/*
 * stdarg.h
 *
 * Provides facilities for stepping through a list of function arguments of
 * an unknown number and type.
 *
 * NOTE: Gcc should provide stdarg.h, and I believe their version will work
 *       with crtdll. If necessary I think you can replace this with the GCC
 *       stdarg.h.
 *
 * Note that the type used in va_arg is supposed to match the actual type
 * *after default promotions*. Thus, va_arg (..., short) is not valid.
 *
 * This file is part of the Mingw32 package.
 *
 * Contributors:
 *  Created by Colin Peters <colin@bird.fu.is.saga-u.ac.jp>
 *
 *  THIS SOFTWARE IS NOT COPYRIGHTED
 *
 *  This source code is offered for use in the public domain. You may
 *  use, modify or distribute it freely.
 *
 *  This code is distributed in the hope that it will be useful but
 *  WITHOUT ANY WARRANTY. ALL WARRANTIES, EXPRESS OR IMPLIED ARE HEREBY
 *  DISCLAMED. This includes but is not limited to warranties of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * $Revision: 1.2 $
 * $Author: noer $
 * $Date: 1998/10/10 00:51:16 $
 *
 */

#ifndef _STDARG_H_
#define _STDARG_H_

/*
 * Don't do any of this stuff for the resource compiler.
 */
#ifndef RC_INVOKED

/* 
 * I was told that Win NT likes this.
 */
#ifndef _VA_LIST_DEFINED
#define _VA_LIST_DEFINED
#endif

#ifndef    _VA_LIST
#define _VA_LIST
typedef char* va_list;
#endif


/*
 * Amount of space required in an argument list (ie. the stack) for an
 * argument of type t.
 */
#define __va_argsiz(t)    \
    (((sizeof(t) + sizeof(int) - 1) / sizeof(int)) * sizeof(int))


/*
 * Start variable argument list processing by setting AP to point to the
 * argument after pN.
 */
#ifdef    __GNUC__
/*
 * In GNU the stack is not necessarily arranged very neatly in order to
 * pack shorts and such into a smaller argument list. Fortunately a
 * neatly arranged version is available through the use of __builtin_next_arg.
 */
#define va_start(ap, pN)    \
    ((ap) = ((va_list) __builtin_next_arg(pN)))
#else
/*
 * For a simple minded compiler this should work (it works in GNU too for
 * vararg lists that don't follow shorts and such).
 */
#define va_start(ap, pN)    \
    ((ap) = ((va_list) (&pN) + __va_argsiz(pN)))
#endif


/*
 * End processing of variable argument list. In this case we do nothing.
 */
#define va_end(ap)    ((void)0)


/*
 * Increment ap to the next argument in the list while returing a
 * pointer to what ap pointed to first, which is of type t.
 *
 * We cast to void* and then to t* because this avoids a warning about
 * increasing the alignment requirement.
 */

#define va_arg(ap, t)                    \
     (((ap) = (ap) + __va_argsiz(t)),        \
      *((t*) (void*) ((ap) - __va_argsiz(t))))

#endif /* Not RC_INVOKED */

#endif /* not _STDARG_H_ */

/*
    Name: 可变参数
    Copyright: 52coder.net
    Author: 52coder
    Date: 04/09/17 23:44
    Description: 可变参数
*/
#include <stdio.h>
#include <stdarg.h>
void print_args(int count, ...);
int main(int argc, char* argv[]) 
{
    print_args(5,1,2,3,4,5);
    return 0;
}
void print_args(int count, ...) 
{
    int i, value;
    va_list arg_ptr;
    va_start(arg_ptr, count);
    for(i=0; i<count; i++) {
        value = va_arg(arg_ptr,int);
        printf("position %d = %d\n", i+1, value);
    }
    va_end(arg_ptr);
}

/*
    Name: 可变参数
    Copyright: 52coder.net
    Author: 52coder
    Date: 04/09/17 23:44
    Description: 可变参数
*/
#include <stdio.h>
#include <stdarg.h>

double average(int num,...)
{
    
    va_list valist;
    double sum = 0.0;
    int i;
    
    /* 为 num 个参数初始化 valist */
    va_start(valist, num);
    
    /* 访问所有赋给 valist 的参数 */
    for (i = 0; i < num; i++)
    {
        sum += va_arg(valist, int);
    }
    /* 清理为 valist 保留的内存 */
    va_end(valist);
    
    return sum/num;
}

int main()
{
    printf("Average of 2, 3, 4, 5 = %f\n", average(4, 2,3,4,5));
    printf("Average of 5, 10, 15 = %f\n", average(3, 5,10,15));
}

#include <stdio.h>
#include <stdarg.h>
#include <assert.h>
void tiny_printf(char * format,...)
{
    int i;
    va_list ap;
    va_start(ap,format);
    for(i = 0;format[i]!='\0';i++)
    {
        switch(format[i])
        {
            case 's':
                printf("%s ",va_arg(ap,char*));
                break;
            case 'd':
                printf("%d ",va_arg(ap,int));
                break;
            default:
                assert(0);
        }
    }
    va_end(ap);
    putchar('\n');
}
int main()
{
    tiny_printf("sdd","result..",3,5);
    return 0;
}