Why is `nullptr` a Better Choice than `NULL` and `0` for Pointers in C ?

Using nullptr: Advantages over NULL and 0

Pointers must be properly initialized to avoid unexpected behavior. While the syntax int* p1 = nullptr;, int* p2 = NULL;, and int* p3 = 0; may seem functionally equivalent, there are significant advantages to using nullptr over the other two options.

Overloading Ambiguity Resolution:

Consider the overloaded functions:

void f(char const *ptr);
void f(int v);

f(NULL);  // ambiguous function call

With NULL, the compiler cannot determine which function to call, as it could be either f(char const *) or f(int). This ambiguity can lead to unexpected errors. However, using nullptr resolves this ambiguity:

f(nullptr); // calls f(char const *)

Template Specialization:

In C , the type of nullptr is nullptr_t. This allows for template specialization for nullptr, providing unparalleled flexibility:

template<typename T, T *ptr>
struct something{};                     // primary template

template<>
struct something<nullptr_t, nullptr>{};  // partial specialization for nullptr

Using this specialization, you can handle nullptr arguments uniquely:

template<typename T>
void f(T *ptr);   // function to handle non-nullptr argument

void f(nullptr_t); // overload to handle nullptr argument

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