Re: [boost] [config] GCC symbol visibility across shared libraries

Subject: Re: [boost] [config] GCC symbol visibility across shared libraries
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-05-19 12:36:21

Beman Dawes wrote:
> On Thu, May 6, 2010 at 12:42 PM, Jürgen Hunold
> <juergen.hunold_at_[hidden]> wrote:
>
>> I've got a working patch set lying around. Please find it attached.
>> Real life got in the way (as usual)...
>
> Your patch has been VERY helpful, and I've used it as the starting
> point! Thanks!
>
>> The patch introduces two Boost.Config macros
>> - BOOST_SYMBOL_EXPORT
>> - BOOST_SYMBOL_IMPORT
>
> AFAICT, a third macro is needed for GCC. I've named it
> BOOST_SYMBOL_VISIBLE and define it as
> __attribute__((visibility("default")))
>
> The need for this macro arises in header only classes like this:
>
>     class BOOST_SYMBOL_VISIBLE my_exception : public
> std::runtime_error { ... };
>
> If you use BOOST_SYMBOL_EXPORT, VC++ will warn because
> __declspec(dllexport) isn't valid in this context. If you don't
> decorate my_exception at all, VC++ is happy, but GCC shared libraries
> compiled with -fvisibility=hidden can't successfully throw exceptions
> up to callers outside the shared library. The only way around that I
> can see is to use a separate macro that is only defined for GCC.

Note: some of this funtionality, or something similar,  might already be 
found in
boost/serialization/force_include.hpp

Robert Ramey