#include "time_impl.h"
#include <errno.h>

time_t mktime(struct tm* tm) {
    struct tm new;
    long opp;
    long long t = __tm_to_secs(tm);

    __secs_to_zone(t, 1, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);

    if (tm->tm_isdst >= 0 && new.tm_isdst != tm->tm_isdst)
        t -= opp - new.__tm_gmtoff;

    t -= new.__tm_gmtoff;
    if ((time_t)t != t)
        goto error;

    __secs_to_zone(t, 0, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);

    if (__secs_to_tm(t + new.__tm_gmtoff, &new) < 0)
        goto error;

    *tm = new;
    return t;

error:
    errno = EOVERFLOW;
    return -1;
}