How do I define a function in C (specifically C89/C90, C99 and newer) which can take a variable number of arguments of any datatype.
The same way as functions like : printf(), scanf(), etc.
To make a function accept a variable number of arguments in C you need to include the header
#include <stdarg.h>
printf() in C is an example of a variadic function that takes variable number of arguments.
int printf(const char *fmt, ...)