Can't you also just say that mmap() is a magical function that you don't know what it does? For all the compiler knows, mmap() could just be a: static Hash_

Can't you also just say that mmap() is a magical function that you don't know what it does? For all the compiler knows, mmap() could just be a: static Hash_Table h; return (void *)&h; And make that the rule for all externally defined functions.