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alignas specifier

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decltype specifier (C++11)
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CV指定
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constexprの指定子 (C++11)
自動指定 (C++11)
alignas指定子 (C++11)
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インラインアセンブリ
 
型またはオブジェクトの整列要求を指定します.
Original:
Specifies the alignment requirement of a type or an object.
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目次

[編集] 構文

alignas( expression ) (C + + 11以来)
alignas( type-id ) (C + + 11以来)

[編集] 説明

alignas指定子は、変数の宣言やクラスのデータメンバに適用することができる、またはそれはクラス/構造体/共用体または列挙型の定義に適用することができます.
Original:
The alignas specifier may be applied to the declaration of a variable or a class data member, or it can be applied to the definition of a class/struct/union or enum.
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フォームalignas(expression)で使用され、expressionが正の値に評価される整数定数式である場合、宣言された実体は、それが型の自然境界整列要件を弱めたい場合を除いて、expressionのまさに結果に設定され、その整列要求を持つことになります。
Original:
When used in form alignas(expression), and expression is an integral constant expression that evaluates to a positive value, the declared entity will have its alignment requirement set to exactly the result of the expression, except if it would weaken the natural alignment requirement of the type.
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フォームalignas(type)で使用する場合は、宣言された実体の整列要件がalignas(alignof(type))のアラインメント要件等しくなり、あるtype、とまったく同じです
Original:
When used in form alignas(type), is exactly equivalent to alignas(alignof(type)), that is, the alignment requirement of the declared entity will be equal the alignment requirement of type
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[編集] ノート

alignas(0)効果がありません.
Original:
alignas(0) has no effect.
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複数alignas指定子は同じ変数またはクラスに適用されると、厳しいものが使用され.
Original:
When multiple alignas specifiers are applied to the same variable or class, the strictest one is used.
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C言語は、ヘッダーalignasでプリプロセッサマクロとして<stdalign.h>を定義していますが、C + +でこれがキーワードであり、ヘッダが<stdalign.h><cstdalign>ようなマクロを定義しないでください。彼らは、しかし、マクロ定数__alignas_is_definedを定義しない.
Original:
The C language defines alignas as a preprocessor macro in the header <stdalign.h>, but in C++ this is a keyword, and the headers <stdalign.h> and <cstdalign> do not define such macro. They do, however, define the macro constant __alignas_is_defined.
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[編集] キーワード

alignas

[編集]

// every object of type sse_t will be aligned to 16-byte boundary
struct alignas(16) sse_t
{
  float sse_data[4];
};
 
// the array "cacheline" will be aligned to 128-byte boundary
char alignas(128) cacheline[128];



[編集] も参照してください

alignof operator queries alignment requirements of a type (C + + 11以来) [edit]
型の整列要求を取得します
Original:
obtains the type's alignment requirements
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(クラステンプレート) [edit]