Why is `nullptr` the Best Choice for Pointer Initialization?

Advantages of Using nullptr

Consider the following scenario where three pointers are initialized with the same conceptual intent of safe pointer initialization:

int* p1 = nullptr;
int* p2 = NULL;
int* p3 = 0;

At a glance, it may seem inconsequential which method you choose. However, the true advantage of nullptr becomes evident when dealing with overloaded functions like this:

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

f(NULL); // Which function will be called?

Intriguingly, the function f(int) will be invoked instead of f(char const *), despite the probable intent. This can lead to subtle and difficult-to-detect bugs.

The solution lies in utilizing nullptr:

f(nullptr); // Now the first function will be called as expected

Furthermore, nullptr offers an additional benefit in templates. Consider the following:

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

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

Since nullptr is recognized as nullptr_t within a template, it enables the creation of overloads specifically tailored for handling nullptr arguments:

template<typename T>
void f(T *ptr);   // Function for non-nullptr arguments

void f(nullptr_t); // Overload for nullptr arguments

In conclusion, nullptr offers significant advantages over NULL and 0. It eliminates the potential for ambiguity in function overloading and allows for more explicit handling of nullptr values in templates, enhancing the overall safety and maintainability of your code.

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