va_start


Initialization of variable for scanning argument list

[Classification]

Standard library

[Syntax]

#include <stdarg.h>

typedef char __near *va_list;

void va_start(va_list ap, last-named-argument);

[Description]

This function initializes variable ap so that it indicates the beginning (argument next to last-named-argument) of the list of the variable arguments.

To define function func having a variable arguments in a portable form, the following format is used.

#include    <stdarg.h>
 
void func(arg-declarations, ...) {
        va_list ap;
        type    argN;
 
        va_start(ap, last-named-argument);
        argN = va_arg(ap, type);
        va_end(ap);
}

Remark

arg-declarations is an argument list with the last-named-argument declared at the end. ", ..." that follows indicates a list of the variable arguments. va_listis the type of the variable (ap in the above example) used to scan the argument list.