不知道是什么原因
#include<iostream>
using namespace std;
typedef struct
{
int year;
int month;
int date;
int hour;
int minute;
int second;
int millisecond;
}CALENDAR;
CALENDAR *getCalendar()
{
CALENDAR cal ;
cal.year = 2015;
cal.month = 8;
cal.date = 15;
cal.hour = 14;
cal.minute = 34;
cal.second = 23;
cal.millisecond = 123;
return &cal;
}
int main()
{
CALENDAR calendar;
CALENDAR* cal;
cal = getCalendar();
memcpy(&calendar, cal, sizeof(CALENDAR));
cout << calendar.year << " "
<< calendar.month << " "
<< calendar.date << " "
<< calendar.hour << " "
<< calendar.minute << " "
<< calendar.second << " "
<< calendar.millisecond << " "
<< sizeof(CALENDAR) << endl;
}
输出是这样的
局部变量CALENDAR cal ;是在栈上定义的,在退出函数作用域时就内存就释放掉了,后续的代码将覆盖这块内存区域,输出就是未确定的值;
可以改用直接返回对象而非指针
CALENDAR getCalendar()
{
CALENDAR cal ;
cal.year = 2015;
cal.month = 8;
cal.date = 15;
cal.hour = 14;
cal.minute = 34;
cal.second = 23;
cal.millisecond = 123;
return cal;
}
也可以改用引用(或指针)传入返回;
void getCalendar(CALENDAR& cal)
{
cal.year = 2015;
cal.month = 8;
cal.date = 15;
cal.hour = 14;
cal.minute = 34;
cal.second = 23;
cal.millisecond = 123;
}
CALENDAR calendar;
getCalendar(calendar);
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