自引用结构和引用(Self referential structs and deferencing)

 如果我有以下代码，如何从根开始访问包含“left here”的字符串？ （不只是使用l->data ）。 
 
 我尝试使用root->left->data但最终出现了seg错误，我尝试使用GDB，但我非常喜欢使用它。 
 
 编辑：还有一个更好的方法来初始化指针指向的结构？ 
 
struct node
{
  char *data;
  struct node *left;
  struct node *right;
} *root, *l, *r;

root->data = "root here";
root->left = l;
root->right = r;

l->data = "left here";  //the data I need
l->left = NULL;
l->right = NULL;

r->data = "right here";
r->left = NULL;
r->right = NULL;

If I have the following code, how do I access the string that contains "left here" starting from the root? (not just using l->data).
 
I tried using root->left->data but ended up with a seg fault, I tried to use GDB but I'm very much a beginner in using it.
 
EDIT: Also is there a nicer way to initialise the structs that the pointers point to?
 
struct node
{
  char *data;
  struct node *left;
  struct node *right;
} *root, *l, *r;

root->data = "root here";
root->left = l;
root->right = r;

l->data = "left here";  //the data I need
l->left = NULL;
l->right = NULL;

r->data = "right here";
r->left = NULL;
r->right = NULL;

原文：https://stackoverflow.com/questions/25332682