The upgrade to Boost.Config symbol visibility macros that has been under discussion has been committed to trunk. This lays the groundwork for resolving #2144, #2309, #3697.
See https://svn.boost.org/trac/boost/changeset/62140
Thanks Jürgen Hunold for his patches and much other work on symbol visibility issues.
The changeset also applied the changes to Boost.System to act as a testbed to ensure the changes are correct. That's a concern because any breakage in Boost.Config could break a lot of other stuff. We also want to get the Boost.Config changes right the first time as they kick off rebuilds of everything that uses the config system.
The changes have been tested locally on Windows, Linux, and the Mac, and Boost.Filesystem has been retested on those systems as a reality check that unmodified user code continues to work.
As trunk regression tests cycle and our confidence builds, we will start to suggest and/or apply changes to other libraries to make use of the new facilities.
Beman, I've added support for symbol visibility to the Intel and Sun compiler configs, and tested with the Math and System libraries with default visibility set to hidden. Everything looks to be working really well, and I was even able to delete some config code from Boost.Math as a result of the changes :-) Many thanks for taking this on, John.