How do I check if one of multiple macros is defined in a single #ifdef?

Question

I have some C++ code, and want to perform an action if the __APPLE__ or __linux macros are defined.

If I did it as a normal if

Answer 1

You can't in a single #ifdef would a single #if do instead?

#if defined(__APPLE__) || defined(__linux)

this also works if you prefer

#if defined __APPLE__ || defined __linux