Re: [Boost-users] BOOST_ALL_DYN_LINK

Subject: Re: [Boost-users] BOOST_ALL_DYN_LINK
From: Paul (elegant_dice_at_[hidden])
Date: 2010-03-08 01:43:33

On 8 March 2010 03:21, Vladimir Prus <vladimir_at_[hidden]> wrote:

> Paul wrote:
>
> > Hi all,
> >
> > I'm confused about boost dynamic linking on windows MSVC90
> >
> > I always define: BOOST_ALL_NO_LIB
> > So that I directly control which DLLs I link to.
> > I add the signals dll for linking.
> >
> > Then, if I define BOOST_ALL_DYN_LINK, I get lots of these messages:
> >
> > boost_1_42_0\boost/signals/detail/signal_base.hpp(113) : 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'
> > 39>        boost_1_42_0\boost/any.hpp(36) : see declaration of
> 'boost::any'
> >
> > I've read up on this and understand why the warnings are shown.
> >
> > BUT,
> > I don't understand why I am able to still link my program if I do NOT
> define
> > BOOST_ALL_DYN_LINK.
> >
> > Without the flag, it compiles without warnings, it links without
> problems,
> > AND the executable requires the signals DLL to be available, so clearly
> it
> > IS dynamically linked.  Right?
>
> Do you include import library for Boost.Signals in the link? Then,
> presumably,
> compiler automatically 'dllimports' the symbol. Please see:
>
>        http://blogs.msdn.com/oldnewthing/archive/2006/07/26/679044.aspx
>
> Does this help?
>
> - Volodya
>
>
This DOES help a lot !

So, I have a few options:

1) Define BOOST_ALL_DYN_LINK and put up with the excess warnings.
   This would be ok if the boost developers could "fix" their headers by
adding #pragmas to hide the warnings when they know its not a problem.

2) Define BOOST_ALL_DYN_LINK and write a couple of header files that wrap
the boost headers with #pragmas (eg especially for boost::signals)

3) Do not define BOOST_ALL_DYN_LINK, and allow Windows the link "the naive
way", which might give slower performance, but maybe not.

Thanks Volodya !