The pre-conditions of the
printf function require that you pass a data pointer as an argument to
%p – and more specifically, a pointer of type
obj1 is not a data pointer; it is an instance of
issue. The behaviour of violating the pre-conditions of
printf is undefined.
obj1.issue_c2 is a pointer, but it is a pointer to
const char rather than
void, so it also violates the pre-condition.