mktime函数

[zhongyj2004]

void main()
{
tm tmDate = {0};
tmDate.tm_mday=31;
tmDate.tm_mon=1;
tmDate.tm_year=106;
time_t m_time=mktime(&tmDate);
cout<<m_time<<endl;
cout<<tmDate.tm_year<<endl;
cout<<tmDate.tm_mon<<endl;
cout<<tmDate.tm_mday<<endl;
}
输出为
106
2
3
是不是mktime函数不仅仅是得到一个秒数，还会修改参数tmDate的值？？？
上面给定的日期是2006－2－31，是一个不存在的日期，经过函数mktime之后就改变了变量，变成2006－3－2号了

[jixingzhong]

mktime
<time.h>

time_t mktime ( struct tm * ptm );
Convert tm structure to time_t value.
Checks the members of the tm structure passed as parameter ptm adjusting the values if the ones provided are not in the possible range or they are incomplete or mistaken and then translates that structure to a time_t value (seconds elapsed since Jan 1, 1970) that is returned.
The original values of tm_wday and tm_yday members of ptm are ignored and filled with the correspondent ones to the calculated date. The range of tm_mday is not checked until tm_mon and tm_year are determined.


Parameters.

ptm
Pointer to a tm structure, that contains data to be computed.
Return Value.
A time_t value corresponding to the date and time passed in ptm parameter.
On error, a -1 value is returned.

Portability.
Defined in ANSI-C.


Example.


/* mktime example: weekday calculator */
#include <stdio.h>
#include <time.h>

int main ()
{
time_t rawtime;
struct tm * timeinfo;
int year, month ,day;
char * weekday[] = { "Sunday", "Monday",
"Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"};

/* prompt user for date */
printf ("Enter year: "); scanf ("%d",&year);
printf ("Enter month: "); scanf ("%d",&month);
printf ("Enter day: "); scanf ("%d",&day);

/* get current timeinfo and modify it to user's choice */
time ( &rawtime );
timeinfo = localtime ( &rawtime );
timeinfo->tm_year = year - 1900;
timeinfo->tm_mon = month - 1;
timeinfo->tm_mday = day;

/* call mktime: timeinfo->tm_wday will be set */
mktime ( timeinfo );

printf ("That day is a %s.\n", weekday[timeinfo->tm_wday]);

return 0;
}

Output:
Enter year: 2000
Enter month: 5
Enter day: 20
That day is a Saturday.

[jixingzhong]

The original values of tm_wday and tm_yday members of ptm are ignored and filled with the correspondent ones to the calculated date. The range of tm_mday is not checked until tm_mon and tm_year are determined.

[zhongyj2004]

英文太差，看了上面的英文，还是不知道