frame->type = NORMAL_FRAME;
create_sentinel_frame (struct regcache *regcache){  struct frame_info *frame = FRAME_OBSTACK_ZALLOC (struct frame_info);  frame->type = NORMAL_FRAME;  frame->level = -1;  /* Explicitly initialize the sentinel frame's cache.  Provide it     with the underlying regcache.  In the future additional     information, such as the frame's thread will be added.  */  frame->prologue_cache = sentinel_frame_cache (regcache);  /* For the moment there is only one sentinel frame implementation.  */  frame->unwind = sentinel_frame_unwind;  /* Link this frame back to itself.  The frame is self referential     (the unwound PC is the same as the pc), so make it so.  */  frame->next = frame;  /* Make the sentinel frame's ID valid, but invalid.  That way all     comparisons with it should fail.  */  frame->this_id.p = 1;  frame->this_id.value = null_frame_id;  if (frame_debug)    {      fprintf_unfiltered (gdb_stdlog, "{ create_sentinel_frame (...) -> ");      fprint_frame (gdb_stdlog, frame);      fprintf_unfiltered (gdb_stdlog, " }\n");    }  return frame;}