sizeof operator
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Dimensione query dell'oggetto o del tipo
Original:
Queries size of the object or type
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Usato quando la dimensione reale dell'oggetto deve essere nota
Original:
Used when actual size of the object must be known
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Indice |
[modifica] Sintassi
sizeof( type )
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sizeof expression None
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Entrambe le versioni restituire una costante di tipo std::size_t.
Original:
Both versions return a constant of type std::size_t.
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[modifica] Spiegazione
1)restituisce la dimensione in byte della rappresentazione di oggetti di type.
2) Original:
returns size in bytes of the object representation of type.
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restituisce la dimensione in byte della rappresentazione oggetto del tipo, che sarebbe restituito da expression, se valutata.
Original:
returns size in bytes of the object representation of the type, that would be returned by expression, if evaluated.
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[modifica] Note
sizeof(char), sizeof(signed char) e sizeof(unsigned char) sempre tornare 1, indipendentemente dal valore di 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 non può essere utilizzato con diversi tipi di funzione, tipi incompleti o bit-field lvalue.
Original:
sizeof cannot be used with function types, incomplete types, or bit-field lvalues.
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Quando applicato ad un tipo di riferimento, il risultato è la dimensione del tipo indicato.
Original:
When applied to a reference type, the result is the size of the referenced type.
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Quando applicato ad un tipo di classe, il risultato è la dimensione di un oggetto di tale classe più qualsiasi imbottitura supplementare richiesto per collocare tale oggetto in un array.
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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Quando viene applicato a un tipo di classe vuota, restituisce sempre 1.
Original:
When applied to an empty class type, always returns 1.
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[modifica] Parole chiave
[modifica] Esempio
L'output di esempio corrisponde a un sistema con puntatori a 64 bit e 32-bit 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'; }
Output:
size of empty class: 1 size of pointer : 8 size of array of 10 int: 40
