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.

[SVN r62140]

test/throw_test.cpp

@@ -0,0 +1,31 @@
+//  throw_test.cpp  --------------------------------------------------------===========-//
+
+//  Copyright Beman Dawes 2010
+
+//  Distributed under the Boost Software License, Version 1.0.
+//  See www.boost.org/LICENSE_1_0.txt
+
+//  Library home page is www.boost.org/libs/system
+
+//--------------------------------------------------------------------------------------// 
+
+//  See dynamic_link_test.cpp comments for use case.
+
+//--------------------------------------------------------------------------------------// 
+
+// define BOOST_SYSTEM_SOURCE so that <boost/system/config.hpp> knows
+// the library is being built (possibly exporting rather than importing code)
+#define BOOST_SYSTEM_SOURCE 
+
+#include <boost/system/system_error.hpp>
+
+namespace boost
+{
+  namespace system
+  {
+    BOOST_SYSTEM_DECL void throw_test()
+    {
+      throw system_error(9999, get_system_category(), "boo boo");
+    }
+  }
+}