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 #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 GCSTEPSIZE	1024u

    27 #define GCSWEEPMAX	40

    28 #define GCSWEEPCOST	10

    29 #define GCFINALIZECOST	100

    30 

    31 

    32 #define maskmarks	cast_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))) \

    56 		reallymarkobject(g, obj2gco(t)); }

    57 

    58 

    59 #define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)

    60 

    61 

    62 static 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 

    69 static 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 

   115 static 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' */

   128 size_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 

   158 static 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 */

   203 static 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 

   224 static 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 

   241 static 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 

   256 static 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 */

   277 static 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 

   323 static 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 */

   337 static 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 */

   351 static 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 

   378 static 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 

   407 static 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 

   431 static 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 

   445 static 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 */

   477 void luaC_callGCTM (lua_State *L) {

   478   while (G(L)->tmudata)

   479     GCTM(L);

   480 }

   481 

   482 

   483 void 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 

   493 static 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 */

   501 static 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 

   515 static 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 

   525 static 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 

   556 static 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 

   610 void 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 

   636 void 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 

   662 void 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 

   675 void 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 

   686 void 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 

   695 void 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