保存断点
保存断点是通过保存行数来完成的，在被中断的地方插入编译器关键字_LINE_，编译器便自动记录所终端的行数。展开那些具有中断功能的宏，可以发现最后保存行数是宏LC_SET，取宏PROCESS_WAIT_EVENT()为例，将其展开得到如下代码：
/**
* Wait for an event to be posted to the process.
*
* This macro blocks the currently running process until the process
* receives an event.
*
* \hideinitializer
*/
#define PROCESS_WAIT_EVENT() PROCESS_YIELD()
/**
* Yield the currently running process.
*
* \hideinitializer
*/
#define PROCESS_YIELD() PT_YIELD(process_pt)
/**
* Yield from the current protothread.
*
* This function will yield the protothread, thereby allowing other
* processing to take place in the system.
*
* \param pt A pointer to the protothread control structure.
*
* \hideinitializer
*/
#define PT_YIELD(pt) \
do { \
PT_YIELD_FLAG = ; \
LC_SET((pt)->lc); \
if(PT_YIELD_FLAG == ) { \
return PT_YIELDED; \
} \
} while() //保存程序断点，下次再运行该进程直接跳到case __LINE__
#define LC_SET(s) s = __LINE__; case __LINE__:
宏LC_SET展开还包含语句case _LINE_，用于下次恢复断点，即下次通过switch语句便可跳转到case的下一句。
恢复断点
被中断程序再次获得执行权时，便从该进程的函数执行体进入，按照Contiki的编程替换，函数体第一条语句是PROCESS_BEGIN()宏，该宏包含一条switch语句，用于跳转到上一次被中断的行，从而恢复执行，宏PROCESS_BEGIN()展开的源代码如下：
/**
* Define the beginning of a process.
*
* This macro defines the beginning of a process, and must always
* appear in a PROCESS_THREAD() definition. The PROCESS_END() macro
* must come at the end of the process.
*
* \hideinitializer
*/
#define PROCESS_BEGIN() PT_BEGIN(process_pt) /**
* Declare the start of a protothread inside the C function
* implementing the protothread.
*
* This macro is used to declare the starting point of a
* protothread. It should be placed at the start of the function in
* which the protothread runs. All C statements above the PT_BEGIN()
* invokation will be executed each time the protothread is scheduled.
*
* \param pt A pointer to the protothread control structure.
*
* \hideinitializer
*/
#define PT_BEGIN(pt) { char PT_YIELD_FLAG = 1; if (PT_YIELD_FLAG) {;} LC_RESUME((pt)->lc) #define LC_RESUME(s) switch(s) { case 0:
//switch语句跳转到被中断的行