Lack of g++ symbol visibility support in boost::system

[rbock@…]

Similar to #2309 (class symbols) and #3347 (method sybols):

If you compile a library which throws boost::system::system_error with

g++ -fvisibility=hidden

the exception cannot be caught as system_error (but as runtime_error).

Using

#pragma GCC visibility push(default)
#include <boost/system/system_error.hpp>
#pragma GCC visibility pop

in the library code helps, but it requires a lot of attention.

It would be really, really cool if all boost libraries would add visibility to the public classes, see also

​http://gcc.gnu.org/wiki/Visibility

Thank you for your time!

Regards,

Roland

[Jürgen Hunold]

This is essentially #2114 and #2309

[Beman Dawes]

(In [62140]) Major upgrade to Boost.Config symbol visibility macros for shared libraries, based on patches from Jürgen Hunold with mods by Beman Dawes. Upgrade Boost.System to use the new visibility macros. Fixes #3697 and provides foundation for fixing 2114, 2309, etc.