push_back上的C++运行时错误,用于自定义对象的向量

Question

在我的课堂上,当我尝试将任何对象推送到矢量myCache时,我收到运行时错误.我知道我正在正确地初始化矢量,并且很难理解为什么会发生这种情况.

#ifndef CACHE_H
#define CACHE_H

#include <iostream>
#include "cacheblock.h"
using namespace std;

class Cache
{
  public:
   Cache(int rows, int numWords);
   ~Cache();
   CacheBlock getBlock(int index);

  private:
   vector<CacheBlock> *myCache;
};

#endif

和

Cache::Cache(int rows, int numWords)
{
   myCache = new vector<CacheBlock>;
   CacheBlock test(rows, 0, 0);
   myCache->push_back(test);

/*
   for (int i = 1; i < rows; i++)
   {
      myCache->push_back(test);
      cout << "inside loop\n\n";
   }
*/
}

CacheBlock.h:

class CacheBlock
{
  public:
   CacheBlock(int numWords, int newIndex, int tagNum);
   CacheBlock(const CacheBlock &newCacheBlock);
   ~CacheBlock();
   void setData(int numWords, int newIndex, int tagNum);

  private:
   bool valid;
   int index;
   int tag;
   vector<int> *dataWords;
};

有人可以帮忙吗？

Answer 1

据推测,有一个工作的复制构造函数CacheBlock？

编辑:感谢您发布附加代码.

如果析构函数用于CacheBlock清除已vector<int> *dataWords删除的分配,则复制构造函数将需要"深度复制"该向量dataWords.没有这个深层复制,当CacheBlock复制时,将有两个CacheBlock具有相同指针的实例vector<int>.当第一个实例被清理时,第二个实例将以一个指向现在删除的副本的迷路指针结束.

值得一提的是,正如评论所暗示的那样,为什么vectors<>要从堆中分配,如果它们没有从堆中分配,但仅仅是成员变量,这些问题都不会发生.

以机智:

#ifndef CACHE_H
#define CACHE_H

#include <iostream>
#include "cacheblock.h"
using namespace std;

class Cache
{
  public:
   Cache(int rows, int numWords);
   // no longer need a destructor, as the auto-generated one by the compiler suffices
   // ~Cache();
   // potential optimization to return by const reference, rather than by copy
   const CacheBlock& getBlock(int index) const;

  private:
   vector<CacheBlock> myCache;
};

#endif

和

Cache::Cache(int rows, int numWords)
{
   // no longer need to construct the vector
   // myCache = new vector<CacheBlock>;
   CacheBlock test(rows, 0, 0);
   myCache->push_back(test);
}

CacheBlock.h:

class CacheBlock
{
  public:
   CacheBlock(int numWords, int newIndex, int tagNum);
   // no longer need a copy constructor
   // CacheBlock(const CacheBlock &newCacheBlock);
   // no longer need a destructor, as the compiler-generated one will suffice
   // ~CacheBlock();
   void setData(int numWords, int newIndex, int tagNum);

  private:
   bool valid;
   int index;
   int tag;
   vector<int> dataWords;
};