尝试从头开始构建动态数组：在append函数中使用delete[]时出现分段错误

Question

我正在尝试从头开始构建一个 C++ 向量来完成作业，但我一整天都在挣扎。我的追加功能坏了。起初它不需要字符串输入，但我已经让它将一个字符串附加到动态列表中。但是，当我尝试将第二个字符串附加到列表中时，临时数组会附加该字符串，但是当我第二次删除现有数据属性数组（前一个临时数组）时，会出现分段错误。我已经包含了很多打印语句来指出这一点。

我尝试使用placement new 实例化一个对象块，因为字符串是对象。这是 DynamicList class.cpp 文件：

#include <iostream>
#include <string>
#include "DynamicList.hpp"
#include <algorithm>
 
//Constructor
template<typename T>
DynamicList<T>::DynamicList(){
        size = 0;
        data = new T[size];
}
 
//Destructor
template<typename T>
DynamicList<T>::~DynamicList(){
        std::cout << "Deleting array of size: " << getSize() << std::endl;
        delete[] data;
 
}
 
//Overloading operators
template<typename T>
DynamicList<T> DynamicList<T>::operator=(DynamicList<T>& obj){
        obj.size = size;
        std::copy(data, data + size, obj.data);
}
template<typename T>
bool DynamicList<T>::operator==(DynamicList<T>& obj){
        if(size != obj.size){
                return false;
        }
        else{
                for(int i = 0; i < size; i++){
                        if(obj.data[i] != data[i]){
                                return false;
                        }
                }
                return true;
        }
 
}
 
template<typename T>
bool DynamicList<T>::operator!=(DynamicList<T>& obj){
        return !(DynamicList<T>::operator==(obj));
}
 
template<typename T>
T DynamicList<T>::operator[](int index){
        for(int i = 0; i < size; i++){
                if(i == index){
                        return data[i];
                }
        }
}
//Returns the size of the list
template<typename T>
int DynamicList<T>::getSize(){
        return size;
}
//Add element to the end of list.
template<typename T>
bool DynamicList<T>::append(T item){
        std::cout << data << std::endl;
        std::cout << item << std::endl;
 
        T* temp = static_cast<T*>(new T(sizeof(T) * (size + 1), alignof(T)));
        if(size > 1){
                for(int i = 0; i < size; i++){
                        T* somePtr = new (&temp[i]) T;
                        *somePtr = data[i];
                }
        }
        T* itemPtr = new (&temp[size]) T;
        *itemPtr = item;
        std::cout << "Ptr made in array slot.\n";
        std::cout << temp << std::endl;
        size++;
        std::cout << "Size increased.\n";
 
        std::cout << data << std::endl;
        std::cout << "AAAAAA\n";
        delete[] data;
        std::cout << "BBBBB\n";
        data = temp;
        std::cout << data[size - 1] << std::endl;
        return true;
}

这是DynamicList的头文件：

#include <iostream>
#include <string>

#ifndef DYNAMICLIST_H
#define DYNAMICLIST_H

template<typename T>
class DynamicList{

        private:
                int size;
                T* data;
        public:
                //constructor
                DynamicList();
                //destructor
                ~DynamicList();
                //Operator overloaders
                DynamicList operator=(DynamicList& obj);
                bool operator==(DynamicList& obj);
                bool operator!=(DynamicList& obj);
                T operator[](int index);
                //Returns the size of the data array
                int getSize();
                //Add an item to the end of the list
                bool append(T item);
                //Remove an item at an index
                bool remove(int index);
};

#endif

这是主要文件：

#include <iostream>
#include <string>
#include "DynamicList.hpp"
#include "DynamicList.cpp"

int main(){

        DynamicList<std::string> stringList;

        stringList.append("test");
        stringList.append("test2");

        return 0;
}

这是 makefile：

all: DynamicList.hpp DynamicList.cpp main.cpp
        g++ -c DynamicList.cpp
        g++ -c main.cpp
        g++ DynamicList.o main.o -o exec

run: all
        ./exec

clean:
        rm -f *.o
        rm -f exec

这是错误：

./exec
0x55c688824eb8
test
Ptr made in array slot.
0x55c6888252f0
Size increased.
0x55c688824eb8
AAAAAA
BBBBB
test
0x55c6888252f0
test2
Ptr made in array slot.
0x55c688824eb0
Size increased.
0x55c6888252f0
AAAAAA
make: *** [makefile:8: run] Segmentation fault (core dumped)

Answer 1

构造函数使用数组

new[]

创建数组，但追加函数使用对象

new

代替。使用数组

new

删除由对象

delete[]

创建的对象，反之亦然是未定义的行为。

您应该将

new

中的对象

append

替换为数组

new[]

:

template<typename T>
bool DynamicList<T>::append(T item) {
        T* temp = new T[size + 1];

        for (int i = 0; i < size; i++) {
                temp[i] = data[i];
        }
        temp[size] = item;
        size++;
 
        delete[] data;
        data = temp;
        return true;
}