va_arg
[extract value from argument list]
SYNOPSIS #include <stdarg.h> type va_arg(va_list ap, type);
DESCRIPTION
va_arg
returns the next unprocessed value from a variable argument list, ap
(which you must previously create with va_start).
Specify the type for the value as the second parameter to the macro, type.
You may pass a va_list object, ap, to a subfunction, and use va_arg from the subfunction rather than from the function actually declared with an ellipsis in the header; however, in that case you may only use va_arg from the subfunction. ANSI C does not permit extracting successive values from a single variable-argument list from different levels of the calling stack.
There is no mechanism for testing whether there is actually a next argument available; you might instead pass an argument count (or some other data that implies an argument count) as one of the fixed arguments in your function call.
RETURNS
va_arg
returns the next argument, an object of type, type.
COMPLIANCE
ANSI C requires va_arg.