Hi, I would like to add symbol visibility support to my library. Using -fvisibility=hidden option I compared the changed symbols, boost::bad_function_call typeinfo was visible previously but with hidden default visibility it is hidden. It compiles just fine, but according to gcc wiki (http://gcc.gnu.org/wiki/Visibility) exceptions must be visible as runtime error might happen because of missing typeinfo. I found bug report (https://svn.boost.org/trac/boost/ticket/2309) that exception class not exported in Boost.Thread, the problem was fixed by adding pragmas. In boost/function/function_base.hpp pragmas or other ways to change visibility isn't used, so the boost::bad_function_call typeinfo became hidden using -fvisibility=hidden. In the former boost bug report (https://svn.boost.org/trac/boost/ticket/2309) runtime error does not even mentioned, I couldn't reproduce the runtime error in my small experiments. In what situations can hidden symbol cause problems? Is it normal that boost::bad_function_call typeinfo is hidden or it is a boost bug that can cause problems and should be fixed? A made a small test library and application. The library has hidden boost::bad_function_call typeinfo, but the application seems catching the exception properly. Can this cause an error, why is it working? Makefile: CXX=g++ test_exception: test_exception.cpp libmydso.so $(CXX) -L. -lmydso $< -o $@ libmydso.so: mydso.cpp $(CXX) -fvisibility=hidden -fPIC -shared -Wl,-soname,$@ $< -o $@ mydso.h: void __attribute__ ((visibility ("default"))) test_exception(); mydso.cpp: #include <boost/function.hpp> #include "mydso.h" void test_exception() { boost::function<int (int, int)> f; f(5, 4); } test_exception.cpp: #include <iostream> #include <stdexcept> #include "mydso.h" int main() { try { test_exception(); } catch (std::runtime_error) { std::cerr << "Got std::runtime_error" << std::endl; } catch (...) { std::cerr << "Got other exception" << std::endl; } } Thanks, Dani