C++内存访问错误
C++ memory access error
我在尝试调用函数Organization:：addWorker时遇到了一个问题，它似乎在内存释放步骤、运算符delete[]失败，但指针显示的内存已经释放。
调用堆栈：
lab1.exe！人员：：setName（char*thename）第80行C++
lab1.exe！同事：：操作员=（同事和同事）线路303 C++
lab1.exe！组织：：addWorker（Coworker&theworker）404行C++
lab1.exe！main（）97行C++
#include <string>
#include "class_Date.h"
using namespace std;
enum workNec { worker, manager, employer };
class Person {
char* name;
char* surname;
Date bd;
public:
Person();
Person(char* thename, char* thesurname, Date thebd);
Person(const Person &theperson);
~Person();
char* getName() { return name; }
char* getSurname() { return surname; }
Date getBD() { return bd; }
void getFullInfo();
Person & setName(char* thename);
Person & setSurname(char* thesurname);
Person & setBD(int dd, int mm, int yy);
Person & setBD(Date thebd);
Person & operator=(Person& thepers);
};
Person::Person() {
name = new char [1];
strcpy(name, "");
surname = new char[1];
strcpy(surname, "");
}
Person::Person(char* thename, char* thesurname, Date thebd) {
name = new char [strlen(thename)+1];
surname = new char [strlen(thesurname)+1];
strcpy(name, thename);
strcpy(surname, thesurname);
bd = thebd;
}
Person::Person(const Person & theperson) {
name = new char[strlen(theperson.name) + 1];
surname = new char[strlen(theperson.surname) + 1];
strcpy(name, theperson.name);
strcpy(surname, theperson.surname);
bd = theperson.bd;
}
Person::~Person() {
cout << "Destructing Person " << name << endl;
delete [] name;
delete [] surname;
}
void Person::getFullInfo() {
cout << name << " " << surname << " "; bd.getFullDate();
}
Person & Person::setName(char* thename) {
delete [] name;
name = new char[strlen(thename) + 1]; strcpy(name, thename);
return *this;
}
Person & Person::setSurname(char* thesurname) {
delete [] surname;
surname = new char[strlen(thesurname) + 1]; strcpy(surname, thesurname);
return *this;
}
Person & Person::setBD(int dd, int mm, int yy) {
bd.setDD(dd); bd.setMM(mm); bd.setYY(yy);
return *this;
}
Person & Person::setBD(Date thebd) {
bd = thebd;
return *this;
}
Person & Person::operator=(Person& thepers) {
delete [] this->name;
delete [] this->surname;
this->name = new char[strlen(thepers.name) + 1];
this->surname = new char[strlen(thepers.surname) + 1];
strcpy(this->name, thepers.name);
strcpy(this->surname, thepers.surname);
bd = thepers.bd;
return *this;
}
//*************************************************************************************************
class Position {
char* department;
workNec wn;
int salary;
public:
Position();
Position(char *thedept, workNec thewn, int thesalary);
Position(const Position & thepos);
~Position();
char* getDept() { return department; }
workNec getWorkNec() { return wn; }
int getSalary() { return salary; }
void getFullInfo();
Position & setDept(char* dept);
Position & setWorkNec(workNec nec);
Position & setSalary(int sal);
};
Position::Position() {
department = new char[1];
strcpy(department, "");
}
Position::Position(char *thedept, workNec thewn, int thesalary) {
department = new char[strlen(thedept) + 1];
strcpy(department, thedept);
wn = thewn;
salary = thesalary;
}
Position::Position(const Position & thepos) {
department = new char[strlen(thepos.department)+1];
strcpy(department, thepos.department);
wn = thepos.wn;
salary = thepos.salary;
}
Position::~Position() {
cout << endl << "Deleting Position " << department << endl;
delete [] department;
}
void Position::getFullInfo() {
cout << department << " " << wn << " " << salary << " ";
}
Position & Position::setDept(char* dept) {
delete [] department;
department = new char[strlen(dept)+1];
strcpy(department, dept);
return *this;
}
Position & Position::setWorkNec(workNec nec) {
wn = nec;
return *this;
}
Position & Position::setSalary(int sal) {
salary = sal;
return *this;
}
//*************************************************************************************************
class Coworker {
Person person;
Position position;
public:
Coworker();
Coworker(Person &theperson, Position &thepos);
Coworker( Coworker & theco);
~Coworker();
Person getPerson() { return person; }
Position getPosition() { return position; }
void getFullInfo();
Coworker & setPerson(Person &per);
Coworker & setPosition(Position &pos);
Coworker & operator=(Coworker& theco);
};
Coworker::Coworker() {
}
Coworker::Coworker(Person &theperson, Position &thepos) {
person.setBD(theperson.getBD());
person.setName(theperson.getName());
person.setSurname(theperson.getSurname());
position.setDept(thepos.getDept());
position.setSalary(thepos.getSalary());
position.setWorkNec(thepos.getWorkNec());
}
Coworker::Coworker(Coworker & theco) {
Person pers;
pers = theco.person;
Position pos = theco.position;
person.setBD(pers.getBD());
person.setName(pers.getName());
person.setSurname(pers.getSurname());
position.setDept(pos.getDept());
position.setSalary(pos.getSalary());
position.setWorkNec(pos.getWorkNec());
}
Coworker::~Coworker() {
cout << endl << "Deleting Coworker " << endl;
}
void Coworker::getFullInfo() {
person.getFullInfo(); cout << " "; position.getFullInfo();
}
Coworker & Coworker::setPerson(Person &per) {
Person tper = per;
person.setBD(tper.getBD());
person.setName(tper.getName());
person.setSurname(tper.getSurname());
return *this;
}
Coworker & Coworker::setPosition(Position &pos) {
Position tpos = pos;
position.setDept(tpos.getDept());
position.setSalary(tpos.getSalary());
position.setWorkNec(tpos.getWorkNec());
return *this;
}
Coworker & Coworker::operator=(Coworker& theco) {
Person pers;
pers = theco.person;
Position pos;
pos = theco.position;
person.setBD(pers.getBD());
person.setName(pers.getName());
person.setSurname(pers.getSurname());
position.setDept(pos.getDept());
position.setSalary(pos.getSalary());
position.setWorkNec(pos.getWorkNec());
return *this;
}
class Organization {
char* title;
Coworker * coworker;
int cwAmount;
public:
Organization();
Organization(char* thetitle, Coworker * theco, int thecw);
Organization(const Organization & org);
~Organization();
void addWorker(Coworker &theworker);
char* getTitle() { return title; }
int getAmount() { return cwAmount; }
Coworker * getCoworker() { return coworker; }
Organization & setTitle(char* tit);
Organization & setAmount(int am);
Organization & setCoworker(Coworker *theco);
void getFullInfo();
void getShortInfo();
};
//*************************************************************************************************
Organization::Organization() {
title = new char[1];
strcpy(title, "");
cwAmount = 0;
coworker = new Coworker[0];
}
Organization::Organization(char* thetitle, Coworker * theco, int thecw) {
title = new char[strlen(thetitle) + 1];
strcpy(title, thetitle);
cwAmount = thecw;
coworker = new Coworker[cwAmount];
for (int i = 0; i < cwAmount; i++) {
coworker[i].setPerson(theco[i].getPerson());
coworker[i].setPosition(theco[i].getPosition());
}
}
Organization::Organization(const Organization & org) {
title = new char[strlen(org.title) + 1];
strcpy(title, org.title);
cwAmount = org.cwAmount;
coworker = new Coworker[cwAmount];
for (int i = 0; i < cwAmount; i++) {
coworker[i].setPerson(org.coworker[i].getPerson());
coworker[i].setPosition(org.coworker[i].getPosition());
}
}
Organization::~Organization() {
cout << endl << "Deleting Organization " <<title<< endl;
delete [] coworker;
};
void Organization::addWorker(Coworker &theworker) {
cout << "a";
Coworker * new_coworker = new Coworker[cwAmount + 1];
for (int i = 0; i < cwAmount; i++) new_coworker[i] = coworker[i];
cwAmount++;
new_coworker[cwAmount] = theworker;
delete [] coworker;
coworker = new_coworker;
}
void Organization::getFullInfo() {
std::cout << title << " " << cwAmount << endl;
for (int i = 0; i < cwAmount; i++) {
coworker[i].getPerson().getFullInfo();
cout << " ";
coworker[i].getPosition().getFullInfo();
cout << endl;
}
}
void Organization::getShortInfo() {
int total = 0;
for (int i = 0; i < cwAmount; i++) {
total += coworker[i].getPosition().getSalary();
}
std::cout << this->title << " " << total << std::endl;
}
Organization & Organization::setTitle(char* tit) {
title = new char[strlen(tit)+1];
strcpy(title, tit);
return *this;
}
Organization & Organization::setAmount(int am) {
cwAmount = am;
return *this;
}
Organization & Organization::setCoworker(Coworker *theco) {
delete [] coworker;
coworker = new Coworker [cwAmount];
for (int i = 0; i < cwAmount; i++) {
coworker[i].setPerson(theco[i].getPerson());
coworker[i].setPosition(theco[i].getPosition());
}
return *this;
}
main.cpp：
#define _CRT_SECURE_NO_WARNINGS
#include "classes_v23.h"
using namespace std;
int main() {
{
Date d1;
Date d2(19, 04, 1995);
Date d3 = d2;
d1.getFullDate(); cout << endl;
d2.getFullDate(); cout << endl;
d3.getFullDate(); cout << endl;
//******************************
Person pers1;
pers1.setBD(d2);
pers1.setName("Ihor");
pers1.setSurname("Pukish");
Person pers2("name2", "surname2", d2);
Person pers3 = pers2;
pers1.getFullInfo(); cout << endl;
pers2.getFullInfo(); cout << endl;
pers3.getFullInfo(); cout << endl;
//******************************
Position pos1;
pos1.setDept("IASA");
pos1.setSalary(100);
pos1.setWorkNec(employer);
Position pos2("dept2", worker, 200);
Position pos3 = pos2;
pos1.getFullInfo(); cout << endl;
pos2.getFullInfo(); cout << endl;
pos3.getFullInfo(); cout << endl;
//******************************
Coworker co1;
co1.setPerson(pers1);
co1.setPosition(pos1);
Coworker co2(pers2, pos2);
Coworker co3 = co2;
Coworker co4(pers1, pos1);
co1.getFullInfo(); cout << endl;
co2.getFullInfo(); cout << endl;
co3.getFullInfo(); cout << endl;
//******************************
Coworker * cow = new Coworker[3];
cow[0] = co1;
cow[1] = co2;
cow[2] = co3;
Organization org1("title", cow, 3);
org1.addWorker(co4);
}
system("pause");
}
我认为问题是：
void Organization::addWorker(Coworker &theworker) {
cout << "a";
Coworker * new_coworker = new Coworker[cwAmount + 1];
for (int i = 0; i < cwAmount; i++) new_coworker[i] = coworker[i];
cwAmount++;
new_coworker[cwAmount] = theworker;
delete [] coworker;
coworker = new_coworker;
}
请注意，在指定theworker之前，要先递增cwAmount。但是我认为你应该先分配，然后递增。空元素位于增量前索引处。
使用向量也可以更容易地实现这一点。
首先，您包含了<string>，但未能使用<string>所提供的内容，即std::string。由于您说必须使用C样式字符串，因此正确的标头是<cstring>，而不是<string>。
其次，如果传递了NULL，或者甚至传递了一个伪指针，则此函数将不起作用：
Person::Person(char* thename, char* thesurname, Date thebd) {
name = new char [strlen(thename)+1]; // undefined behavior if NULL is passed
surname = new char [strlen(thesurname)+1]; // undefined behavior if NULL is passed
//...
}
该函数应该检查NULL指针参数。但即便如此，也存在被传递的指针不指向有效缓冲区的风险。
现在，正如其他人所说，您需要正确地为每个具有指向动态分配内存的指针的类编写赋值运算符。
让我们从Person赋值运算符开始：
Person & Person::operator=(Person& thepers) {
delete [] this->name;
delete [] this->surname;
this->name = new char[strlen(thepers.name) + 1];
this->surname = new char[strlen(thepers.surname) + 1];
strcpy(this->name, thepers.name);
strcpy(this->surname, thepers.surname);
bd = thepers.bd;
return *this;
}
这不仅是多余的（大部分代码都在复制构造函数中），而且由于以下原因而失败：
- 你
delete[]的名字和姓氏。如果以下new[]抛出异常，会发生什么情况？在您确信新的不会失败之前，您就删除了数据，从而将对象搞砸了 - 你不检查自我分配
- 该项应作为常量引用传递
修复的方法很简单，我建议您对所有其他类都这样做。
#include <algorithm>
//...
Person & Person::operator=(const Person& thepers)
{
Person other(thepers);
swap(*this, other);
return *this;
}
void Person::swap(Person& left, Person& right)
{
std::swap(left.name, right.name);
std::swap(left.surname, right.surname);
std::swap(left.bd, right.bd);
}
就这样，没有别的。这被称为copy/swap习语。只要您已经编写了一个有效且正确的复制构造函数，上面的代码不仅可以正确复制，还可以解决自分配和过早销毁成员的问题。
它的工作方式是创建一个临时的，通过用临时的东西交换你的东西来"偷走"临时的东西，然后让临时的东西和你的旧东西一起死去。用外行的话说，这就是正在发生的事情。
请为其他班级这样做。例如，Coworker:
Coworker & Coworker::operator=(const Coworker& theco)
{
Coworker temp(theco);
swap(*this, temp);
return *this;
}
void Coworker::swap(Coworker& left, Coworker& right)
{
std::swap(left.person, right.person);
std::swap(left.position, right.position);
}
此外，您的Organization类缺少一个赋值运算符。只需使用上述技术添加一个即可。
此外，您的setName函数在重新分配之前也会删除内存：
Person & Person::setName(char* thename) {
delete [] name;
name = new char[strlen(thename) + 1]; strcpy(name, thename);
return *this;
}
也可以通过先分配给临时，然后分配功能结束时的临时：
Person & Person::setName(char* thename)
{
char *tempname = new char[strlen(thename) + 1];
strcpy(tempname, thename);
delete [] name;
name = tempname;
return *this;
}
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