“nullptr“ should be used to denote the null pointer

Before C++11, the only way to refer to a null pointer was by using the integer literal 0, which created ambiguity with regard to whether a pointer or an integer was intended. Even with the NULL macro, the underlying value is still 0.

C++11 introduced the keyword nullptr, which is unambiguous and should be used systematically.

Noncompliant Code Example

void f(char *c);
void g(int i);
void h()
{
    f(0); // Noncompliant
    f(NULL); // Noncompliant
    g(0); // Compliant, a real integer
    g(NULL); // Noncompliant, NULL should not be used for a real integer
}

Compliant Solution

void f(char *c);
void g(int i);
void h()
{
    f(nullptr); // Compliant
    g(0);  // Compliant, a real integer
}

See

• C++ Core Guidelines ES.47 - Use nullptr rather than 0 or NULL

For example