LUA_MINSTACK
const int extra = LUA_MINSTACK;
luaD_checkstack(L, LUA_MINSTACK); /* ensure minimum stack size */
ci->top = L->top + LUA_MINSTACK;
luaD_checkstack(L, LUA_MINSTACK); /* ensure minimum stack size */
ci->top = L->top + LUA_MINSTACK;
ci->top = L1->top + LUA_MINSTACK;
#define BASIC_STACK_SIZE (2*LUA_MINSTACK)