Function is_leap_year

app/redis-6.2.6/src/localtime.c:52–57

This is a safe version of localtime() which contains no locks and is * fork() friendly. Even the _r version of localtime() cannot be used safely * in Redis. Another thread may be calling localtime() while the main thread * forks(). Later when the child process calls localtime() again, for instance * in order to log something to the Redis log, it may deadlock: in the copy * of the address spac

 * designed to work with what time(NULL) may return, and to support Redis
 * logging of the dates, it's not really a complete implementation. */
static int is_leap_year(time_t year) {
    if (year % 4) return 0;         /* A year not divisible by 4 is not leap. */
    else if (year % 100) return 1;  /* If div by 4 and not 100 is surely leap. */
    else if (year % 400) return 0;  /* If div by 100 *and* not by 400 is not leap. */
    else return 1;                  /* If div by 100 and 400 is leap. */
}

void nolocks_localtime(struct tm *tmp, time_t t, time_t tz, int dst) {
    const time_t secs_min = 60;