https://www.reddit.com/r/C_Programming/comments/yjbe62/combining_default_named_and_positional_arguments/

{{{c
struct fooParam { int x, y; };
#define foo(...) foo((struct fooParam) {__VA_ARGS__ })
int (foo)(struct fooParam p) {
	return p.x + p.y;
}

int main() {
	printf("%d\n", foo(.y = 20, .x = 10));
}
}}}