Kwargs (keyword arguments) in C programming language. (Positional and optional arguments)

kwargs-in-c.c

#include <stdio.h>

/** KW(fn): Just a macro that expands to fn_kwargs
 *      - fn: the function's name
 */
#define KW(fn) struct fn ## _kwargs

/** def_kwargs(fn, definition)
 *      - fn: the function's name
 *      - definition: a block with internal definition of arguments
 *
 *  Usage:
 *      def_kwargs(function, { int arg1; double arg2 });
 *
 *  Expansion:
 *      struct function_kwargs { int arg1; double arg2 };
 */
#define def_kwargs(fn, definition) KW(fn) definition;

/**  **  Implementation  **  **/

/** struct print_user_kwargs
 *      - char [65]name;
 *      - char [65]repository;
 *      - int commits;
 */
def_kwargs(print_user, { char name[65]; char repository[65]; int commits; });

/** print_user(unsigned id, **kwargs): Prints the user's information
 *      - id: it's the user's id
 *      - kwargs:
 *        obligatory:
 *          - int commits: the amount of commits in that repo
 *        optionals:
 *          - char [65]name = "Anonymous": the user's name
 *          - char [65]repository = "Private": the user's repo
 */
#define print_user(id, ...)                                     \
        internal_print_user((id), (KW(print_user)){             \
                .name = "Anonymous", .repository = "Private",   \
                __VA_ARGS__ })

static void internal_print_user(unsigned int id, KW(print_user) kwargs)
{
        // don't forget to #include <stdio.h>
        printf("ID: %d\n",              id);
        printf("  user: %s\n",          kwargs.name);
        printf("  repository: %s\n",    kwargs.repository);
        printf("  commits: %d\n",       kwargs.commits);
        return;
}

int main(void)
{
	print_user(10, .name = "RickBarretto", .repository = "proto.c", .commits = 15);
}