LG
int lg = LG;
lua_assert(gettotalbytes(g) == sizeof(LG));
(*g->frealloc)(g->ud, fromstate(L), sizeof(LG), 0); /* free main block */
LG *l = cast(LG *, (*f)(ud, NULL, LUA_TTHREAD, sizeof(LG)));
g->totalbytes = sizeof(LG);