sizeof operator
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Запросы размера объекта или типа
Original:
Queries size of the object or type
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Используется, когда фактический размер объекта должны быть известны
Original:
Used when actual size of the object must be known
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Содержание |
[править] Синтаксис
sizeof( type )
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sizeof expression None
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Обе версии возвращают константу типа std::size_t.
Original:
Both versions return a constant of type std::size_t.
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[править] Объяснение
1)возвращает размер в байтах объекта представления type.
2) Original:
returns size in bytes of the object representation of type.
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возвращает размер в байтах объекта представления типа, который будет возвращен по expression, если оценивать.
Original:
returns size in bytes of the object representation of the type, that would be returned by expression, if evaluated.
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[править] Notes
sizeof(char), sizeof(signed char), и sizeof(unsigned char) всегда возвращаются 1, независимо от стоимости CHAR_BIT.
Original:
sizeof(char), sizeof(signed char), and sizeof(unsigned char) always return 1, regardless of the value of CHAR_BIT.
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SizeOf не может быть использована с функцией типа, неполные типы, или битовые поля lvalues .
Original:
sizeof cannot be used with function types, incomplete types, or bit-field lvalues.
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При нанесении на ссылочный тип, то результат будет размер указанного типа.
Original:
When applied to a reference type, the result is the size of the referenced type.
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При применении к типу класса, в результате размер объекта этого класса плюс любые дополнительные обивка требуется разместить такой объект в массиве.
Original:
When applied to a class type, the result is the size of an object of that class plus any additional padding required to place such object in an array.
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При нанесении на пустой тип класса, всегда возвращает 1.
Original:
When applied to an empty class type, always returns 1.
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[править] Ключевые слова
[править] Пример
Например выходе соответствует системе с 64-разрядными указателями и 32-битных Int .
Original:
The example output corresponds to a system with 64-bit pointers and 32-bit int.
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#include <iostream> struct Empty {}; struct Bit {unsigned bit:1; }; int main() { Empty e; Bit b; std::cout << "size of empty class: " << sizeof e << '\n' << "size of pointer : " << sizeof &e << '\n' // << "size of function: " << sizeof(void()) << '\n' // compile error // << "size of incomplete type: " << sizeof(int[]) << '\n' // compile error // << "size of bit field: " << sizeof b.bit << '\n' // compile error << "size of array of 10 int: " << sizeof(int[10]) << '\n'; }
Вывод:
size of empty class: 1 size of pointer : 8 size of array of 10 int: 40
