The C++ standard has a clause prohibiting macros that re-#define keywords if the translation unit also #includes a standard header. I guess this is to clarify w

The C++ standard has a clause prohibiting macros that re-#define keywords if the translation unit also #includes a standard header. I guess this is to clarify whether the standard-library functionality is expected to still work even in the face of such a #define, by specifying that implementors don't need to worry about that situation. I don't believe C has any such restrictions, though.