How to understand OS_SCHEDULE ?

[Yevpator]

Dear,

I have failed to understand the last row in the following macro definition that resides in cocoos.h. To be more specific, I have two questions:
1. What does "case (__LINE__+ofs):" do after return command ?
2. What is the "case" doing here without any "switch "?

#define OS_SCHEDULE(ofs) os_task_internal_state_set(running_tid, __LINE__+ofs);\
running_tid = NO_TID;\
return;\
case (__LINE__+ofs):

Thanks in advance!

[peter]