Wouldn't it be better to change the class to use the __declspec(export) as others do? Or would this not solve the problem? At least I am unsure what would happen when trying to mix DLL and static boost libs that both derive from noncopyable.
I think it would be OK to delare an all-header class as __declspec(dllimport), but I'm not completely sure (where does the RTTI information end up if there is no source file? I think this normally gets placed in the cpp file that has the first non-inline member function, but I'm not completely sure).
BTW. this seems to me only a special case to a more general question. When using a DLL version of a class that derives from some other class, this would force every other lib that uses the same base, also to be used in DLL version. Is this correct?
Correct, the problem comes when you're using third party code, which uses other third party code and so on, just try using std::list<myclass> in an exported class and you'll see what I mean. See also the discussion of dependencies at http://www.boost.org/more/separate_compilation.html#dlls John.