Is it safe to #define NULL nullptr?

Question

I have seen below macro in many topmost header files:

#define NULL 0  // C++03

In all over the code, NULL and 0 are u

Answer 1

Maybe Not

If you have a particular format of overloading behaviour:

void foo(int);
void foo(char*);

Then the behaviour of the code:

foo(NULL);

will change depending on whether NULL is changed to nullptr or not.

Of course, there's another question as to whether it's safe to write such code as is present in this answer...