FGRAPH_FRAME_OFFSET
(SHADOW_STACK_OFFSET - (FGRAPH_FRAME_OFFSET + 1 + FGRAPH_ARRAY_SIZE))
(FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET;
val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET;
if (current->curr_ret_stack + FGRAPH_FRAME_OFFSET + 1 >= SHADOW_STACK_MAX_OFFSET) {
offset += FGRAPH_FRAME_OFFSET;
current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1;
*offset += FGRAPH_FRAME_OFFSET;
current->curr_ret_stack = offset - FGRAPH_FRAME_OFFSET;