alignas specifier
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指定的种类或对象的对齐要求，.
Original:
Specifies the alignment requirement of a type or an object.
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目录 |
[编辑] 语法
alignas( expression )
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（C++11 起） | ||||||||
alignas( type-id )
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（C++11 起） | ||||||||
[编辑] 解释
alignas说明变量或类的数据成员的声明，或者它可以被应用到一个类/结构/联合或枚举的定义.
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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alignas(expression)的形式，当使用expression是一个不可分割的常量表达式的计算结果为正值，声明的实体将有对齐要求设置的expression准确的结果，除非它会削弱类型的自然对齐要求的。
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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当使用的形式alignas(type)，是完全等同于alignas(alignof(type))，也就是声明的实体的对齐要求，将是平等的对齐要求，type
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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[编辑] 注释
alignas(0)有没有效果.
Original:
alignas(0) has no effect.
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当多个alignas说明适用于相同的变量或类的，最严格的人用了
Original:
When multiple alignas specifiers are applied to the same variable or class, the strictest one is used.
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C语言定义alignas作为一个宏在头<stdalign.h>，但在C + +中，这是一个关键字，并在头<stdalign.h>和<cstdalign>没有定义这样的宏。不必说什么，否则情况更糟，不过，他们定义宏不变__alignas_is_defined.
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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[编辑] 关键字
[编辑] 为例
// 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];
[编辑] 另请参阅
| alignof operator | queries alignment requirements of a type （C++11 起） |
| （C++11） |
获得该类型的对齐要求 Original: obtains the type's alignment requirements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （类模板） |
