将子目录名称存储为列表中的节点时出错

Question

我打开一个目录，该目录包含多个带有国家名称的子目录。我想要的是制作一个列表并将这些目录的路径存储在节点中。当我打印列表和析构函数时，问题就出现了。我似乎没有发现问题所在，因为我以前多次使用这些功能，没有出现任何问题。

目录看起来像这样：

input_dir
   >Tanzania
   >Honduras
   >iTaiwan
   >Albania
   >Qatar
   >Grenada
   >Thailand
   >Croatia
   >Guatemala
   >Uruguay

所有代码如下：我的主要：

int main(int argc, char *argv[])
{
  int num_elements; //command line arguments
  char* input_dir_path;

  num_elements = stoi(argv[1]);
  strcpy(input_dir_path, argv[2]);

  Countries all_countries;
  fetch_countries(num_elements,all_countries,input_dir_path);

  all_countries.print();

  return 0;
}

这是我打开目录并将路径存储在列表中的函数：

void fetch_countries( int num_monitors,  Countries& all_countries, char* input_dir_path)
{
  DIR * input_dir = opendir(input_dir_path); // open the path

  if(input_dir == NULL){
    cout<< "Error opening directory" << endl;
    exit(1);
  }

  char buffer[257];
  struct dirent *entry;  // for the directory entries
  
  while ((entry = readdir(input_dir)) != NULL)
  {
    char *f_name = entry->d_name;
    if (entry->d_type != DT_DIR || !strcmp(f_name, ".") || !strcmp(f_name, ".."))  // Ignore . and .. dirs
      continue;
    // buffer contains instance: input_dir/Uruguay
    sprintf(buffer, "%s/%s", input_dir_path, f_name);
    all_countries.Insertion(buffer);  // storing all of the countries on a list
  }
  closedir(input_dir);
}

最后是列表函数：

class CountryNode
{
public:
    string country;
    CountryNode* next;
    CountryNode(const string country);
    ~CountryNode();
};

class Countries
{
public:
    CountryNode* head;
    CountryNode* tail;
    Countries();
    ~Countries();
    void Insertion(const string country);
    void print();
};

void Countries::Insertion(const string country)
{
  CountryNode* newnode = new CountryNode(country);

  //the list is empty
  if(head == NULL)
  {
    head = newnode;
    tail = newnode;
    return;
  }
  tail->next = newnode;
  tail = newnode;
}

Countries::Countries()
{
  head = NULL;
  tail = NULL;
}

void Countries::print()
{ // now we print the nodes
  CountryNode* current;
  current=head;
  while (current != NULL)
  {
    cout << current->country << endl;
    if (current->next != NULL)
      cout << "->";
    current = current->next;
  }
  cout << endl;
}

Countries::~Countries()
{
  CountryNode* current = head;
  CountryNode* next;

  while (current != NULL)
  {
    next = current->next;
    delete current;
    current = next;
  }
  
  head = NULL;
  tail = NULL;
}

CountryNode::CountryNode(const string country)
:country(country)
{}

CountryNode::~CountryNode() {}

最后我得到的错误是：

input_dir/Tanzania
->input_dir/Honduras
->input_dir/Taiwan
->input_dir/Albania
->input_dir/Qatar
->input_dir/Grenada
->input_dir/Thailand
->input_dir/Croatia
->input_dir/Guatemala
->input_dir/Uruguay
==16098== Conditional jump or move depends on uninitialised value(s)
==16098==    at 0x10BA29: Countries::print() (in /home/...)
==16098==    by 0x10A8F4: main (in /home/...)
==16098== 
==16098== Conditional jump or move depends on uninitialised value(s)
==16098==    at 0x10B9F4: Countries::print() (in /home/...)
==16098==    by 0x10A8F4: main (in /home/...)
==16098== 

==16098== Conditional jump or move depends on uninitialised value(s)
==16098==    at 0x10BA87: Countries::~Countries() (in /home/...)
==16098==    by 0x10A980: main (in /home/....)
==16098== 
==16098== 
==16098== HEAP SUMMARY:
==16098==     in use at exit: 0 bytes in 0 blocks
==16098==   total heap usage: 533 allocs, 533 frees, 153,121 bytes allocated
==16098== 
==16098== All heap blocks were freed -- no leaks are possible
==16098== 
==16098== Use --track-origins=yes to see where uninitialised values come from
==16098== For lists of detected and suppressed errors, rerun with: -s
==16098== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

有什么我没看到的吗？任何帮助将不胜感激

Answer 1

您从未将 newnode->next 设置为 NULL。因此，当您循环遍历节点列表时，当您到达最后一个节点时，您运行进入一个未初始化的指针。

您可以更改 CountryNode 构造函数以将其初始化为此默认值。

CountryNode::CountryNode(const string country)
    :country(country), next(NULL)
{}

将子目录名称存储为列表中的节点时出错

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