lgc.c

   1 /*
   2 ** $Id: lgc.c,v 2.38.1.1 2007/12/27 13:02:25 roberto Exp $
   3 ** Garbage Collector
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7 #if 0
   8 #include <string.h>
   9 #endif
  10
  11 #define lgc_c
  12 #define LUA_CORE
  13
  14 #include "lua.h"
  15
  16 #include "ldebug.h"
  17 #include "ldo.h"
  18 #include "lfunc.h"
  19 #include "lgc.h"
  20 #include "lmem.h"
  21 #include "lobject.h"
  22 #include "lstate.h"
  23 #include "lstring.h"
  24 #include "ltable.h"
  25 #include "ltm.h"
  26
  27
  28 #define GCSTEPSIZE      1024u
  29 #define GCSWEEPMAX      40
  30 #define GCSWEEPCOST     10
  31 #define GCFINALIZECOST  100
  32
  33
  34 #define maskmarks       cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
  35
  36 #define makewhite(g,x)  \
  37    ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
  38
  39 #define white2gray(x)   reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
  40 #define black2gray(x)   resetbit((x)->gch.marked, BLACKBIT)
  41
  42 #define stringmark(s)   reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
  43
  44
  45 #define isfinalized(u)          testbit((u)->marked, FINALIZEDBIT)
  46 #define markfinalized(u)        l_setbit((u)->marked, FINALIZEDBIT)
  47
  48
  49 #define KEYWEAK         bitmask(KEYWEAKBIT)
  50 #define VALUEWEAK       bitmask(VALUEWEAKBIT)
  51
  52
  53
  54 #define markvalue(g,o) { checkconsistency(o); \
  55   if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
  56
  57 #define markobject(g,t) { if (iswhite(obj2gco(t))) \
  58                 reallymarkobject(g, obj2gco(t)); }
  59
  60
  61 #define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)
  62
  63
  64 static void removeentry (Node *n) {
  65   lua_assert(ttisnil(gval(n)));
  66   if (iscollectable(gkey(n)))
  67     setttype(gkey(n), LUA_TDEADKEY);  /* dead key; remove it */
  68 }
  69
  70
  71 static void reallymarkobject (global_State *g, GCObject *o) {
  72   lua_assert(iswhite(o) && !isdead(g, o));
  73   white2gray(o);
  74   switch (o->gch.tt) {
  75     case LUA_TSTRING: {
  76       return;
  77     }
  78     case LUA_TUSERDATA: {
  79       Table *mt = gco2u(o)->metatable;
  80       gray2black(o);  /* udata are never gray */
  81       if (mt) markobject(g, mt);
  82       markobject(g, gco2u(o)->env);
  83       return;
  84     }
  85     case LUA_TUPVAL: {
  86       UpVal *uv = gco2uv(o);
  87       markvalue(g, uv->v);
  88       if (uv->v == &uv->u.value)  /* closed? */
  89         gray2black(o);  /* open upvalues are never black */
  90       return;
  91     }
  92     case LUA_TFUNCTION: {
  93       gco2cl(o)->c.gclist = g->gray;
  94       g->gray = o;
  95       break;
  96     }
  97     case LUA_TTABLE: {
  98       gco2h(o)->gclist = g->gray;
  99       g->gray = o;
 100       break;
 101     }
 102     case LUA_TTHREAD: {
 103       gco2th(o)->gclist = g->gray;
 104       g->gray = o;
 105       break;
 106     }
 107     case LUA_TPROTO: {
 108       gco2p(o)->gclist = g->gray;
 109       g->gray = o;
 110       break;
 111     }
 112     default: lua_assert(0);
 113   }
 114 }
 115
 116
 117 static void marktmu (global_State *g) {
 118   GCObject *u = g->tmudata;
 119   if (u) {
 120     do {
 121       u = u->gch.next;
 122       makewhite(g, u);  /* may be marked, if left from previous GC */
 123       reallymarkobject(g, u);
 124     } while (u != g->tmudata);
 125   }
 126 }
 127
 128
 129 /* move `dead' udata that need finalization to list `tmudata' */
 130 size_t luaC_separateudata (lua_State *L, int all) {
 131   global_State *g = G(L);
 132   size_t deadmem = 0;
 133   GCObject **p = &g->mainthread->next;
 134   GCObject *curr;
 135   while ((curr = *p) != NULL) {
 136     if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
 137       p = &curr->gch.next;  /* don't bother with them */
 138     else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
 139       markfinalized(gco2u(curr));  /* don't need finalization */
 140       p = &curr->gch.next;
 141     }
 142     else {  /* must call its gc method */
 143       deadmem += sizeudata(gco2u(curr));
 144       markfinalized(gco2u(curr));
 145       *p = curr->gch.next;
 146       /* link `curr' at the end of `tmudata' list */
 147       if (g->tmudata == NULL)  /* list is empty? */
 148         g->tmudata = curr->gch.next = curr;  /* creates a circular list */
 149       else {
 150         curr->gch.next = g->tmudata->gch.next;
 151         g->tmudata->gch.next = curr;
 152         g->tmudata = curr;
 153       }
 154     }
 155   }
 156   return deadmem;
 157 }
 158
 159
 160 static int traversetable (global_State *g, Table *h) {
 161   int i;
 162   int weakkey = 0;
 163   int weakvalue = 0;
 164   const TValue *mode;
 165   if (h->metatable)
 166     markobject(g, h->metatable);
 167   mode = gfasttm(g, h->metatable, TM_MODE);
 168   if (mode && ttisstring(mode)) {  /* is there a weak mode? */
 169     weakkey = (strchr(svalue(mode), 'k') != NULL);
 170     weakvalue = (strchr(svalue(mode), 'v') != NULL);
 171     if (weakkey || weakvalue) {  /* is really weak? */
 172       h->marked &= ~(KEYWEAK | VALUEWEAK);  /* clear bits */
 173       h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
 174                              (weakvalue << VALUEWEAKBIT));
 175       h->gclist = g->weak;  /* must be cleared after GC, ... */
 176       g->weak = obj2gco(h);  /* ... so put in the appropriate list */
 177     }
 178   }
 179   if (weakkey && weakvalue) return 1;
 180   if (!weakvalue) {
 181     i = h->sizearray;
 182     while (i--)
 183       markvalue(g, &h->array[i]);
 184   }
 185   i = sizenode(h);
 186   while (i--) {
 187     Node *n = gnode(h, i);
 188     lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
 189     if (ttisnil(gval(n)))
 190       removeentry(n);  /* remove empty entries */
 191     else {
 192       lua_assert(!ttisnil(gkey(n)));
 193       if (!weakkey) markvalue(g, gkey(n));
 194       if (!weakvalue) markvalue(g, gval(n));
 195     }
 196   }
 197   return weakkey || weakvalue;
 198 }
 199
 200
 201 /*
 202 ** All marks are conditional because a GC may happen while the
 203 ** prototype is still being created
 204 */
 205 static void traverseproto (global_State *g, Proto *f) {
 206   int i;
 207   if (f->source) stringmark(f->source);
 208   for (i=0; i<f->sizek; i++)  /* mark literals */
 209     markvalue(g, &f->k[i]);
 210   for (i=0; i<f->sizeupvalues; i++) {  /* mark upvalue names */
 211     if (f->upvalues[i])
 212       stringmark(f->upvalues[i]);
 213   }
 214   for (i=0; i<f->sizep; i++) {  /* mark nested protos */
 215     if (f->p[i])
 216       markobject(g, f->p[i]);
 217   }
 218   for (i=0; i<f->sizelocvars; i++) {  /* mark local-variable names */
 219     if (f->locvars[i].varname)
 220       stringmark(f->locvars[i].varname);
 221   }
 222 }
 223
 224
 225
 226 static void traverseclosure (global_State *g, Closure *cl) {
 227   markobject(g, cl->c.env);
 228   if (cl->c.isC) {
 229     int i;
 230     for (i=0; i<cl->c.nupvalues; i++)  /* mark its upvalues */
 231       markvalue(g, &cl->c.upvalue[i]);
 232   }
 233   else {
 234     int i;
 235     lua_assert(cl->l.nupvalues == cl->l.p->nups);
 236     markobject(g, cl->l.p);
 237     for (i=0; i<cl->l.nupvalues; i++)  /* mark its upvalues */
 238       markobject(g, cl->l.upvals[i]);
 239   }
 240 }
 241
 242
 243 static void checkstacksizes (lua_State *L, StkId max) {
 244   int ci_used = cast_int(L->ci - L->base_ci);  /* number of `ci' in use */
 245   int s_used = cast_int(max - L->stack);  /* part of stack in use */
 246   if (L->size_ci > LUAI_MAXCALLS)  /* handling overflow? */
 247     return;  /* do not touch the stacks */
 248   if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
 249     luaD_reallocCI(L, L->size_ci/2);  /* still big enough... */
 250   condhardstacktests(luaD_reallocCI(L, ci_used + 1));
 251   if (4*s_used < L->stacksize &&
 252       2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
 253     luaD_reallocstack(L, L->stacksize/2);  /* still big enough... */
 254   condhardstacktests(luaD_reallocstack(L, s_used));
 255 }
 256
 257
 258 static void traversestack (global_State *g, lua_State *l) {
 259   StkId o, lim;
 260   CallInfo *ci;
 261   markvalue(g, gt(l));
 262   lim = l->top;
 263   for (ci = l->base_ci; ci <= l->ci; ci++) {
 264     lua_assert(ci->top <= l->stack_last);
 265     if (lim < ci->top) lim = ci->top;
 266   }
 267   for (o = l->stack; o < l->top; o++)
 268     markvalue(g, o);
 269   for (; o <= lim; o++)
 270     setnilvalue(o);
 271   checkstacksizes(l, lim);
 272 }
 273
 274
 275 /*
 276 ** traverse one gray object, turning it to black.
 277 ** Returns `quantity' traversed.
 278 */
 279 static l_mem propagatemark (global_State *g) {
 280   GCObject *o = g->gray;
 281   lua_assert(isgray(o));
 282   gray2black(o);
 283   switch (o->gch.tt) {
 284     case LUA_TTABLE: {
 285       Table *h = gco2h(o);
 286       g->gray = h->gclist;
 287       if (traversetable(g, h))  /* table is weak? */
 288         black2gray(o);  /* keep it gray */
 289       return sizeof(Table) + sizeof(TValue) * h->sizearray +
 290                              sizeof(Node) * sizenode(h);
 291     }
 292     case LUA_TFUNCTION: {
 293       Closure *cl = gco2cl(o);
 294       g->gray = cl->c.gclist;
 295       traverseclosure(g, cl);
 296       return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
 297                            sizeLclosure(cl->l.nupvalues);
 298     }
 299     case LUA_TTHREAD: {
 300       lua_State *th = gco2th(o);
 301       g->gray = th->gclist;
 302       th->gclist = g->grayagain;
 303       g->grayagain = o;
 304       black2gray(o);
 305       traversestack(g, th);
 306       return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
 307                                  sizeof(CallInfo) * th->size_ci;
 308     }
 309     case LUA_TPROTO: {
 310       Proto *p = gco2p(o);
 311       g->gray = p->gclist;
 312       traverseproto(g, p);
 313       return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
 314                              sizeof(Proto *) * p->sizep +
 315                              sizeof(TValue) * p->sizek +
 316                              sizeof(int) * p->sizelineinfo +
 317                              sizeof(LocVar) * p->sizelocvars +
 318                              sizeof(TString *) * p->sizeupvalues;
 319     }
 320     default: lua_assert(0); return 0;
 321   }
 322 }
 323
 324
 325 static size_t propagateall (global_State *g) {
 326   size_t m = 0;
 327   while (g->gray) m += propagatemark(g);
 328   return m;
 329 }
 330
 331
 332 /*
 333 ** The next function tells whether a key or value can be cleared from
 334 ** a weak table. Non-collectable objects are never removed from weak
 335 ** tables. Strings behave as `values', so are never removed too. for
 336 ** other objects: if really collected, cannot keep them; for userdata
 337 ** being finalized, keep them in keys, but not in values
 338 */
 339 static int iscleared (const TValue *o, int iskey) {
 340   if (!iscollectable(o)) return 0;
 341   if (ttisstring(o)) {
 342     stringmark(rawtsvalue(o));  /* strings are `values', so are never weak */
 343     return 0;
 344   }
 345   return iswhite(gcvalue(o)) ||
 346     (ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
 347 }
 348
 349
 350 /*
 351 ** clear collected entries from weaktables
 352 */
 353 static void cleartable (GCObject *l) {
 354   while (l) {
 355     Table *h = gco2h(l);
 356     int i = h->sizearray;
 357     lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
 358                testbit(h->marked, KEYWEAKBIT));
 359     if (testbit(h->marked, VALUEWEAKBIT)) {
 360       while (i--) {
 361         TValue *o = &h->array[i];
 362         if (iscleared(o, 0))  /* value was collected? */
 363           setnilvalue(o);  /* remove value */
 364       }
 365     }
 366     i = sizenode(h);
 367     while (i--) {
 368       Node *n = gnode(h, i);
 369       if (!ttisnil(gval(n)) &&  /* non-empty entry? */
 370           (iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
 371         setnilvalue(gval(n));  /* remove value ... */
 372         removeentry(n);  /* remove entry from table */
 373       }
 374     }
 375     l = h->gclist;
 376   }
 377 }
 378
 379
 380 static void freeobj (lua_State *L, GCObject *o) {
 381   switch (o->gch.tt) {
 382     case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
 383     case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
 384     case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
 385     case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
 386     case LUA_TTHREAD: {
 387       lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
 388       luaE_freethread(L, gco2th(o));
 389       break;
 390     }
 391     case LUA_TSTRING: {
 392       G(L)->strt.nuse--;
 393       luaM_freemem(L, o, sizestring(gco2ts(o)));
 394       break;
 395     }
 396     case LUA_TUSERDATA: {
 397       luaM_freemem(L, o, sizeudata(gco2u(o)));
 398       break;
 399     }
 400     default: lua_assert(0);
 401   }
 402 }
 403
 404
 405
 406 #define sweepwholelist(L,p)     sweeplist(L,p,MAX_LUMEM)
 407
 408
 409 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
 410   GCObject *curr;
 411   global_State *g = G(L);
 412   int deadmask = otherwhite(g);
 413   while ((curr = *p) != NULL && count-- > 0) {
 414     if (curr->gch.tt == LUA_TTHREAD)  /* sweep open upvalues of each thread */
 415       sweepwholelist(L, &gco2th(curr)->openupval);
 416     if ((curr->gch.marked ^ WHITEBITS) & deadmask) {  /* not dead? */
 417       lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
 418       makewhite(g, curr);  /* make it white (for next cycle) */
 419       p = &curr->gch.next;
 420     }
 421     else {  /* must erase `curr' */
 422       lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
 423       *p = curr->gch.next;
 424       if (curr == g->rootgc)  /* is the first element of the list? */
 425         g->rootgc = curr->gch.next;  /* adjust first */
 426       freeobj(L, curr);
 427     }
 428   }
 429   return p;
 430 }
 431
 432
 433 static void checkSizes (lua_State *L) {
 434   global_State *g = G(L);
 435   /* check size of string hash */
 436   if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
 437       g->strt.size > MINSTRTABSIZE*2)
 438     luaS_resize(L, g->strt.size/2);  /* table is too big */
 439   /* check size of buffer */
 440   if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) {  /* buffer too big? */
 441     size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
 442     luaZ_resizebuffer(L, &g->buff, newsize);
 443   }
 444 }
 445
 446
 447 static void GCTM (lua_State *L) {
 448   global_State *g = G(L);
 449   GCObject *o = g->tmudata->gch.next;  /* get first element */
 450   Udata *udata = rawgco2u(o);
 451   const TValue *tm;
 452   /* remove udata from `tmudata' */
 453   if (o == g->tmudata)  /* last element? */
 454     g->tmudata = NULL;
 455   else
 456     g->tmudata->gch.next = udata->uv.next;
 457   udata->uv.next = g->mainthread->next;  /* return it to `root' list */
 458   g->mainthread->next = o;
 459   makewhite(g, o);
 460   tm = fasttm(L, udata->uv.metatable, TM_GC);
 461   if (tm != NULL) {
 462     lu_byte oldah = L->allowhook;
 463     lu_mem oldt = g->GCthreshold;
 464     L->allowhook = 0;  /* stop debug hooks during GC tag method */
 465     g->GCthreshold = 2*g->totalbytes;  /* avoid GC steps */
 466     setobj2s(L, L->top, tm);
 467     setuvalue(L, L->top+1, udata);
 468     L->top += 2;
 469     luaD_call(L, L->top - 2, 0);
 470     L->allowhook = oldah;  /* restore hooks */
 471     g->GCthreshold = oldt;  /* restore threshold */
 472   }
 473 }
 474
 475
 476 /*
 477 ** Call all GC tag methods
 478 */
 479 void luaC_callGCTM (lua_State *L) {
 480   while (G(L)->tmudata)
 481     GCTM(L);
 482 }
 483
 484
 485 void luaC_freeall (lua_State *L) {
 486   global_State *g = G(L);
 487   int i;
 488   g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT);  /* mask to collect all elements */
 489   sweepwholelist(L, &g->rootgc);
 490   for (i = 0; i < g->strt.size; i++)  /* free all string lists */
 491     sweepwholelist(L, &g->strt.hash[i]);
 492 }
 493
 494
 495 static void markmt (global_State *g) {
 496   int i;
 497   for (i=0; i<NUM_TAGS; i++)
 498     if (g->mt[i]) markobject(g, g->mt[i]);
 499 }
 500
 501
 502 /* mark root set */
 503 static void markroot (lua_State *L) {
 504   global_State *g = G(L);
 505   g->gray = NULL;
 506   g->grayagain = NULL;
 507   g->weak = NULL;
 508   markobject(g, g->mainthread);
 509   /* make global table be traversed before main stack */
 510   markvalue(g, gt(g->mainthread));
 511   markvalue(g, registry(L));
 512   markmt(g);
 513   g->gcstate = GCSpropagate;
 514 }
 515
 516
 517 static void remarkupvals (global_State *g) {
 518   UpVal *uv;
 519   for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
 520     lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
 521     if (isgray(obj2gco(uv)))
 522       markvalue(g, uv->v);
 523   }
 524 }
 525
 526
 527 static void atomic (lua_State *L) {
 528   global_State *g = G(L);
 529   size_t udsize;  /* total size of userdata to be finalized */
 530   /* remark occasional upvalues of (maybe) dead threads */
 531   remarkupvals(g);
 532   /* traverse objects cautch by write barrier and by 'remarkupvals' */
 533   propagateall(g);
 534   /* remark weak tables */
 535   g->gray = g->weak;
 536   g->weak = NULL;
 537   lua_assert(!iswhite(obj2gco(g->mainthread)));
 538   markobject(g, L);  /* mark running thread */
 539   markmt(g);  /* mark basic metatables (again) */
 540   propagateall(g);
 541   /* remark gray again */
 542   g->gray = g->grayagain;
 543   g->grayagain = NULL;
 544   propagateall(g);
 545   udsize = luaC_separateudata(L, 0);  /* separate userdata to be finalized */
 546   marktmu(g);  /* mark `preserved' userdata */
 547   udsize += propagateall(g);  /* remark, to propagate `preserveness' */
 548   cleartable(g->weak);  /* remove collected objects from weak tables */
 549   /* flip current white */
 550   g->currentwhite = cast_byte(otherwhite(g));
 551   g->sweepstrgc = 0;
 552   g->sweepgc = &g->rootgc;
 553   g->gcstate = GCSsweepstring;
 554   g->estimate = g->totalbytes - udsize;  /* first estimate */
 555 }
 556
 557
 558 static l_mem singlestep (lua_State *L) {
 559   global_State *g = G(L);
 560   /*lua_checkmemory(L);*/
 561   switch (g->gcstate) {
 562     case GCSpause: {
 563       markroot(L);  /* start a new collection */
 564       return 0;
 565     }
 566     case GCSpropagate: {
 567       if (g->gray)
 568         return propagatemark(g);
 569       else {  /* no more `gray' objects */
 570         atomic(L);  /* finish mark phase */
 571         return 0;
 572       }
 573     }
 574     case GCSsweepstring: {
 575       lu_mem old = g->totalbytes;
 576       sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
 577       if (g->sweepstrgc >= g->strt.size)  /* nothing more to sweep? */
 578         g->gcstate = GCSsweep;  /* end sweep-string phase */
 579       lua_assert(old >= g->totalbytes);
 580       g->estimate -= old - g->totalbytes;
 581       return GCSWEEPCOST;
 582     }
 583     case GCSsweep: {
 584       lu_mem old = g->totalbytes;
 585       g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
 586       if (*g->sweepgc == NULL) {  /* nothing more to sweep? */
 587         checkSizes(L);
 588         g->gcstate = GCSfinalize;  /* end sweep phase */
 589       }
 590       lua_assert(old >= g->totalbytes);
 591       g->estimate -= old - g->totalbytes;
 592       return GCSWEEPMAX*GCSWEEPCOST;
 593     }
 594     case GCSfinalize: {
 595       if (g->tmudata) {
 596         GCTM(L);
 597         if (g->estimate > GCFINALIZECOST)
 598           g->estimate -= GCFINALIZECOST;
 599         return GCFINALIZECOST;
 600       }
 601       else {
 602         g->gcstate = GCSpause;  /* end collection */
 603         g->gcdept = 0;
 604         return 0;
 605       }
 606     }
 607     default: lua_assert(0); return 0;
 608   }
 609 }
 610
 611
 612 void luaC_step (lua_State *L) {
 613   global_State *g = G(L);
 614   l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
 615   if (lim == 0)
 616     lim = (MAX_LUMEM-1)/2;  /* no limit */
 617   g->gcdept += g->totalbytes - g->GCthreshold;
 618   do {
 619     lim -= singlestep(L);
 620     if (g->gcstate == GCSpause)
 621       break;
 622   } while (lim > 0);
 623   if (g->gcstate != GCSpause) {
 624     if (g->gcdept < GCSTEPSIZE)
 625       g->GCthreshold = g->totalbytes + GCSTEPSIZE;  /* - lim/g->gcstepmul;*/
 626     else {
 627       g->gcdept -= GCSTEPSIZE;
 628       g->GCthreshold = g->totalbytes;
 629     }
 630   }
 631   else {
 632     lua_assert(g->totalbytes >= g->estimate);
 633     setthreshold(g);
 634   }
 635 }
 636
 637
 638 void luaC_fullgc (lua_State *L) {
 639   global_State *g = G(L);
 640   if (g->gcstate <= GCSpropagate) {
 641     /* reset sweep marks to sweep all elements (returning them to white) */
 642     g->sweepstrgc = 0;
 643     g->sweepgc = &g->rootgc;
 644     /* reset other collector lists */
 645     g->gray = NULL;
 646     g->grayagain = NULL;
 647     g->weak = NULL;
 648     g->gcstate = GCSsweepstring;
 649   }
 650   lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
 651   /* finish any pending sweep phase */
 652   while (g->gcstate != GCSfinalize) {
 653     lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
 654     singlestep(L);
 655   }
 656   markroot(L);
 657   while (g->gcstate != GCSpause) {
 658     singlestep(L);
 659   }
 660   setthreshold(g);
 661 }
 662
 663
 664 void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
 665   global_State *g = G(L);
 666   lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
 667   lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
 668   lua_assert(ttype(&o->gch) != LUA_TTABLE);
 669   /* must keep invariant? */
 670   if (g->gcstate == GCSpropagate)
 671     reallymarkobject(g, v);  /* restore invariant */
 672   else  /* don't mind */
 673     makewhite(g, o);  /* mark as white just to avoid other barriers */
 674 }
 675
 676
 677 void luaC_barrierback (lua_State *L, Table *t) {
 678   global_State *g = G(L);
 679   GCObject *o = obj2gco(t);
 680   lua_assert(isblack(o) && !isdead(g, o));
 681   lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
 682   black2gray(o);  /* make table gray (again) */
 683   t->gclist = g->grayagain;
 684   g->grayagain = o;
 685 }
 686
 687
 688 void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
 689   global_State *g = G(L);
 690   o->gch.next = g->rootgc;
 691   g->rootgc = o;
 692   o->gch.marked = luaC_white(g);
 693   o->gch.tt = tt;
 694 }
 695
 696
 697 void luaC_linkupval (lua_State *L, UpVal *uv) {
 698   global_State *g = G(L);
 699   GCObject *o = obj2gco(uv);
 700   o->gch.next = g->rootgc;  /* link upvalue into `rootgc' list */
 701   g->rootgc = o;
 702   if (isgray(o)) {
 703     if (g->gcstate == GCSpropagate) {
 704       gray2black(o);  /* closed upvalues need barrier */
 705       luaC_barrier(L, uv, uv->v);
 706     }
 707     else {  /* sweep phase: sweep it (turning it into white) */
 708       makewhite(g, o);
 709       lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
 710     }
 711   }
 712 }
 713