That's a fine general sentiment. However, in this context it's a problem if you want to assign NULL to a pointer without a cast, which is why C++ added the magi

That's a fine general sentiment. However, in this context it's a problem if you want to assign NULL to a pointer without a cast, which is why C++ added the magically convertible nullptr in addition to the magically convertible `0` constant. char *x = 0; // ok in C and C++ char *y = (void*)0; // ok in C, error in C++ char *z = nullptr; // ok in C++ therefore: #define NULL ((void*)0) // Required by Posix C, invalid C++ #define NULL 0 // Pre-nullptr, the only valid C++ definition C++ can't define NULL the safe way that Posix C does. I don't understand why it's more acceptable to allow magic `0` conversions than magic `(void*)0` conversions, given that the latter is far less likely to happen by accident -- but here we are.