C Programming - Variable Number of Arguments - Discussion

num = va_arg(ptr, int); // means num fetches the next element in the arguments that is of int type.

First time, it fetches the argument with 1 value. Neglecting the char * as it's not of type int
and second time, it fetches the argument with the 4 value.

It is the ellipse program it is used to send multiple number of argument.
fun("indiabix",1,4,7,11,0);//fun call.
va_list ptr;//ptr is pointer of va_list;
num=va_arg(ptr,int);//num is int type ;
So it print 4;

Here, va_list, it is only focused to the defined values in the func arguments. As same here, here we have char msg also, that is totally differ on output. Main thing is on First call of var_arg it takes the first value of the argument and second time by default it moves on next value, that's what we got the output as 4.

First of all va_start and va_arg are a macro defined in stdarg.h header file.

Va_list type is also defined in the stdarg.h,
Here ptr is va_list type variable.

Va_start macro and int parameter is used to initialize the va_list variable to an argument list.
Then we use va_arg macro and va_list variable to access each item in an argument list.
So num=va_arg(ptr,int); assigns integer value to num i.e.1.
Then the second statement num=va_arg(ptr,int);assigns 4 to num.
Then printf statement is given so 4 is printed and hence the output.

@All.

What was the answer to this code?

Please explain it with the answer.

#include<stdio.h>
Void main()
{
char CHAR='\328';
char CHAR1='\323'
printf("CHAR=%d\n CHAR1=%d\n",CHAR,CHAR1);
}

Good explanation @Shiv.

How to work this?

Please anyone explain me clearly.

1. There are three macros available in file "stdarg.h" --->.

- va_start: is used to initialize the pointer to the beginning of the list of optional arguments.
- va_arg: is used to advance the pointer to next argument *.
- va_list: va_list is like any other type.

The C library macro type va_arg(va_list ap, type) retrieves the next argument in the parameter list of the function with type.

Va_list ptr;

Va_list is not struct name than why we are creating a new pointer of Va_list type.

What is this? Is any data type?

Is Va_start is builtin function?

I am very confused please tell me the every thing in a proper manner.