extern "C" in SDL_syswm.h

It seems like SDL_syswm.h is meant to be included in addition to SDL.h when it’s needed. But it doesn’t have extern "C" {} guards. Can that be added?

My problem is that my project has a C++ file that includes SDL_syswm.h, which includes DirectFB headers, which is including some low-level headers inside of it that use the register keyword. So I get errors like error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]

EDIT: Actually, I don’t think extern "C" {} would help me in my particular case.