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1/*
2** $Id: lgc.c,v 2.38 2006/05/24 14:34:06 roberto Exp $
3** Garbage Collector
4** See Copyright Notice in lua.h
5*/
6
7#include <string.h>
8
9#define lgc_c
10#define LUA_CORE
11
12#include "lua.h"
13
14#include "ldebug.h"
15#include "ldo.h"
16#include "lfunc.h"
17#include "lgc.h"
18#include "lmem.h"
19#include "lobject.h"
20#include "lstate.h"
21#include "lstring.h"
22#include "ltable.h"
23#include "ltm.h"
24
25
26#define GCSTEPSIZE1024u
27#define GCSWEEPMAX40
28#define GCSWEEPCOST10
29#define GCFINALIZECOST100
30
31
32#define maskmarkscast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
33
34#define makewhite(g,x)\
35 ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
36
37#define white2gray(x)reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
38#define black2gray(x)resetbit((x)->gch.marked, BLACKBIT)
39
40#define stringmark(s)reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
41
42
43#define isfinalized(u)testbit((u)->marked, FINALIZEDBIT)
44#define markfinalized(u)l_setbit((u)->marked, FINALIZEDBIT)
45
46
47#define KEYWEAK bitmask(KEYWEAKBIT)
48#define VALUEWEAK bitmask(VALUEWEAKBIT)
49
50
51
52#define markvalue(g,o) { checkconsistency(o); \
53 if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
54
55#define markobject(g,t) { if (iswhite(obj2gco(t))) \
56reallymarkobject(g, obj2gco(t)); }
57
58
59#define setthreshold(g) (g->GCthreshold = (g->estimate/100) * g->gcpause)
60
61
62static void removeentry (Node *n) {
63 lua_assert(ttisnil(gval(n)));
64 if (iscollectable(gkey(n)))
65 setttype(gkey(n), LUA_TDEADKEY); /* dead key; remove it */
66}
67
68
69static void reallymarkobject (global_State *g, GCObject *o) {
70 lua_assert(iswhite(o) && !isdead(g, o));
71 white2gray(o);
72 switch (o->gch.tt) {
73 case LUA_TSTRING: {
74 return;
75 }
76 case LUA_TUSERDATA: {
77 Table *mt = gco2u(o)->metatable;
78 gray2black(o); /* udata are never gray */
79 if (mt) markobject(g, mt);
80 markobject(g, gco2u(o)->env);
81 return;
82 }
83 case LUA_TUPVAL: {
84 UpVal *uv = gco2uv(o);
85 markvalue(g, uv->v);
86 if (uv->v == &uv->u.value) /* closed? */
87 gray2black(o); /* open upvalues are never black */
88 return;
89 }
90 case LUA_TFUNCTION: {
91 gco2cl(o)->c.gclist = g->gray;
92 g->gray = o;
93 break;
94 }
95 case LUA_TTABLE: {
96 gco2h(o)->gclist = g->gray;
97 g->gray = o;
98 break;
99 }
100 case LUA_TTHREAD: {
101 gco2th(o)->gclist = g->gray;
102 g->gray = o;
103 break;
104 }
105 case LUA_TPROTO: {
106 gco2p(o)->gclist = g->gray;
107 g->gray = o;
108 break;
109 }
110 default: lua_assert(0);
111 }
112}
113
114
115static void marktmu (global_State *g) {
116 GCObject *u = g->tmudata;
117 if (u) {
118 do {
119 u = u->gch.next;
120 makewhite(g, u); /* may be marked, if left from previous GC */
121 reallymarkobject(g, u);
122 } while (u != g->tmudata);
123 }
124}
125
126
127/* move `dead' udata that need finalization to list `tmudata' */
128size_t luaC_separateudata (lua_State *L, int all) {
129 global_State *g = G(L);
130 size_t deadmem = 0;
131 GCObject **p = &g->mainthread->next;
132 GCObject *curr;
133 while ((curr = *p) != NULL) {
134 if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
135 p = &curr->gch.next; /* don't bother with them */
136 else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
137 markfinalized(gco2u(curr)); /* don't need finalization */
138 p = &curr->gch.next;
139 }
140 else { /* must call its gc method */
141 deadmem += sizeudata(gco2u(curr));
142 markfinalized(gco2u(curr));
143 *p = curr->gch.next;
144 /* link `curr' at the end of `tmudata' list */
145 if (g->tmudata == NULL) /* list is empty? */
146 g->tmudata = curr->gch.next = curr; /* creates a circular list */
147 else {
148 curr->gch.next = g->tmudata->gch.next;
149 g->tmudata->gch.next = curr;
150 g->tmudata = curr;
151 }
152 }
153 }
154 return deadmem;
155}
156
157
158static int traversetable (global_State *g, Table *h) {
159 int i;
160 int weakkey = 0;
161 int weakvalue = 0;
162 const TValue *mode;
163 if (h->metatable)
164 markobject(g, h->metatable);
165 mode = gfasttm(g, h->metatable, TM_MODE);
166 if (mode && ttisstring(mode)) { /* is there a weak mode? */
167 weakkey = (strchr(svalue(mode), 'k') != NULL);
168 weakvalue = (strchr(svalue(mode), 'v') != NULL);
169 if (weakkey || weakvalue) { /* is really weak? */
170 h->marked &= ~(KEYWEAK | VALUEWEAK); /* clear bits */
171 h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
172 (weakvalue << VALUEWEAKBIT));
173 h->gclist = g->weak; /* must be cleared after GC, ... */
174 g->weak = obj2gco(h); /* ... so put in the appropriate list */
175 }
176 }
177 if (weakkey && weakvalue) return 1;
178 if (!weakvalue) {
179 i = h->sizearray;
180 while (i--)
181 markvalue(g, &h->array[i]);
182 }
183 i = sizenode(h);
184 while (i--) {
185 Node *n = gnode(h, i);
186 lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
187 if (ttisnil(gval(n)))
188 removeentry(n); /* remove empty entries */
189 else {
190 lua_assert(!ttisnil(gkey(n)));
191 if (!weakkey) markvalue(g, gkey(n));
192 if (!weakvalue) markvalue(g, gval(n));
193 }
194 }
195 return weakkey || weakvalue;
196}
197
198
199/*
200** All marks are conditional because a GC may happen while the
201** prototype is still being created
202*/
203static void traverseproto (global_State *g, Proto *f) {
204 int i;
205 if (f->source) stringmark(f->source);
206 for (i=0; i<f->sizek; i++) /* mark literals */
207 markvalue(g, &f->k[i]);
208 for (i=0; i<f->sizeupvalues; i++) { /* mark upvalue names */
209 if (f->upvalues[i])
210 stringmark(f->upvalues[i]);
211 }
212 for (i=0; i<f->sizep; i++) { /* mark nested protos */
213 if (f->p[i])
214 markobject(g, f->p[i]);
215 }
216 for (i=0; i<f->sizelocvars; i++) { /* mark local-variable names */
217 if (f->locvars[i].varname)
218 stringmark(f->locvars[i].varname);
219 }
220}
221
222
223
224static void traverseclosure (global_State *g, Closure *cl) {
225 markobject(g, cl->c.env);
226 if (cl->c.isC) {
227 int i;
228 for (i=0; i<cl->c.nupvalues; i++) /* mark its upvalues */
229 markvalue(g, &cl->c.upvalue[i]);
230 }
231 else {
232 int i;
233 lua_assert(cl->l.nupvalues == cl->l.p->nups);
234 markobject(g, cl->l.p);
235 for (i=0; i<cl->l.nupvalues; i++) /* mark its upvalues */
236 markobject(g, cl->l.upvals[i]);
237 }
238}
239
240
241static void checkstacksizes (lua_State *L, StkId max) {
242 int ci_used = cast_int(L->ci - L->base_ci); /* number of `ci' in use */
243 int s_used = cast_int(max - L->stack); /* part of stack in use */
244 if (L->size_ci > LUAI_MAXCALLS) /* handling overflow? */
245 return; /* do not touch the stacks */
246 if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
247 luaD_reallocCI(L, L->size_ci/2); /* still big enough... */
248 condhardstacktests(luaD_reallocCI(L, ci_used + 1));
249 if (4*s_used < L->stacksize &&
250 2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
251 luaD_reallocstack(L, L->stacksize/2); /* still big enough... */
252 condhardstacktests(luaD_reallocstack(L, s_used));
253}
254
255
256static void traversestack (global_State *g, lua_State *l) {
257 StkId o, lim;
258 CallInfo *ci;
259 markvalue(g, gt(l));
260 lim = l->top;
261 for (ci = l->base_ci; ci <= l->ci; ci++) {
262 lua_assert(ci->top <= l->stack_last);
263 if (lim < ci->top) lim = ci->top;
264 }
265 for (o = l->stack; o < l->top; o++)
266 markvalue(g, o);
267 for (; o <= lim; o++)
268 setnilvalue(o);
269 checkstacksizes(l, lim);
270}
271
272
273/*
274** traverse one gray object, turning it to black.
275** Returns `quantity' traversed.
276*/
277static l_mem propagatemark (global_State *g) {
278 GCObject *o = g->gray;
279 lua_assert(isgray(o));
280 gray2black(o);
281 switch (o->gch.tt) {
282 case LUA_TTABLE: {
283 Table *h = gco2h(o);
284 g->gray = h->gclist;
285 if (traversetable(g, h)) /* table is weak? */
286 black2gray(o); /* keep it gray */
287 return sizeof(Table) + sizeof(TValue) * h->sizearray +
288 sizeof(Node) * sizenode(h);
289 }
290 case LUA_TFUNCTION: {
291 Closure *cl = gco2cl(o);
292 g->gray = cl->c.gclist;
293 traverseclosure(g, cl);
294 return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
295 sizeLclosure(cl->l.nupvalues);
296 }
297 case LUA_TTHREAD: {
298 lua_State *th = gco2th(o);
299 g->gray = th->gclist;
300 th->gclist = g->grayagain;
301 g->grayagain = o;
302 black2gray(o);
303 traversestack(g, th);
304 return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
305 sizeof(CallInfo) * th->size_ci;
306 }
307 case LUA_TPROTO: {
308 Proto *p = gco2p(o);
309 g->gray = p->gclist;
310 traverseproto(g, p);
311 return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
312 sizeof(Proto *) * p->sizep +
313 sizeof(TValue) * p->sizek +
314 sizeof(int) * p->sizelineinfo +
315 sizeof(LocVar) * p->sizelocvars +
316 sizeof(TString *) * p->sizeupvalues;
317 }
318 default: lua_assert(0); return 0;
319 }
320}
321
322
323static size_t propagateall (global_State *g) {
324 size_t m = 0;
325 while (g->gray) m += propagatemark(g);
326 return m;
327}
328
329
330/*
331** The next function tells whether a key or value can be cleared from
332** a weak table. Non-collectable objects are never removed from weak
333** tables. Strings behave as `values', so are never removed too. for
334** other objects: if really collected, cannot keep them; for userdata
335** being finalized, keep them in keys, but not in values
336*/
337static int iscleared (const TValue *o, int iskey) {
338 if (!iscollectable(o)) return 0;
339 if (ttisstring(o)) {
340 stringmark(rawtsvalue(o)); /* strings are `values', so are never weak */
341 return 0;
342 }
343 return iswhite(gcvalue(o)) ||
344 (ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
345}
346
347
348/*
349** clear collected entries from weaktables
350*/
351static void cleartable (GCObject *l) {
352 while (l) {
353 Table *h = gco2h(l);
354 int i = h->sizearray;
355 lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
356 testbit(h->marked, KEYWEAKBIT));
357 if (testbit(h->marked, VALUEWEAKBIT)) {
358 while (i--) {
359 TValue *o = &h->array[i];
360 if (iscleared(o, 0)) /* value was collected? */
361 setnilvalue(o); /* remove value */
362 }
363 }
364 i = sizenode(h);
365 while (i--) {
366 Node *n = gnode(h, i);
367 if (!ttisnil(gval(n)) && /* non-empty entry? */
368 (iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
369 setnilvalue(gval(n)); /* remove value ... */
370 removeentry(n); /* remove entry from table */
371 }
372 }
373 l = h->gclist;
374 }
375}
376
377
378static void freeobj (lua_State *L, GCObject *o) {
379 switch (o->gch.tt) {
380 case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
381 case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
382 case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
383 case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
384 case LUA_TTHREAD: {
385 lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
386 luaE_freethread(L, gco2th(o));
387 break;
388 }
389 case LUA_TSTRING: {
390 G(L)->strt.nuse--;
391 luaM_freemem(L, o, sizestring(gco2ts(o)));
392 break;
393 }
394 case LUA_TUSERDATA: {
395 luaM_freemem(L, o, sizeudata(gco2u(o)));
396 break;
397 }
398 default: lua_assert(0);
399 }
400}
401
402
403
404#define sweepwholelist(L,p)sweeplist(L,p,MAX_LUMEM)
405
406
407static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
408 GCObject *curr;
409 global_State *g = G(L);
410 int deadmask = otherwhite(g);
411 while ((curr = *p) != NULL && count-- > 0) {
412 if (curr->gch.tt == LUA_TTHREAD) /* sweep open upvalues of each thread */
413 sweepwholelist(L, &gco2th(curr)->openupval);
414 if ((curr->gch.marked ^ WHITEBITS) & deadmask) { /* not dead? */
415 lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
416 makewhite(g, curr); /* make it white (for next cycle) */
417 p = &curr->gch.next;
418 }
419 else { /* must erase `curr' */
420 lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
421 *p = curr->gch.next;
422 if (curr == g->rootgc) /* is the first element of the list? */
423 g->rootgc = curr->gch.next; /* adjust first */
424 freeobj(L, curr);
425 }
426 }
427 return p;
428}
429
430
431static void checkSizes (lua_State *L) {
432 global_State *g = G(L);
433 /* check size of string hash */
434 if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
435 g->strt.size > MINSTRTABSIZE*2)
436 luaS_resize(L, g->strt.size/2); /* table is too big */
437 /* check size of buffer */
438 if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) { /* buffer too big? */
439 size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
440 luaZ_resizebuffer(L, &g->buff, newsize);
441 }
442}
443
444
445static void GCTM (lua_State *L) {
446 global_State *g = G(L);
447 GCObject *o = g->tmudata->gch.next; /* get first element */
448 Udata *udata = rawgco2u(o);
449 const TValue *tm;
450 /* remove udata from `tmudata' */
451 if (o == g->tmudata) /* last element? */
452 g->tmudata = NULL;
453 else
454 g->tmudata->gch.next = udata->uv.next;
455 udata->uv.next = g->mainthread->next; /* return it to `root' list */
456 g->mainthread->next = o;
457 makewhite(g, o);
458 tm = fasttm(L, udata->uv.metatable, TM_GC);
459 if (tm != NULL) {
460 lu_byte oldah = L->allowhook;
461 lu_mem oldt = g->GCthreshold;
462 L->allowhook = 0; /* stop debug hooks during GC tag method */
463 g->GCthreshold = 2*g->totalbytes; /* avoid GC steps */
464 setobj2s(L, L->top, tm);
465 setuvalue(L, L->top+1, udata);
466 L->top += 2;
467 luaD_call(L, L->top - 2, 0);
468 L->allowhook = oldah; /* restore hooks */
469 g->GCthreshold = oldt; /* restore threshold */
470 }
471}
472
473
474/*
475** Call all GC tag methods
476*/
477void luaC_callGCTM (lua_State *L) {
478 while (G(L)->tmudata)
479 GCTM(L);
480}
481
482
483void luaC_freeall (lua_State *L) {
484 global_State *g = G(L);
485 int i;
486 g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT); /* mask to collect all elements */
487 sweepwholelist(L, &g->rootgc);
488 for (i = 0; i < g->strt.size; i++) /* free all string lists */
489 sweepwholelist(L, &g->strt.hash[i]);
490}
491
492
493static void markmt (global_State *g) {
494 int i;
495 for (i=0; i<NUM_TAGS; i++)
496 if (g->mt[i]) markobject(g, g->mt[i]);
497}
498
499
500/* mark root set */
501static void markroot (lua_State *L) {
502 global_State *g = G(L);
503 g->gray = NULL;
504 g->grayagain = NULL;
505 g->weak = NULL;
506 markobject(g, g->mainthread);
507 /* make global table be traversed before main stack */
508 markvalue(g, gt(g->mainthread));
509 markvalue(g, registry(L));
510 markmt(g);
511 g->gcstate = GCSpropagate;
512}
513
514
515static void remarkupvals (global_State *g) {
516 UpVal *uv;
517 for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
518 lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
519 if (isgray(obj2gco(uv)))
520 markvalue(g, uv->v);
521 }
522}
523
524
525static void atomic (lua_State *L) {
526 global_State *g = G(L);
527 size_t udsize; /* total size of userdata to be finalized */
528 /* remark occasional upvalues of (maybe) dead threads */
529 remarkupvals(g);
530 /* traverse objects cautch by write barrier and by 'remarkupvals' */
531 propagateall(g);
532 /* remark weak tables */
533 g->gray = g->weak;
534 g->weak = NULL;
535 lua_assert(!iswhite(obj2gco(g->mainthread)));
536 markobject(g, L); /* mark running thread */
537 markmt(g); /* mark basic metatables (again) */
538 propagateall(g);
539 /* remark gray again */
540 g->gray = g->grayagain;
541 g->grayagain = NULL;
542 propagateall(g);
543 udsize = luaC_separateudata(L, 0); /* separate userdata to be finalized */
544 marktmu(g); /* mark `preserved' userdata */
545 udsize += propagateall(g); /* remark, to propagate `preserveness' */
546 cleartable(g->weak); /* remove collected objects from weak tables */
547 /* flip current white */
548 g->currentwhite = cast_byte(otherwhite(g));
549 g->sweepstrgc = 0;
550 g->sweepgc = &g->rootgc;
551 g->gcstate = GCSsweepstring;
552 g->estimate = g->totalbytes - udsize; /* first estimate */
553}
554
555
556static l_mem singlestep (lua_State *L) {
557 global_State *g = G(L);
558 /*lua_checkmemory(L);*/
559 switch (g->gcstate) {
560 case GCSpause: {
561 markroot(L); /* start a new collection */
562 return 0;
563 }
564 case GCSpropagate: {
565 if (g->gray)
566 return propagatemark(g);
567 else { /* no more `gray' objects */
568 atomic(L); /* finish mark phase */
569 return 0;
570 }
571 }
572 case GCSsweepstring: {
573 lu_mem old = g->totalbytes;
574 sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
575 if (g->sweepstrgc >= g->strt.size) /* nothing more to sweep? */
576 g->gcstate = GCSsweep; /* end sweep-string phase */
577 lua_assert(old >= g->totalbytes);
578 g->estimate -= old - g->totalbytes;
579 return GCSWEEPCOST;
580 }
581 case GCSsweep: {
582 lu_mem old = g->totalbytes;
583 g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
584 if (*g->sweepgc == NULL) { /* nothing more to sweep? */
585 checkSizes(L);
586 g->gcstate = GCSfinalize; /* end sweep phase */
587 }
588 lua_assert(old >= g->totalbytes);
589 g->estimate -= old - g->totalbytes;
590 return GCSWEEPMAX*GCSWEEPCOST;
591 }
592 case GCSfinalize: {
593 if (g->tmudata) {
594 GCTM(L);
595 if (g->estimate > GCFINALIZECOST)
596 g->estimate -= GCFINALIZECOST;
597 return GCFINALIZECOST;
598 }
599 else {
600 g->gcstate = GCSpause; /* end collection */
601 g->gcdept = 0;
602 return 0;
603 }
604 }
605 default: lua_assert(0); return 0;
606 }
607}
608
609
610void luaC_step (lua_State *L) {
611 global_State *g = G(L);
612 l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
613 if (lim == 0)
614 lim = (MAX_LUMEM-1)/2; /* no limit */
615 g->gcdept += g->totalbytes - g->GCthreshold;
616 do {
617 lim -= singlestep(L);
618 if (g->gcstate == GCSpause)
619 break;
620 } while (lim > 0);
621 if (g->gcstate != GCSpause) {
622 if (g->gcdept < GCSTEPSIZE)
623 g->GCthreshold = g->totalbytes + GCSTEPSIZE; /* - lim/g->gcstepmul;*/
624 else {
625 g->gcdept -= GCSTEPSIZE;
626 g->GCthreshold = g->totalbytes;
627 }
628 }
629 else {
630 lua_assert(g->totalbytes >= g->estimate);
631 setthreshold(g);
632 }
633}
634
635
636void luaC_fullgc (lua_State *L) {
637 global_State *g = G(L);
638 if (g->gcstate <= GCSpropagate) {
639 /* reset sweep marks to sweep all elements (returning them to white) */
640 g->sweepstrgc = 0;
641 g->sweepgc = &g->rootgc;
642 /* reset other collector lists */
643 g->gray = NULL;
644 g->grayagain = NULL;
645 g->weak = NULL;
646 g->gcstate = GCSsweepstring;
647 }
648 lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
649 /* finish any pending sweep phase */
650 while (g->gcstate != GCSfinalize) {
651 lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
652 singlestep(L);
653 }
654 markroot(L);
655 while (g->gcstate != GCSpause) {
656 singlestep(L);
657 }
658 setthreshold(g);
659}
660
661
662void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
663 global_State *g = G(L);
664 lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
665 lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
666 lua_assert(ttype(&o->gch) != LUA_TTABLE);
667 /* must keep invariant? */
668 if (g->gcstate == GCSpropagate)
669 reallymarkobject(g, v); /* restore invariant */
670 else /* don't mind */
671 makewhite(g, o); /* mark as white just to avoid other barriers */
672}
673
674
675void luaC_barrierback (lua_State *L, Table *t) {
676 global_State *g = G(L);
677 GCObject *o = obj2gco(t);
678 lua_assert(isblack(o) && !isdead(g, o));
679 lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
680 black2gray(o); /* make table gray (again) */
681 t->gclist = g->grayagain;
682 g->grayagain = o;
683}
684
685
686void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
687 global_State *g = G(L);
688 o->gch.next = g->rootgc;
689 g->rootgc = o;
690 o->gch.marked = luaC_white(g);
691 o->gch.tt = tt;
692}
693
694
695void luaC_linkupval (lua_State *L, UpVal *uv) {
696 global_State *g = G(L);
697 GCObject *o = obj2gco(uv);
698 o->gch.next = g->rootgc; /* link upvalue into `rootgc' list */
699 g->rootgc = o;
700 if (isgray(o)) {
701 if (g->gcstate == GCSpropagate) {
702 gray2black(o); /* closed upvalues need barrier */
703 luaC_barrier(L, uv, uv->v);
704 }
705 else { /* sweep phase: sweep it (turning it into white) */
706 makewhite(g, o);
707 lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
708 }
709 }
710}
711

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