va_arg macro — Gets next argument
T va_arg(va_list ap, T)
The va_arg
macro fetches
the next argument, which must be of type T
. The ap
parameter must have been initialized by
calling va_start
. The type
T
must be a type that results
from the standard type promotions (Chapter 3) or else the behavior is
undefined. For example, T
cannot
be char
, but must be int
because the standard promotion of type
char
is to type int
(or, in rare circumstances, unsigned
int
). The behavior is undefined if there
is no next argument.