c语言可变参数实现示例

#include <stdio.h>
#include <stdlib.h> // itoa() and ltoa()
#include <string.h> // strcat() and strlen()

// echo("$i, $s, $l, $c", arg1, arg2, arg3, arg4)
// $i -- int, $s -- string, $l -- long, $c -- char
void echo(char *fmt, ...)

    int i, fmtlen = strlen(fmt);
    int *args = (int *)((char *)(&fmt) +sizeof(char *));

    char cbuff = '\0', nbuff = '\0'; // #define BUFSIZ 512 in <stdio.h>

    for (i = 0; i < fmtlen; i++)
   
        if (('$' == fmt) && ((i + 1) < fmtlen))
       
            switch (fmti + 1)
           
            case 's': strcat(cbuff, (char *)(*args));
                break;
            case 'c': cbuffstrlen(cbuff) = (char)(*args);
                break;
            case 'i': itoa(*args, nbuff, 10); strcat(cbuff, nbuff);
                break;
            case 'l': ltoa((long)(*args), nbuff, 10); strcat(cbuff, nbuff);
                break;
            default: break;
           
            ++args, ++i;
       
        else
            cbuffstrlen(cbuff) = fmt;
   

    cbuffstrlen(cbuff) + 1 = '\0';
    fputs(cbuff, stdout);

int main()

    echo("arg_list = $i, $s, $l, $c", 2, "hello", 8, 'a'); // Si -- %d, $s -- %s, $l -- %ld, $c -- %c

    return 0;