[ST-users] About st lib stack data preservation in MD_INIT_CONTEXT

[j. <jin...@qq...>]

Hi experts:

I'm reading the st source codes, and meet a question. In my understanding, the st should save the user-thread context pointers and the datas on the stack. That is, the  MD_INIT_CONTEXT should be like this:


1: #define MD_INIT_CONTEXT(_thread, _sp, _bsp, _main)                       \
2:   ST_BEGIN_MACRO                                                         \
3:   if (MD_SETJMP((_thread)->context))                                     \
4:    _main();                                                             \
5:  memcpy((char *)(_bsp) - MD_STACK_PAD_SIZE,                             \
         (char *)(_thread)->context[0].__jmpbuf[17] - MD_STACK_PAD_SIZE, \
         MD_STACK_PAD_SIZE);                                             \
6:  (_thread)->context[0].__jmpbuf[0]  = (long) (_sp);                     \
7:  (_thread)->context[0].__jmpbuf[17] = (long) (_bsp);                    \
  ST_END_MACRO

memcpy does the copying of the stack frame data from stack to per st_thread.stack , while line 6-7 copies the context pointers. But I only see this definition of MD_INIT_CONTEXT under IA_64 architecture, while the common MD_INIT_CONTEXT does't have memcpy. It's like this:


#define MD_INIT_CONTEXT(_thread, _sp, _main) \
  ST_BEGIN_MACRO                             \
  if (MD_SETJMP((_thread)->context))         \
    _main();                                 \
  MD_GET_SP(_thread) = (long) (_sp);         \
  ST_END_MACRO



Do I have any misunderstanding about this question? st should save context pointers and the frame data on the stack, is it right? Do I miss something important somewhere?