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  1. /*
  2. ** $Id: lgc.c $
  3. ** Garbage Collector
  4. ** See Copyright Notice in lua.h
  5. */
  6.  
  7. #define lgc_c
  8. #define LUA_CORE
  9.  
  10. #include "lprefix.h"
  11.  
  12. #include <stdio.h>
  13. #include <string.h>
  14.  
  15.  
  16. #include "lua.h"
  17.  
  18. #include "ldebug.h"
  19. #include "ldo.h"
  20. #include "lfunc.h"
  21. #include "lgc.h"
  22. #include "lmem.h"
  23. #include "lobject.h"
  24. #include "lstate.h"
  25. #include "lstring.h"
  26. #include "ltable.h"
  27. #include "ltm.h"
  28.  
  29.  
  30. /*
  31. ** Maximum number of elements to sweep in each single step.
  32. ** (Large enough to dissipate fixed overheads but small enough
  33. ** to allow small steps for the collector.)
  34. */
  35. #define GCSWEEPMAX      100
  36.  
  37. /*
  38. ** Maximum number of finalizers to call in each single step.
  39. */
  40. #define GCFINMAX        10
  41.  
  42.  
  43. /*
  44. ** Cost of calling one finalizer.
  45. */
  46. #define GCFINALIZECOST  50
  47.  
  48.  
  49. /*
  50. ** The equivalent, in bytes, of one unit of "work" (visiting a slot,
  51. ** sweeping an object, etc.)
  52. */
  53. #define WORK2MEM        sizeof(TValue)
  54.  
  55.  
  56. /*
  57. ** macro to adjust 'pause': 'pause' is actually used like
  58. ** 'pause / PAUSEADJ' (value chosen by tests)
  59. */
  60. #define PAUSEADJ                100
  61.  
  62.  
  63. /* mask with all color bits */
  64. #define maskcolors      (bitmask(BLACKBIT) | WHITEBITS)
  65.  
  66. /* mask with all GC bits */
  67. #define maskgcbits      (maskcolors | AGEBITS)
  68.  
  69.  
  70. /* macro to erase all color bits then set only the current white bit */
  71. #define makewhite(g,x)  \
  72.   (x->marked = cast_byte((x->marked & ~maskcolors) | luaC_white(g)))
  73.  
  74. /* make an object gray (neither white nor black) */
  75. #define set2gray(x)     resetbits(x->marked, maskcolors)
  76.  
  77.  
  78. /* make an object black (coming from any color) */
  79. #define set2black(x)  \
  80.   (x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT)))
  81.  
  82.  
  83. #define valiswhite(x)   (iscollectable(x) && iswhite(gcvalue(x)))
  84.  
  85. #define keyiswhite(n)   (keyiscollectable(n) && iswhite(gckey(n)))
  86.  
  87.  
  88. /*
  89. ** Protected access to objects in values
  90. */
  91. #define gcvalueN(o)     (iscollectable(o) ? gcvalue(o) : NULL)
  92.  
  93.  
  94. #define markvalue(g,o) { checkliveness(g->mainthread,o); \
  95.   if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
  96.  
  97. #define markkey(g, n)   { if keyiswhite(n) reallymarkobject(g,gckey(n)); }
  98.  
  99. #define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); }
  100.  
  101. /*
  102. ** mark an object that can be NULL (either because it is really optional,
  103. ** or it was stripped as debug info, or inside an uncompleted structure)
  104. */
  105. #define markobjectN(g,t)        { if (t) markobject(g,t); }
  106.  
  107. static void reallymarkobject (global_State *g, GCObject *o);
  108. static lu_mem atomic (lua_State *L);
  109. static void entersweep (lua_State *L);
  110.  
  111.  
  112. /*
  113. ** {======================================================
  114. ** Generic functions
  115. ** =======================================================
  116. */
  117.  
  118.  
  119. /*
  120. ** one after last element in a hash array
  121. */
  122. #define gnodelast(h)    gnode(h, cast_sizet(sizenode(h)))
  123.  
  124.  
  125. static GCObject **getgclist (GCObject *o) {
  126.   switch (o->tt) {
  127.     case LUA_VTABLE: return &gco2t(o)->gclist;
  128.     case LUA_VLCL: return &gco2lcl(o)->gclist;
  129.     case LUA_VCCL: return &gco2ccl(o)->gclist;
  130.     case LUA_VTHREAD: return &gco2th(o)->gclist;
  131.     case LUA_VPROTO: return &gco2p(o)->gclist;
  132.     case LUA_VUSERDATA: {
  133.       Udata *u = gco2u(o);
  134.       lua_assert(u->nuvalue > 0);
  135.       return &u->gclist;
  136.     }
  137.     default: lua_assert(0); return 0;
  138.   }
  139. }
  140.  
  141.  
  142. /*
  143. ** Link a collectable object 'o' with a known type into the list 'p'.
  144. ** (Must be a macro to access the 'gclist' field in different types.)
  145. */
  146. #define linkgclist(o,p) linkgclist_(obj2gco(o), &(o)->gclist, &(p))
  147.  
  148. static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) {
  149.   lua_assert(!isgray(o));  /* cannot be in a gray list */
  150.   *pnext = *list;
  151.   *list = o;
  152.   set2gray(o);  /* now it is */
  153. }
  154.  
  155.  
  156. /*
  157. ** Link a generic collectable object 'o' into the list 'p'.
  158. */
  159. #define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p))
  160.  
  161.  
  162.  
  163. /*
  164. ** Clear keys for empty entries in tables. If entry is empty, mark its
  165. ** entry as dead. This allows the collection of the key, but keeps its
  166. ** entry in the table: its removal could break a chain and could break
  167. ** a table traversal.  Other places never manipulate dead keys, because
  168. ** its associated empty value is enough to signal that the entry is
  169. ** logically empty.
  170. */
  171. static void clearkey (Node *n) {
  172.   lua_assert(isempty(gval(n)));
  173.   if (keyiscollectable(n))
  174.     setdeadkey(n);  /* unused key; remove it */
  175. }
  176.  
  177.  
  178. /*
  179. ** tells whether a key or value can be cleared from a weak
  180. ** table. Non-collectable objects are never removed from weak
  181. ** tables. Strings behave as 'values', so are never removed too. for
  182. ** other objects: if really collected, cannot keep them; for objects
  183. ** being finalized, keep them in keys, but not in values
  184. */
  185. static int iscleared (global_State *g, const GCObject *o) {
  186.   if (o == NULL) return 0;  /* non-collectable value */
  187.   else if (novariant(o->tt) == LUA_TSTRING) {
  188.     markobject(g, o);  /* strings are 'values', so are never weak */
  189.     return 0;
  190.   }
  191.   else return iswhite(o);
  192. }
  193.  
  194.  
  195. /*
  196. ** Barrier that moves collector forward, that is, marks the white object
  197. ** 'v' being pointed by the black object 'o'.  In the generational
  198. ** mode, 'v' must also become old, if 'o' is old; however, it cannot
  199. ** be changed directly to OLD, because it may still point to non-old
  200. ** objects. So, it is marked as OLD0. In the next cycle it will become
  201. ** OLD1, and in the next it will finally become OLD (regular old). By
  202. ** then, any object it points to will also be old.  If called in the
  203. ** incremental sweep phase, it clears the black object to white (sweep
  204. ** it) to avoid other barrier calls for this same object. (That cannot
  205. ** be done is generational mode, as its sweep does not distinguish
  206. ** whites from deads.)
  207. */
  208. void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
  209.   global_State *g = G(L);
  210.   lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
  211.   if (keepinvariant(g)) {  /* must keep invariant? */
  212.     reallymarkobject(g, v);  /* restore invariant */
  213.     if (isold(o)) {
  214.       lua_assert(!isold(v));  /* white object could not be old */
  215.       setage(v, G_OLD0);  /* restore generational invariant */
  216.     }
  217.   }
  218.   else {  /* sweep phase */
  219.     lua_assert(issweepphase(g));
  220.     if (g->gckind == KGC_INC)  /* incremental mode? */
  221.       makewhite(g, o);  /* mark 'o' as white to avoid other barriers */
  222.   }
  223. }
  224.  
  225.  
  226. /*
  227. ** barrier that moves collector backward, that is, mark the black object
  228. ** pointing to a white object as gray again.
  229. */
  230. void luaC_barrierback_ (lua_State *L, GCObject *o) {
  231.   global_State *g = G(L);
  232.   lua_assert(isblack(o) && !isdead(g, o));
  233.   lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1));
  234.   if (getage(o) == G_TOUCHED2)  /* already in gray list? */
  235.     set2gray(o);  /* make it gray to become touched1 */
  236.   else  /* link it in 'grayagain' and paint it gray */
  237.     linkobjgclist(o, g->grayagain);
  238.   if (isold(o))  /* generational mode? */
  239.     setage(o, G_TOUCHED1);  /* touched in current cycle */
  240. }
  241.  
  242.  
  243. void luaC_fix (lua_State *L, GCObject *o) {
  244.   global_State *g = G(L);
  245.   lua_assert(g->allgc == o);  /* object must be 1st in 'allgc' list! */
  246.   set2gray(o);  /* they will be gray forever */
  247.   setage(o, G_OLD);  /* and old forever */
  248.   g->allgc = o->next;  /* remove object from 'allgc' list */
  249.   o->next = g->fixedgc;  /* link it to 'fixedgc' list */
  250.   g->fixedgc = o;
  251. }
  252.  
  253.  
  254. /*
  255. ** create a new collectable object (with given type and size) and link
  256. ** it to 'allgc' list.
  257. */
  258. GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
  259.   global_State *g = G(L);
  260.   GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz));
  261.   o->marked = luaC_white(g);
  262.   o->tt = tt;
  263.   o->next = g->allgc;
  264.   g->allgc = o;
  265.   return o;
  266. }
  267.  
  268. /* }====================================================== */
  269.  
  270.  
  271.  
  272. /*
  273. ** {======================================================
  274. ** Mark functions
  275. ** =======================================================
  276. */
  277.  
  278.  
  279. /*
  280. ** Mark an object.  Userdata with no user values, strings, and closed
  281. ** upvalues are visited and turned black here.  Open upvalues are
  282. ** already indirectly linked through their respective threads in the
  283. ** 'twups' list, so they don't go to the gray list; nevertheless, they
  284. ** are kept gray to avoid barriers, as their values will be revisited
  285. ** by the thread or by 'remarkupvals'.  Other objects are added to the
  286. ** gray list to be visited (and turned black) later.  Both userdata and
  287. ** upvalues can call this function recursively, but this recursion goes
  288. ** for at most two levels: An upvalue cannot refer to another upvalue
  289. ** (only closures can), and a userdata's metatable must be a table.
  290. */
  291. static void reallymarkobject (global_State *g, GCObject *o) {
  292.   switch (o->tt) {
  293.     case LUA_VSHRSTR:
  294.     case LUA_VLNGSTR: {
  295.       set2black(o);  /* nothing to visit */
  296.       break;
  297.     }
  298.     case LUA_VUPVAL: {
  299.       UpVal *uv = gco2upv(o);
  300.       if (upisopen(uv))
  301.         set2gray(uv);  /* open upvalues are kept gray */
  302.       else
  303.         set2black(uv);  /* closed upvalues are visited here */
  304.       markvalue(g, uv->v);  /* mark its content */
  305.       break;
  306.     }
  307.     case LUA_VUSERDATA: {
  308.       Udata *u = gco2u(o);
  309.       if (u->nuvalue == 0) {  /* no user values? */
  310.         markobjectN(g, u->metatable);  /* mark its metatable */
  311.         set2black(u);  /* nothing else to mark */
  312.         break;
  313.       }
  314.       /* else... */
  315.     }  /* FALLTHROUGH */
  316.     case LUA_VLCL: case LUA_VCCL: case LUA_VTABLE:
  317.     case LUA_VTHREAD: case LUA_VPROTO: {
  318.       linkobjgclist(o, g->gray);  /* to be visited later */
  319.       break;
  320.     }
  321.     default: lua_assert(0); break;
  322.   }
  323. }
  324.  
  325.  
  326. /*
  327. ** mark metamethods for basic types
  328. */
  329. static void markmt (global_State *g) {
  330.   int i;
  331.   for (i=0; i < LUA_NUMTAGS; i++)
  332.     markobjectN(g, g->mt[i]);
  333. }
  334.  
  335.  
  336. /*
  337. ** mark all objects in list of being-finalized
  338. */
  339. static lu_mem markbeingfnz (global_State *g) {
  340.   GCObject *o;
  341.   lu_mem count = 0;
  342.   for (o = g->tobefnz; o != NULL; o = o->next) {
  343.     count++;
  344.     markobject(g, o);
  345.   }
  346.   return count;
  347. }
  348.  
  349.  
  350. /*
  351. ** For each non-marked thread, simulates a barrier between each open
  352. ** upvalue and its value. (If the thread is collected, the value will be
  353. ** assigned to the upvalue, but then it can be too late for the barrier
  354. ** to act. The "barrier" does not need to check colors: A non-marked
  355. ** thread must be young; upvalues cannot be older than their threads; so
  356. ** any visited upvalue must be young too.) Also removes the thread from
  357. ** the list, as it was already visited. Removes also threads with no
  358. ** upvalues, as they have nothing to be checked. (If the thread gets an
  359. ** upvalue later, it will be linked in the list again.)
  360. */
  361. static int remarkupvals (global_State *g) {
  362.   lua_State *thread;
  363.   lua_State **p = &g->twups;
  364.   int work = 0;  /* estimate of how much work was done here */
  365.   while ((thread = *p) != NULL) {
  366.     work++;
  367.     if (!iswhite(thread) && thread->openupval != NULL)
  368.       p = &thread->twups;  /* keep marked thread with upvalues in the list */
  369.     else {  /* thread is not marked or without upvalues */
  370.       UpVal *uv;
  371.       lua_assert(!isold(thread) || thread->openupval == NULL);
  372.       *p = thread->twups;  /* remove thread from the list */
  373.       thread->twups = thread;  /* mark that it is out of list */
  374.       for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
  375.         lua_assert(getage(uv) <= getage(thread));
  376.         work++;
  377.         if (!iswhite(uv)) {  /* upvalue already visited? */
  378.           lua_assert(upisopen(uv) && isgray(uv));
  379.           markvalue(g, uv->v);  /* mark its value */
  380.         }
  381.       }
  382.     }
  383.   }
  384.   return work;
  385. }
  386.  
  387.  
  388. static void cleargraylists (global_State *g) {
  389.   g->gray = g->grayagain = NULL;
  390.   g->weak = g->allweak = g->ephemeron = NULL;
  391. }
  392.  
  393.  
  394. /*
  395. ** mark root set and reset all gray lists, to start a new collection
  396. */
  397. static void restartcollection (global_State *g) {
  398.   cleargraylists(g);
  399.   markobject(g, g->mainthread);
  400.   markvalue(g, &g->l_registry);
  401.   markmt(g);
  402.   markbeingfnz(g);  /* mark any finalizing object left from previous cycle */
  403. }
  404.  
  405. /* }====================================================== */
  406.  
  407.  
  408. /*
  409. ** {======================================================
  410. ** Traverse functions
  411. ** =======================================================
  412. */
  413.  
  414.  
  415. /*
  416. ** Check whether object 'o' should be kept in the 'grayagain' list for
  417. ** post-processing by 'correctgraylist'. (It could put all old objects
  418. ** in the list and leave all the work to 'correctgraylist', but it is
  419. ** more efficient to avoid adding elements that will be removed.) Only
  420. ** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go
  421. ** back to a gray list, but then it must become OLD. (That is what
  422. ** 'correctgraylist' does when it finds a TOUCHED2 object.)
  423. */
  424. static void genlink (global_State *g, GCObject *o) {
  425.   lua_assert(isblack(o));
  426.   if (getage(o) == G_TOUCHED1) {  /* touched in this cycle? */
  427.     linkobjgclist(o, g->grayagain);  /* link it back in 'grayagain' */
  428.   }  /* everything else do not need to be linked back */
  429.   else if (getage(o) == G_TOUCHED2)
  430.     changeage(o, G_TOUCHED2, G_OLD);  /* advance age */
  431. }
  432.  
  433.  
  434. /*
  435. ** Traverse a table with weak values and link it to proper list. During
  436. ** propagate phase, keep it in 'grayagain' list, to be revisited in the
  437. ** atomic phase. In the atomic phase, if table has any white value,
  438. ** put it in 'weak' list, to be cleared.
  439. */
  440. static void traverseweakvalue (global_State *g, Table *h) {
  441.   Node *n, *limit = gnodelast(h);
  442.   /* if there is array part, assume it may have white values (it is not
  443.      worth traversing it now just to check) */
  444.   int hasclears = (h->alimit > 0);
  445.   for (n = gnode(h, 0); n < limit; n++) {  /* traverse hash part */
  446.     if (isempty(gval(n)))  /* entry is empty? */
  447.       clearkey(n);  /* clear its key */
  448.     else {
  449.       lua_assert(!keyisnil(n));
  450.       markkey(g, n);
  451.       if (!hasclears && iscleared(g, gcvalueN(gval(n))))  /* a white value? */
  452.         hasclears = 1;  /* table will have to be cleared */
  453.     }
  454.   }
  455.   if (g->gcstate == GCSatomic && hasclears)
  456.     linkgclist(h, g->weak);  /* has to be cleared later */
  457.   else
  458.     linkgclist(h, g->grayagain);  /* must retraverse it in atomic phase */
  459. }
  460.  
  461.  
  462. /*
  463. ** Traverse an ephemeron table and link it to proper list. Returns true
  464. ** iff any object was marked during this traversal (which implies that
  465. ** convergence has to continue). During propagation phase, keep table
  466. ** in 'grayagain' list, to be visited again in the atomic phase. In
  467. ** the atomic phase, if table has any white->white entry, it has to
  468. ** be revisited during ephemeron convergence (as that key may turn
  469. ** black). Otherwise, if it has any white key, table has to be cleared
  470. ** (in the atomic phase). In generational mode, some tables
  471. ** must be kept in some gray list for post-processing; this is done
  472. ** by 'genlink'.
  473. */
  474. static int traverseephemeron (global_State *g, Table *h, int inv) {
  475.   int marked = 0;  /* true if an object is marked in this traversal */
  476.   int hasclears = 0;  /* true if table has white keys */
  477.   int hasww = 0;  /* true if table has entry "white-key -> white-value" */
  478.   unsigned int i;
  479.   unsigned int asize = luaH_realasize(h);
  480.   unsigned int nsize = sizenode(h);
  481.   /* traverse array part */
  482.   for (i = 0; i < asize; i++) {
  483.     if (valiswhite(&h->array[i])) {
  484.       marked = 1;
  485.       reallymarkobject(g, gcvalue(&h->array[i]));
  486.     }
  487.   }
  488.   /* traverse hash part; if 'inv', traverse descending
  489.      (see 'convergeephemerons') */
  490.   for (i = 0; i < nsize; i++) {
  491.     Node *n = inv ? gnode(h, nsize - 1 - i) : gnode(h, i);
  492.     if (isempty(gval(n)))  /* entry is empty? */
  493.       clearkey(n);  /* clear its key */
  494.     else if (iscleared(g, gckeyN(n))) {  /* key is not marked (yet)? */
  495.       hasclears = 1;  /* table must be cleared */
  496.       if (valiswhite(gval(n)))  /* value not marked yet? */
  497.         hasww = 1;  /* white-white entry */
  498.     }
  499.     else if (valiswhite(gval(n))) {  /* value not marked yet? */
  500.       marked = 1;
  501.       reallymarkobject(g, gcvalue(gval(n)));  /* mark it now */
  502.     }
  503.   }
  504.   /* link table into proper list */
  505.   if (g->gcstate == GCSpropagate)
  506.     linkgclist(h, g->grayagain);  /* must retraverse it in atomic phase */
  507.   else if (hasww)  /* table has white->white entries? */
  508.     linkgclist(h, g->ephemeron);  /* have to propagate again */
  509.   else if (hasclears)  /* table has white keys? */
  510.     linkgclist(h, g->allweak);  /* may have to clean white keys */
  511.   else
  512.     genlink(g, obj2gco(h));  /* check whether collector still needs to see it */
  513.   return marked;
  514. }
  515.  
  516.  
  517. static void traversestrongtable (global_State *g, Table *h) {
  518.   Node *n, *limit = gnodelast(h);
  519.   unsigned int i;
  520.   unsigned int asize = luaH_realasize(h);
  521.   for (i = 0; i < asize; i++)  /* traverse array part */
  522.     markvalue(g, &h->array[i]);
  523.   for (n = gnode(h, 0); n < limit; n++) {  /* traverse hash part */
  524.     if (isempty(gval(n)))  /* entry is empty? */
  525.       clearkey(n);  /* clear its key */
  526.     else {
  527.       lua_assert(!keyisnil(n));
  528.       markkey(g, n);
  529.       markvalue(g, gval(n));
  530.     }
  531.   }
  532.   genlink(g, obj2gco(h));
  533. }
  534.  
  535.  
  536. static lu_mem traversetable (global_State *g, Table *h) {
  537.   const char *weakkey, *weakvalue;
  538.   const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
  539.   markobjectN(g, h->metatable);
  540.   if (mode && ttisstring(mode) &&  /* is there a weak mode? */
  541.       (cast_void(weakkey = strchr(svalue(mode), 'k')),
  542.        cast_void(weakvalue = strchr(svalue(mode), 'v')),
  543.        (weakkey || weakvalue))) {  /* is really weak? */
  544.     if (!weakkey)  /* strong keys? */
  545.       traverseweakvalue(g, h);
  546.     else if (!weakvalue)  /* strong values? */
  547.       traverseephemeron(g, h, 0);
  548.     else  /* all weak */
  549.       linkgclist(h, g->allweak);  /* nothing to traverse now */
  550.   }
  551.   else  /* not weak */
  552.     traversestrongtable(g, h);
  553.   return 1 + h->alimit + 2 * allocsizenode(h);
  554. }
  555.  
  556.  
  557. static int traverseudata (global_State *g, Udata *u) {
  558.   int i;
  559.   markobjectN(g, u->metatable);  /* mark its metatable */
  560.   for (i = 0; i < u->nuvalue; i++)
  561.     markvalue(g, &u->uv[i].uv);
  562.   genlink(g, obj2gco(u));
  563.   return 1 + u->nuvalue;
  564. }
  565.  
  566.  
  567. /*
  568. ** Traverse a prototype. (While a prototype is being build, its
  569. ** arrays can be larger than needed; the extra slots are filled with
  570. ** NULL, so the use of 'markobjectN')
  571. */
  572. static int traverseproto (global_State *g, Proto *f) {
  573.   int i;
  574.   markobjectN(g, f->source);
  575.   for (i = 0; i < f->sizek; i++)  /* mark literals */
  576.     markvalue(g, &f->k[i]);
  577.   for (i = 0; i < f->sizeupvalues; i++)  /* mark upvalue names */
  578.     markobjectN(g, f->upvalues[i].name);
  579.   for (i = 0; i < f->sizep; i++)  /* mark nested protos */
  580.     markobjectN(g, f->p[i]);
  581.   for (i = 0; i < f->sizelocvars; i++)  /* mark local-variable names */
  582.     markobjectN(g, f->locvars[i].varname);
  583.   return 1 + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars;
  584. }
  585.  
  586.  
  587. static int traverseCclosure (global_State *g, CClosure *cl) {
  588.   int i;
  589.   for (i = 0; i < cl->nupvalues; i++)  /* mark its upvalues */
  590.     markvalue(g, &cl->upvalue[i]);
  591.   return 1 + cl->nupvalues;
  592. }
  593.  
  594. /*
  595. ** Traverse a Lua closure, marking its prototype and its upvalues.
  596. ** (Both can be NULL while closure is being created.)
  597. */
  598. static int traverseLclosure (global_State *g, LClosure *cl) {
  599.   int i;
  600.   markobjectN(g, cl->p);  /* mark its prototype */
  601.   for (i = 0; i < cl->nupvalues; i++) {  /* visit its upvalues */
  602.     UpVal *uv = cl->upvals[i];
  603.     markobjectN(g, uv);  /* mark upvalue */
  604.   }
  605.   return 1 + cl->nupvalues;
  606. }
  607.  
  608.  
  609. /*
  610. ** Traverse a thread, marking the elements in the stack up to its top
  611. ** and cleaning the rest of the stack in the final traversal. That
  612. ** ensures that the entire stack have valid (non-dead) objects.
  613. ** Threads have no barriers. In gen. mode, old threads must be visited
  614. ** at every cycle, because they might point to young objects.  In inc.
  615. ** mode, the thread can still be modified before the end of the cycle,
  616. ** and therefore it must be visited again in the atomic phase. To ensure
  617. ** these visits, threads must return to a gray list if they are not new
  618. ** (which can only happen in generational mode) or if the traverse is in
  619. ** the propagate phase (which can only happen in incremental mode).
  620. */
  621. static int traversethread (global_State *g, lua_State *th) {
  622.   UpVal *uv;
  623.   StkId o = th->stack;
  624.   if (isold(th) || g->gcstate == GCSpropagate)
  625.     linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
  626.   if (o == NULL)
  627.     return 1;  /* stack not completely built yet */
  628.   lua_assert(g->gcstate == GCSatomic ||
  629.              th->openupval == NULL || isintwups(th));
  630.   for (; o < th->top; o++)  /* mark live elements in the stack */
  631.     markvalue(g, s2v(o));
  632.   for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
  633.     markobject(g, uv);  /* open upvalues cannot be collected */
  634.   if (g->gcstate == GCSatomic) {  /* final traversal? */
  635.     for (; o < th->stack_last + EXTRA_STACK; o++)
  636.       setnilvalue(s2v(o));  /* clear dead stack slice */
  637.     /* 'remarkupvals' may have removed thread from 'twups' list */
  638.     if (!isintwups(th) && th->openupval != NULL) {
  639.       th->twups = g->twups;  /* link it back to the list */
  640.       g->twups = th;
  641.     }
  642.   }
  643.   else if (!g->gcemergency)
  644.     luaD_shrinkstack(th); /* do not change stack in emergency cycle */
  645.   return 1 + stacksize(th);
  646. }
  647.  
  648.  
  649. /*
  650. ** traverse one gray object, turning it to black.
  651. */
  652. static lu_mem propagatemark (global_State *g) {
  653.   GCObject *o = g->gray;
  654.   nw2black(o);
  655.   g->gray = *getgclist(o);  /* remove from 'gray' list */
  656.   switch (o->tt) {
  657.     case LUA_VTABLE: return traversetable(g, gco2t(o));
  658.     case LUA_VUSERDATA: return traverseudata(g, gco2u(o));
  659.     case LUA_VLCL: return traverseLclosure(g, gco2lcl(o));
  660.     case LUA_VCCL: return traverseCclosure(g, gco2ccl(o));
  661.     case LUA_VPROTO: return traverseproto(g, gco2p(o));
  662.     case LUA_VTHREAD: return traversethread(g, gco2th(o));
  663.     default: lua_assert(0); return 0;
  664.   }
  665. }
  666.  
  667.  
  668. static lu_mem propagateall (global_State *g) {
  669.   lu_mem tot = 0;
  670.   while (g->gray)
  671.     tot += propagatemark(g);
  672.   return tot;
  673. }
  674.  
  675.  
  676. /*
  677. ** Traverse all ephemeron tables propagating marks from keys to values.
  678. ** Repeat until it converges, that is, nothing new is marked. 'dir'
  679. ** inverts the direction of the traversals, trying to speed up
  680. ** convergence on chains in the same table.
  681. **
  682. */
  683. static void convergeephemerons (global_State *g) {
  684.   int changed;
  685.   int dir = 0;
  686.   do {
  687.     GCObject *w;
  688.     GCObject *next = g->ephemeron;  /* get ephemeron list */
  689.     g->ephemeron = NULL;  /* tables may return to this list when traversed */
  690.     changed = 0;
  691.     while ((w = next) != NULL) {  /* for each ephemeron table */
  692.       Table *h = gco2t(w);
  693.       next = h->gclist;  /* list is rebuilt during loop */
  694.       nw2black(h);  /* out of the list (for now) */
  695.       if (traverseephemeron(g, h, dir)) {  /* marked some value? */
  696.         propagateall(g);  /* propagate changes */
  697.         changed = 1;  /* will have to revisit all ephemeron tables */
  698.       }
  699.     }
  700.     dir = !dir;  /* invert direction next time */
  701.   } while (changed);  /* repeat until no more changes */
  702. }
  703.  
  704. /* }====================================================== */
  705.  
  706.  
  707. /*
  708. ** {======================================================
  709. ** Sweep Functions
  710. ** =======================================================
  711. */
  712.  
  713.  
  714. /*
  715. ** clear entries with unmarked keys from all weaktables in list 'l'
  716. */
  717. static void clearbykeys (global_State *g, GCObject *l) {
  718.   for (; l; l = gco2t(l)->gclist) {
  719.     Table *h = gco2t(l);
  720.     Node *limit = gnodelast(h);
  721.     Node *n;
  722.     for (n = gnode(h, 0); n < limit; n++) {
  723.       if (iscleared(g, gckeyN(n)))  /* unmarked key? */
  724.         setempty(gval(n));  /* remove entry */
  725.       if (isempty(gval(n)))  /* is entry empty? */
  726.         clearkey(n);  /* clear its key */
  727.     }
  728.   }
  729. }
  730.  
  731.  
  732. /*
  733. ** clear entries with unmarked values from all weaktables in list 'l' up
  734. ** to element 'f'
  735. */
  736. static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
  737.   for (; l != f; l = gco2t(l)->gclist) {
  738.     Table *h = gco2t(l);
  739.     Node *n, *limit = gnodelast(h);
  740.     unsigned int i;
  741.     unsigned int asize = luaH_realasize(h);
  742.     for (i = 0; i < asize; i++) {
  743.       TValue *o = &h->array[i];
  744.       if (iscleared(g, gcvalueN(o)))  /* value was collected? */
  745.         setempty(o);  /* remove entry */
  746.     }
  747.     for (n = gnode(h, 0); n < limit; n++) {
  748.       if (iscleared(g, gcvalueN(gval(n))))  /* unmarked value? */
  749.         setempty(gval(n));  /* remove entry */
  750.       if (isempty(gval(n)))  /* is entry empty? */
  751.         clearkey(n);  /* clear its key */
  752.     }
  753.   }
  754. }
  755.  
  756.  
  757. static void freeupval (lua_State *L, UpVal *uv) {
  758.   if (upisopen(uv))
  759.     luaF_unlinkupval(uv);
  760.   luaM_free(L, uv);
  761. }
  762.  
  763.  
  764. static void freeobj (lua_State *L, GCObject *o) {
  765.   switch (o->tt) {
  766.     case LUA_VPROTO:
  767.       luaF_freeproto(L, gco2p(o));
  768.       break;
  769.     case LUA_VUPVAL:
  770.       freeupval(L, gco2upv(o));
  771.       break;
  772.     case LUA_VLCL: {
  773.       LClosure *cl = gco2lcl(o);
  774.       luaM_freemem(L, cl, sizeLclosure(cl->nupvalues));
  775.       break;
  776.     }
  777.     case LUA_VCCL: {
  778.       CClosure *cl = gco2ccl(o);
  779.       luaM_freemem(L, cl, sizeCclosure(cl->nupvalues));
  780.       break;
  781.     }
  782.     case LUA_VTABLE:
  783.       luaH_free(L, gco2t(o));
  784.       break;
  785.     case LUA_VTHREAD:
  786.       luaE_freethread(L, gco2th(o));
  787.       break;
  788.     case LUA_VUSERDATA: {
  789.       Udata *u = gco2u(o);
  790.       luaM_freemem(L, o, sizeudata(u->nuvalue, u->len));
  791.       break;
  792.     }
  793.     case LUA_VSHRSTR: {
  794.       TString *ts = gco2ts(o);
  795.       luaS_remove(L, ts);  /* remove it from hash table */
  796.       luaM_freemem(L, ts, sizelstring(ts->shrlen));
  797.       break;
  798.     }
  799.     case LUA_VLNGSTR: {
  800.       TString *ts = gco2ts(o);
  801.       luaM_freemem(L, ts, sizelstring(ts->u.lnglen));
  802.       break;
  803.     }
  804.     default: lua_assert(0);
  805.   }
  806. }
  807.  
  808.  
  809. /*
  810. ** sweep at most 'countin' elements from a list of GCObjects erasing dead
  811. ** objects, where a dead object is one marked with the old (non current)
  812. ** white; change all non-dead objects back to white, preparing for next
  813. ** collection cycle. Return where to continue the traversal or NULL if
  814. ** list is finished. ('*countout' gets the number of elements traversed.)
  815. */
  816. static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
  817.                              int *countout) {
  818.   global_State *g = G(L);
  819.   int ow = otherwhite(g);
  820.   int i;
  821.   int white = luaC_white(g);  /* current white */
  822.   for (i = 0; *p != NULL && i < countin; i++) {
  823.     GCObject *curr = *p;
  824.     int marked = curr->marked;
  825.     if (isdeadm(ow, marked)) {  /* is 'curr' dead? */
  826.       *p = curr->next;  /* remove 'curr' from list */
  827.       freeobj(L, curr);  /* erase 'curr' */
  828.     }
  829.     else {  /* change mark to 'white' */
  830.       curr->marked = cast_byte((marked & ~maskgcbits) | white);
  831.       p = &curr->next;  /* go to next element */
  832.     }
  833.   }
  834.   if (countout)
  835.     *countout = i;  /* number of elements traversed */
  836.   return (*p == NULL) ? NULL : p;
  837. }
  838.  
  839.  
  840. /*
  841. ** sweep a list until a live object (or end of list)
  842. */
  843. static GCObject **sweeptolive (lua_State *L, GCObject **p) {
  844.   GCObject **old = p;
  845.   do {
  846.     p = sweeplist(L, p, 1, NULL);
  847.   } while (p == old);
  848.   return p;
  849. }
  850.  
  851. /* }====================================================== */
  852.  
  853.  
  854. /*
  855. ** {======================================================
  856. ** Finalization
  857. ** =======================================================
  858. */
  859.  
  860. /*
  861. ** If possible, shrink string table.
  862. */
  863. static void checkSizes (lua_State *L, global_State *g) {
  864.   if (!g->gcemergency) {
  865.     if (g->strt.nuse < g->strt.size / 4) {  /* string table too big? */
  866.       l_mem olddebt = g->GCdebt;
  867.       luaS_resize(L, g->strt.size / 2);
  868.       g->GCestimate += g->GCdebt - olddebt;  /* correct estimate */
  869.     }
  870.   }
  871. }
  872.  
  873.  
  874. /*
  875. ** Get the next udata to be finalized from the 'tobefnz' list, and
  876. ** link it back into the 'allgc' list.
  877. */
  878. static GCObject *udata2finalize (global_State *g) {
  879.   GCObject *o = g->tobefnz;  /* get first element */
  880.   lua_assert(tofinalize(o));
  881.   g->tobefnz = o->next;  /* remove it from 'tobefnz' list */
  882.   o->next = g->allgc;  /* return it to 'allgc' list */
  883.   g->allgc = o;
  884.   resetbit(o->marked, FINALIZEDBIT);  /* object is "normal" again */
  885.   if (issweepphase(g))
  886.     makewhite(g, o);  /* "sweep" object */
  887.   else if (getage(o) == G_OLD1)
  888.     g->firstold1 = o;  /* it is the first OLD1 object in the list */
  889.   return o;
  890. }
  891.  
  892.  
  893. static void dothecall (lua_State *L, void *ud) {
  894.   UNUSED(ud);
  895.   luaD_callnoyield(L, L->top - 2, 0);
  896. }
  897.  
  898.  
  899. static void GCTM (lua_State *L) {
  900.   global_State *g = G(L);
  901.   const TValue *tm;
  902.   TValue v;
  903.   lua_assert(!g->gcemergency);
  904.   setgcovalue(L, &v, udata2finalize(g));
  905.   tm = luaT_gettmbyobj(L, &v, TM_GC);
  906.   if (!notm(tm)) {  /* is there a finalizer? */
  907.     int status;
  908.     lu_byte oldah = L->allowhook;
  909.     int oldgcstp  = g->gcstp;
  910.     g->gcstp |= GCSTPGC;  /* avoid GC steps */
  911.     L->allowhook = 0;  /* stop debug hooks during GC metamethod */
  912.     setobj2s(L, L->top++, tm);  /* push finalizer... */
  913.     setobj2s(L, L->top++, &v);  /* ... and its argument */
  914.     L->ci->callstatus |= CIST_FIN;  /* will run a finalizer */
  915.     status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
  916.     L->ci->callstatus &= ~CIST_FIN;  /* not running a finalizer anymore */
  917.     L->allowhook = oldah;  /* restore hooks */
  918.     g->gcstp = oldgcstp;  /* restore state */
  919.     if (l_unlikely(status != LUA_OK)) {  /* error while running __gc? */
  920.       luaE_warnerror(L, "__gc");
  921.       L->top--;  /* pops error object */
  922.     }
  923.   }
  924. }
  925.  
  926.  
  927. /*
  928. ** Call a few finalizers
  929. */
  930. static int runafewfinalizers (lua_State *L, int n) {
  931.   global_State *g = G(L);
  932.   int i;
  933.   for (i = 0; i < n && g->tobefnz; i++)
  934.     GCTM(L);  /* call one finalizer */
  935.   return i;
  936. }
  937.  
  938.  
  939. /*
  940. ** call all pending finalizers
  941. */
  942. static void callallpendingfinalizers (lua_State *L) {
  943.   global_State *g = G(L);
  944.   while (g->tobefnz)
  945.     GCTM(L);
  946. }
  947.  
  948.  
  949. /*
  950. ** find last 'next' field in list 'p' list (to add elements in its end)
  951. */
  952. static GCObject **findlast (GCObject **p) {
  953.   while (*p != NULL)
  954.     p = &(*p)->next;
  955.   return p;
  956. }
  957.  
  958.  
  959. /*
  960. ** Move all unreachable objects (or 'all' objects) that need
  961. ** finalization from list 'finobj' to list 'tobefnz' (to be finalized).
  962. ** (Note that objects after 'finobjold1' cannot be white, so they
  963. ** don't need to be traversed. In incremental mode, 'finobjold1' is NULL,
  964. ** so the whole list is traversed.)
  965. */
  966. static void separatetobefnz (global_State *g, int all) {
  967.   GCObject *curr;
  968.   GCObject **p = &g->finobj;
  969.   GCObject **lastnext = findlast(&g->tobefnz);
  970.   while ((curr = *p) != g->finobjold1) {  /* traverse all finalizable objects */
  971.     lua_assert(tofinalize(curr));
  972.     if (!(iswhite(curr) || all))  /* not being collected? */
  973.       p = &curr->next;  /* don't bother with it */
  974.     else {
  975.       if (curr == g->finobjsur)  /* removing 'finobjsur'? */
  976.         g->finobjsur = curr->next;  /* correct it */
  977.       *p = curr->next;  /* remove 'curr' from 'finobj' list */
  978.       curr->next = *lastnext;  /* link at the end of 'tobefnz' list */
  979.       *lastnext = curr;
  980.       lastnext = &curr->next;
  981.     }
  982.   }
  983. }
  984.  
  985.  
  986. /*
  987. ** If pointer 'p' points to 'o', move it to the next element.
  988. */
  989. static void checkpointer (GCObject **p, GCObject *o) {
  990.   if (o == *p)
  991.     *p = o->next;
  992. }
  993.  
  994.  
  995. /*
  996. ** Correct pointers to objects inside 'allgc' list when
  997. ** object 'o' is being removed from the list.
  998. */
  999. static void correctpointers (global_State *g, GCObject *o) {
  1000.   checkpointer(&g->survival, o);
  1001.   checkpointer(&g->old1, o);
  1002.   checkpointer(&g->reallyold, o);
  1003.   checkpointer(&g->firstold1, o);
  1004. }
  1005.  
  1006.  
  1007. /*
  1008. ** if object 'o' has a finalizer, remove it from 'allgc' list (must
  1009. ** search the list to find it) and link it in 'finobj' list.
  1010. */
  1011. void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
  1012.   global_State *g = G(L);
  1013.   if (tofinalize(o) ||                 /* obj. is already marked... */
  1014.       gfasttm(g, mt, TM_GC) == NULL ||    /* or has no finalizer... */
  1015.       (g->gcstp & GCSTPCLS))                   /* or closing state? */
  1016.     return;  /* nothing to be done */
  1017.   else {  /* move 'o' to 'finobj' list */
  1018.     GCObject **p;
  1019.     if (issweepphase(g)) {
  1020.       makewhite(g, o);  /* "sweep" object 'o' */
  1021.       if (g->sweepgc == &o->next)  /* should not remove 'sweepgc' object */
  1022.         g->sweepgc = sweeptolive(L, g->sweepgc);  /* change 'sweepgc' */
  1023.     }
  1024.     else
  1025.       correctpointers(g, o);
  1026.     /* search for pointer pointing to 'o' */
  1027.     for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
  1028.     *p = o->next;  /* remove 'o' from 'allgc' list */
  1029.     o->next = g->finobj;  /* link it in 'finobj' list */
  1030.     g->finobj = o;
  1031.     l_setbit(o->marked, FINALIZEDBIT);  /* mark it as such */
  1032.   }
  1033. }
  1034.  
  1035. /* }====================================================== */
  1036.  
  1037.  
  1038. /*
  1039. ** {======================================================
  1040. ** Generational Collector
  1041. ** =======================================================
  1042. */
  1043.  
  1044. static void setpause (global_State *g);
  1045.  
  1046.  
  1047. /*
  1048. ** Sweep a list of objects to enter generational mode.  Deletes dead
  1049. ** objects and turns the non dead to old. All non-dead threads---which
  1050. ** are now old---must be in a gray list. Everything else is not in a
  1051. ** gray list. Open upvalues are also kept gray.
  1052. */
  1053. static void sweep2old (lua_State *L, GCObject **p) {
  1054.   GCObject *curr;
  1055.   global_State *g = G(L);
  1056.   while ((curr = *p) != NULL) {
  1057.     if (iswhite(curr)) {  /* is 'curr' dead? */
  1058.       lua_assert(isdead(g, curr));
  1059.       *p = curr->next;  /* remove 'curr' from list */
  1060.       freeobj(L, curr);  /* erase 'curr' */
  1061.     }
  1062.     else {  /* all surviving objects become old */
  1063.       setage(curr, G_OLD);
  1064.       if (curr->tt == LUA_VTHREAD) {  /* threads must be watched */
  1065.         lua_State *th = gco2th(curr);
  1066.         linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
  1067.       }
  1068.       else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr)))
  1069.         set2gray(curr);  /* open upvalues are always gray */
  1070.       else  /* everything else is black */
  1071.         nw2black(curr);
  1072.       p = &curr->next;  /* go to next element */
  1073.     }
  1074.   }
  1075. }
  1076.  
  1077.  
  1078. /*
  1079. ** Sweep for generational mode. Delete dead objects. (Because the
  1080. ** collection is not incremental, there are no "new white" objects
  1081. ** during the sweep. So, any white object must be dead.) For
  1082. ** non-dead objects, advance their ages and clear the color of
  1083. ** new objects. (Old objects keep their colors.)
  1084. ** The ages of G_TOUCHED1 and G_TOUCHED2 objects cannot be advanced
  1085. ** here, because these old-generation objects are usually not swept
  1086. ** here.  They will all be advanced in 'correctgraylist'. That function
  1087. ** will also remove objects turned white here from any gray list.
  1088. */
  1089. static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
  1090.                             GCObject *limit, GCObject **pfirstold1) {
  1091.   static const lu_byte nextage[] = {
  1092.     G_SURVIVAL,  /* from G_NEW */
  1093.     G_OLD1,      /* from G_SURVIVAL */
  1094.     G_OLD1,      /* from G_OLD0 */
  1095.     G_OLD,       /* from G_OLD1 */
  1096.     G_OLD,       /* from G_OLD (do not change) */
  1097.     G_TOUCHED1,  /* from G_TOUCHED1 (do not change) */
  1098.     G_TOUCHED2   /* from G_TOUCHED2 (do not change) */
  1099.   };
  1100.   int white = luaC_white(g);
  1101.   GCObject *curr;
  1102.   while ((curr = *p) != limit) {
  1103.     if (iswhite(curr)) {  /* is 'curr' dead? */
  1104.       lua_assert(!isold(curr) && isdead(g, curr));
  1105.       *p = curr->next;  /* remove 'curr' from list */
  1106.       freeobj(L, curr);  /* erase 'curr' */
  1107.     }
  1108.     else {  /* correct mark and age */
  1109.       if (getage(curr) == G_NEW) {  /* new objects go back to white */
  1110.         int marked = curr->marked & ~maskgcbits;  /* erase GC bits */
  1111.         curr->marked = cast_byte(marked | G_SURVIVAL | white);
  1112.       }
  1113.       else {  /* all other objects will be old, and so keep their color */
  1114.         setage(curr, nextage[getage(curr)]);
  1115.         if (getage(curr) == G_OLD1 && *pfirstold1 == NULL)
  1116.           *pfirstold1 = curr;  /* first OLD1 object in the list */
  1117.       }
  1118.       p = &curr->next;  /* go to next element */
  1119.     }
  1120.   }
  1121.   return p;
  1122. }
  1123.  
  1124.  
  1125. /*
  1126. ** Traverse a list making all its elements white and clearing their
  1127. ** age. In incremental mode, all objects are 'new' all the time,
  1128. ** except for fixed strings (which are always old).
  1129. */
  1130. static void whitelist (global_State *g, GCObject *p) {
  1131.   int white = luaC_white(g);
  1132.   for (; p != NULL; p = p->next)
  1133.     p->marked = cast_byte((p->marked & ~maskgcbits) | white);
  1134. }
  1135.  
  1136.  
  1137. /*
  1138. ** Correct a list of gray objects. Return pointer to where rest of the
  1139. ** list should be linked.
  1140. ** Because this correction is done after sweeping, young objects might
  1141. ** be turned white and still be in the list. They are only removed.
  1142. ** 'TOUCHED1' objects are advanced to 'TOUCHED2' and remain on the list;
  1143. ** Non-white threads also remain on the list; 'TOUCHED2' objects become
  1144. ** regular old; they and anything else are removed from the list.
  1145. */
  1146. static GCObject **correctgraylist (GCObject **p) {
  1147.   GCObject *curr;
  1148.   while ((curr = *p) != NULL) {
  1149.     GCObject **next = getgclist(curr);
  1150.     if (iswhite(curr))
  1151.       goto remove;  /* remove all white objects */
  1152.     else if (getage(curr) == G_TOUCHED1) {  /* touched in this cycle? */
  1153.       lua_assert(isgray(curr));
  1154.       nw2black(curr);  /* make it black, for next barrier */
  1155.       changeage(curr, G_TOUCHED1, G_TOUCHED2);
  1156.       goto remain;  /* keep it in the list and go to next element */
  1157.     }
  1158.     else if (curr->tt == LUA_VTHREAD) {
  1159.       lua_assert(isgray(curr));
  1160.       goto remain;  /* keep non-white threads on the list */
  1161.     }
  1162.     else {  /* everything else is removed */
  1163.       lua_assert(isold(curr));  /* young objects should be white here */
  1164.       if (getage(curr) == G_TOUCHED2)  /* advance from TOUCHED2... */
  1165.         changeage(curr, G_TOUCHED2, G_OLD);  /* ... to OLD */
  1166.       nw2black(curr);  /* make object black (to be removed) */
  1167.       goto remove;
  1168.     }
  1169.     remove: *p = *next; continue;
  1170.     remain: p = next; continue;
  1171.   }
  1172.   return p;
  1173. }
  1174.  
  1175.  
  1176. /*
  1177. ** Correct all gray lists, coalescing them into 'grayagain'.
  1178. */
  1179. static void correctgraylists (global_State *g) {
  1180.   GCObject **list = correctgraylist(&g->grayagain);
  1181.   *list = g->weak; g->weak = NULL;
  1182.   list = correctgraylist(list);
  1183.   *list = g->allweak; g->allweak = NULL;
  1184.   list = correctgraylist(list);
  1185.   *list = g->ephemeron; g->ephemeron = NULL;
  1186.   correctgraylist(list);
  1187. }
  1188.  
  1189.  
  1190. /*
  1191. ** Mark black 'OLD1' objects when starting a new young collection.
  1192. ** Gray objects are already in some gray list, and so will be visited
  1193. ** in the atomic step.
  1194. */
  1195. static void markold (global_State *g, GCObject *from, GCObject *to) {
  1196.   GCObject *p;
  1197.   for (p = from; p != to; p = p->next) {
  1198.     if (getage(p) == G_OLD1) {
  1199.       lua_assert(!iswhite(p));
  1200.       changeage(p, G_OLD1, G_OLD);  /* now they are old */
  1201.       if (isblack(p))
  1202.         reallymarkobject(g, p);
  1203.     }
  1204.   }
  1205. }
  1206.  
  1207.  
  1208. /*
  1209. ** Finish a young-generation collection.
  1210. */
  1211. static void finishgencycle (lua_State *L, global_State *g) {
  1212.   correctgraylists(g);
  1213.   checkSizes(L, g);
  1214.   g->gcstate = GCSpropagate;  /* skip restart */
  1215.   if (!g->gcemergency)
  1216.     callallpendingfinalizers(L);
  1217. }
  1218.  
  1219.  
  1220. /*
  1221. ** Does a young collection. First, mark 'OLD1' objects. Then does the
  1222. ** atomic step. Then, sweep all lists and advance pointers. Finally,
  1223. ** finish the collection.
  1224. */
  1225. static void youngcollection (lua_State *L, global_State *g) {
  1226.   GCObject **psurvival;  /* to point to first non-dead survival object */
  1227.   GCObject *dummy;  /* dummy out parameter to 'sweepgen' */
  1228.   lua_assert(g->gcstate == GCSpropagate);
  1229.   if (g->firstold1) {  /* are there regular OLD1 objects? */
  1230.     markold(g, g->firstold1, g->reallyold);  /* mark them */
  1231.     g->firstold1 = NULL;  /* no more OLD1 objects (for now) */
  1232.   }
  1233.   markold(g, g->finobj, g->finobjrold);
  1234.   markold(g, g->tobefnz, NULL);
  1235.   atomic(L);
  1236.  
  1237.   /* sweep nursery and get a pointer to its last live element */
  1238.   g->gcstate = GCSswpallgc;
  1239.   psurvival = sweepgen(L, g, &g->allgc, g->survival, &g->firstold1);
  1240.   /* sweep 'survival' */
  1241.   sweepgen(L, g, psurvival, g->old1, &g->firstold1);
  1242.   g->reallyold = g->old1;
  1243.   g->old1 = *psurvival;  /* 'survival' survivals are old now */
  1244.   g->survival = g->allgc;  /* all news are survivals */
  1245.  
  1246.   /* repeat for 'finobj' lists */
  1247.   dummy = NULL;  /* no 'firstold1' optimization for 'finobj' lists */
  1248.   psurvival = sweepgen(L, g, &g->finobj, g->finobjsur, &dummy);
  1249.   /* sweep 'survival' */
  1250.   sweepgen(L, g, psurvival, g->finobjold1, &dummy);
  1251.   g->finobjrold = g->finobjold1;
  1252.   g->finobjold1 = *psurvival;  /* 'survival' survivals are old now */
  1253.   g->finobjsur = g->finobj;  /* all news are survivals */
  1254.  
  1255.   sweepgen(L, g, &g->tobefnz, NULL, &dummy);
  1256.   finishgencycle(L, g);
  1257. }
  1258.  
  1259.  
  1260. /*
  1261. ** Clears all gray lists, sweeps objects, and prepare sublists to enter
  1262. ** generational mode. The sweeps remove dead objects and turn all
  1263. ** surviving objects to old. Threads go back to 'grayagain'; everything
  1264. ** else is turned black (not in any gray list).
  1265. */
  1266. static void atomic2gen (lua_State *L, global_State *g) {
  1267.   cleargraylists(g);
  1268.   /* sweep all elements making them old */
  1269.   g->gcstate = GCSswpallgc;
  1270.   sweep2old(L, &g->allgc);
  1271.   /* everything alive now is old */
  1272.   g->reallyold = g->old1 = g->survival = g->allgc;
  1273.   g->firstold1 = NULL;  /* there are no OLD1 objects anywhere */
  1274.  
  1275.   /* repeat for 'finobj' lists */
  1276.   sweep2old(L, &g->finobj);
  1277.   g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj;
  1278.  
  1279.   sweep2old(L, &g->tobefnz);
  1280.  
  1281.   g->gckind = KGC_GEN;
  1282.   g->lastatomic = 0;
  1283.   g->GCestimate = gettotalbytes(g);  /* base for memory control */
  1284.   finishgencycle(L, g);
  1285. }
  1286.  
  1287.  
  1288. /*
  1289. ** Enter generational mode. Must go until the end of an atomic cycle
  1290. ** to ensure that all objects are correctly marked and weak tables
  1291. ** are cleared. Then, turn all objects into old and finishes the
  1292. ** collection.
  1293. */
  1294. static lu_mem entergen (lua_State *L, global_State *g) {
  1295.   lu_mem numobjs;
  1296.   luaC_runtilstate(L, bitmask(GCSpause));  /* prepare to start a new cycle */
  1297.   luaC_runtilstate(L, bitmask(GCSpropagate));  /* start new cycle */
  1298.   numobjs = atomic(L);  /* propagates all and then do the atomic stuff */
  1299.   atomic2gen(L, g);
  1300.   return numobjs;
  1301. }
  1302.  
  1303.  
  1304. /*
  1305. ** Enter incremental mode. Turn all objects white, make all
  1306. ** intermediate lists point to NULL (to avoid invalid pointers),
  1307. ** and go to the pause state.
  1308. */
  1309. static void enterinc (global_State *g) {
  1310.   whitelist(g, g->allgc);
  1311.   g->reallyold = g->old1 = g->survival = NULL;
  1312.   whitelist(g, g->finobj);
  1313.   whitelist(g, g->tobefnz);
  1314.   g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
  1315.   g->gcstate = GCSpause;
  1316.   g->gckind = KGC_INC;
  1317.   g->lastatomic = 0;
  1318. }
  1319.  
  1320.  
  1321. /*
  1322. ** Change collector mode to 'newmode'.
  1323. */
  1324. void luaC_changemode (lua_State *L, int newmode) {
  1325.   global_State *g = G(L);
  1326.   if (newmode != g->gckind) {
  1327.     if (newmode == KGC_GEN)  /* entering generational mode? */
  1328.       entergen(L, g);
  1329.     else
  1330.       enterinc(g);  /* entering incremental mode */
  1331.   }
  1332.   g->lastatomic = 0;
  1333. }
  1334.  
  1335.  
  1336. /*
  1337. ** Does a full collection in generational mode.
  1338. */
  1339. static lu_mem fullgen (lua_State *L, global_State *g) {
  1340.   enterinc(g);
  1341.   return entergen(L, g);
  1342. }
  1343.  
  1344.  
  1345. /*
  1346. ** Set debt for the next minor collection, which will happen when
  1347. ** memory grows 'genminormul'%.
  1348. */
  1349. static void setminordebt (global_State *g) {
  1350.   luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul));
  1351. }
  1352.  
  1353.  
  1354. /*
  1355. ** Does a major collection after last collection was a "bad collection".
  1356. **
  1357. ** When the program is building a big structure, it allocates lots of
  1358. ** memory but generates very little garbage. In those scenarios,
  1359. ** the generational mode just wastes time doing small collections, and
  1360. ** major collections are frequently what we call a "bad collection", a
  1361. ** collection that frees too few objects. To avoid the cost of switching
  1362. ** between generational mode and the incremental mode needed for full
  1363. ** (major) collections, the collector tries to stay in incremental mode
  1364. ** after a bad collection, and to switch back to generational mode only
  1365. ** after a "good" collection (one that traverses less than 9/8 objects
  1366. ** of the previous one).
  1367. ** The collector must choose whether to stay in incremental mode or to
  1368. ** switch back to generational mode before sweeping. At this point, it
  1369. ** does not know the real memory in use, so it cannot use memory to
  1370. ** decide whether to return to generational mode. Instead, it uses the
  1371. ** number of objects traversed (returned by 'atomic') as a proxy. The
  1372. ** field 'g->lastatomic' keeps this count from the last collection.
  1373. ** ('g->lastatomic != 0' also means that the last collection was bad.)
  1374. */
  1375. static void stepgenfull (lua_State *L, global_State *g) {
  1376.   lu_mem newatomic;  /* count of traversed objects */
  1377.   lu_mem lastatomic = g->lastatomic;  /* count from last collection */
  1378.   if (g->gckind == KGC_GEN)  /* still in generational mode? */
  1379.     enterinc(g);  /* enter incremental mode */
  1380.   luaC_runtilstate(L, bitmask(GCSpropagate));  /* start new cycle */
  1381.   newatomic = atomic(L);  /* mark everybody */
  1382.   if (newatomic < lastatomic + (lastatomic >> 3)) {  /* good collection? */
  1383.     atomic2gen(L, g);  /* return to generational mode */
  1384.     setminordebt(g);
  1385.   }
  1386.   else {  /* another bad collection; stay in incremental mode */
  1387.     g->GCestimate = gettotalbytes(g);  /* first estimate */;
  1388.     entersweep(L);
  1389.     luaC_runtilstate(L, bitmask(GCSpause));  /* finish collection */
  1390.     setpause(g);
  1391.     g->lastatomic = newatomic;
  1392.   }
  1393. }
  1394.  
  1395.  
  1396. /*
  1397. ** Does a generational "step".
  1398. ** Usually, this means doing a minor collection and setting the debt to
  1399. ** make another collection when memory grows 'genminormul'% larger.
  1400. **
  1401. ** However, there are exceptions.  If memory grows 'genmajormul'%
  1402. ** larger than it was at the end of the last major collection (kept
  1403. ** in 'g->GCestimate'), the function does a major collection. At the
  1404. ** end, it checks whether the major collection was able to free a
  1405. ** decent amount of memory (at least half the growth in memory since
  1406. ** previous major collection). If so, the collector keeps its state,
  1407. ** and the next collection will probably be minor again. Otherwise,
  1408. ** we have what we call a "bad collection". In that case, set the field
  1409. ** 'g->lastatomic' to signal that fact, so that the next collection will
  1410. ** go to 'stepgenfull'.
  1411. **
  1412. ** 'GCdebt <= 0' means an explicit call to GC step with "size" zero;
  1413. ** in that case, do a minor collection.
  1414. */
  1415. static void genstep (lua_State *L, global_State *g) {
  1416.   if (g->lastatomic != 0)  /* last collection was a bad one? */
  1417.     stepgenfull(L, g);  /* do a full step */
  1418.   else {
  1419.     lu_mem majorbase = g->GCestimate;  /* memory after last major collection */
  1420.     lu_mem majorinc = (majorbase / 100) * getgcparam(g->genmajormul);
  1421.     if (g->GCdebt > 0 && gettotalbytes(g) > majorbase + majorinc) {
  1422.       lu_mem numobjs = fullgen(L, g);  /* do a major collection */
  1423.       if (gettotalbytes(g) < majorbase + (majorinc / 2)) {
  1424.         /* collected at least half of memory growth since last major
  1425.            collection; keep doing minor collections */
  1426.         setminordebt(g);
  1427.       }
  1428.       else {  /* bad collection */
  1429.         g->lastatomic = numobjs;  /* signal that last collection was bad */
  1430.         setpause(g);  /* do a long wait for next (major) collection */
  1431.       }
  1432.     }
  1433.     else {  /* regular case; do a minor collection */
  1434.       youngcollection(L, g);
  1435.       setminordebt(g);
  1436.       g->GCestimate = majorbase;  /* preserve base value */
  1437.     }
  1438.   }
  1439.   lua_assert(isdecGCmodegen(g));
  1440. }
  1441.  
  1442. /* }====================================================== */
  1443.  
  1444.  
  1445. /*
  1446. ** {======================================================
  1447. ** GC control
  1448. ** =======================================================
  1449. */
  1450.  
  1451.  
  1452. /*
  1453. ** Set the "time" to wait before starting a new GC cycle; cycle will
  1454. ** start when memory use hits the threshold of ('estimate' * pause /
  1455. ** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero,
  1456. ** because Lua cannot even start with less than PAUSEADJ bytes).
  1457. */
  1458. static void setpause (global_State *g) {
  1459.   l_mem threshold, debt;
  1460.   int pause = getgcparam(g->gcpause);
  1461.   l_mem estimate = g->GCestimate / PAUSEADJ;  /* adjust 'estimate' */
  1462.   lua_assert(estimate > 0);
  1463.   threshold = (pause < MAX_LMEM / estimate)  /* overflow? */
  1464.             ? estimate * pause  /* no overflow */
  1465.             : MAX_LMEM;  /* overflow; truncate to maximum */
  1466.   debt = gettotalbytes(g) - threshold;
  1467.   if (debt > 0) debt = 0;
  1468.   luaE_setdebt(g, debt);
  1469. }
  1470.  
  1471.  
  1472. /*
  1473. ** Enter first sweep phase.
  1474. ** The call to 'sweeptolive' makes the pointer point to an object
  1475. ** inside the list (instead of to the header), so that the real sweep do
  1476. ** not need to skip objects created between "now" and the start of the
  1477. ** real sweep.
  1478. */
  1479. static void entersweep (lua_State *L) {
  1480.   global_State *g = G(L);
  1481.   g->gcstate = GCSswpallgc;
  1482.   lua_assert(g->sweepgc == NULL);
  1483.   g->sweepgc = sweeptolive(L, &g->allgc);
  1484. }
  1485.  
  1486.  
  1487. /*
  1488. ** Delete all objects in list 'p' until (but not including) object
  1489. ** 'limit'.
  1490. */
  1491. static void deletelist (lua_State *L, GCObject *p, GCObject *limit) {
  1492.   while (p != limit) {
  1493.     GCObject *next = p->next;
  1494.     freeobj(L, p);
  1495.     p = next;
  1496.   }
  1497. }
  1498.  
  1499.  
  1500. /*
  1501. ** Call all finalizers of the objects in the given Lua state, and
  1502. ** then free all objects, except for the main thread.
  1503. */
  1504. void luaC_freeallobjects (lua_State *L) {
  1505.   global_State *g = G(L);
  1506.   g->gcstp = GCSTPCLS;  /* no extra finalizers after here */
  1507.   luaC_changemode(L, KGC_INC);
  1508.   separatetobefnz(g, 1);  /* separate all objects with finalizers */
  1509.   lua_assert(g->finobj == NULL);
  1510.   callallpendingfinalizers(L);
  1511.   deletelist(L, g->allgc, obj2gco(g->mainthread));
  1512.   lua_assert(g->finobj == NULL);  /* no new finalizers */
  1513.   deletelist(L, g->fixedgc, NULL);  /* collect fixed objects */
  1514.   lua_assert(g->strt.nuse == 0);
  1515. }
  1516.  
  1517.  
  1518. static lu_mem atomic (lua_State *L) {
  1519.   global_State *g = G(L);
  1520.   lu_mem work = 0;
  1521.   GCObject *origweak, *origall;
  1522.   GCObject *grayagain = g->grayagain;  /* save original list */
  1523.   g->grayagain = NULL;
  1524.   lua_assert(g->ephemeron == NULL && g->weak == NULL);
  1525.   lua_assert(!iswhite(g->mainthread));
  1526.   g->gcstate = GCSatomic;
  1527.   markobject(g, L);  /* mark running thread */
  1528.   /* registry and global metatables may be changed by API */
  1529.   markvalue(g, &g->l_registry);
  1530.   markmt(g);  /* mark global metatables */
  1531.   work += propagateall(g);  /* empties 'gray' list */
  1532.   /* remark occasional upvalues of (maybe) dead threads */
  1533.   work += remarkupvals(g);
  1534.   work += propagateall(g);  /* propagate changes */
  1535.   g->gray = grayagain;
  1536.   work += propagateall(g);  /* traverse 'grayagain' list */
  1537.   convergeephemerons(g);
  1538.   /* at this point, all strongly accessible objects are marked. */
  1539.   /* Clear values from weak tables, before checking finalizers */
  1540.   clearbyvalues(g, g->weak, NULL);
  1541.   clearbyvalues(g, g->allweak, NULL);
  1542.   origweak = g->weak; origall = g->allweak;
  1543.   separatetobefnz(g, 0);  /* separate objects to be finalized */
  1544.   work += markbeingfnz(g);  /* mark objects that will be finalized */
  1545.   work += propagateall(g);  /* remark, to propagate 'resurrection' */
  1546.   convergeephemerons(g);
  1547.   /* at this point, all resurrected objects are marked. */
  1548.   /* remove dead objects from weak tables */
  1549.   clearbykeys(g, g->ephemeron);  /* clear keys from all ephemeron tables */
  1550.   clearbykeys(g, g->allweak);  /* clear keys from all 'allweak' tables */
  1551.   /* clear values from resurrected weak tables */
  1552.   clearbyvalues(g, g->weak, origweak);
  1553.   clearbyvalues(g, g->allweak, origall);
  1554.   luaS_clearcache(g);
  1555.   g->currentwhite = cast_byte(otherwhite(g));  /* flip current white */
  1556.   lua_assert(g->gray == NULL);
  1557.   return work;  /* estimate of slots marked by 'atomic' */
  1558. }
  1559.  
  1560.  
  1561. static int sweepstep (lua_State *L, global_State *g,
  1562.                       int nextstate, GCObject **nextlist) {
  1563.   if (g->sweepgc) {
  1564.     l_mem olddebt = g->GCdebt;
  1565.     int count;
  1566.     g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX, &count);
  1567.     g->GCestimate += g->GCdebt - olddebt;  /* update estimate */
  1568.     return count;
  1569.   }
  1570.   else {  /* enter next state */
  1571.     g->gcstate = nextstate;
  1572.     g->sweepgc = nextlist;
  1573.     return 0;  /* no work done */
  1574.   }
  1575. }
  1576.  
  1577.  
  1578. static lu_mem singlestep (lua_State *L) {
  1579.   global_State *g = G(L);
  1580.   lu_mem work;
  1581.   lua_assert(!g->gcstopem);  /* collector is not reentrant */
  1582.   g->gcstopem = 1;  /* no emergency collections while collecting */
  1583.   switch (g->gcstate) {
  1584.     case GCSpause: {
  1585.       restartcollection(g);
  1586.       g->gcstate = GCSpropagate;
  1587.       work = 1;
  1588.       break;
  1589.     }
  1590.     case GCSpropagate: {
  1591.       if (g->gray == NULL) {  /* no more gray objects? */
  1592.         g->gcstate = GCSenteratomic;  /* finish propagate phase */
  1593.         work = 0;
  1594.       }
  1595.       else
  1596.         work = propagatemark(g);  /* traverse one gray object */
  1597.       break;
  1598.     }
  1599.     case GCSenteratomic: {
  1600.       work = atomic(L);  /* work is what was traversed by 'atomic' */
  1601.       entersweep(L);
  1602.       g->GCestimate = gettotalbytes(g);  /* first estimate */;
  1603.       break;
  1604.     }
  1605.     case GCSswpallgc: {  /* sweep "regular" objects */
  1606.       work = sweepstep(L, g, GCSswpfinobj, &g->finobj);
  1607.       break;
  1608.     }
  1609.     case GCSswpfinobj: {  /* sweep objects with finalizers */
  1610.       work = sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
  1611.       break;
  1612.     }
  1613.     case GCSswptobefnz: {  /* sweep objects to be finalized */
  1614.       work = sweepstep(L, g, GCSswpend, NULL);
  1615.       break;
  1616.     }
  1617.     case GCSswpend: {  /* finish sweeps */
  1618.       checkSizes(L, g);
  1619.       g->gcstate = GCScallfin;
  1620.       work = 0;
  1621.       break;
  1622.     }
  1623.     case GCScallfin: {  /* call remaining finalizers */
  1624.       if (g->tobefnz && !g->gcemergency) {
  1625.         g->gcstopem = 0;  /* ok collections during finalizers */
  1626.         work = runafewfinalizers(L, GCFINMAX) * GCFINALIZECOST;
  1627.       }
  1628.       else {  /* emergency mode or no more finalizers */
  1629.         g->gcstate = GCSpause;  /* finish collection */
  1630.         work = 0;
  1631.       }
  1632.       break;
  1633.     }
  1634.     default: lua_assert(0); return 0;
  1635.   }
  1636.   g->gcstopem = 0;
  1637.   return work;
  1638. }
  1639.  
  1640.  
  1641. /*
  1642. ** advances the garbage collector until it reaches a state allowed
  1643. ** by 'statemask'
  1644. */
  1645. void luaC_runtilstate (lua_State *L, int statesmask) {
  1646.   global_State *g = G(L);
  1647.   while (!testbit(statesmask, g->gcstate))
  1648.     singlestep(L);
  1649. }
  1650.  
  1651.  
  1652.  
  1653. /*
  1654. ** Performs a basic incremental step. The debt and step size are
  1655. ** converted from bytes to "units of work"; then the function loops
  1656. ** running single steps until adding that many units of work or
  1657. ** finishing a cycle (pause state). Finally, it sets the debt that
  1658. ** controls when next step will be performed.
  1659. */
  1660. static void incstep (lua_State *L, global_State *g) {
  1661.   int stepmul = (getgcparam(g->gcstepmul) | 1);  /* avoid division by 0 */
  1662.   l_mem debt = (g->GCdebt / WORK2MEM) * stepmul;
  1663.   l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem))
  1664.                  ? ((cast(l_mem, 1) << g->gcstepsize) / WORK2MEM) * stepmul
  1665.                  : MAX_LMEM;  /* overflow; keep maximum value */
  1666.   do {  /* repeat until pause or enough "credit" (negative debt) */
  1667.     lu_mem work = singlestep(L);  /* perform one single step */
  1668.     debt -= work;
  1669.   } while (debt > -stepsize && g->gcstate != GCSpause);
  1670.   if (g->gcstate == GCSpause)
  1671.     setpause(g);  /* pause until next cycle */
  1672.   else {
  1673.     debt = (debt / stepmul) * WORK2MEM;  /* convert 'work units' to bytes */
  1674.     luaE_setdebt(g, debt);
  1675.   }
  1676. }
  1677.  
  1678. /*
  1679. ** performs a basic GC step if collector is running
  1680. */
  1681. void luaC_step (lua_State *L) {
  1682.   global_State *g = G(L);
  1683.   lua_assert(!g->gcemergency);
  1684.   if (gcrunning(g)) {  /* running? */
  1685.     if(isdecGCmodegen(g))
  1686.       genstep(L, g);
  1687.     else
  1688.       incstep(L, g);
  1689.   }
  1690. }
  1691.  
  1692.  
  1693. /*
  1694. ** Perform a full collection in incremental mode.
  1695. ** Before running the collection, check 'keepinvariant'; if it is true,
  1696. ** there may be some objects marked as black, so the collector has
  1697. ** to sweep all objects to turn them back to white (as white has not
  1698. ** changed, nothing will be collected).
  1699. */
  1700. static void fullinc (lua_State *L, global_State *g) {
  1701.   if (keepinvariant(g))  /* black objects? */
  1702.     entersweep(L); /* sweep everything to turn them back to white */
  1703.   /* finish any pending sweep phase to start a new cycle */
  1704.   luaC_runtilstate(L, bitmask(GCSpause));
  1705.   luaC_runtilstate(L, bitmask(GCScallfin));  /* run up to finalizers */
  1706.   /* estimate must be correct after a full GC cycle */
  1707.   lua_assert(g->GCestimate == gettotalbytes(g));
  1708.   luaC_runtilstate(L, bitmask(GCSpause));  /* finish collection */
  1709.   setpause(g);
  1710. }
  1711.  
  1712.  
  1713. /*
  1714. ** Performs a full GC cycle; if 'isemergency', set a flag to avoid
  1715. ** some operations which could change the interpreter state in some
  1716. ** unexpected ways (running finalizers and shrinking some structures).
  1717. */
  1718. void luaC_fullgc (lua_State *L, int isemergency) {
  1719.   global_State *g = G(L);
  1720.   lua_assert(!g->gcemergency);
  1721.   g->gcemergency = isemergency;  /* set flag */
  1722.   if (g->gckind == KGC_INC)
  1723.     fullinc(L, g);
  1724.   else
  1725.     fullgen(L, g);
  1726.   g->gcemergency = 0;
  1727. }
  1728.  
  1729. /* }====================================================== */
  1730.  
  1731.  
  1732.