结构体内可以包含自身的指针（链表实现方法）或 引用 但不可以包含自身变量即递归 （因为这样一来结构体大小就无法确定了）

例子：
CCScheduler.cpp
中一段代码

typedef struct _listEntry
{
struct _listEntry *prev, *next;
CCObject *target; // not retained (retained by hashUpdateEntry)
int priority;
bool paused;
bool markedForDeletion; // selector will no longer be called and entry will be removed at end of the next tick
} tListEntry;