c - mktime() セグメント障害

Question

日付情報を含むイベント構造体に週を繰り返し追加しようとしています。特定の時間までイベントの複数のインスタンスを作成するためにこれを行っています。full_time = mktime(&caltime); の mktime 関数でセグ フォールトが発生します。理由はわかりません。

void multiple(icalevent event, int is_location){
    icalevent temp;
    int rrule_bound = atoi(event.rrule);
    int rtime_bound = atoi(event.rtime);
    int start_bound = atoi(event.start);
    int stime_bound = atoi(event.stime);
    char buffer[9];
    struct tm caltime;
    time_t full_time;
    char time_str[15];

    temp = cpystruct(event, is_location); 
    while((start_bound <= rrule_bound) && (stime_bound <= rtime_bound)){
        memset(&caltime, 0, sizeof(struct tm));
        strncpy(time_str, temp.start, 9);
        strncat(time_str, temp.stime, 6);

        strptime(time_str, "%Y%m%d%H%M%S", &caltime);
        caltime.tm_mday += 7;
        full_time = mktime(&caltime);
        if(caltime.tm_isdst == 1){
            caltime.tm_hour -= 1;
        }
        full_time = mktime(&caltime);

        strftime(buffer, 9, "%Y%m%d", &caltime);
        start_bound = atoi(buffer);
        strncpy(temp.end, buffer, 8);
        strncpy(temp.start, buffer, 8);

        if((start_bound <= rrule_bound) && (stime_bound <= rtime_bound)){
            /*create a sort string*/

            calendar[percent_full] = cpystruct(temp, is_location);
            printst(calendar[percent_full]);
            percent_full++;
        }
        else{
            break;
        }

    }

    return;
    }

icalevent構造:

    typedef struct{
        char start[9]; /*"YYYYMMDD*/
        char stime[7]; /*"HHMMSS"*/
        char end[9]; /*"YYYYMMDD"*/
        char etime[7]; /*"HHMMSS"*/
        char rrule[9]; /*"YYYYMMDD"*/
        char rtime[7]; /*"HHMMSS"*/
        char *location; /*"2343 fake street"*/
        char *summary; /*"Halloween party"*/
        char *sort_str; /*"YYYYMMDDHHMMSSHalloween party*/
     } icalevent

編集：

icalevent cpystruct(icalevent temp, int is_location) {
    icalevent perm;
    strncpy(perm.start, temp.start, 9);
    strncpy(perm.stime, temp.stime, 7);
    strncpy(perm.end, temp.end, 9);
    strncpy(perm.etime, temp.etime, 7);
    strncpy(perm.rrule, temp.rrule, 9);
    strncpy(perm.rtime, temp.rtime, 7);
    if(is_location) {
        perm.location = strdup(temp.location);
    } else {
        perm.location = NULL;
    }

    perm.summary = strdup(temp.summary);
    perm.sort_str = strdup(temp.sort_str);
    return perm;
}