在學習Linux驅動的過程中，遇到一個宏叫做container_of。該宏定義在include/linux/kernel.h中，首先來貼出它的代碼：
/**
* container_of - cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
* */
#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})<pre name="code" class="cpp">再看上述代碼的第3行，其中需要說明的是offsetof，它定義在include/linux/stddef.h中，其定義如下：#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
