luaD_reallocstack
luaD_reallocstack(L, ERRORSTACKSIZE);
luaD_reallocstack(L, newsize);
luaD_reallocstack(L, goodsize); /* shrink it */
LUAI_FUNC void luaD_reallocstack (lua_State *L, int newsize);
#define condmovestack(L) luaD_reallocstack((L), (L)->stacksize)