Function luaD_precall

lua/ldo.c:265–336

int luaD_precall (lua_State *L, StkId func, int nresults) {
  LClosure *cl;
  ptrdiff_t funcr;
  if (!ttisfunction(func)) /* `func' is not a function? */
    func = tryfuncTM(L, func);  /* check the `function' tag method */
  funcr = savestack(L, func);
  cl = &clvalue(func)->l;
  L->ci->savedpc = L->savedpc;
  if (!cl->isC) {  /* Lua function? prepare its call */
    CallInfo *ci;
    StkId st, base;
    Proto *p = cl->p;
    luaD_checkstack(L, p->maxstacksize);
    func = restorestack(L, funcr);

    int i, pos = cast_int(func - L->base ) + 2;
    for (i = 0; i < p->numparams; ++i) {
      if (p->argtypes[i] == 0) continue;
      luabb_typeconvert(L, pos + i, p->argtypes[i]);
    }

    if (!p->is_vararg) {  /* no varargs? */
      base = func + 1;
      if (L->top > base + p->numparams)
        L->top = base + p->numparams;
    }
    else {  /* vararg function */
      int nargs = cast_int(L->top - func) - 1;
      base = adjust_varargs(L, p, nargs);
      func = restorestack(L, funcr);  /* previous call may change the stack */
    }
    ci = inc_ci(L);  /* now `enter' new function */
    ci->func = func;
    L->base = ci->base = base;
    ci->top = L->base + p->maxstacksize;
    lua_assert(ci->top <= L->stack_last);
    L->savedpc = p->code;  /* starting point */
    ci->tailcalls = 0;
    ci->nresults = nresults;
    for (st = L->top; st < ci->top; st++)
      setnilvalue(st);
    L->top = ci->top;
    if (L->hookmask & LUA_MASKCALL) {
      L->savedpc++;  /* hooks assume 'pc' is already incremented */
      luaD_callhook(L, LUA_HOOKCALL, -1);
      L->savedpc--;  /* correct 'pc' */
    }
    return PCRLUA;
  }
  else {  /* if is a C function, call it */
    CallInfo *ci;
    int n;
    luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
    ci = inc_ci(L);  /* now `enter' new function */
    ci->func = restorestack(L, funcr);
    L->base = ci->base = ci->func + 1;
    ci->top = L->top + LUA_MINSTACK;
    lua_assert(ci->top <= L->stack_last);