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Toute la documentation sur la certification Linux LPI

stdarg

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stdarg, va_start, va_arg, va_end, va_copy - ¸Ä¿ô¡¦·¿¤¬²ÄÊѤʰú¿ô¥ê¥¹¥È

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#include <stdarg.h>

void va_start(va_list ap, last);
type va_arg(va_list ap, type);
void va_end(va_list ap);
void va_copy(va_list dest, va_list src);

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va_start

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va_arg

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va_end

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va_copy

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    va_list aq = ap;

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    va_list aq;

    *aq = *ap;

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    va_list aq;

    va_copy(aq, ap);

    ...

    va_end(aq);

va_copy() ¤¬¼Â¹Ô¤µ¤ì¤ë¤´¤È¤Ë¡¢ Âбþ¤¹¤ë va_end() ¤òƱ¤¸´Ø¿ôÆâ¤Ç¼Â¹Ô¤·¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£ ¤³¤Î̾Á°¤Ï¤Þ¤À draft proposal ¤Ê¤Î¤Ç¡¢ va_copy() ¤ÎÂå¤ï¤ê¤Ë __va_copy ¤òÍѤ¤¤ë¥·¥¹¥Æ¥à¤â¤¢¤ë¡£

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#include <varargs.h>



void

foo(va_alist)

    va_dcl

{

    va_list ap;



    va_start(ap);

    while(...) {

        ...

        x = va_arg(ap, type);

        ...

    }

    va_end(ap);

}

va_start ¥Þ¥¯¥í¤Ë '{' ¤ò´Þ¤ß¡¢ va_end ¥Þ¥¯¥í¤ËÂбþ¤¹¤ë '}' ¤ò´Þ¤à¥·¥¹¥Æ¥à¤â¤¢¤ë¤Î¤Ç¡¢ ¤³¤ÎÆó¤Ä¤Î¥Þ¥¯¥í¤ÏƱ¤¸´Ø¿ô¤Ë¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£

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varargs ¥Þ¥¯¥í¤È¤Ï°Û¤Ê¤ê¡¢ stdarg ¥Þ¥¯¥í¤Ç¤Ï¸ÇÄê°ú¤­¿ô¤Ê¤·¤Ç´Ø¿ô¤ò»ØÄꤹ¤ë¤³¤È¤¬µö¤µ¤ì¤Æ¤¤¤Ê¤¤¡£ ¤³¤ì¤Ï varargs ¥Ù¡¼¥¹¤Î¥³¡¼¥É¤ò stdarg ¤Î¥³¡¼¥É¤Ë½ñ¤­´¹¤¨¤ë¤È¤­¤Ë¡¢ÌÌÅݤʺî¶È¤Î¤â¤È¤Ë¤Ê¤ë¡£ ¤Þ¤¿¡¢¤¹¤Ù¤Æ¤Î°ú¤­¿ô¤ò va_list ¤È¤·¤Æ²ÄÊѸĻØÄꤷ¤¿¤¤¤è¤¦¤Ê¾ì¹ç (vfprintf(3) ¤Ê¤É) ¤Ë¤â¾ã³²¤È¤Ê¤ë¡£

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´Ø¿ô foo ¤Ï½ñ¼°Ê¸»ú¤«¤é¤Ê¤ëʸ»úÎó¤ò¼õ¤±Æþ¤ì¡¢¤½¤Î½ñ¼°Ê¸»ú¤ËÂбþ¤¹¤ë·¿¤Ç²ÄÊѸĤΠ°ú¤­¿ô¤òÆɤ߹þ¤ß¡¢°õ»ú¤¹¤ë¡£

#include <stdio.h>

#include <stdarg.h>



void

foo(char *fmt, ...)

{

    va_list ap;

    int d;

    char c, *s;



    va_start(ap, fmt);

    while (*fmt)

        switch(*fmt++) {

        case 's':              /* string */

            s = va_arg(ap, char *);

            printf("string %s\n", s);

            break;

        case 'd':              /* int */

            d = va_arg(ap, int);

            printf("int %d\n", d);

            break;

        case 'c':              /* char */

            /* need a cast here since va_arg only

               takes fully promoted types */

            c = (char) va_arg(ap, int);

            printf("char %c\n", c);

            break;

        }

    va_end(ap);

}