名前空間
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offsetof

提供: cppreference.com
< cpp‎ | types

 
 
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支援を入力します (basic types, RTTI, type traits)
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関数オブジェクト
initializer_list(C++11)
bitset
hash(C++11)
関係演算子
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Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
ペアとタプル
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Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
フォワード、スワップ、および移動
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Swap, forward and move
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
支援を入力します
基本的なタイプ
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Basic types
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基本的なタイプ
固定幅の整数型 (C++11)
nullptr_t(C++11)
offsetof
NULL
数値の限界
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Numeric limits
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numeric_limits
Cの数値は、インターフェイスを制限します
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Runtime type information
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型の特徴
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Type traits
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プライマリタイプカテゴリ
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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)
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is_member_pointer(C++11)
is_member_object_pointer(C++11)
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Type properties
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is_const(C++11)
is_volatile(C++11)
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is_empty(C++11)
is_polymorphic(C++11)
is_abstract(C++11)
サポートされる操作
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Supported operations
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is_constructible
is_trivially_constructible
is_nothrow_constructible
(C++11)
(C++11)
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is_default_constructible
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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)
リレーションシップとプロパティクエリ
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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)
型の変更
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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)
型変換
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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)
形質定数を入力します
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Type trait constants
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integral_constant(C++11)
 
Defined in header <cstddef>
#define offsetof(type, member) /*implementation-defined*/
マクロoffsetofstd::size_t型の定数に展開され、値が指定された型のオブジェクトの先頭から、もしあればパディングを含め、指定したメンバーに、バイト単位でオフセットされます.
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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目次

[編集] ノート

typeは、標準レイアウト型でない場合、動作は未定義です.
Original:
If type is not a standard-layout type, the behavior is undefined.
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memberは静的メンバあるいは関数メンバである場合、動作は未定義です.
Original:
If member is a static member or a function member, the behavior is undefined.
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標準レイアウトの種類の最初のメンバのオフセット(空のベース最適化必須です)は常にゼロです
Original:
The offset of the first member of a standard-layout type is always zero (空のベース最適化 is mandatory)
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[編集] 可能な実装

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

[編集]

#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

[編集] も参照してください

sizeof子によって戻された符号なし整数型
Original:
unsigned integer type returned by the sizeof operator
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(typedefです) [edit]
タイプかどうかをチェックするには、標準レイアウトタイプです
Original:
checks if a type is standard-layout type
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(クラステンプレート) [edit]