/* Error in context of caller. */
LJ_NOINLINE void lj_err_callermsg(lua_State *L, const char *msg)
{
  TValue *frame = L->base-1;
  TValue *pframe = NULL;
  if (frame_islua(frame)) {
    pframe = frame_prevl(frame);
  } else if (frame_iscont(frame)) {
    if (frame_iscont_fficb(frame)) {
      pframe = frame;
      frame = NULL;
    } else {
      pframe = frame_prevd(frame);
#if LJ_HASFFI
      /* Remove frame for FFI metamethods. */
      if (frame_func(frame)->c.ffid >= FF_ffi_meta___index &&
	  frame_func(frame)->c.ffid <= FF_ffi_meta___tostring) {
	L->base = pframe+1;
	L->top = frame;
	setcframe_pc(cframe_raw(L->cframe), frame_contpc(frame));
      }
#endif
    }
  }
  lj_debug_addloc(L, msg, pframe, frame);
  lj_err_run(L);
}
/* Return bytecode position for function/frame or NO_BCPOS. */
static BCPos debug_framepc(lua_State *L, GCfunc *fn, cTValue *nextframe)
{
  const BCIns *ins;
  GCproto *pt;
  BCPos pos;
  lua_assert(fn->c.gct == ~LJ_TFUNC || fn->c.gct == ~LJ_TTHREAD);
  if (!isluafunc(fn)) {  /* Cannot derive a PC for non-Lua functions. */
    return NO_BCPOS;
  } else if (nextframe == NULL) {  /* Lua function on top. */
    void *cf = cframe_raw(L->cframe);
    if (cf == NULL || (char *)cframe_pc(cf) == (char *)cframe_L(cf))
      return NO_BCPOS;
    ins = cframe_pc(cf);  /* Only happens during error/hook handling. */
  } else {
    if (frame_islua(nextframe)) {
      ins = frame_pc(nextframe);
    } else if (frame_iscont(nextframe)) {
      ins = frame_contpc(nextframe);
    } else {
      /* Lua function below errfunc/gc/hook: find cframe to get the PC. */
      void *cf = cframe_raw(L->cframe);
      TValue *f = L->base-1;
      for (;;) {
	if (cf == NULL)
	  return NO_BCPOS;
	while (cframe_nres(cf) < 0) {
	  if (f >= restorestack(L, -cframe_nres(cf)))
	    break;
	  cf = cframe_raw(cframe_prev(cf));
	  if (cf == NULL)
	    return NO_BCPOS;
	}
	if (f < nextframe)
	  break;
	if (frame_islua(f)) {
	  f = frame_prevl(f);
	} else {
	  if (frame_isc(f) || (frame_iscont(f) && frame_iscont_fficb(f)))
	    cf = cframe_raw(cframe_prev(cf));
	  f = frame_prevd(f);
	}
      }
      ins = cframe_pc(cf);
    }
  }
  pt = funcproto(fn);
  pos = proto_bcpos(pt, ins) - 1;
#if LJ_HASJIT
  if (pos > pt->sizebc) {  /* Undo the effects of lj_trace_exit for JLOOP. */
    GCtrace *T = (GCtrace *)((char *)(ins-1) - offsetof(GCtrace, startins));
    lua_assert(bc_isret(bc_op(ins[-1])));
    pos = proto_bcpos(pt, mref(T->startpc, const BCIns));
  }
/* Find error function for runtime errors. Requires an extra stack traversal. */
static ptrdiff_t finderrfunc(lua_State *L)
{
  cTValue *frame = L->base-1, *bot = tvref(L->stack)+LJ_FR2;
  void *cf = L->cframe;
  while (frame > bot && cf) {
    while (cframe_nres(cframe_raw(cf)) < 0) {  /* cframe without frame? */
      if (frame >= restorestack(L, -cframe_nres(cf)))
	break;
      if (cframe_errfunc(cf) >= 0)  /* Error handler not inherited (-1)? */
	return cframe_errfunc(cf);
      cf = cframe_prev(cf);  /* Else unwind cframe and continue searching. */
      if (cf == NULL)
	return 0;
    }
    switch (frame_typep(frame)) {
    case FRAME_LUA:
    case FRAME_LUAP:
      frame = frame_prevl(frame);
      break;
    case FRAME_C:
      cf = cframe_prev(cf);
      /* fallthrough */
    case FRAME_VARG:
      frame = frame_prevd(frame);
      break;
    case FRAME_CONT:
      if (frame_iscont_fficb(frame))
	cf = cframe_prev(cf);
      frame = frame_prevd(frame);
      break;
    case FRAME_CP:
      if (cframe_canyield(cf)) return 0;
      if (cframe_errfunc(cf) >= 0)
	return cframe_errfunc(cf);
      frame = frame_prevd(frame);
      break;
    case FRAME_PCALL:
    case FRAME_PCALLH:
      if (frame_func(frame_prevd(frame))->c.ffid == FF_xpcall)
	return savestack(L, frame_prevd(frame)+1);  /* xpcall's errorfunc. */
      return 0;
    default:
      lua_assert(0);
      return 0;
    }
  }
  return 0;
}
/* Unwind until stop frame. Optionally cleanup frames. */
static void *err_unwind(lua_State *L, void *stopcf, int errcode)
{
  TValue *frame = L->base-1;
  void *cf = L->cframe;
  while (cf) {
    int32_t nres = cframe_nres(cframe_raw(cf));
    if (nres < 0) {  /* C frame without Lua frame? */
      TValue *top = restorestack(L, -nres);
      if (frame < top) {  /* Frame reached? */
	if (errcode) {
	  L->base = frame+1;
	  L->cframe = cframe_prev(cf);
	  unwindstack(L, top);
	}
	return cf;
      }
    }
    if (frame <= tvref(L->stack)+LJ_FR2)
      break;
    switch (frame_typep(frame)) {
    case FRAME_LUA:  /* Lua frame. */
    case FRAME_LUAP:
      frame = frame_prevl(frame);
      break;
    case FRAME_C:  /* C frame. */
    unwind_c:
#if LJ_UNWIND_EXT
      if (errcode) {
	L->base = frame_prevd(frame) + 1;
	L->cframe = cframe_prev(cf);
	unwindstack(L, frame - LJ_FR2);
      } else if (cf != stopcf) {
	cf = cframe_prev(cf);
	frame = frame_prevd(frame);
	break;
      }
      return NULL;  /* Continue unwinding. */
#else
      UNUSED(stopcf);
      cf = cframe_prev(cf);
      frame = frame_prevd(frame);
      break;
#endif
    case FRAME_CP:  /* Protected C frame. */
      if (cframe_canyield(cf)) {  /* Resume? */
	if (errcode) {
	  hook_leave(G(L));  /* Assumes nobody uses coroutines inside hooks. */
	  L->cframe = NULL;
	  L->status = (uint8_t)errcode;
	}
	return cf;
      }
      if (errcode) {
	L->base = frame_prevd(frame) + 1;
	L->cframe = cframe_prev(cf);
	unwindstack(L, frame - LJ_FR2);
      }
      return cf;
    case FRAME_CONT:  /* Continuation frame. */
      if (frame_iscont_fficb(frame))
	goto unwind_c;
    case FRAME_VARG:  /* Vararg frame. */
      frame = frame_prevd(frame);
      break;
    case FRAME_PCALL:  /* FF pcall() frame. */
    case FRAME_PCALLH:  /* FF pcall() frame inside hook. */
      if (errcode) {
	if (errcode == LUA_YIELD) {
	  frame = frame_prevd(frame);
	  break;
	}
	if (frame_typep(frame) == FRAME_PCALL)
	  hook_leave(G(L));
	L->base = frame_prevd(frame) + 1;
	L->cframe = cf;
	unwindstack(L, L->base);
      }
      return (void *)((intptr_t)cf | CFRAME_UNWIND_FF);
    }
  }
  /* No C frame. */
  if (errcode) {
    L->base = tvref(L->stack)+1+LJ_FR2;
    L->cframe = NULL;
    unwindstack(L, L->base);
    if (G(L)->panic)
      G(L)->panic(L);
    exit(EXIT_FAILURE);
  }
  return L;  /* Anything non-NULL will do. */
}