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  1. /*
  2. ** $Id: lgc.c,v 2.215.1.2 2017/08/31 16:15:27 roberto Exp $
  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.  
  13. #include <string.h>
  14.  
  15. #include "lua.h"
  16.  
  17. #include "ldebug.h"
  18. #include "ldo.h"
  19. #include "lfunc.h"
  20. #include "lgc.h"
  21. #include "lmem.h"
  22. #include "lobject.h"
  23. #include "lstate.h"
  24. #include "lstring.h"
  25. #include "ltable.h"
  26. #include "ltm.h"
  27.  
  28.  
  29. /*
  30. ** internal state for collector while inside the atomic phase. The
  31. ** collector should never be in this state while running regular code.
  32. */
  33. #define GCSinsideatomic         (GCSpause + 1)
  34.  
  35. /*
  36. ** cost of sweeping one element (the size of a small object divided
  37. ** by some adjust for the sweep speed)
  38. */
  39. #define GCSWEEPCOST     ((sizeof(TString) + 4) / 4)
  40.  
  41. /* maximum number of elements to sweep in each single step */
  42. #define GCSWEEPMAX      (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
  43.  
  44. /* cost of calling one finalizer */
  45. #define GCFINALIZECOST  GCSWEEPCOST
  46.  
  47.  
  48. /*
  49. ** macro to adjust 'stepmul': 'stepmul' is actually used like
  50. ** 'stepmul / STEPMULADJ' (value chosen by tests)
  51. */
  52. #define STEPMULADJ              200
  53.  
  54.  
  55. /*
  56. ** macro to adjust 'pause': 'pause' is actually used like
  57. ** 'pause / PAUSEADJ' (value chosen by tests)
  58. */
  59. #define PAUSEADJ                100
  60.  
  61.  
  62. /*
  63. ** 'makewhite' erases all color bits then sets only the current white
  64. ** bit
  65. */
  66. #define maskcolors      (~(bitmask(BLACKBIT) | WHITEBITS))
  67. #define makewhite(g,x)  \
  68.  (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g)))
  69.  
  70. #define white2gray(x)   resetbits(x->marked, WHITEBITS)
  71. #define black2gray(x)   resetbit(x->marked, BLACKBIT)
  72.  
  73.  
  74. #define valiswhite(x)   (iscollectable(x) && iswhite(gcvalue(x)))
  75.  
  76. #define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
  77.  
  78.  
  79. #define checkconsistency(obj)  \
  80.   lua_longassert(!iscollectable(obj) || righttt(obj))
  81.  
  82.  
  83. #define markvalue(g,o) { checkconsistency(o); \
  84.   if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
  85.  
  86. #define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); }
  87.  
  88. /*
  89. ** mark an object that can be NULL (either because it is really optional,
  90. ** or it was stripped as debug info, or inside an uncompleted structure)
  91. */
  92. #define markobjectN(g,t)        { if (t) markobject(g,t); }
  93.  
  94. static void reallymarkobject (global_State *g, GCObject *o);
  95.  
  96.  
  97. /*
  98. ** {======================================================
  99. ** Generic functions
  100. ** =======================================================
  101. */
  102.  
  103.  
  104. /*
  105. ** one after last element in a hash array
  106. */
  107. #define gnodelast(h)    gnode(h, cast(size_t, sizenode(h)))
  108.  
  109.  
  110. /*
  111. ** link collectable object 'o' into list pointed by 'p'
  112. */
  113. #define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o))
  114.  
  115.  
  116. /*
  117. ** If key is not marked, mark its entry as dead. This allows key to be
  118. ** collected, but keeps its entry in the table.  A dead node is needed
  119. ** when Lua looks up for a key (it may be part of a chain) and when
  120. ** traversing a weak table (key might be removed from the table during
  121. ** traversal). Other places never manipulate dead keys, because its
  122. ** associated nil value is enough to signal that the entry is logically
  123. ** empty.
  124. */
  125. static void removeentry (Node *n) {
  126.   lua_assert(ttisnil(gval(n)));
  127.   if (valiswhite(gkey(n)))
  128.     setdeadvalue(wgkey(n));  /* unused and unmarked key; remove it */
  129. }
  130.  
  131.  
  132. /*
  133. ** tells whether a key or value can be cleared from a weak
  134. ** table. Non-collectable objects are never removed from weak
  135. ** tables. Strings behave as 'values', so are never removed too. for
  136. ** other objects: if really collected, cannot keep them; for objects
  137. ** being finalized, keep them in keys, but not in values
  138. */
  139. static int iscleared (global_State *g, const TValue *o) {
  140.   if (!iscollectable(o)) return 0;
  141.   else if (ttisstring(o)) {
  142.     markobject(g, tsvalue(o));  /* strings are 'values', so are never weak */
  143.     return 0;
  144.   }
  145.   else return iswhite(gcvalue(o));
  146. }
  147.  
  148.  
  149. /*
  150. ** barrier that moves collector forward, that is, mark the white object
  151. ** being pointed by a black object. (If in sweep phase, clear the black
  152. ** object to white [sweep it] to avoid other barrier calls for this
  153. ** same object.)
  154. */
  155. void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
  156.   global_State *g = G(L);
  157.   lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
  158.   if (keepinvariant(g))  /* must keep invariant? */
  159.     reallymarkobject(g, v);  /* restore invariant */
  160.   else {  /* sweep phase */
  161.     lua_assert(issweepphase(g));
  162.     makewhite(g, o);  /* mark main obj. as white to avoid other barriers */
  163.   }
  164. }
  165.  
  166.  
  167. /*
  168. ** barrier that moves collector backward, that is, mark the black object
  169. ** pointing to a white object as gray again.
  170. */
  171. void luaC_barrierback_ (lua_State *L, Table *t) {
  172.   global_State *g = G(L);
  173.   lua_assert(isblack(t) && !isdead(g, t));
  174.   black2gray(t);  /* make table gray (again) */
  175.   linkgclist(t, g->grayagain);
  176. }
  177.  
  178.  
  179. /*
  180. ** barrier for assignments to closed upvalues. Because upvalues are
  181. ** shared among closures, it is impossible to know the color of all
  182. ** closures pointing to it. So, we assume that the object being assigned
  183. ** must be marked.
  184. */
  185. void luaC_upvalbarrier_ (lua_State *L, UpVal *uv) {
  186.   global_State *g = G(L);
  187.   GCObject *o = gcvalue(uv->v);
  188.   lua_assert(!upisopen(uv));  /* ensured by macro luaC_upvalbarrier */
  189.   if (keepinvariant(g))
  190.     markobject(g, o);
  191. }
  192.  
  193.  
  194. void luaC_fix (lua_State *L, GCObject *o) {
  195.   global_State *g = G(L);
  196.   lua_assert(g->allgc == o);  /* object must be 1st in 'allgc' list! */
  197.   white2gray(o);  /* they will be gray forever */
  198.   g->allgc = o->next;  /* remove object from 'allgc' list */
  199.   o->next = g->fixedgc;  /* link it to 'fixedgc' list */
  200.   g->fixedgc = o;
  201. }
  202.  
  203.  
  204. /*
  205. ** create a new collectable object (with given type and size) and link
  206. ** it to 'allgc' list.
  207. */
  208. GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
  209.   global_State *g = G(L);
  210.   GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz));
  211.   o->marked = luaC_white(g);
  212.   o->tt = tt;
  213.   o->next = g->allgc;
  214.   g->allgc = o;
  215.   return o;
  216. }
  217.  
  218. /* }====================================================== */
  219.  
  220.  
  221.  
  222. /*
  223. ** {======================================================
  224. ** Mark functions
  225. ** =======================================================
  226. */
  227.  
  228.  
  229. /*
  230. ** mark an object. Userdata, strings, and closed upvalues are visited
  231. ** and turned black here. Other objects are marked gray and added
  232. ** to appropriate list to be visited (and turned black) later. (Open
  233. ** upvalues are already linked in 'headuv' list.)
  234. */
  235. static void reallymarkobject (global_State *g, GCObject *o) {
  236.  reentry:
  237.   white2gray(o);
  238.   switch (o->tt) {
  239.     case LUA_TSHRSTR: {
  240.       gray2black(o);
  241.       g->GCmemtrav += sizelstring(gco2ts(o)->shrlen);
  242.       break;
  243.     }
  244.     case LUA_TLNGSTR: {
  245.       gray2black(o);
  246.       g->GCmemtrav += sizelstring(gco2ts(o)->u.lnglen);
  247.       break;
  248.     }
  249.     case LUA_TUSERDATA: {
  250.       TValue uvalue;
  251.       markobjectN(g, gco2u(o)->metatable);  /* mark its metatable */
  252.       gray2black(o);
  253.       g->GCmemtrav += sizeudata(gco2u(o));
  254.       getuservalue(g->mainthread, gco2u(o), &uvalue);
  255.       if (valiswhite(&uvalue)) {  /* markvalue(g, &uvalue); */
  256.         o = gcvalue(&uvalue);
  257.         goto reentry;
  258.       }
  259.       break;
  260.     }
  261.     case LUA_TLCL: {
  262.       linkgclist(gco2lcl(o), g->gray);
  263.       break;
  264.     }
  265.     case LUA_TCCL: {
  266.       linkgclist(gco2ccl(o), g->gray);
  267.       break;
  268.     }
  269.     case LUA_TTABLE: {
  270.       linkgclist(gco2t(o), g->gray);
  271.       break;
  272.     }
  273.     case LUA_TTHREAD: {
  274.       linkgclist(gco2th(o), g->gray);
  275.       break;
  276.     }
  277.     case LUA_TPROTO: {
  278.       linkgclist(gco2p(o), g->gray);
  279.       break;
  280.     }
  281.     default: lua_assert(0); break;
  282.   }
  283. }
  284.  
  285.  
  286. /*
  287. ** mark metamethods for basic types
  288. */
  289. static void markmt (global_State *g) {
  290.   int i;
  291.   for (i=0; i < LUA_NUMTAGS; i++)
  292.     markobjectN(g, g->mt[i]);
  293. }
  294.  
  295.  
  296. /*
  297. ** mark all objects in list of being-finalized
  298. */
  299. static void markbeingfnz (global_State *g) {
  300.   GCObject *o;
  301.   for (o = g->tobefnz; o != NULL; o = o->next)
  302.     markobject(g, o);
  303. }
  304.  
  305.  
  306. /*
  307. ** Mark all values stored in marked open upvalues from non-marked threads.
  308. ** (Values from marked threads were already marked when traversing the
  309. ** thread.) Remove from the list threads that no longer have upvalues and
  310. ** not-marked threads.
  311. */
  312. static void remarkupvals (global_State *g) {
  313.   lua_State *thread;
  314.   lua_State **p = &g->twups;
  315.   while ((thread = *p) != NULL) {
  316.     lua_assert(!isblack(thread));  /* threads are never black */
  317.     if (isgray(thread) && thread->openupval != NULL)
  318.       p = &thread->twups;  /* keep marked thread with upvalues in the list */
  319.     else {  /* thread is not marked or without upvalues */
  320.       UpVal *uv;
  321.       *p = thread->twups;  /* remove thread from the list */
  322.       thread->twups = thread;  /* mark that it is out of list */
  323.       for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
  324.         if (uv->u.open.touched) {
  325.           markvalue(g, uv->v);  /* remark upvalue's value */
  326.           uv->u.open.touched = 0;
  327.         }
  328.       }
  329.     }
  330.   }
  331. }
  332.  
  333.  
  334. /*
  335. ** mark root set and reset all gray lists, to start a new collection
  336. */
  337. static void restartcollection (global_State *g) {
  338.   g->gray = g->grayagain = NULL;
  339.   g->weak = g->allweak = g->ephemeron = NULL;
  340.   markobject(g, g->mainthread);
  341.   markvalue(g, &g->l_registry);
  342.   markmt(g);
  343.   markbeingfnz(g);  /* mark any finalizing object left from previous cycle */
  344. }
  345.  
  346. /* }====================================================== */
  347.  
  348.  
  349. /*
  350. ** {======================================================
  351. ** Traverse functions
  352. ** =======================================================
  353. */
  354.  
  355. /*
  356. ** Traverse a table with weak values and link it to proper list. During
  357. ** propagate phase, keep it in 'grayagain' list, to be revisited in the
  358. ** atomic phase. In the atomic phase, if table has any white value,
  359. ** put it in 'weak' list, to be cleared.
  360. */
  361. static void traverseweakvalue (global_State *g, Table *h) {
  362.   Node *n, *limit = gnodelast(h);
  363.   /* if there is array part, assume it may have white values (it is not
  364.      worth traversing it now just to check) */
  365.   int hasclears = (h->sizearray > 0);
  366.   for (n = gnode(h, 0); n < limit; n++) {  /* traverse hash part */
  367.     checkdeadkey(n);
  368.     if (ttisnil(gval(n)))  /* entry is empty? */
  369.       removeentry(n);  /* remove it */
  370.     else {
  371.       lua_assert(!ttisnil(gkey(n)));
  372.       markvalue(g, gkey(n));  /* mark key */
  373.       if (!hasclears && iscleared(g, gval(n)))  /* is there a white value? */
  374.         hasclears = 1;  /* table will have to be cleared */
  375.     }
  376.   }
  377.   if (g->gcstate == GCSpropagate)
  378.     linkgclist(h, g->grayagain);  /* must retraverse it in atomic phase */
  379.   else if (hasclears)
  380.     linkgclist(h, g->weak);  /* has to be cleared later */
  381. }
  382.  
  383.  
  384. /*
  385. ** Traverse an ephemeron table and link it to proper list. Returns true
  386. ** iff any object was marked during this traversal (which implies that
  387. ** convergence has to continue). During propagation phase, keep table
  388. ** in 'grayagain' list, to be visited again in the atomic phase. In
  389. ** the atomic phase, if table has any white->white entry, it has to
  390. ** be revisited during ephemeron convergence (as that key may turn
  391. ** black). Otherwise, if it has any white key, table has to be cleared
  392. ** (in the atomic phase).
  393. */
  394. static int traverseephemeron (global_State *g, Table *h) {
  395.   int marked = 0;  /* true if an object is marked in this traversal */
  396.   int hasclears = 0;  /* true if table has white keys */
  397.   int hasww = 0;  /* true if table has entry "white-key -> white-value" */
  398.   Node *n, *limit = gnodelast(h);
  399.   unsigned int i;
  400.   /* traverse array part */
  401.   for (i = 0; i < h->sizearray; i++) {
  402.     if (valiswhite(&h->array[i])) {
  403.       marked = 1;
  404.       reallymarkobject(g, gcvalue(&h->array[i]));
  405.     }
  406.   }
  407.   /* traverse hash part */
  408.   for (n = gnode(h, 0); n < limit; n++) {
  409.     checkdeadkey(n);
  410.     if (ttisnil(gval(n)))  /* entry is empty? */
  411.       removeentry(n);  /* remove it */
  412.     else if (iscleared(g, gkey(n))) {  /* key is not marked (yet)? */
  413.       hasclears = 1;  /* table must be cleared */
  414.       if (valiswhite(gval(n)))  /* value not marked yet? */
  415.         hasww = 1;  /* white-white entry */
  416.     }
  417.     else if (valiswhite(gval(n))) {  /* value not marked yet? */
  418.       marked = 1;
  419.       reallymarkobject(g, gcvalue(gval(n)));  /* mark it now */
  420.     }
  421.   }
  422.   /* link table into proper list */
  423.   if (g->gcstate == GCSpropagate)
  424.     linkgclist(h, g->grayagain);  /* must retraverse it in atomic phase */
  425.   else if (hasww)  /* table has white->white entries? */
  426.     linkgclist(h, g->ephemeron);  /* have to propagate again */
  427.   else if (hasclears)  /* table has white keys? */
  428.     linkgclist(h, g->allweak);  /* may have to clean white keys */
  429.   return marked;
  430. }
  431.  
  432.  
  433. static void traversestrongtable (global_State *g, Table *h) {
  434.   Node *n, *limit = gnodelast(h);
  435.   unsigned int i;
  436.   for (i = 0; i < h->sizearray; i++)  /* traverse array part */
  437.     markvalue(g, &h->array[i]);
  438.   for (n = gnode(h, 0); n < limit; n++) {  /* traverse hash part */
  439.     checkdeadkey(n);
  440.     if (ttisnil(gval(n)))  /* entry is empty? */
  441.       removeentry(n);  /* remove it */
  442.     else {
  443.       lua_assert(!ttisnil(gkey(n)));
  444.       markvalue(g, gkey(n));  /* mark key */
  445.       markvalue(g, gval(n));  /* mark value */
  446.     }
  447.   }
  448. }
  449.  
  450.  
  451. static lu_mem traversetable (global_State *g, Table *h) {
  452.   const char *weakkey, *weakvalue;
  453.   const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
  454.   markobjectN(g, h->metatable);
  455.   if (mode && ttisstring(mode) &&  /* is there a weak mode? */
  456.       ((weakkey = strchr(svalue(mode), 'k')),
  457.        (weakvalue = strchr(svalue(mode), 'v')),
  458.        (weakkey || weakvalue))) {  /* is really weak? */
  459.     black2gray(h);  /* keep table gray */
  460.     if (!weakkey)  /* strong keys? */
  461.       traverseweakvalue(g, h);
  462.     else if (!weakvalue)  /* strong values? */
  463.       traverseephemeron(g, h);
  464.     else  /* all weak */
  465.       linkgclist(h, g->allweak);  /* nothing to traverse now */
  466.   }
  467.   else  /* not weak */
  468.     traversestrongtable(g, h);
  469.   return sizeof(Table) + sizeof(TValue) * h->sizearray +
  470.                          sizeof(Node) * cast(size_t, allocsizenode(h));
  471. }
  472.  
  473.  
  474. /*
  475. ** Traverse a prototype. (While a prototype is being build, its
  476. ** arrays can be larger than needed; the extra slots are filled with
  477. ** NULL, so the use of 'markobjectN')
  478. */
  479. static int traverseproto (global_State *g, Proto *f) {
  480.   int i;
  481.   if (f->cache && iswhite(f->cache))
  482.     f->cache = NULL;  /* allow cache to be collected */
  483.   markobjectN(g, f->source);
  484.   for (i = 0; i < f->sizek; i++)  /* mark literals */
  485.     markvalue(g, &f->k[i]);
  486.   for (i = 0; i < f->sizeupvalues; i++)  /* mark upvalue names */
  487.     markobjectN(g, f->upvalues[i].name);
  488.   for (i = 0; i < f->sizep; i++)  /* mark nested protos */
  489.     markobjectN(g, f->p[i]);
  490.   for (i = 0; i < f->sizelocvars; i++)  /* mark local-variable names */
  491.     markobjectN(g, f->locvars[i].varname);
  492.   return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
  493.                          sizeof(Proto *) * f->sizep +
  494.                          sizeof(TValue) * f->sizek +
  495.                          sizeof(int) * f->sizelineinfo +
  496.                          sizeof(LocVar) * f->sizelocvars +
  497.                          sizeof(Upvaldesc) * f->sizeupvalues;
  498. }
  499.  
  500.  
  501. static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
  502.   int i;
  503.   for (i = 0; i < cl->nupvalues; i++)  /* mark its upvalues */
  504.     markvalue(g, &cl->upvalue[i]);
  505.   return sizeCclosure(cl->nupvalues);
  506. }
  507.  
  508. /*
  509. ** open upvalues point to values in a thread, so those values should
  510. ** be marked when the thread is traversed except in the atomic phase
  511. ** (because then the value cannot be changed by the thread and the
  512. ** thread may not be traversed again)
  513. */
  514. static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
  515.   int i;
  516.   markobjectN(g, cl->p);  /* mark its prototype */
  517.   for (i = 0; i < cl->nupvalues; i++) {  /* mark its upvalues */
  518.     UpVal *uv = cl->upvals[i];
  519.     if (uv != NULL) {
  520.       if (upisopen(uv) && g->gcstate != GCSinsideatomic)
  521.         uv->u.open.touched = 1;  /* can be marked in 'remarkupvals' */
  522.       else
  523.         markvalue(g, uv->v);
  524.     }
  525.   }
  526.   return sizeLclosure(cl->nupvalues);
  527. }
  528.  
  529.  
  530. static lu_mem traversethread (global_State *g, lua_State *th) {
  531.   StkId o = th->stack;
  532.   if (o == NULL)
  533.     return 1;  /* stack not completely built yet */
  534.   lua_assert(g->gcstate == GCSinsideatomic ||
  535.              th->openupval == NULL || isintwups(th));
  536.   for (; o < th->top; o++)  /* mark live elements in the stack */
  537.     markvalue(g, o);
  538.   if (g->gcstate == GCSinsideatomic) {  /* final traversal? */
  539.     StkId lim = th->stack + th->stacksize;  /* real end of stack */
  540.     for (; o < lim; o++)  /* clear not-marked stack slice */
  541.       setnilvalue(o);
  542.     /* 'remarkupvals' may have removed thread from 'twups' list */
  543.     if (!isintwups(th) && th->openupval != NULL) {
  544.       th->twups = g->twups;  /* link it back to the list */
  545.       g->twups = th;
  546.     }
  547.   }
  548.   else if (g->gckind != KGC_EMERGENCY)
  549.     luaD_shrinkstack(th); /* do not change stack in emergency cycle */
  550.   return (sizeof(lua_State) + sizeof(TValue) * th->stacksize +
  551.           sizeof(CallInfo) * th->nci);
  552. }
  553.  
  554.  
  555. /*
  556. ** traverse one gray object, turning it to black (except for threads,
  557. ** which are always gray).
  558. */
  559. static void propagatemark (global_State *g) {
  560.   lu_mem size;
  561.   GCObject *o = g->gray;
  562.   lua_assert(isgray(o));
  563.   gray2black(o);
  564.   switch (o->tt) {
  565.     case LUA_TTABLE: {
  566.       Table *h = gco2t(o);
  567.       g->gray = h->gclist;  /* remove from 'gray' list */
  568.       size = traversetable(g, h);
  569.       break;
  570.     }
  571.     case LUA_TLCL: {
  572.       LClosure *cl = gco2lcl(o);
  573.       g->gray = cl->gclist;  /* remove from 'gray' list */
  574.       size = traverseLclosure(g, cl);
  575.       break;
  576.     }
  577.     case LUA_TCCL: {
  578.       CClosure *cl = gco2ccl(o);
  579.       g->gray = cl->gclist;  /* remove from 'gray' list */
  580.       size = traverseCclosure(g, cl);
  581.       break;
  582.     }
  583.     case LUA_TTHREAD: {
  584.       lua_State *th = gco2th(o);
  585.       g->gray = th->gclist;  /* remove from 'gray' list */
  586.       linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
  587.       black2gray(o);
  588.       size = traversethread(g, th);
  589.       break;
  590.     }
  591.     case LUA_TPROTO: {
  592.       Proto *p = gco2p(o);
  593.       g->gray = p->gclist;  /* remove from 'gray' list */
  594.       size = traverseproto(g, p);
  595.       break;
  596.     }
  597.     default: lua_assert(0); return;
  598.   }
  599.   g->GCmemtrav += size;
  600. }
  601.  
  602.  
  603. static void propagateall (global_State *g) {
  604.   while (g->gray) propagatemark(g);
  605. }
  606.  
  607.  
  608. static void convergeephemerons (global_State *g) {
  609.   int changed;
  610.   do {
  611.     GCObject *w;
  612.     GCObject *next = g->ephemeron;  /* get ephemeron list */
  613.     g->ephemeron = NULL;  /* tables may return to this list when traversed */
  614.     changed = 0;
  615.     while ((w = next) != NULL) {
  616.       next = gco2t(w)->gclist;
  617.       if (traverseephemeron(g, gco2t(w))) {  /* traverse marked some value? */
  618.         propagateall(g);  /* propagate changes */
  619.         changed = 1;  /* will have to revisit all ephemeron tables */
  620.       }
  621.     }
  622.   } while (changed);
  623. }
  624.  
  625. /* }====================================================== */
  626.  
  627.  
  628. /*
  629. ** {======================================================
  630. ** Sweep Functions
  631. ** =======================================================
  632. */
  633.  
  634.  
  635. /*
  636. ** clear entries with unmarked keys from all weaktables in list 'l' up
  637. ** to element 'f'
  638. */
  639. static void clearkeys (global_State *g, GCObject *l, GCObject *f) {
  640.   for (; l != f; l = gco2t(l)->gclist) {
  641.     Table *h = gco2t(l);
  642.     Node *n, *limit = gnodelast(h);
  643.     for (n = gnode(h, 0); n < limit; n++) {
  644.       if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) {
  645.         setnilvalue(gval(n));  /* remove value ... */
  646.       }
  647.       if (ttisnil(gval(n)))  /* is entry empty? */
  648.         removeentry(n);  /* remove entry from table */
  649.     }
  650.   }
  651. }
  652.  
  653.  
  654. /*
  655. ** clear entries with unmarked values from all weaktables in list 'l' up
  656. ** to element 'f'
  657. */
  658. static void clearvalues (global_State *g, GCObject *l, GCObject *f) {
  659.   for (; l != f; l = gco2t(l)->gclist) {
  660.     Table *h = gco2t(l);
  661.     Node *n, *limit = gnodelast(h);
  662.     unsigned int i;
  663.     for (i = 0; i < h->sizearray; i++) {
  664.       TValue *o = &h->array[i];
  665.       if (iscleared(g, o))  /* value was collected? */
  666.         setnilvalue(o);  /* remove value */
  667.     }
  668.     for (n = gnode(h, 0); n < limit; n++) {
  669.       if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
  670.         setnilvalue(gval(n));  /* remove value ... */
  671.         removeentry(n);  /* and remove entry from table */
  672.       }
  673.     }
  674.   }
  675. }
  676.  
  677.  
  678. void luaC_upvdeccount (lua_State *L, UpVal *uv) {
  679.   lua_assert(uv->refcount > 0);
  680.   uv->refcount--;
  681.   if (uv->refcount == 0 && !upisopen(uv))
  682.     luaM_free(L, uv);
  683. }
  684.  
  685.  
  686. static void freeLclosure (lua_State *L, LClosure *cl) {
  687.   int i;
  688.   for (i = 0; i < cl->nupvalues; i++) {
  689.     UpVal *uv = cl->upvals[i];
  690.     if (uv)
  691.       luaC_upvdeccount(L, uv);
  692.   }
  693.   luaM_freemem(L, cl, sizeLclosure(cl->nupvalues));
  694. }
  695.  
  696.  
  697. static void freeobj (lua_State *L, GCObject *o) {
  698.   switch (o->tt) {
  699.     case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
  700.     case LUA_TLCL: {
  701.       freeLclosure(L, gco2lcl(o));
  702.       break;
  703.     }
  704.     case LUA_TCCL: {
  705.       luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
  706.       break;
  707.     }
  708.     case LUA_TTABLE: luaH_free(L, gco2t(o)); break;
  709.     case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break;
  710.     case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break;
  711.     case LUA_TSHRSTR:
  712.       luaS_remove(L, gco2ts(o));  /* remove it from hash table */
  713.       luaM_freemem(L, o, sizelstring(gco2ts(o)->shrlen));
  714.       break;
  715.     case LUA_TLNGSTR: {
  716.       luaM_freemem(L, o, sizelstring(gco2ts(o)->u.lnglen));
  717.       break;
  718.     }
  719.     default: lua_assert(0);
  720.   }
  721. }
  722.  
  723.  
  724. #define sweepwholelist(L,p)     sweeplist(L,p,MAX_LUMEM)
  725. static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
  726.  
  727.  
  728. /*
  729. ** sweep at most 'count' elements from a list of GCObjects erasing dead
  730. ** objects, where a dead object is one marked with the old (non current)
  731. ** white; change all non-dead objects back to white, preparing for next
  732. ** collection cycle. Return where to continue the traversal or NULL if
  733. ** list is finished.
  734. */
  735. static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
  736.   global_State *g = G(L);
  737.   int ow = otherwhite(g);
  738.   int white = luaC_white(g);  /* current white */
  739.   while (*p != NULL && count-- > 0) {
  740.     GCObject *curr = *p;
  741.     int marked = curr->marked;
  742.     if (isdeadm(ow, marked)) {  /* is 'curr' dead? */
  743.       *p = curr->next;  /* remove 'curr' from list */
  744.       freeobj(L, curr);  /* erase 'curr' */
  745.     }
  746.     else {  /* change mark to 'white' */
  747.       curr->marked = cast_byte((marked & maskcolors) | white);
  748.       p = &curr->next;  /* go to next element */
  749.     }
  750.   }
  751.   return (*p == NULL) ? NULL : p;
  752. }
  753.  
  754.  
  755. /*
  756. ** sweep a list until a live object (or end of list)
  757. */
  758. static GCObject **sweeptolive (lua_State *L, GCObject **p) {
  759.   GCObject **old = p;
  760.   do {
  761.     p = sweeplist(L, p, 1);
  762.   } while (p == old);
  763.   return p;
  764. }
  765.  
  766. /* }====================================================== */
  767.  
  768.  
  769. /*
  770. ** {======================================================
  771. ** Finalization
  772. ** =======================================================
  773. */
  774.  
  775. /*
  776. ** If possible, shrink string table
  777. */
  778. static void checkSizes (lua_State *L, global_State *g) {
  779.   if (g->gckind != KGC_EMERGENCY) {
  780.     l_mem olddebt = g->GCdebt;
  781.     if (g->strt.nuse < g->strt.size / 4)  /* string table too big? */
  782.       luaS_resize(L, g->strt.size / 2);  /* shrink it a little */
  783.     g->GCestimate += g->GCdebt - olddebt;  /* update estimate */
  784.   }
  785. }
  786.  
  787.  
  788. static GCObject *udata2finalize (global_State *g) {
  789.   GCObject *o = g->tobefnz;  /* get first element */
  790.   lua_assert(tofinalize(o));
  791.   g->tobefnz = o->next;  /* remove it from 'tobefnz' list */
  792.   o->next = g->allgc;  /* return it to 'allgc' list */
  793.   g->allgc = o;
  794.   resetbit(o->marked, FINALIZEDBIT);  /* object is "normal" again */
  795.   if (issweepphase(g))
  796.     makewhite(g, o);  /* "sweep" object */
  797.   return o;
  798. }
  799.  
  800.  
  801. static void dothecall (lua_State *L, void *ud) {
  802.   UNUSED(ud);
  803.   luaD_callnoyield(L, L->top - 2, 0);
  804. }
  805.  
  806.  
  807. static void GCTM (lua_State *L, int propagateerrors) {
  808.   global_State *g = G(L);
  809.   const TValue *tm;
  810.   TValue v;
  811.   setgcovalue(L, &v, udata2finalize(g));
  812.   tm = luaT_gettmbyobj(L, &v, TM_GC);
  813.   if (tm != NULL && ttisfunction(tm)) {  /* is there a finalizer? */
  814.     int status;
  815.     lu_byte oldah = L->allowhook;
  816.     int running  = g->gcrunning;
  817.     L->allowhook = 0;  /* stop debug hooks during GC metamethod */
  818.     g->gcrunning = 0;  /* avoid GC steps */
  819.     setobj2s(L, L->top, tm);  /* push finalizer... */
  820.     setobj2s(L, L->top + 1, &v);  /* ... and its argument */
  821.     L->top += 2;  /* and (next line) call the finalizer */
  822.     L->ci->callstatus |= CIST_FIN;  /* will run a finalizer */
  823.     status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
  824.     L->ci->callstatus &= ~CIST_FIN;  /* not running a finalizer anymore */
  825.     L->allowhook = oldah;  /* restore hooks */
  826.     g->gcrunning = running;  /* restore state */
  827.     if (status != LUA_OK && propagateerrors) {  /* error while running __gc? */
  828.       if (status == LUA_ERRRUN) {  /* is there an error object? */
  829.         const char *msg = (ttisstring(L->top - 1))
  830.                             ? svalue(L->top - 1)
  831.                             : "no message";
  832.         luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
  833.         status = LUA_ERRGCMM;  /* error in __gc metamethod */
  834.       }
  835.       luaD_throw(L, status);  /* re-throw error */
  836.     }
  837.   }
  838. }
  839.  
  840.  
  841. /*
  842. ** call a few (up to 'g->gcfinnum') finalizers
  843. */
  844. static int runafewfinalizers (lua_State *L) {
  845.   global_State *g = G(L);
  846.   unsigned int i;
  847.   lua_assert(!g->tobefnz || g->gcfinnum > 0);
  848.   for (i = 0; g->tobefnz && i < g->gcfinnum; i++)
  849.     GCTM(L, 1);  /* call one finalizer */
  850.   g->gcfinnum = (!g->tobefnz) ? 0  /* nothing more to finalize? */
  851.                     : g->gcfinnum * 2;  /* else call a few more next time */
  852.   return i;
  853. }
  854.  
  855.  
  856. /*
  857. ** call all pending finalizers
  858. */
  859. static void callallpendingfinalizers (lua_State *L) {
  860.   global_State *g = G(L);
  861.   while (g->tobefnz)
  862.     GCTM(L, 0);
  863. }
  864.  
  865.  
  866. /*
  867. ** find last 'next' field in list 'p' list (to add elements in its end)
  868. */
  869. static GCObject **findlast (GCObject **p) {
  870.   while (*p != NULL)
  871.     p = &(*p)->next;
  872.   return p;
  873. }
  874.  
  875.  
  876. /*
  877. ** move all unreachable objects (or 'all' objects) that need
  878. ** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
  879. */
  880. static void separatetobefnz (global_State *g, int all) {
  881.   GCObject *curr;
  882.   GCObject **p = &g->finobj;
  883.   GCObject **lastnext = findlast(&g->tobefnz);
  884.   while ((curr = *p) != NULL) {  /* traverse all finalizable objects */
  885.     lua_assert(tofinalize(curr));
  886.     if (!(iswhite(curr) || all))  /* not being collected? */
  887.       p = &curr->next;  /* don't bother with it */
  888.     else {
  889.       *p = curr->next;  /* remove 'curr' from 'finobj' list */
  890.       curr->next = *lastnext;  /* link at the end of 'tobefnz' list */
  891.       *lastnext = curr;
  892.       lastnext = &curr->next;
  893.     }
  894.   }
  895. }
  896.  
  897.  
  898. /*
  899. ** if object 'o' has a finalizer, remove it from 'allgc' list (must
  900. ** search the list to find it) and link it in 'finobj' list.
  901. */
  902. void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
  903.   global_State *g = G(L);
  904.   if (tofinalize(o) ||                 /* obj. is already marked... */
  905.       gfasttm(g, mt, TM_GC) == NULL)   /* or has no finalizer? */
  906.     return;  /* nothing to be done */
  907.   else {  /* move 'o' to 'finobj' list */
  908.     GCObject **p;
  909.     if (issweepphase(g)) {
  910.       makewhite(g, o);  /* "sweep" object 'o' */
  911.       if (g->sweepgc == &o->next)  /* should not remove 'sweepgc' object */
  912.         g->sweepgc = sweeptolive(L, g->sweepgc);  /* change 'sweepgc' */
  913.     }
  914.     /* search for pointer pointing to 'o' */
  915.     for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
  916.     *p = o->next;  /* remove 'o' from 'allgc' list */
  917.     o->next = g->finobj;  /* link it in 'finobj' list */
  918.     g->finobj = o;
  919.     l_setbit(o->marked, FINALIZEDBIT);  /* mark it as such */
  920.   }
  921. }
  922.  
  923. /* }====================================================== */
  924.  
  925.  
  926.  
  927. /*
  928. ** {======================================================
  929. ** GC control
  930. ** =======================================================
  931. */
  932.  
  933.  
  934. /*
  935. ** Set a reasonable "time" to wait before starting a new GC cycle; cycle
  936. ** will start when memory use hits threshold. (Division by 'estimate'
  937. ** should be OK: it cannot be zero (because Lua cannot even start with
  938. ** less than PAUSEADJ bytes).
  939. */
  940. static void setpause (global_State *g) {
  941.   l_mem threshold, debt;
  942.   l_mem estimate = g->GCestimate / PAUSEADJ;  /* adjust 'estimate' */
  943.   lua_assert(estimate > 0);
  944.   threshold = (g->gcpause < MAX_LMEM / estimate)  /* overflow? */
  945.             ? estimate * g->gcpause  /* no overflow */
  946.             : MAX_LMEM;  /* overflow; truncate to maximum */
  947.   debt = gettotalbytes(g) - threshold;
  948.   luaE_setdebt(g, debt);
  949. }
  950.  
  951.  
  952. /*
  953. ** Enter first sweep phase.
  954. ** The call to 'sweeplist' tries to make pointer point to an object
  955. ** inside the list (instead of to the header), so that the real sweep do
  956. ** not need to skip objects created between "now" and the start of the
  957. ** real sweep.
  958. */
  959. static void entersweep (lua_State *L) {
  960.   global_State *g = G(L);
  961.   g->gcstate = GCSswpallgc;
  962.   lua_assert(g->sweepgc == NULL);
  963.   g->sweepgc = sweeplist(L, &g->allgc, 1);
  964. }
  965.  
  966.  
  967. void luaC_freeallobjects (lua_State *L) {
  968.   global_State *g = G(L);
  969.   separatetobefnz(g, 1);  /* separate all objects with finalizers */
  970.   lua_assert(g->finobj == NULL);
  971.   callallpendingfinalizers(L);
  972.   lua_assert(g->tobefnz == NULL);
  973.   g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
  974.   g->gckind = KGC_NORMAL;
  975.   sweepwholelist(L, &g->finobj);
  976.   sweepwholelist(L, &g->allgc);
  977.   sweepwholelist(L, &g->fixedgc);  /* collect fixed objects */
  978.   lua_assert(g->strt.nuse == 0);
  979. }
  980.  
  981.  
  982. static l_mem atomic (lua_State *L) {
  983.   global_State *g = G(L);
  984.   l_mem work;
  985.   GCObject *origweak, *origall;
  986.   GCObject *grayagain = g->grayagain;  /* save original list */
  987.   lua_assert(g->ephemeron == NULL && g->weak == NULL);
  988.   lua_assert(!iswhite(g->mainthread));
  989.   g->gcstate = GCSinsideatomic;
  990.   g->GCmemtrav = 0;  /* start counting work */
  991.   markobject(g, L);  /* mark running thread */
  992.   /* registry and global metatables may be changed by API */
  993.   markvalue(g, &g->l_registry);
  994.   markmt(g);  /* mark global metatables */
  995.   /* remark occasional upvalues of (maybe) dead threads */
  996.   remarkupvals(g);
  997.   propagateall(g);  /* propagate changes */
  998.   work = g->GCmemtrav;  /* stop counting (do not recount 'grayagain') */
  999.   g->gray = grayagain;
  1000.   propagateall(g);  /* traverse 'grayagain' list */
  1001.   g->GCmemtrav = 0;  /* restart counting */
  1002.   convergeephemerons(g);
  1003.   /* at this point, all strongly accessible objects are marked. */
  1004.   /* Clear values from weak tables, before checking finalizers */
  1005.   clearvalues(g, g->weak, NULL);
  1006.   clearvalues(g, g->allweak, NULL);
  1007.   origweak = g->weak; origall = g->allweak;
  1008.   work += g->GCmemtrav;  /* stop counting (objects being finalized) */
  1009.   separatetobefnz(g, 0);  /* separate objects to be finalized */
  1010.   g->gcfinnum = 1;  /* there may be objects to be finalized */
  1011.   markbeingfnz(g);  /* mark objects that will be finalized */
  1012.   propagateall(g);  /* remark, to propagate 'resurrection' */
  1013.   g->GCmemtrav = 0;  /* restart counting */
  1014.   convergeephemerons(g);
  1015.   /* at this point, all resurrected objects are marked. */
  1016.   /* remove dead objects from weak tables */
  1017.   clearkeys(g, g->ephemeron, NULL);  /* clear keys from all ephemeron tables */
  1018.   clearkeys(g, g->allweak, NULL);  /* clear keys from all 'allweak' tables */
  1019.   /* clear values from resurrected weak tables */
  1020.   clearvalues(g, g->weak, origweak);
  1021.   clearvalues(g, g->allweak, origall);
  1022.   luaS_clearcache(g);
  1023.   g->currentwhite = cast_byte(otherwhite(g));  /* flip current white */
  1024.   work += g->GCmemtrav;  /* complete counting */
  1025.   return work;  /* estimate of memory marked by 'atomic' */
  1026. }
  1027.  
  1028.  
  1029. static lu_mem sweepstep (lua_State *L, global_State *g,
  1030.                          int nextstate, GCObject **nextlist) {
  1031.   if (g->sweepgc) {
  1032.     l_mem olddebt = g->GCdebt;
  1033.     g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
  1034.     g->GCestimate += g->GCdebt - olddebt;  /* update estimate */
  1035.     if (g->sweepgc)  /* is there still something to sweep? */
  1036.       return (GCSWEEPMAX * GCSWEEPCOST);
  1037.   }
  1038.   /* else enter next state */
  1039.   g->gcstate = nextstate;
  1040.   g->sweepgc = nextlist;
  1041.   return 0;
  1042. }
  1043.  
  1044.  
  1045. static lu_mem singlestep (lua_State *L) {
  1046.   global_State *g = G(L);
  1047.   switch (g->gcstate) {
  1048.     case GCSpause: {
  1049.       g->GCmemtrav = g->strt.size * sizeof(GCObject*);
  1050.       restartcollection(g);
  1051.       g->gcstate = GCSpropagate;
  1052.       return g->GCmemtrav;
  1053.     }
  1054.     case GCSpropagate: {
  1055.       g->GCmemtrav = 0;
  1056.       lua_assert(g->gray);
  1057.       propagatemark(g);
  1058.        if (g->gray == NULL)  /* no more gray objects? */
  1059.         g->gcstate = GCSatomic;  /* finish propagate phase */
  1060.       return g->GCmemtrav;  /* memory traversed in this step */
  1061.     }
  1062.     case GCSatomic: {
  1063.       lu_mem work;
  1064.       propagateall(g);  /* make sure gray list is empty */
  1065.       work = atomic(L);  /* work is what was traversed by 'atomic' */
  1066.       entersweep(L);
  1067.       g->GCestimate = gettotalbytes(g);  /* first estimate */;
  1068.       return work;
  1069.     }
  1070.     case GCSswpallgc: {  /* sweep "regular" objects */
  1071.       return sweepstep(L, g, GCSswpfinobj, &g->finobj);
  1072.     }
  1073.     case GCSswpfinobj: {  /* sweep objects with finalizers */
  1074.       return sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
  1075.     }
  1076.     case GCSswptobefnz: {  /* sweep objects to be finalized */
  1077.       return sweepstep(L, g, GCSswpend, NULL);
  1078.     }
  1079.     case GCSswpend: {  /* finish sweeps */
  1080.       makewhite(g, g->mainthread);  /* sweep main thread */
  1081.       checkSizes(L, g);
  1082.       g->gcstate = GCScallfin;
  1083.       return 0;
  1084.     }
  1085.     case GCScallfin: {  /* call remaining finalizers */
  1086.       if (g->tobefnz && g->gckind != KGC_EMERGENCY) {
  1087.         int n = runafewfinalizers(L);
  1088.         return (n * GCFINALIZECOST);
  1089.       }
  1090.       else {  /* emergency mode or no more finalizers */
  1091.         g->gcstate = GCSpause;  /* finish collection */
  1092.         return 0;
  1093.       }
  1094.     }
  1095.     default: lua_assert(0); return 0;
  1096.   }
  1097. }
  1098.  
  1099.  
  1100. /*
  1101. ** advances the garbage collector until it reaches a state allowed
  1102. ** by 'statemask'
  1103. */
  1104. void luaC_runtilstate (lua_State *L, int statesmask) {
  1105.   global_State *g = G(L);
  1106.   while (!testbit(statesmask, g->gcstate))
  1107.     singlestep(L);
  1108. }
  1109.  
  1110.  
  1111. /*
  1112. ** get GC debt and convert it from Kb to 'work units' (avoid zero debt
  1113. ** and overflows)
  1114. */
  1115. static l_mem getdebt (global_State *g) {
  1116.   l_mem debt = g->GCdebt;
  1117.   int stepmul = g->gcstepmul;
  1118.   if (debt <= 0) return 0;  /* minimal debt */
  1119.   else {
  1120.     debt = (debt / STEPMULADJ) + 1;
  1121.     debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
  1122.     return debt;
  1123.   }
  1124. }
  1125.  
  1126. /*
  1127. ** performs a basic GC step when collector is running
  1128. */
  1129. void luaC_step (lua_State *L) {
  1130.   global_State *g = G(L);
  1131.   l_mem debt = getdebt(g);  /* GC deficit (be paid now) */
  1132.   if (!g->gcrunning) {  /* not running? */
  1133.     luaE_setdebt(g, -GCSTEPSIZE * 10);  /* avoid being called too often */
  1134.     return;
  1135.   }
  1136.   do {  /* repeat until pause or enough "credit" (negative debt) */
  1137.     lu_mem work = singlestep(L);  /* perform one single step */
  1138.     debt -= work;
  1139.   } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
  1140.   if (g->gcstate == GCSpause)
  1141.     setpause(g);  /* pause until next cycle */
  1142.   else {
  1143.     debt = (debt / g->gcstepmul) * STEPMULADJ;  /* convert 'work units' to Kb */
  1144.     luaE_setdebt(g, debt);
  1145.     runafewfinalizers(L);
  1146.   }
  1147. }
  1148.  
  1149.  
  1150. /*
  1151. ** Performs a full GC cycle; if 'isemergency', set a flag to avoid
  1152. ** some operations which could change the interpreter state in some
  1153. ** unexpected ways (running finalizers and shrinking some structures).
  1154. ** Before running the collection, check 'keepinvariant'; if it is true,
  1155. ** there may be some objects marked as black, so the collector has
  1156. ** to sweep all objects to turn them back to white (as white has not
  1157. ** changed, nothing will be collected).
  1158. */
  1159. void luaC_fullgc (lua_State *L, int isemergency) {
  1160.   global_State *g = G(L);
  1161.   lua_assert(g->gckind == KGC_NORMAL);
  1162.   if (isemergency) g->gckind = KGC_EMERGENCY;  /* set flag */
  1163.   if (keepinvariant(g)) {  /* black objects? */
  1164.     entersweep(L); /* sweep everything to turn them back to white */
  1165.   }
  1166.   /* finish any pending sweep phase to start a new cycle */
  1167.   luaC_runtilstate(L, bitmask(GCSpause));
  1168.   luaC_runtilstate(L, ~bitmask(GCSpause));  /* start new collection */
  1169.   luaC_runtilstate(L, bitmask(GCScallfin));  /* run up to finalizers */
  1170.   /* estimate must be correct after a full GC cycle */
  1171.   lua_assert(g->GCestimate == gettotalbytes(g));
  1172.   luaC_runtilstate(L, bitmask(GCSpause));  /* finish collection */
  1173.   g->gckind = KGC_NORMAL;
  1174.   setpause(g);
  1175. }
  1176.  
  1177. /* }====================================================== */
  1178.  
  1179.  
  1180.