C言語の関数可変パラメータ

前のコード:

#include<cstdarg> #include<iostream> #include<string>

using namespace std; void error(char* format,...){//        ，   ...       va_list ap; int d,flag; char c, *s; va_start(ap,*format);// args            ，va_start,va_end   

    while (*format){ switch (*format) { case 's':              /* string */

                   if(!flag) break; s = va_arg(ap, char *); cout<<s;flag=0; break; case 'd':              /* int */

                    if(!flag) break; d = va_arg(ap, int); cout<<d;flag=0; break; case 'c':              /* char */

                   /* need a cast here since va_arg only takes fully promoted types */

                   if(!flag) break; c = (char) va_arg(ap, int); cout<<c;flag=0; break; case '%': flag=1; break; default: putchar(*format); } format++; } putchar('
'); /*for(i=0;i<args;i++){//         //printf("%d",va_arg(ap,int)); }*/ va_end(ap);//destroy va_list;

} int main(){ char s[]="rich"; error("I am %s,I have %d %c",s,100,'$'); //getchar();

    return 0; }
  error()   printf           。
#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);
    va_arg ，     ap       ，  man  ：
va_arg()
 The va_arg() macro expands to an expression that has the type and value
 of the next argument in the call. The argument ap is the va_list ap
 initialized by va_start(). Each call to va_arg() modifies ap so that
 the next call returns the next argument. The argument type is a type
 name specified so that the type of a pointer to an object that has the
 specified type can be obtained simply by adding a * to type.

 The first use of the va_arg() macro after that of the va_start() macro
 returns the argument after last. Successive invocations return the
 values of the remaining arguments.

 If there is no next argument, or if type is not compatible with the
 type of the actual next argument (as promoted according to the default
 argument promotions), random errors will occur.

 If ap is passed to a function that uses va_arg(ap,type) then the value
 of ap is undefined after the return of that function.