What would be a proper invalid value for a pointer?

Question

Suppose I have this code. Your basic \"if the caller doesn\'t provide a value, calculate value\" scenario.

void fun(const char* ptr = NULL)
{
   if (ptr==NULL) {         


        

Answer 1

Depending on your platform, a pointer is likely either a 32 or 64-bit value.

In those cases, consider using:

0xFFFFFFFF or  0xFFFFFFFFFFFFFFFF

But I think the bigger question is, "How can NULL be passed as a valid parameter?"

I'd recommend instead having another parameter:

void fun(bool isValidPtr, const char* ptr = NULL)

or maybe:

void fun( /*enum*/ ptrState, const char* ptr = NULL)