74 /* make an object gray (neither white nor black) */
149   lua_assert(!isgray(o));  /* cannot be in a gray list */  in linkgclist_()
228 ** pointing to a white object as gray again.
234   if (getage(o) == G_TOUCHED2)  /* already in gray list? */  in luaC_barrierback_()
235     set2gray(o);  /* make it gray to become touched1 */  in luaC_barrierback_()
236   else  /* link it in 'grayagain' and paint it gray */  in luaC_barrierback_()
246   set2gray(o);  /* they will be gray forever */  in luaC_fix()
289 ** 'twups' list, so they don't go to the gray list; nevertheless, they
290 ** are kept gray to avoid barriers, as their values will be revisited
292 ** gray list to be visited (and turned black) later.  Both userdata and
307         set2gray(uv);  /* open upvalues are kept gray */  in reallymarkobject()
324       linkobjgclist(o, g->gray);  /* to be visited later */  in reallymarkobject()
395   g->gray = g->grayagain = NULL;  in cleargraylists()
401 ** mark root set and reset all gray lists, to start a new collection
427 ** back to a gray list, but then it must become OLD. (That is what
477 ** must be kept in some gray list for post-processing; this is done
623 ** these visits, threads must return to a gray list if they are not new
656 ** traverse one gray object, turning it to black.
659   GCObject *o = g->gray;  in propagatemark()
661   g->gray = *getgclist(o);  /* remove from 'gray' list */  in propagatemark()
676   while (g->gray)  in propagateall()
1074 ** are now old---must be in a gray list. Everything else is not in a
1075 ** gray list. Open upvalues are also kept gray.
1093         set2gray(curr);  /* open upvalues are always gray */  in sweep2old()
1111 ** will also remove objects turned white here from any gray list.
1162 ** Correct a list of gray objects. Return pointer to where rest of the
1201 ** Correct all gray lists, coalescing them into 'grayagain'.
1216 ** Gray objects are already in some gray list, and so will be visited
1285 ** Clears all gray lists, sweeps objects, and prepare sublists to enter
1288 ** else is turned black (not in any gray list).
1536   work += propagateall(g);  /* empties 'gray' list */  in atomic()
1540   g->gray = grayagain;  in atomic()
1561   lua_assert(g->gray == NULL);  in atomic()
1596       if (g->gray == NULL) {  /* no more gray objects? */  in singlestep()
1601         work = propagatemark(g);  /* traverse one gray object */  in singlestep()