nullptr, the pointer literal

 

C++

컴파일러 지원

Freestanding and hosted

언어

표준 라이브러리 헤더

명명된 요구사항

Feature test macros (C++20)

언어 지원 라이브러리

개념 (C++20)

Diagnostics library

유틸리티 라이브러리

문자열 라이브러리

컨테이너 라이브러리

반복자 라이브러리

범위 라이브러리 (C++20)

알고리즘 라이브러리

수치 라이브러리

지역화 라이브러리

입/출력 라이브러리

파일시스템 라이브러리 (C++17)

정규 표현식 라이브러리 (C++11)

아토믹 연산 라이브러리 (C++11)

쓰레드 지원 라이브러리 (C++11)

Technical specifications

Symbols index

외부 라이브러리들

 

C++ 언어

General topics
Preprocessor Comments Keywords	ASCII chart Escape sequences History of C++
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Initialization
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Literals
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Expressions
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alternative representations
Utilities
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표현식

일반

value categories (lvalue, rvalue, xvalue)

order of evaluation (sequence points)

constant expressions

unevaluated expressions

primary expressions

lambda-expression(C++11)

리터럴

integer literals

floating-point literals

boolean literals

character literals including escape sequences

string literals

null pointer literal(C++11)

user-defined literal(C++11)

연산자

Assignment operators: a=b, a+=b, a-=b, a*=b, a/=b, a%=b, a&=b, a|=b, a^=b, a<<=b, a>>=b

Increment and decrement: ++a, --a, a++, a--

Arithmetic operators: +a, -a, a+b, a-b, a*b, a/b, a%b, ~a, a&b, a|b, a^b, a<<b, a>>b

Logical operators: a||b, a&&b, !a

Comparison operators: a==b, a!=b, a<b, a>b, a<=b, a>=b, a<=>b(C++20)

Member access operators: a[b], *a, &a, a->b, a.b, a->*b, a.*b

Other operators: a(...), a,b, a?b:c

new-expression

delete-expression

throw-expression

alignof

sizeof

sizeof...(C++11)

typeid

noexcept(C++11)

Fold expression(C++17)

Alternative representations of operators

Precedence and associativity

Operator overloading

Default comparisons(C++20)

변환

Implicit conversions

const_cast

static_cast

reinterpret_cast

dynamic_cast

Explicit conversions (T)a, T(a)

User-defined conversion

 

Syntax

nullptr		(since C++11)

Explanation

See More

The keyword nullptr denotes the pointer literal. It is a prvalue of type std::nullptr_t. There exist implicit conversions from nullptr to null pointer value of any pointer type and any pointer to member type. Similar conversions exist for any null pointer constant, which includes values of type std::nullptr_t as well as the macro NULL.

Example

Demonstrates that nullptr retains the meaning of null pointer constant even if it is no longer a literal.

코드 실행

#include <cstddef>
#include <iostream>

template<class T>
constexpr T clone(const T& t)
{
    return t;
}

void g(int*)
{
    std::cout << "Function g called\n";
}

int main()
{
    g(nullptr);        // Fine
    g(NULL);           // Fine
    g(0);              // Fine

    g(clone(nullptr)); // Fine
//  g(clone(NULL));    // ERROR: non-literal zero cannot be a null pointer constant
//  g(clone(0));       // ERROR: non-literal zero cannot be a null pointer constant
}

Output:

Function g called
Function g called
Function g called
Function g called

Keywords

nullptr

References

• C++20 standard (ISO/IEC 14882:2020):

• 7.3.12 Pointer conversions [conv.ptr]

• C++17 standard (ISO/IEC 14882:2017):

• 7.11 Pointer conversions [conv.ptr]

• C++14 standard (ISO/IEC 14882:2014):

• 4.10 Pointer conversions [conv.ptr]

• C++11 standard (ISO/IEC 14882:2011):

• 4.10 Pointer conversions [conv.ptr]

See also

NULL	구현에서 정의한 널 포인터 상수 (macro constant)
nullptr_t (C++11)	널 포인터 리터럴인 nullptr 의 형 (typedef)