Assuming bar isn't inlined (eg separate compilation unit, as you mentioned), the null check in MACRO is not unnecessary, because bar can be called from places o

Assuming bar isn't inlined (eg separate compilation unit, as you mentioned), the null check in MACRO is not unnecessary, because bar can be called from places other than foo, and those places might pass null pointer. This is one of several situations where it might be useful for the compiler to excercise it's perogative to implement operations without regard for undefined behaviour to rewrite `use(*p);` as `if(!p) abort(); use(*p);`, which would make the null check in MACRO unnecessary, but unless it does so, the check is not unnecessary, just insufficient.