C Primer Plus®, Third Edition

Variable Arguments: stdarg.h

The stdarg.h header file provides a means for defining a function having a variable number of arguments. The prototype for such a function should have a parameter list with at least one parameter followed by ellipses:

void f1(int n, ...);                 /* valid   */
int f2(int n, const char * s, ...);  /* valid   */
double  f3(...);                     /* invalid */

In the following, the term lastparm is the identifier used for the last parameter preceding the ellipses. In the preceding examples, lastparm would be n for the first case and s for the second case.

The header file declares a va_list type to represent a data object used to hold the parameters corresponding to the ellipses part of the parameter list. Table F.11 lists three macros to be used ...