 w/ dynamic linking
#define BOOST_ALL_DYN_LINK
#include 
int main(int argc, char* argv[])
{
   return 0;
}
</code>
I get some compiler warnings under MSVC 7.1 / Boost 1.32. Is there 
something I
can do about it?
Here is the compiler output I get:
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\connection.hpp(111) 
:
warning C4251: 'boost::signals::connection::con' : class 
'boost::shared_ptr<T>'
needs to have dll-interface to be used by clients of class
'boost::signals::connection'
There is not a great deal you can with this warning other than turn it off.

#pragma warning (disable: 4251)
  ---- ------
#pragma warning (default: 4251)

We do this often. The alternative is to explicitly instantiate your template 
code and do the usuall things with __declspec(dllexport) etc.. which turn 
into a nightmare to maintain and a serious code bloat as well as exported 
dll entries and import libraies.

I try to keep the warning switches as close to the offending code as 
possible for documentation reasons, even inside a class declaration:
Here is an example:

class MYPROJECT_EXPORT MyClass
{
 private:
   #pragma warning (disable: 4251)
     std::list Talkers;
   #pragma warning (default: 4251)
.....
};

(NB: beware of warnings that make it into precompiled headers)

regards,
Conrad Weyns
...
with
       [
           T=boost::signals::detail::basic_connection
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\trackable.hpp(55) 
:
warning C4251: 'boost::signals::trackable::connected_signals' : class
'std::list<_Ty>' needs to have dll-interface to be used by clients of 
class
'boost::signals::trackable'
       with
       [
           _Ty=boost::signals::connection
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\slot.hpp(51) : 
warning
C4251: 'boost::signals::detail::slot_base::data' : class 
'boost::shared_ptr<T>'
needs to have dll-interface to be used by clients of class
'boost::signals::detail::slot_base'
       with
       [
           T=boost::signals::detail::slot_base::data_t
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\named_slot_map.hpp(100)
: warning C4251: 'boost::signals::detail::named_slot_map_iterator::impl_' 
:
class 'boost::scoped_ptr<T>' needs to have dll-interface to be used by 
clients
of class 'boost::signals::detail::named_slot_map_iterator'
       with
       [
           T=boost::signals::detail::named_slot_map_iterator::impl
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\named_slot_map.hpp(129)
: warning C4251: 'boost::signals::detail::named_slot_map::impl_' : class
'boost::scoped_ptr<T>' needs to have dll-interface to be used by clients 
of
class 'boost::signals::detail::named_slot_map'
       with
       [
           T=boost::signals::detail::named_slot_map::impl
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\signal_base.hpp(40)
: warning C4251: 'boost::signals::detail::call_notification::impl' : class
'boost::shared_ptr<T>' needs to have dll-interface to be used by clients 
of
class 'boost::signals::detail::call_notification'
       with
       [
           T=boost::signals::detail::signal_base_impl
       ]
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\signal_base.hpp(114)
: warning C4251: 'boost::signals::detail::signal_base_impl::combiner_' : 
class
'boost::any' needs to have dll-interface to be used by clients of class
'boost::signals::detail::signal_base_impl'
       c:\dev\Libraries\Boost\include\boost-1_32\boost\any.hpp(22) : see
declaration of 'boost::any'
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\signal_base.hpp(120)
: warning C4275: non dll-interface class 
'boost::noncopyable_::noncopyable' used
as base for dll-interface class 'boost::signals::detail::signal_base'
       c:\dev\Libraries\Boost\include\boost-1_32\boost\noncopyable.hpp(22) 
:
see declaration of 'boost::noncopyable_::noncopyable'
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\signal_base.hpp(120)
: see declaration of 'boost::signals::detail::signal_base'
c:\dev\Libraries\Boost\include\boost-1_32\boost\signals\detail\signal_base.hpp(150)
: warning C4251: 'boost::signals::detail::signal_base::impl' : class
'boost::shared_ptr<T>' needs to have dll-interface to be used by clients 
of
class 'boost::signals::detail::signal_base'
       with
       [
           T=boost::signals::detail::signal_base_impl
       ]
Best,
Klaus
--
Klaus Nowikow
DECOMSYS - Dependable Computer Systems
Development Engineer
Stumpergasse 48/14, A-1060 Wien, Austria
Phone: +43 1 59983-31
Fax: +43 1 59983-731
http://www.decomsys.com
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