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offsetof

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C++
 
Utilities-Bibliothek
 
Geben Sie Unterstützung
Grundtypen
Original:
Basic types
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Grundtypen
Feste Breite Integer-Typen (C++11)
nullptr_t(C++11)
offsetof
NULL
Numerische Grenzen
Original:
Numeric limits
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numeric_limits
C numerische begrenzt Schnittstelle
Laufzeit-Typinformationen
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Runtime type information
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Exterieur
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Type traits
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Primären Typ Kategorien
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Primary type categories
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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)
Typ Eigenschaften
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Type properties
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is_const(C++11)
is_volatile(C++11)
is_pod(C++11)
is_empty(C++11)
is_polymorphic(C++11)
is_abstract(C++11)
Unterstützte Operationen
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Supported operations
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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)
Beziehungen und Eigentum Abfragen
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Relationships and property queries
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is_same(C++11)
is_base_of(C++11)
is_convertible(C++11)
alignment_of(C++11)
rank(C++11)
extent(C++11)
Typ Modifikationen
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Type modifications
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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)
Typ Transformationen
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Type transformations
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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)
Typ-Trait-Konstanten
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Type trait constants
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integral_constant(C++11)
 
definiert in Header <cstddef>
#define offsetof(type, member) /*implementation-defined*/
Die Makro offsetof expandiert zu einer Konstante vom Typ std::size_t, deren Wert von den Offset in Bytes vom Anfang eines Objekts der angegebenen Typs in ihren angegebenen Elements einschließlich der Polsterung gegebenenfalls .. ist
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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Inhaltsverzeichnis

[Bearbeiten] Notes

Wenn type nicht ein Standard-Layout-Typ, ist das Verhalten undefiniert .
Original:
If type is not a standard-layout type, the behavior is undefined.
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Wenn member ein statisches Element oder ein Funktionselement ist, ist das Verhalten undefiniert .
Original:
If member is a static member or a function member, the behavior is undefined.
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Die des ersten Teils eines Standard-Tastaturbelegung Offset ist immer Null (empty-base-Optimierung ist obligatorisch)
Original:
The offset of the first member of a standard-layout type is always zero (empty-base-Optimierung is mandatory)
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[Bearbeiten] Mögliche Implementierung

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

[Bearbeiten] Beispiel

#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

[Bearbeiten] Siehe auch
vorzeichenloser Ganzzahltyp, der vom Operator sizeof zurückgegeben wird
Original:
unsigned integer type returned by the sizeof operator
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(typedef) [edit]
(C++11)
prüft, ob ein Typ ist Standard-Layout-Typ
Original:
checks if a type is standard-layout type
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(Klassen-Template) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/types/offsetof&oldid=28224“