C中可变参数列表操作

使用头文件<stdarg.h>中定义的宏va_list, va_start, va_arg, va_end，K&R的《The C Programming Language》中的例子：

#include <stdarg.h>

/* minprintf: minimal printf with variable argument list */
void minprintf(char *fmt, ...)
{
    va_list ap; /* points to each unnamed arg in turn */
    char *p, *sval;
    int ival;
    double dval;
   
    va_start(ap, fmt); /* make ap point to 1st unnamed arg */
    for (p = fmt; *p; p++) {
        if (*p !='%') {
            putchar(*p);
            continue;
        }
        switch (*++p) {
        case 'd':
            ival = va_arg(ap, int);
            printf("%d", ival);
            break;
        case 'f':
            dval = va_arg(ap, double);
            printf("%f", dval);
            break;
        case 's':
            for (sval = va_arg(ap, char *); *sval; sval++)
            putchar(*sval);
            break;
        default:
            putchar(*p);
            break;
        }
    }
    va_end(ap); /* clean up when done */
}