c++ - 为什么将 'char' 分配给 'char' 会产生段错误？ C++

Question

我有一个看起来像这样的类:

class myTreeNode
{
     public:   
        char Data;
        myTreeNode *childA = NULL;   //A's always go in child1
        myTreeNode *childT = NULL;   //T's always go in child2
        myTreeNode *childC = NULL;   //c's always go in child3
        myTreeNode *childG = NULL;   //G's always go in child4
};

但是，当我为 Data 分配一个值时，我收到了一个段错误。我这样做是这样的:

root->childT->Data = p_data;

其中 p_data 是一个 char = t 而 root 是由 myTreeNode *root = new myTreeNode 创建的指针;。为什么在为 Data 赋值时会出现段错误？这不就和做 char Data = 't' 一样吗？

Answer 1

您的 child 没有指向任何内存位置。您只为根节点创建了一个新实例。您遇到了段错误，因为您正在取消引用空指针。

例如:

class myTreeNode
{
public:
  char Data;
  myTreeNode *childA = NULL;   //A's always go in child1
  myTreeNode *childT = NULL;   //T's always go in child2
  myTreeNode *childC = NULL;   //c's always go in child3
  myTreeNode *childG = NULL;   //G's always go in child4
};

int main()
{
  // allocate memory
  myTreeNode *root = new myTreeNode;
  root->childT = new myTreeNode; // allocate child

  root->childT->Data = 'a';

  // delete allocated memory
  delete root->childT;
  delete root;
  return 0;
}