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c++ - 为什么我的删除功能总是出现分段错误

问题描述

我有一个任务，我需要使用重载的析构函数来删除动态分配的指针。但是，当它运行时，我的一些指针被删除，直到我的一个对象的指针出现分段错误，一个指向“和第二个”，使用参数化构造函数。我试图通过并确保删除运算符有括号（因为我的新运算符有）我通过打印出它的信息和地址来确保该对象仍然存在。我试图重写我的分配函数，我试图检查我的析构函数，看看它在哪里搞砸了。如果有帮助，我已经包含了我的析构函数、分配函数、解除分配函数和参数化构造函数。

'''
//Destructor
MyString::~MyString()
{
  buffer_deallocate();
};

void MyString::buffer_deallocate() {
  cout << m_buffer << endl;
  delete[](m_buffer);
  m_buffer = NULL;
  m_size = 0;

}

void MyString::buffer_allocate(size_t size) {
  try {

    m_buffer = new char[size];
    m_size = size;
  }
  catch(bad_alloc&)
    {
      cout << "Errror: Unable to allocate memory" << endl;
      buffer_deallocate();
    }

}


//Parameterized Constructor
MyString::MyString(const char * str)
  :m_size(0)
{
  const char * strPtr = str;
  while(*strPtr)
    {
      strPtr++;
      m_size++;
    }

    buffer_allocate(m_size);

    for(int i = 0; i < m_size; i++)
      {
        m_buffer[i] = str[i];
      }

};
'''

然而，每次我在“第二个”之后得到输出是分段错误（核心转储）

编辑：我已经尝试了大部分推荐的内容。至少我的理解是，问题仍然存在，我现在意识到我的代码有点稀疏。（请原谅我，我还在学习。）这是新代码以及函数文件的其余部分供参考：

'''
#include<iostream>
#include<string.h>
using namespace std;

#include"MyString.h"


//Default Constructor
MyString::MyString()
:m_size(0), m_buffer(NULL)
{
        buffer_allocate(0);
};



//Parameterized Constructor
MyString::MyString(const char * str)
  :m_size(strlen(str)+1), m_buffer(NULL)
{
        buffer_allocate(m_size);
        strncpy(m_buffer, str, m_size);

};



//Copy Constructor
MyString::MyString(const MyString & other)
  :m_size(0), m_buffer(NULL)
{
  const char * otherPtr = other.c_str();
  buffer_allocate(other.size());

  for(int i = 0; i < size(); i++)
    {
      m_buffer[i] = otherPtr[i];
    }
        m_buffer[m_size] = '\0';
};


//Destructor
MyString::~MyString()
{
  buffer_deallocate();
};



size_t MyString::size() const
{
  return m_size;
}



size_t MyString::length() const{
  return m_size-1;
}



const char * MyString::c_str() const{
  return m_buffer;
}


bool MyString::operator==(const MyString & other) const {
  char * m_bufferPointer = m_buffer;
  while(*m_bufferPointer++)
    {
      const char * str_ptr = other.c_str();
      if(*m_buffer != *str_ptr++)
        {
          return 0;
        }
    }
  return 1;
}


MyString & MyString::operator=(const MyString & rhs) {
  buffer_deallocate();

  buffer_allocate(rhs.size());
  const char * c_strPtr = rhs.c_str();
  int i;
  for(i = 0; i < rhs.size(); i++)
    {
      this->m_buffer[i] = c_strPtr[i];
    }
  return *this;
}




MyString MyString::operator+ (const MyString & other_myStr) const {

  char * temp_pointer;
  temp_pointer;
  size_t temp_size = m_size + other_myStr.size();
  //New Combined Buffer for Concatanation
  try {
    temp_pointer = new char[temp_size];
    temp_pointer = strcat(this->m_buffer, other_myStr.c_str());

  }
  catch(bad_alloc&)
    {
      cout << "Error: Unable to Allocate Memory";
      return NULL;
    }
  return MyString(temp_pointer);
}



char & MyString:: operator[](size_t index) {
  return m_buffer[index];
}


const char & MyString::operator[] (size_t index) const {
  return m_buffer[index];
}


ostream & operator << (ostream& os, const MyString & myStr) {
  os << myStr.m_buffer;
  return os;

}

void MyString::buffer_deallocate() {



  cout << "Trying to delete : " <<m_buffer << endl;
        if(m_buffer){
                delete[](m_buffer);
        }
        cout << " Success" <<endl;
  m_buffer = NULL;
  m_size = 0;

}

void MyString::buffer_allocate(size_t size) {
        try {

    m_buffer = new char[size];
    m_size = size;
  }
  catch(bad_alloc&)
    {
      cout << "Errror: Unable to allocate memory" << endl;
        m_size = 0;
    }

}

'''

标签： c++segmentation-faultdynamic-memory-allocationdelete-operator

解决方案

所以我不得不将它重新制作为一些工作代码。问题可能是字符串长度必须扩展为 1 以添加 nul 终止符。所以这使得：

// prevent some MSVS warnings->errors
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <string>
#include <cstring>


//Destructor
class MyString {
private:
    size_t m_size;
    char* m_buffer;

    void buffer_allocate(size_t size) {
        try {
            m_buffer = new char[size];
            m_size = size;
        }
        catch (std::bad_alloc&)
        {
            std::cout << "Errror: Unable to allocate memory\n";
            // allocation failed, nothing changed, don't delete/
            m_size = 0;
        }

    }

    void buffer_deallocate() {
        // printing in the buffer deallocation??
        delete[] m_buffer;
        m_buffer = nullptr;
        m_size = 0;
    }

public:
    MyString(const char* str)
        : m_size(std::strlen(str)+1) // add null termination
        , m_buffer(nullptr)
    {
        buffer_allocate(m_size);
        std::strncpy(m_buffer, str, m_size);
    }

    ~MyString() {
        buffer_deallocate();
    }

    void Print() const {
        std::cout << m_buffer << '\n';
    }
};

int main() {
    std::string input{ "Hello World!" };
    MyString myString(input.c_str());
    myString.Print();
}

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