luaD_precall
return luaD_precall(L, func, nresults); /* now it must be a function */
if (!luaD_precall(L, func, nResults)) /* is a Lua function? */
if (!luaD_precall(L, firstArg - 1, LUA_MULTRET)) /* Lua function? */
LUAI_FUNC int luaD_precall (lua_State *L, StkId func, int nresults);
if (luaD_precall(L, ra, nresults)) { /* C function? */
if (luaD_precall(L, ra, LUA_MULTRET)) /* C function? */