As long as you can link old-C++ and new-C++ together, there shouldn't be any big problems. You'll write your new code in new-C++ and wrap your old code in exter

As long as you can link old-C++ and new-C++ together, there shouldn't be any big problems. You'll write your new code in new-C++ and wrap your old code in extern "old-C++". The same way you can mix C code in C++ projects today.