Implementation defined behavior control

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Linguaggio C + +
Temi generali
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General topics
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Controllo del flusso
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Flow control
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Dichiarazioni esecuzione condizionale
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Conditional execution statements
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Iterazione dichiarazioni
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Iteration statements
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Vai dichiarazioni
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Jump statements
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Funzioni
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Functions
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dichiarazione di funzione
lambda funzione dichiarazione
funzione di modello
specificatore inline
eccezioni specifiche(deprecato)
noexcept specificatore(C++11)
Eccezioni
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Exceptions
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Spazi dei nomi
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Namespaces
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Tipi
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Types
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decltype specifier(C++11)
Specifiers
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Specifiers
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cv specificatori
Durata di stoccaggio specificatori
constexpr specificatore(C++11)
specificatore auto(C++11)
alignas specificatore(C++11)
Inizializzazione
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Initialization
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Letterali
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Literals
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Espressioni
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Expressions
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rappresentazioni alternative
Utilities
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Utilities
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Tipi
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Types
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typedef declaration
Tipo alias dichiarazione(C++11)
attributi(C++11)
Lancia
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Casts
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conversioni implicite
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
Fusione C-stile e funzionale
Occupazione della memoria
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Memory allocation
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Classi
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Classes
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Specifiche per una classe di funzioni proprietà
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Class-specific function properties
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Funzioni membro speciali
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Special member functions
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Modelli
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Templates
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classe template
funzione di modello
modello di specializzazione
parametri confezioni(C++11)
Varie
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Miscellaneous
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Montaggio in linea
 
 
Comportamento di attuazione definito è controllato dalla direttiva #pragma.
Original:
Implementation defined behavior is controlled by #pragma directive.
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Indice

[modifica]Sintassi

#pragmapragma_params

[modifica]Spiegazione

Direttiva Pragma controlla l'attuazione comportamento specifico del compilatore, ad esempio disabilitando gli avvisi del compilatore o mutate esigenze di allineamento. Qualsiasi pragma che non viene riconosciuto viene ignorato.
Original:
Pragma directive controls implementation-specific behavior of the compiler, such as disabling compiler warnings or changing alignment requirements. Any pragma that is not recognized is ignored.
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[modifica]Pragma standard

I seguenti tre pragma sono definiti dal linguaggio standard:
Original:
The following three pragmas are defined by the language standard:
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#pragma STDC FENV_ACCESS arg (1)
#pragma STDC FP_CONTRACT arg (2)
#pragma STDC CX_LIMITED_RANGE arg (3)
dove arg è o ON o OFF o DEFAULT.
Original:
where arg is either ON or OFF or DEFAULT.
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1)
Se impostato su ON, informa il compilatore che il programma accedere o modificare floating-point ambiente, il che significa che le ottimizzazioni che potrebbero sovvertire i test di bandiera e cambiamenti di modalità (ad esempio, l'eliminazione globale sottoespressione comune, il movimento di codice, e piegatura costante) sono proibiti. Il valore di default è definito dall'implementazione, solitamente OFF.
Original:
If set to ON, informs the compiler that the program will access or modify floating-point ambiente, which means that optimizations that could subvert flag tests and mode changes (e.g., global common subexpression elimination, code motion, and constant folding) are prohibited. The default value is implementation-defined, usually OFF.
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2)
Consente' appalto di espressioni in virgola mobile, che è ottimizzazioni che omettono gli errori di arrotondamento e virgola mobile eccezioni che sarebbero osservati se l'espressione è stata valutata esattamente come è scritto. Il valore di default è definito dall'implementazione, solitamente ON.
Original:
Allows contracting of floating-point expressions, that is optimizations that omit rounding errors and floating-point exceptions that would be observed if the expression was evaluated exactly as written. The default value is implementation-defined, usually ON.
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3)
Informa il compilatore che la moltiplicazione, divisione, e il valore assoluto dei numeri complessi possono usare semplificate formule matematiche, nonostante la possibilità di un overflow intermedio. La gamma dei valori passati a quelli funzione dovrebbe essere limitata. Il valore predefinito è OFF
Original:
Informs the compiler that multiplication, division, and absolute value of complex numbers may use simplified mathematical formulas, despite the possibility of intermediate overflow. The range of the values passed to those function is expected to be limited. The default value is OFF
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[modifica]Collegamenti esterni

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