15. Variable-Length Argument Lists

15.1 I heard that you have to #include <stdio.h> before calling printf. Why?

15.2 How can %f be used for both float and double arguments in printf?

15.3 Why don't function prototypes guard against mismatches in printf's arguments?

15.4 How can I write a function that takes a variable number of arguments?

15.5 How can I write a function that takes a format string and a variable number of arguments, like printf, and passes them to printf to do most of the work?

15.6 How can I write a function analogous to scanf, that calls scanf to do most of the work?

15.7 I have a pre-ANSI compiler, without <stdarg.h>. What can I do?

15.8 How can I discover how many arguments a function was actually called with?

15.9 My compiler isn't letting me declare a function that accepts only variable arguments.

15.10 Why isn't "va_arg(argp, float)" working?

15.11 I can't get va_arg to pull in an argument of type pointer-to-function.

15.12 How can I write a function which takes a variable number of arguments and passes them to some other function ?

15.13 How can I call a function with an argument list built up at run time?