程序代码：

#include <stdio.h>
#include <time.h>

int main(void)
{
    time_t t;
  
    time(&t);
    printf("Today's date and time: %s\n", ctime(&t));
    printf("The string address 1 : %x\n", ctime(&t));
    printf("The string address 2 : %x\n", ctime(&t));
    return 0;
}

程序代码：

/* 这里的函数在GNU libc的locale/C-time.c中定义  */
#include <stdio.h>
#include <time.h>

extern const struct locale_data _nl_C_LC_TIME attribute_hidden;

#define ab_day_name(DAY) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABDAY_1)+(DAY)].string)
#define ab_month_name(MON) (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (ABMON_1)+(MON)].string)

static const char format[] = "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n";
static char result[ 3+1+3+1+20+1+20+1+20+1+20+1+20+1+1];

static char * asctime_internal (const struct tm *tp, char *buf, size_t buflen)
{
  if (tp == NULL)
    {
      __set_errno (EINVAL);
      return NULL;
    }
  if (__builtin_expect (tp->tm_year > INT_MAX - 1900, 0))
    {
    eoverflow:
      __set_errno (EOVERFLOW);
      return NULL;
    }
  int n = __snprintf (buf, buflen, format,
              (tp->tm_wday < 0 || tp->tm_wday >= 7 ?
               "???" : ab_day_name (tp->tm_wday)),
              (tp->tm_mon < 0 || tp->tm_mon >= 12 ?
               "???" : ab_month_name (tp->tm_mon)),
              tp->tm_mday, tp->tm_hour, tp->tm_min,
              tp->tm_sec, 1900 + tp->tm_year);
  if (n < 0)
    return NULL;
  if (n >= buflen)
    goto eoverflow;
  return buf;
}

char * __asctime_r (const struct tm *tp, char *buf)
{
  return asctime_internal (tp, buf, 26);
}

weak_alias (__asctime_r, asctime_r)

char * asctime (const struct tm *tp)
{
  return asctime_internal (tp, result, sizeof (result));
}

libc_hidden_def (asctime)

char * ctime (const time_t *t)
{
  return asctime (localtime (t));
}