我有两个班级（约会，日程安排）和一个司机（主要）。
main.cpp中：
#include <iostream>
#include "schedule.h"
#include "appointment.h"
using namespace std;
int main()
{
schedule mySch2("hello");
appointment myAppt(100002,"appointment",10,1,2013);
myAppt.printS(cout,2);
mySch2.addtoSchedule(myAppt);
system("PAUSE");
return EXIT_SUCCESS;
}
schedule.h
#ifndef SCHEDULE_H
#define SCHEDULE_H
#include<iostream>
#include "appointment.h"
using namespace::std;
const int SCH_ENTRIES = 10;
class schedule
{
public:
schedule(void);
schedule(const char *p);
bool addtoSchedule(const appointment &);
private:
char title[40];
int count;
appointment appointmentArray[SCH_ENTRIES];
};
#endif
schedule.cpp
#include "schedule.h"
#include "appointment.h"
#include <iostream>
using namespace::std;
schedule::schedule(void)
{
}
schedule::schedule(const char *p)
{
strcpy(title, p);
count = 0;
cout << title << endl;
cout << count << endl;
cout << "----" << endl;
}
bool schedule::addtoSchedule(const appointment & myAppt)
{
cout << appointmentArray[0].getDay();
return false;
}
appointment.h（我没有写这个，这是提供的） - 对这个问题不是非常重要
#ifndef APPOINTMENT_H
#define APPOINTMENT_H
#include <fstream>
#include <cstring>
using std::ostream;
// The Designer decides upon the following data and actions (i.e. Functions)
// and places the class in the file appointment.h
class appointment
{
public:
appointment(void); // default constructor
appointment(long, const char [],int d, int m, int y); // 5 argument constructor
appointment(const appointment &); // copy constructor
void keyBoardInput(void); // Assume no blanks in the desc
long getSource(void) const; // return source
void setSource(long); // change source
void setMonth(int);
void setDay(int);
void setYear(int);
int getMonth(void) const;
int getDay(void) const;
int getYear(void) const;
const char *getDescription(void) const; // return the address of the description
void changeDescription(const char *) ; // change an existing description
void copyTo(appointment &) const; // copy invoking instance to parameter
void incrementDate (void); // advance the date by ONE day
// You can assume 30 days in each month
void printS(ostream &, int dateFormat) const; // print all fields
// dateFormat == 1 month/day/year
// dateFormat == 2 day/month/year
~appointment(); // destructor - indicate the address
// of the variable that is leaving
private:
void setDescription(const char *); // used to allocated memory
// data
long source; // id of the person scheduling the appointment
char * desc; // description of the appointment - Dynamic Data
int day; // day, month, and year when the appointment
int month; // will happen
int year;
};
#endif
appointment.cpp（我没有写这个，这是提供的） - 对这个问题不是非常重要
#include "appointment.h"
#include <iostream>
using std::cin;
using std::cout;
appointment::appointment()
{
day = 0;
cout << "default appt\n";
}
appointment::appointment(long lSource, const char cDescription[], int d, int m, int y)
{
source = lSource;
day = d;
month = m;
year = y;
setDescription(cDescription);
}
appointment::appointment(const appointment & aToCopy)
{
source = aToCopy.getSource();
day = aToCopy.getDay();
month = aToCopy.getMonth();
year = aToCopy.getYear();
setDescription(aToCopy.getDescription());
}
void appointment::setDescription(const char * cSource)
{
if (desc != NULL) free (desc);
if (cSource == NULL)
return;
desc = (char *)malloc (strlen (cSource) + 1);
strcpy(desc, cSource);
}
long appointment::getSource(void) const
{
return source;
}
void appointment::setSource(long lSource)
{
source = lSource;
}
void appointment::setMonth(int iMonth)
{
month = iMonth;
}
void appointment::setDay(int iDay)
{
day = iDay;
}
void appointment::setYear(int iYear)
{
year = iYear;
}
int appointment::getMonth(void) const
{
return month;
}
int appointment::getDay(void) const
{
return day;
}
int appointment::getYear(void) const
{
return year;
}
//return the address of the description
const char * appointment::getDescription(void) const
{
return desc;
}
//change an existing description
void appointment::changeDescription(const char * cDescription)
{
setDescription(cDescription);
}
void appointment::copyTo(appointment &p) const
{
p.source = source;
p.day = day;
p.month = month;
p.year = year;
p.setDescription(desc);
}
void appointment::incrementDate(void)
{
int days;
switch (month)
{
case 1: // Jan: 31 Days
case 3: // Mar: 31 Days
case 5: // May: 31 Days
case 7: // Jul: 31 Days
case 10: // Oct: 31 Days
case 12: // Dec: 31 Days
days = 31;
break;
case 4: // Apr: 30
case 6: // Jun: 30
case 8: // Aug: 30
case 9: // Sep: 30
case 11: // Nov: 30
days = 30;
break;
case 2: // Feb: 28/29 Days (Depends on year modulus 4 a modulus 100).
days = !(year % 4) || !(year % 100) ? 29 : 28;
break;
}
day++;
if (day > days)
{
month++;
day = 1;
if (month > 12)
{
month = 1;
year++;
}
}
}
void appointment::printS(ostream &out, int dateFormat) const
{
if (dateFormat == 1)
{
out << month << "/" << day << "/" << year << "\n";
}
else if (dateFormat == 2)
{
out << day << "/" << month << "/" << year << "\n";
}
else
out << "Unsupported dateFormat parameter specified (should be 1 or 2).";
}
appointment::~appointment()
{
if (desc != NULL)
{
free (desc);
desc = NULL;
}
}
void appointment::keyBoardInput()
{
char temp[1024];
cout << "Please type the description: ";
cin.getline (temp, sizeof(temp) - 1, '\n');
cout << std::endl;
setDescription(temp);
}
主驱动程序调用mySch2.addtoSchedule（myAppt）时发生错误;
如果我取消注释schedule scheduleArray [0] .getDay（）中的行，那么一切都运行正常，没有分段错误。一旦该行被取消注释，它就会在运行时抛出错误（在崩溃之后我进入调试器并逐步执行该程序）。
答案 0 :(得分：0)
在调用desc之前，您永远不会为类nullptr初始化appointment到setDescription。这在两个构造函数中都会发生。学习使用初始化列表：
appointment::appointment()
: source(), desc(), day(), month(), year()
{
cout << "default appt\n";
}
appointment::appointment(long lSource, const char cDescription[], int d, int m, int y)
: source(lSource), desc(), day(d), month(m), year(y)
{
setDescription(cDescription);
}
appointment::appointment(const appointment & aToCopy)
: source(aToCopy.getSource())
, desc()
, day(aToCopy.getDay())
, month(aToCopy.getMonth())
, year(aToCopy.getYear())
{
setDescription(aToCopy.getDescription());
}
为什么会出错？
如果没有初始化，desc中的值是不确定的，因此未定义的行为要取消引用，当然也要传递给free。
void appointment::setDescription(const char * cSource)
{
if (desc != NULL) free (desc); // desc contains non-null garbage.
if (cSource == NULL)
return;
desc = (char *)malloc (strlen (cSource) + 1);
strcpy(desc, cSource);
}
那就是说，我强烈建议改用std::string。它会使这个类的copy-consructor完全消失，并且默认的构造函数是微不足道的。
关于在保留的C ++程序中使用malloc()的评论，因为这个观点已经全部 - 但已经在这个论坛上被击败（我赞同te流行观点）。