va_start

<metanoindex/>

 

C++

Linguaggio

Concetti

Libreria di Utilità

Stringhe

Contenitori

Algoritmi

Iteratori

Libreria matematca

Input/output

Localizzazione

Espressioni regolari (C++11)

Operazioni atomicche (C++11)

Multithreading (C++11)

 

Utilità libreria

Tipo di supporto (basic types, RTTI, type traits)

Gestione della memoria dinamica

La gestione degli errori

Programma di utilità

Funzioni variadic

Data e ora

Funzione oggetti

initializer_list (C++11)

bitset

hash (C++11)

Gli operatori relazionali Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Coppie e tuple Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, in avanti e spostare Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Funzioni variadic

va_start

va_arg

va_copy

va_end

va_list

 

<tbody>

Elemento definito nell'header <cstdarg>

<tbody> </tbody>

void va_start(va_list ap, parm_n);

</tbody>

La macro va_start permette di accedere ai seguenti argomenti variabili l'argomento di nome parm_n.

Original:

The va_start macro enables access to the variable arguments following the named argument parm_n.

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va_start deve essere richiamato con un istanza con un oggetto valido va_list ap prima delle chiamate al va_arg.

Original:

va_start should be invoked with an instance to a valid va_list object ap before any calls to va_arg.

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Parametri

ap	-	un'istanza del tipo va_list Original: an instance of the va_list type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
parm_n	-	il parametro denominato precedente il primo parametro variabile Original: the named parameter preceding the first variable parameter The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Expanded valore

(Nessuno)

Original:

(none)

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Esempio

#include <iostream>
#include <cstdarg>

int add_nums(int count, ...) 
{
    int result = 0;
    va_list args;
    va_start(args, count);
    for (int i = 0; i < count; ++i) {
        result += va_arg(args, int);
    }
    return result;
}

int main() 
{
    std::cout << add_nums(4, 25, 25, 50, 50) << '\n';
}

Output:

150

Vedi anche

va_arg	accede l'argomento successivo funzione variadic Original: accesses the next variadic function argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione macro)
va_end	termina attraversamento degli argomenti della funzione variadic Original: ends traversal of the variadic function arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione macro)