How does setrlimit work when the value is 0?

rlimit.c

/*
 *
 * gcc -o rlimit rlimit.c
 */
#include <sys/resource.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

int main(int argv, char *argc[])
{
    struct rlimit r;
    int rv;

    r.rlim_max = r.rlim_cur = 0;

    if (setrlimit(RLIMIT_NOFILE, &r) != 0) {
        printf("setrlimit() failed with errno=%d, %s\n", errno, strerror(errno));
        exit(1);
    }

    if (getrlimit(RLIMIT_NOFILE, &r) != 0) {
        printf("getrlimit() failed with errno=%d, %s\n", errno, strerror(errno));
        exit(1);
    }

    printf("The soft limit is %llu\n", r.rlim_cur);
    printf("The hard limit is %llu\n", r.rlim_max);

    if (open("./rlimit.c", O_RDONLY)) {
        printf("open() failed with errno=%d, %s\n", errno, strerror(errno));
        exit(1);
    }

    return 0;
}