如何为二进制兼容的可扩展性设计一个c++ API

I am designing an API for a C++ library which will be distributed in a dll / shared object. The library contains polymorhic classes with virtual functions. I am concerned that if I expose these virtual functions on the DLL API, I cut myself from the possibility of extending the same classes with more virtual functions without breaking binary compatibility with applications built for the previous version of the library.I am designing an API for a C++ library which w