Optional independent variables for C-language functions

function: macro va_arg () is used to pass a variable-length argument list to a function.

1. First, you must call Va_start () to pass a valid argument list va_list and the first argument of the function coercion. The first parameter represents the number of arguments that will be passed.
2. Second, call Va_arg () to pass the argument list va_list and the type of the parameter that will be returned. The return value of Va_arg () is the current parameter.
3. Again, repeat the call to all parameters Va_arg ()
4. Finally, it is necessary to call Va_end () to pass va_list to the completion of the purge.

1#include <stdio.h>2#include <stdarg.h>3 intSumint, ... );4 5     intMainvoid ) 6 {7 8     9 Ten       intAnswer = SUM (4,4,3,2,1 ); One  Aprintf"The answer is%d\n", answer); -  -      the  -       return(0 ); -  - } +  -      +  A     intSumintnum, ...)  at { -  -       intAnswer =0; -  - va_list argptr; -  in va_start (argptr, num); -  to        for(; num >0; num-- ) +  -Answer + = Va_arg (Argptr,int ); the  * va_end (argptr); $ Panax Notoginseng       return(answer); -  the}

This code shows that they are 4+3+2+1.

Optional independent variables for C-language functions