Zilog ZUSBOPTS Manual do Utilizador descarregar pdf (Página 484)

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101

Standard Functions UM017105-0511

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Zilog Developer Studio II – ZNEO™

User Manual

Example

The function f1 gathers into an array a list of arguments that are pointers to strings (but not

more than MAXARGS arguments), then passes the array as a single argument to function

f2. The number of pointers is specified by the first argument to f1.

#include <stdarg.h>

extern void f2(int n, char *array[]);

#define MAXARGS 31

void f1(int n_ptrs,...) {

va_list ap; 

char *array[MAXARGS];

int ptr_no = 0;

if (n_ptrs > MAXARGS)

n_ptrs = MAXARGS;

va_start(ap, n_ptrs);

while (ptr_no < n_ptrs)

array[ptr_no++] = va_arg(ap, char *);

va_end(ap);

f2(n_ptrs, array);

}

Each call to f1 has in scope the definition of the function of a declaration such as void

f1(int, ...);

vprintf

Equivalent to printf, with the variable argument list replaced by arg, which has been ini-

tialized by the

va_start macro (and possibly subsequent va_arg calls). The vprintf

function does not invoke the

va_end function.

Synopsis

#include <stdarg.h>

#include <stdio.h>

int vprintf(const char *format, va_list arg);

Returns

The number of characters transmitted or a negative value if an output error occurred.

Example

va_list va;

/* initialize the variable argument va here */

vprintf("%d %d %d",va);

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