offsetof

 

C++

Idioma

Conceptos

Utilidades de la biblioteca

Strings biblioteca

Contenedores biblioteca

Algoritmos biblioteca

Los iteradores biblioteca

Numéricos biblioteca

Entrada / salida de la biblioteca

Localizaciones biblioteca

Expresiones biblioteca Regular (C++11)

Operaciones de biblioteca Atómica (C++11)

Tema Biblioteca de ayuda (C++11)

 

Utilidades de la biblioteca

Escriba apoyo (basic types, RTTI, type traits)

Gestión de memoria dinámica

Gestión de errores

Programa de servicios públicos

Funciones variadic

Fecha y hora

Objetos Function

initializer_list (C++11)

bitset

hash (C++11)

Operadores relacionales Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pares y tuplas Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Cambiar, hacia adelante y mover Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Escriba apoyo

Tipos básicos Original: Basic types The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Tipos fundamentales
Tipos fijos ancho enteros (C++11)
ptrdiff_t size_t max_align_t (C++11)	nullptr_t (C++11) offsetof NULL
Límites numéricos Original: Numeric limits The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
numeric_limits
C numérico limita interfaz
Información de tipo en tiempo de ejecución Original: Runtime type information The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
type_info type_index (C++11)	bad_typeid bad_cast
Caracteres de tipo Original: Type traits The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Categorías primarias de tipo Original: Primary type categories The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_void (C++11) is_array (C++11) is_pointer (C++11) is_enum (C++11) is_union (C++11) is_class (C++11) is_function (C++11)	is_object (C++11) is_scalar (C++11) is_compound (C++11) is_integral (C++11) is_floating_point (C++11) is_fundamental (C++11) is_arithmetic (C++11)
is_reference (C++11)
is_lvalue_reference (C++11)
is_rvalue_reference (C++11)
is_member_pointer (C++11)
is_member_object_pointer (C++11)
is_member_function_pointer (C++11)

Propiedades de tipo Original: Type properties The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_const (C++11) is_volatile (C++11) is_pod (C++11) is_empty (C++11) is_polymorphic (C++11) is_abstract (C++11)	is_trivial (C++11) is_trivially_copyable (C++11) is_standard_layout (C++11) is_literal_type (C++11) is_signed (C++11) is_unsigned (C++11)

Operaciones compatibles Original: Supported operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_constructible is_trivially_constructible is_nothrow_constructible (C++11) (C++11) (C++11)
is_default_constructible is_trivially_default_constructible is_nothrow_default_constructible (C++11) (C++11) (C++11)
is_copy_constructible is_trivially_copy_constructible is_nothrow_copy_constructible (C++11) (C++11) (C++11)
is_move_constructible is_trivially_move_constructible is_nothrow_move_constructible (C++11) (C++11) (C++11)
is_assignable is_trivially_assignable is_nothrow_assignable (C++11) (C++11) (C++11)
is_copy_assignable is_trivially_copy_assignable is_nothrow_copy_assignable (C++11) (C++11) (C++11)
is_move_assignable is_trivially_move_assignable is_nothrow_move_assignable (C++11) (C++11) (C++11)
is_destructible is_trivially_destructible is_nothrow_destructible (C++11) (C++11) (C++11)
has_virtual_destructor (C++11)
Relaciones y consultas de propiedad Original: Relationships and property queries The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_same (C++11) is_base_of (C++11) is_convertible (C++11)	alignment_of (C++11) rank (C++11) extent (C++11)
Modificaciones de tipo Original: Type modifications The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
remove_cv remove_const remove_volatile (C++11) (C++11) (C++11) add_cv add_const add_volatile (C++11) (C++11) (C++11) make_signed (C++11) make_unsigned (C++11)	remove_reference (C++11) add_lvalue_reference add_rvalue_reference (C++11) (C++11) remove_pointer (C++11) add_pointer (C++11) remove_extent (C++11) remove_all_extents (C++11)
Transformaciones de tipo Original: Type transformations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
aligned_storage (C++11) aligned_union (C++11) decay (C++11) enable_if (C++11)	conditional (C++11) common_type (C++11) underlying_type (C++11) result_of (C++11)
Escriba constantes rasgos Original: Type trait constants The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
integral_constant (C++11)

 

Defined in header <cstddef>
#define offsetof(type, member) /*implementation-defined*/

El offsetof macro se expande a una constante de std::size_t tipo, el valor de los cuales es el desplazamiento, en bytes, desde el principio de un objeto del tipo especificado para su miembro especificado, incluido el relleno, si cualquier .

Original:

The macro offsetof expands to a constant of type std::size_t, the value of which is the offset, in bytes, from the beginning of an object of specified type to its specified member, including padding if any.

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Notas

Si type no es un tipo de normas de diseño, el comportamiento no está definido .

Original:

If type is not a standard-layout type, the behavior is undefined.

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Si member es un miembro estático o un miembro de la función, el comportamiento es indefinido .

Original:

If member is a static member or a function member, the behavior is undefined.

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El desplazamiento del primer elemento de un tipo de diseño de estándar es siempre cero (vacío-base optimización es obligatorio)

Original:

The offset of the first member of a standard-layout type is always zero (vacío-base optimización is mandatory)

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Posible implementación

#define offsetof(type,member) ((std::size_t) &(((type*)0)->member))

Ejemplo

#include <iostream>
#include <cstddef>
struct S {
    char c;
    double d;
};
int main()
{
    std::cout << "the first element is at offset " << offsetof(S, c) << '\n'
              << "the double is at offset " << offsetof(S, d) << '\n';
}

Output:

the first element is at offset 0
the double is at offset 8

Ver también

size_t	tipo entero sin signo devuelto por el operador sizeof Original: unsigned integer type returned by the sizeof operator The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (typedef)
is_standard_layout (C++11)	comprueba si un tipo es estándar de diseño de tipo Original: checks if a type is standard-layout type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (clase de plantilla)