RTC set time overflow after January 1, 2070

rtc_set_time_overflow.c

// Compile:
//   gcc -o test_ioctl_tm_struct test_ioctl_tm_struct.c
// Run on Linux:
//   ./test_ioctl_tm_struct
// Expected output:
//   RTC time set successfully.
//
// Actual result:
//   Failed to set RTC time: Invalid argument
//
// Notes:
//   Originally caused by `hwclock --systohc`

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <time.h>
#include <unistd.h>

int main() {
    int rtc_fd;
    struct rtc_time rtc_tm;

    // Open the real-time clock device
    rtc_fd = open("/dev/rtc0", O_RDWR);
    if (rtc_fd == -1) {
        perror("Failed to open RTC device");
        return 1;
    }

    // Set the time structure
    rtc_tm.tm_sec = 0;
    rtc_tm.tm_min = 0;
    rtc_tm.tm_hour = 0;
    rtc_tm.tm_mday = 1;
    rtc_tm.tm_mon = 0;  // January (0-indexed)
    rtc_tm.tm_year = 170;  // Years since 1900
    rtc_tm.tm_wday = 0;
    rtc_tm.tm_yday = 0;
    rtc_tm.tm_isdst = 0;

    // Use ioctl to set the RTC time
    if (ioctl(rtc_fd, RTC_SET_TIME, &rtc_tm) == -1) {
        perror("Failed to set RTC time");
        close(rtc_fd);
        return 1;
    }

    printf("RTC time set successfully.\n");

    // Close the RTC device
    close(rtc_fd);

    return 0;
}