1 files changed, 454 insertions, 963 deletions

diff --git a/apps/plugins/lua/lgc.c b/apps/plugins/lua/lgc.c
index 52460dcdd5..d9e0b78294 100644
--- a/apps/plugins/lua/lgc.c
+++ b/apps/plugins/lua/lgc.c
@@ -1,5 +1,5 @@
 /*
-** $Id: lgc.c,v 2.140.1.2 2013/04/26 18:22:05 roberto Exp $
+** $Id: lgc.c,v 2.38.1.1 2007/12/27 13:02:25 roberto Exp $
 ** Garbage Collector
 ** See Copyright Notice in lua.h
 */
@@ -23,1079 +23,583 @@
 #include "ltm.h"
 
 
+#define GCSTEPSIZE      1024u
+#define GCSWEEPMAX      40
+#define GCSWEEPCOST     10
+#define GCFINALIZECOST  100
 
-/*
-** cost of sweeping one element (the size of a small object divided
-** by some adjust for the sweep speed)
-*/
-#define GCSWEEPCOST     ((sizeof(TString) + 4) / 4)
-
-/* maximum number of elements to sweep in each single step */
-#define GCSWEEPMAX      (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
-
-/* maximum number of finalizers to call in each GC step */
-#define GCFINALIZENUM   4
-
-
-/*
-** macro to adjust 'stepmul': 'stepmul' is actually used like
-** 'stepmul / STEPMULADJ' (value chosen by tests)
-*/
-#define STEPMULADJ              200
-
-
-/*
-** macro to adjust 'pause': 'pause' is actually used like
-** 'pause / PAUSEADJ' (value chosen by tests)
-*/
-#define PAUSEADJ                100
 
+#define maskmarks       cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
 
-/*
-** 'makewhite' erases all color bits plus the old bit and then
-** sets only the current white bit
-*/
-#define maskcolors      (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS))
 #define makewhite(g,x)  \
- (gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g)))
+   ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
 
-#define white2gray(x)   resetbits(gch(x)->marked, WHITEBITS)
-#define black2gray(x)   resetbit(gch(x)->marked, BLACKBIT)
+#define white2gray(x)   reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
+#define black2gray(x)   resetbit((x)->gch.marked, BLACKBIT)
 
+#define stringmark(s)   reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
 
-#define isfinalized(x)          testbit(gch(x)->marked, FINALIZEDBIT)
 
-#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
+#define isfinalized(u)          testbit((u)->marked, FINALIZEDBIT)
+#define markfinalized(u)        l_setbit((u)->marked, FINALIZEDBIT)
 
 
-#define checkconsistency(obj)  \
-  lua_longassert(!iscollectable(obj) || righttt(obj))
+#define KEYWEAK         bitmask(KEYWEAKBIT)
+#define VALUEWEAK       bitmask(VALUEWEAKBIT)
+
 
 
 #define markvalue(g,o) { checkconsistency(o); \
-  if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
+  if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
 
-#define markobject(g,t) { if ((t) && iswhite(obj2gco(t))) \
+#define markobject(g,t) { if (iswhite(obj2gco(t))) \
                 reallymarkobject(g, obj2gco(t)); }
 
-static void reallymarkobject (global_State *g, GCObject *o);
-
-
-/*
-** {======================================================
-** Generic functions
-** =======================================================
-*/
-
-
-/*
-** one after last element in a hash array
-*/
-#define gnodelast(h)    gnode(h, cast(size_t, sizenode(h)))
-
 
-/*
-** link table 'h' into list pointed by 'p'
-*/
-#define linktable(h,p)  ((h)->gclist = *(p), *(p) = obj2gco(h))
+#define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)
 
 
-/*
-** if key is not marked, mark its entry as dead (therefore removing it
-** from the table)
-*/
 static void removeentry (Node *n) {
   lua_assert(ttisnil(gval(n)));
-  if (valiswhite(gkey(n)))
-    setdeadvalue(gkey(n));  /* unused and unmarked key; remove it */
-}
-
-
-/*
-** tells whether a key or value can be cleared from a weak
-** table. Non-collectable objects are never removed from weak
-** tables. Strings behave as `values', so are never removed too. for
-** other objects: if really collected, cannot keep them; for objects
-** being finalized, keep them in keys, but not in values
-*/
-static int iscleared (global_State *g, const TValue *o) {
-  if (!iscollectable(o)) return 0;
-  else if (ttisstring(o)) {
-    markobject(g, rawtsvalue(o));  /* strings are `values', so are never weak */
-    return 0;
-  }
-  else return iswhite(gcvalue(o));
+  if (iscollectable(gkey(n)))
+    setttype(gkey(n), LUA_TDEADKEY);  /* dead key; remove it */
 }
 
 
-/*
-** barrier that moves collector forward, that is, mark the white object
-** being pointed by a black object.
-*/
-void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
-  global_State *g = G(L);
-  lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
-  lua_assert(g->gcstate != GCSpause);
-  lua_assert(gch(o)->tt != LUA_TTABLE);
-  if (keepinvariantout(g))  /* must keep invariant? */
-    reallymarkobject(g, v);  /* restore invariant */
-  else {  /* sweep phase */
-    lua_assert(issweepphase(g));
-    makewhite(g, o);  /* mark main obj. as white to avoid other barriers */
-  }
-}
-
-
-/*
-** barrier that moves collector backward, that is, mark the black object
-** pointing to a white object as gray again. (Current implementation
-** only works for tables; access to 'gclist' is not uniform across
-** different types.)
-*/
-void luaC_barrierback_ (lua_State *L, GCObject *o) {
-  global_State *g = G(L);
-  lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE);
-  black2gray(o);  /* make object gray (again) */
-  gco2t(o)->gclist = g->grayagain;
-  g->grayagain = o;
-}
-
-
-/*
-** barrier for prototypes. When creating first closure (cache is
-** NULL), use a forward barrier; this may be the only closure of the
-** prototype (if it is a "regular" function, with a single instance)
-** and the prototype may be big, so it is better to avoid traversing
-** it again. Otherwise, use a backward barrier, to avoid marking all
-** possible instances.
-*/
-LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c) {
-  global_State *g = G(L);
-  lua_assert(isblack(obj2gco(p)));
-  if (p->cache == NULL) {  /* first time? */
-    luaC_objbarrier(L, p, c);
-  }
-  else {  /* use a backward barrier */
-    black2gray(obj2gco(p));  /* make prototype gray (again) */
-    p->gclist = g->grayagain;
-    g->grayagain = obj2gco(p);
-  }
-}
-
-
-/*
-** check color (and invariants) for an upvalue that was closed,
-** i.e., moved into the 'allgc' list
-*/
-void luaC_checkupvalcolor (global_State *g, UpVal *uv) {
-  GCObject *o = obj2gco(uv);
-  lua_assert(!isblack(o));  /* open upvalues are never black */
-  if (isgray(o)) {
-    if (keepinvariant(g)) {
-      resetoldbit(o);  /* see MOVE OLD rule */
-      gray2black(o);  /* it is being visited now */
-      markvalue(g, uv->v);
-    }
-    else {
-      lua_assert(issweepphase(g));
-      makewhite(g, o);
-    }
-  }
-}
-
-
-/*
-** create a new collectable object (with given type and size) and link
-** it to '*list'. 'offset' tells how many bytes to allocate before the
-** object itself (used only by states).
-*/
-GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list,
-                       int offset) {
-  global_State *g = G(L);
-  char *raw = cast(char *, luaM_newobject(L, novariant(tt), sz));
-  GCObject *o = obj2gco(raw + offset);
-  if (list == NULL)
-    list = &g->allgc;  /* standard list for collectable objects */
-  gch(o)->marked = luaC_white(g);
-  gch(o)->tt = tt;
-  gch(o)->next = *list;
-  *list = o;
-  return o;
-}
-
-/* }====================================================== */
-
-
-
-/*
-** {======================================================
-** Mark functions
-** =======================================================
-*/
-
-
-/*
-** mark an object. Userdata, strings, and closed upvalues are visited
-** and turned black here. Other objects are marked gray and added
-** to appropriate list to be visited (and turned black) later. (Open
-** upvalues are already linked in 'headuv' list.)
-*/
 static void reallymarkobject (global_State *g, GCObject *o) {
-  lu_mem size;
+  lua_assert(iswhite(o) && !isdead(g, o));
   white2gray(o);
-  switch (gch(o)->tt) {
-    case LUA_TSHRSTR:
-    case LUA_TLNGSTR: {
-      size = sizestring(gco2ts(o));
-      break;  /* nothing else to mark; make it black */
+  switch (o->gch.tt) {
+    case LUA_TSTRING: {
+      return;
     }
     case LUA_TUSERDATA: {
       Table *mt = gco2u(o)->metatable;
-      markobject(g, mt);
+      gray2black(o);  /* udata are never gray */
+      if (mt) markobject(g, mt);
       markobject(g, gco2u(o)->env);
-      size = sizeudata(gco2u(o));
-      break;
+      return;
     }
     case LUA_TUPVAL: {
       UpVal *uv = gco2uv(o);
       markvalue(g, uv->v);
-      if (uv->v != &uv->u.value)  /* open? */
-        return;  /* open upvalues remain gray */
-      size = sizeof(UpVal);
-      break;
-    }
-    case LUA_TLCL: {
-      gco2lcl(o)->gclist = g->gray;
-      g->gray = o;
+      if (uv->v == &uv->u.value)  /* closed? */
+        gray2black(o);  /* open upvalues are never black */
       return;
     }
-    case LUA_TCCL: {
-      gco2ccl(o)->gclist = g->gray;
+    case LUA_TFUNCTION: {
+      gco2cl(o)->c.gclist = g->gray;
       g->gray = o;
-      return;
+      break;
     }
     case LUA_TTABLE: {
-      linktable(gco2t(o), &g->gray);
-      return;
+      gco2h(o)->gclist = g->gray;
+      g->gray = o;
+      break;
     }
     case LUA_TTHREAD: {
       gco2th(o)->gclist = g->gray;
       g->gray = o;
-      return;
+      break;
     }
     case LUA_TPROTO: {
       gco2p(o)->gclist = g->gray;
       g->gray = o;
-      return;
+      break;
     }
-    default: lua_assert(0); return;
+    default: lua_assert(0);
   }
-  gray2black(o);
-  g->GCmemtrav += size;
-}
-
-
-/*
-** mark metamethods for basic types
-*/
-static void markmt (global_State *g) {
-  int i;
-  for (i=0; i < LUA_NUMTAGS; i++)
-    markobject(g, g->mt[i]);
 }
 
 
-/*
-** mark all objects in list of being-finalized
-*/
-static void markbeingfnz (global_State *g) {
-  GCObject *o;
-  for (o = g->tobefnz; o != NULL; o = gch(o)->next) {
-    makewhite(g, o);
-    reallymarkobject(g, o);
+static void marktmu (global_State *g) {
+  GCObject *u = g->tmudata;
+  if (u) {
+    do {
+      u = u->gch.next;
+      makewhite(g, u);  /* may be marked, if left from previous GC */
+      reallymarkobject(g, u);
+    } while (u != g->tmudata);
   }
 }
 
 
-/*
-** mark all values stored in marked open upvalues. (See comment in
-** 'lstate.h'.)
-*/
-static void remarkupvals (global_State *g) {
-  UpVal *uv;
-  for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
-    if (isgray(obj2gco(uv)))
-      markvalue(g, uv->v);
+/* move `dead' udata that need finalization to list `tmudata' */
+size_t luaC_separateudata (lua_State *L, int all) {
+  global_State *g = G(L);
+  size_t deadmem = 0;
+  GCObject **p = &g->mainthread->next;
+  GCObject *curr;
+  while ((curr = *p) != NULL) {
+    if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
+      p = &curr->gch.next;  /* don't bother with them */
+    else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
+      markfinalized(gco2u(curr));  /* don't need finalization */
+      p = &curr->gch.next;
+    }
+    else {  /* must call its gc method */
+      deadmem += sizeudata(gco2u(curr));
+      markfinalized(gco2u(curr));
+      *p = curr->gch.next;
+      /* link `curr' at the end of `tmudata' list */
+      if (g->tmudata == NULL)  /* list is empty? */
+        g->tmudata = curr->gch.next = curr;  /* creates a circular list */
+      else {
+        curr->gch.next = g->tmudata->gch.next;
+        g->tmudata->gch.next = curr;
+        g->tmudata = curr;
+      }
+    }
   }
+  return deadmem;
 }
 
 
-/*
-** mark root set and reset all gray lists, to start a new
-** incremental (or full) collection
-*/
-static void restartcollection (global_State *g) {
-  g->gray = g->grayagain = NULL;
-  g->weak = g->allweak = g->ephemeron = NULL;
-  markobject(g, g->mainthread);
-  markvalue(g, &g->l_registry);
-  markmt(g);
-  markbeingfnz(g);  /* mark any finalizing object left from previous cycle */
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** Traverse functions
-** =======================================================
-*/
-
-static void traverseweakvalue (global_State *g, Table *h) {
-  Node *n, *limit = gnodelast(h);
-  /* if there is array part, assume it may have white values (do not
-     traverse it just to check) */
-  int hasclears = (h->sizearray > 0);
-  for (n = gnode(h, 0); n < limit; n++) {
-    checkdeadkey(n);
-    if (ttisnil(gval(n)))  /* entry is empty? */
-      removeentry(n);  /* remove it */
+static int traversetable (global_State *g, Table *h) {
+  int i;
+  int weakkey = 0;
+  int weakvalue = 0;
+  const TValue *mode;
+  if (h->metatable)
+    markobject(g, h->metatable);
+  mode = gfasttm(g, h->metatable, TM_MODE);
+  if (mode && ttisstring(mode)) {  /* is there a weak mode? */
+    weakkey = (strchr(svalue(mode), 'k') != NULL);
+    weakvalue = (strchr(svalue(mode), 'v') != NULL);
+    if (weakkey || weakvalue) {  /* is really weak? */
+      h->marked &= ~(KEYWEAK | VALUEWEAK);  /* clear bits */
+      h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
+                             (weakvalue << VALUEWEAKBIT));
+      h->gclist = g->weak;  /* must be cleared after GC, ... */
+      g->weak = obj2gco(h);  /* ... so put in the appropriate list */
+    }
+  }
+  if (weakkey && weakvalue) return 1;
+  if (!weakvalue) {
+    i = h->sizearray;
+    while (i--)
+      markvalue(g, &h->array[i]);
+  }
+  i = sizenode(h);
+  while (i--) {
+    Node *n = gnode(h, i);
+    lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
+    if (ttisnil(gval(n)))
+      removeentry(n);  /* remove empty entries */
     else {
       lua_assert(!ttisnil(gkey(n)));
-      markvalue(g, gkey(n));  /* mark key */
-      if (!hasclears && iscleared(g, gval(n)))  /* is there a white value? */
-        hasclears = 1;  /* table will have to be cleared */
+      if (!weakkey) markvalue(g, gkey(n));
+      if (!weakvalue) markvalue(g, gval(n));
     }
   }
-  if (hasclears)
-    linktable(h, &g->weak);  /* has to be cleared later */
-  else  /* no white values */
-    linktable(h, &g->grayagain);  /* no need to clean */
+  return weakkey || weakvalue;
 }
 
 
-static int traverseephemeron (global_State *g, Table *h) {
-  int marked = 0;  /* true if an object is marked in this traversal */
-  int hasclears = 0;  /* true if table has white keys */
-  int prop = 0;  /* true if table has entry "white-key -> white-value" */
-  Node *n, *limit = gnodelast(h);
+/*
+** All marks are conditional because a GC may happen while the
+** prototype is still being created
+*/
+static void traverseproto (global_State *g, Proto *f) {
   int i;
-  /* traverse array part (numeric keys are 'strong') */
-  for (i = 0; i < h->sizearray; i++) {
-    if (valiswhite(&h->array[i])) {
-      marked = 1;
-      reallymarkobject(g, gcvalue(&h->array[i]));
-    }
+  if (f->source) stringmark(f->source);
+  for (i=0; i<f->sizek; i++)  /* mark literals */
+    markvalue(g, &f->k[i]);
+  for (i=0; i<f->sizeupvalues; i++) {  /* mark upvalue names */
+    if (f->upvalues[i])
+      stringmark(f->upvalues[i]);
   }
-  /* traverse hash part */
-  for (n = gnode(h, 0); n < limit; n++) {
-    checkdeadkey(n);
-    if (ttisnil(gval(n)))  /* entry is empty? */
-      removeentry(n);  /* remove it */
-    else if (iscleared(g, gkey(n))) {  /* key is not marked (yet)? */
-      hasclears = 1;  /* table must be cleared */
-      if (valiswhite(gval(n)))  /* value not marked yet? */
-        prop = 1;  /* must propagate again */
-    }
-    else if (valiswhite(gval(n))) {  /* value not marked yet? */
-      marked = 1;
-      reallymarkobject(g, gcvalue(gval(n)));  /* mark it now */
-    }
+  for (i=0; i<f->sizep; i++) {  /* mark nested protos */
+    if (f->p[i])
+      markobject(g, f->p[i]);
   }
-  if (prop)
-    linktable(h, &g->ephemeron);  /* have to propagate again */
-  else if (hasclears)  /* does table have white keys? */
-    linktable(h, &g->allweak);  /* may have to clean white keys */
-  else  /* no white keys */
-    linktable(h, &g->grayagain);  /* no need to clean */
-  return marked;
-}
-
-
-static void traversestrongtable (global_State *g, Table *h) {
-  Node *n, *limit = gnodelast(h);
-  int i;
-  for (i = 0; i < h->sizearray; i++)  /* traverse array part */
-    markvalue(g, &h->array[i]);
-  for (n = gnode(h, 0); n < limit; n++) {  /* traverse hash part */
-    checkdeadkey(n);
-    if (ttisnil(gval(n)))  /* entry is empty? */
-      removeentry(n);  /* remove it */
-    else {
-      lua_assert(!ttisnil(gkey(n)));
-      markvalue(g, gkey(n));  /* mark key */
-      markvalue(g, gval(n));  /* mark value */
-    }
+  for (i=0; i<f->sizelocvars; i++) {  /* mark local-variable names */
+    if (f->locvars[i].varname)
+      stringmark(f->locvars[i].varname);
   }
 }
 
 
-static lu_mem traversetable (global_State *g, Table *h) {
-  const char *weakkey, *weakvalue;
-  const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
-  markobject(g, h->metatable);
-  if (mode && ttisstring(mode) &&  /* is there a weak mode? */
-      ((weakkey = strchr(svalue(mode), 'k')),
-       (weakvalue = strchr(svalue(mode), 'v')),
-       (weakkey || weakvalue))) {  /* is really weak? */
-    black2gray(obj2gco(h));  /* keep table gray */
-    if (!weakkey)  /* strong keys? */
-      traverseweakvalue(g, h);
-    else if (!weakvalue)  /* strong values? */
-      traverseephemeron(g, h);
-    else  /* all weak */
-      linktable(h, &g->allweak);  /* nothing to traverse now */
-  }
-  else  /* not weak */
-    traversestrongtable(g, h);
-  return sizeof(Table) + sizeof(TValue) * h->sizearray +
-                         sizeof(Node) * cast(size_t, sizenode(h));
-}
 
-
-static int traverseproto (global_State *g, Proto *f) {
-  int i;
-  if (f->cache && iswhite(obj2gco(f->cache)))
-    f->cache = NULL;  /* allow cache to be collected */
-  markobject(g, f->source);
-  for (i = 0; i < f->sizek; i++)  /* mark literals */
-    markvalue(g, &f->k[i]);
-  for (i = 0; i < f->sizeupvalues; i++)  /* mark upvalue names */
-    markobject(g, f->upvalues[i].name);
-  for (i = 0; i < f->sizep; i++)  /* mark nested protos */
-    markobject(g, f->p[i]);
-  for (i = 0; i < f->sizelocvars; i++)  /* mark local-variable names */
-    markobject(g, f->locvars[i].varname);
-  return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
-                         sizeof(Proto *) * f->sizep +
-                         sizeof(TValue) * f->sizek +
-                         sizeof(int) * f->sizelineinfo +
-                         sizeof(LocVar) * f->sizelocvars +
-                         sizeof(Upvaldesc) * f->sizeupvalues;
+static void traverseclosure (global_State *g, Closure *cl) {
+  markobject(g, cl->c.env);
+  if (cl->c.isC) {
+    int i;
+    for (i=0; i<cl->c.nupvalues; i++)  /* mark its upvalues */
+      markvalue(g, &cl->c.upvalue[i]);
+  }
+  else {
+    int i;
+    lua_assert(cl->l.nupvalues == cl->l.p->nups);
+    markobject(g, cl->l.p);
+    for (i=0; i<cl->l.nupvalues; i++)  /* mark its upvalues */
+      markobject(g, cl->l.upvals[i]);
+  }
 }
 
 
-static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
-  int i;
-  for (i = 0; i < cl->nupvalues; i++)  /* mark its upvalues */
-    markvalue(g, &cl->upvalue[i]);
-  return sizeCclosure(cl->nupvalues);
+static void checkstacksizes (lua_State *L, StkId max) {
+  int ci_used = cast_int(L->ci - L->base_ci);  /* number of `ci' in use */
+  int s_used = cast_int(max - L->stack);  /* part of stack in use */
+  if (L->size_ci > LUAI_MAXCALLS)  /* handling overflow? */
+    return;  /* do not touch the stacks */
+  if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
+    luaD_reallocCI(L, L->size_ci/2);  /* still big enough... */
+  condhardstacktests(luaD_reallocCI(L, ci_used + 1));
+  if (4*s_used < L->stacksize &&
+      2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
+    luaD_reallocstack(L, L->stacksize/2);  /* still big enough... */
+  condhardstacktests(luaD_reallocstack(L, s_used));
 }
 
-static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
-  int i;
-  markobject(g, cl->p);  /* mark its prototype */
-  for (i = 0; i < cl->nupvalues; i++)  /* mark its upvalues */
-    markobject(g, cl->upvals[i]);
-  return sizeLclosure(cl->nupvalues);
-}
 
-
-static lu_mem traversestack (global_State *g, lua_State *th) {
-  int n = 0;
-  StkId o = th->stack;
-  if (o == NULL)
-    return 1;  /* stack not completely built yet */
-  for (; o < th->top; o++)  /* mark live elements in the stack */
-    markvalue(g, o);
-  if (g->gcstate == GCSatomic) {  /* final traversal? */
-    StkId lim = th->stack + th->stacksize;  /* real end of stack */
-    for (; o < lim; o++)  /* clear not-marked stack slice */
-      setnilvalue(o);
-  }
-  else {  /* count call infos to compute size */
-    CallInfo *ci;
-    for (ci = &th->base_ci; ci != th->ci; ci = ci->next)
-      n++;
+static void traversestack (global_State *g, lua_State *l) {
+  StkId o, lim;
+  CallInfo *ci;
+  markvalue(g, gt(l));
+  lim = l->top;
+  for (ci = l->base_ci; ci <= l->ci; ci++) {
+    lua_assert(ci->top <= l->stack_last);
+    if (lim < ci->top) lim = ci->top;
   }
-  return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
-         sizeof(CallInfo) * n;
+  for (o = l->stack; o < l->top; o++)
+    markvalue(g, o);
+  for (; o <= lim; o++)
+    setnilvalue(o);
+  checkstacksizes(l, lim);
 }
 
 
 /*
-** traverse one gray object, turning it to black (except for threads,
-** which are always gray).
+** traverse one gray object, turning it to black.
+** Returns `quantity' traversed.
 */
-static void propagatemark (global_State *g) {
-  lu_mem size;
+static l_mem propagatemark (global_State *g) {
   GCObject *o = g->gray;
   lua_assert(isgray(o));
   gray2black(o);
-  switch (gch(o)->tt) {
+  switch (o->gch.tt) {
     case LUA_TTABLE: {
-      Table *h = gco2t(o);
-      g->gray = h->gclist;  /* remove from 'gray' list */
-      size = traversetable(g, h);
-      break;
-    }
-    case LUA_TLCL: {
-      LClosure *cl = gco2lcl(o);
-      g->gray = cl->gclist;  /* remove from 'gray' list */
-      size = traverseLclosure(g, cl);
-      break;
-    }
-    case LUA_TCCL: {
-      CClosure *cl = gco2ccl(o);
-      g->gray = cl->gclist;  /* remove from 'gray' list */
-      size = traverseCclosure(g, cl);
-      break;
+      Table *h = gco2h(o);
+      g->gray = h->gclist;
+      if (traversetable(g, h))  /* table is weak? */
+        black2gray(o);  /* keep it gray */
+      return sizeof(Table) + sizeof(TValue) * h->sizearray +
+                             sizeof(Node) * sizenode(h);
+    }
+    case LUA_TFUNCTION: {
+      Closure *cl = gco2cl(o);
+      g->gray = cl->c.gclist;
+      traverseclosure(g, cl);
+      return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
+                           sizeLclosure(cl->l.nupvalues);
     }
     case LUA_TTHREAD: {
       lua_State *th = gco2th(o);
-      g->gray = th->gclist;  /* remove from 'gray' list */
+      g->gray = th->gclist;
       th->gclist = g->grayagain;
-      g->grayagain = o;  /* insert into 'grayagain' list */
+      g->grayagain = o;
       black2gray(o);
-      size = traversestack(g, th);
-      break;
+      traversestack(g, th);
+      return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
+                                 sizeof(CallInfo) * th->size_ci;
     }
     case LUA_TPROTO: {
       Proto *p = gco2p(o);
-      g->gray = p->gclist;  /* remove from 'gray' list */
-      size = traverseproto(g, p);
-      break;
+      g->gray = p->gclist;
+      traverseproto(g, p);
+      return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
+                             sizeof(Proto *) * p->sizep +
+                             sizeof(TValue) * p->sizek + 
+                             sizeof(int) * p->sizelineinfo +
+                             sizeof(LocVar) * p->sizelocvars +
+                             sizeof(TString *) * p->sizeupvalues;
     }
-    default: lua_assert(0); return;
+    default: lua_assert(0); return 0;
   }
-  g->GCmemtrav += size;
-}
-
-
-static void propagateall (global_State *g) {
-  while (g->gray) propagatemark(g);
-}
-
-
-static void propagatelist (global_State *g, GCObject *l) {
-  lua_assert(g->gray == NULL);  /* no grays left */
-  g->gray = l;
-  propagateall(g);  /* traverse all elements from 'l' */
-}
-
-/*
-** retraverse all gray lists. Because tables may be reinserted in other
-** lists when traversed, traverse the original lists to avoid traversing
-** twice the same table (which is not wrong, but inefficient)
-*/
-static void retraversegrays (global_State *g) {
-  GCObject *weak = g->weak;  /* save original lists */
-  GCObject *grayagain = g->grayagain;
-  GCObject *ephemeron = g->ephemeron;
-  g->weak = g->grayagain = g->ephemeron = NULL;
-  propagateall(g);  /* traverse main gray list */
-  propagatelist(g, grayagain);
-  propagatelist(g, weak);
-  propagatelist(g, ephemeron);
 }
 
 
-static void convergeephemerons (global_State *g) {
-  int changed;
-  do {
-    GCObject *w;
-    GCObject *next = g->ephemeron;  /* get ephemeron list */
-    g->ephemeron = NULL;  /* tables will return to this list when traversed */
-    changed = 0;
-    while ((w = next) != NULL) {
-      next = gco2t(w)->gclist;
-      if (traverseephemeron(g, gco2t(w))) {  /* traverse marked some value? */
-        propagateall(g);  /* propagate changes */
-        changed = 1;  /* will have to revisit all ephemeron tables */
-      }
-    }
-  } while (changed);
+static size_t propagateall (global_State *g) {
+  size_t m = 0;
+  while (g->gray) m += propagatemark(g);
+  return m;
 }
 
-/* }====================================================== */
-
 
 /*
-** {======================================================
-** Sweep Functions
-** =======================================================
-*/
-
-
-/*
-** clear entries with unmarked keys from all weaktables in list 'l' up
-** to element 'f'
+** The next function tells whether a key or value can be cleared from
+** a weak table. Non-collectable objects are never removed from weak
+** tables. Strings behave as `values', so are never removed too. for
+** other objects: if really collected, cannot keep them; for userdata
+** being finalized, keep them in keys, but not in values
 */
-static void clearkeys (global_State *g, GCObject *l, GCObject *f) {
-  for (; l != f; l = gco2t(l)->gclist) {
-    Table *h = gco2t(l);
-    Node *n, *limit = gnodelast(h);
-    for (n = gnode(h, 0); n < limit; n++) {
-      if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) {
-        setnilvalue(gval(n));  /* remove value ... */
-        removeentry(n);  /* and remove entry from table */
-      }
-    }
+static int iscleared (const TValue *o, int iskey) {
+  if (!iscollectable(o)) return 0;
+  if (ttisstring(o)) {
+    stringmark(rawtsvalue(o));  /* strings are `values', so are never weak */
+    return 0;
   }
+  return iswhite(gcvalue(o)) ||
+    (ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
 }
 
 
 /*
-** clear entries with unmarked values from all weaktables in list 'l' up
-** to element 'f'
+** clear collected entries from weaktables
 */
-static void clearvalues (global_State *g, GCObject *l, GCObject *f) {
-  for (; l != f; l = gco2t(l)->gclist) {
-    Table *h = gco2t(l);
-    Node *n, *limit = gnodelast(h);
-    int i;
-    for (i = 0; i < h->sizearray; i++) {
-      TValue *o = &h->array[i];
-      if (iscleared(g, o))  /* value was collected? */
-        setnilvalue(o);  /* remove value */
+static void cleartable (GCObject *l) {
+  while (l) {
+    Table *h = gco2h(l);
+    int i = h->sizearray;
+    lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
+               testbit(h->marked, KEYWEAKBIT));
+    if (testbit(h->marked, VALUEWEAKBIT)) {
+      while (i--) {
+        TValue *o = &h->array[i];
+        if (iscleared(o, 0))  /* value was collected? */
+          setnilvalue(o);  /* remove value */
+      }
     }
-    for (n = gnode(h, 0); n < limit; n++) {
-      if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
+    i = sizenode(h);
+    while (i--) {
+      Node *n = gnode(h, i);
+      if (!ttisnil(gval(n)) &&  /* non-empty entry? */
+          (iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
         setnilvalue(gval(n));  /* remove value ... */
-        removeentry(n);  /* and remove entry from table */
+        removeentry(n);  /* remove entry from table */
       }
     }
+    l = h->gclist;
   }
 }
 
 
 static void freeobj (lua_State *L, GCObject *o) {
-  switch (gch(o)->tt) {
+  switch (o->gch.tt) {
     case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
-    case LUA_TLCL: {
-      luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues));
-      break;
-    }
-    case LUA_TCCL: {
-      luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
+    case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
+    case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
+    case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
+    case LUA_TTHREAD: {
+      lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
+      luaE_freethread(L, gco2th(o));
       break;
     }
-    case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
-    case LUA_TTABLE: luaH_free(L, gco2t(o)); break;
-    case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break;
-    case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break;
-    case LUA_TSHRSTR:
+    case LUA_TSTRING: {
       G(L)->strt.nuse--;
-      /* go through */
-    case LUA_TLNGSTR: {
       luaM_freemem(L, o, sizestring(gco2ts(o)));
       break;
     }
+    case LUA_TUSERDATA: {
+      luaM_freemem(L, o, sizeudata(gco2u(o)));
+      break;
+    }
     default: lua_assert(0);
   }
 }
 
 
-#define sweepwholelist(L,p)     sweeplist(L,p,MAX_LUMEM)
-static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
-
 
-/*
-** sweep the (open) upvalues of a thread and resize its stack and
-** list of call-info structures.
-*/
-static void sweepthread (lua_State *L, lua_State *L1) {
-  if (L1->stack == NULL) return;  /* stack not completely built yet */
-  sweepwholelist(L, &L1->openupval);  /* sweep open upvalues */
-  luaE_freeCI(L1);  /* free extra CallInfo slots */
-  /* should not change the stack during an emergency gc cycle */
-  if (G(L)->gckind != KGC_EMERGENCY)
-    luaD_shrinkstack(L1);
-}
+#define sweepwholelist(L,p)     sweeplist(L,p,MAX_LUMEM)
 
 
-/*
-** sweep at most 'count' elements from a list of GCObjects erasing dead
-** objects, where a dead (not alive) object is one marked with the "old"
-** (non current) white and not fixed.
-** In non-generational mode, change all non-dead objects back to white,
-** preparing for next collection cycle.
-** In generational mode, keep black objects black, and also mark them as
-** old; stop when hitting an old object, as all objects after that
-** one will be old too.
-** When object is a thread, sweep its list of open upvalues too.
-*/
 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
+  GCObject *curr;
   global_State *g = G(L);
-  int ow = otherwhite(g);
-  int toclear, toset;  /* bits to clear and to set in all live objects */
-  int tostop;  /* stop sweep when this is true */
-  if (isgenerational(g)) {  /* generational mode? */
-    toclear = ~0;  /* clear nothing */
-    toset = bitmask(OLDBIT);  /* set the old bit of all surviving objects */
-    tostop = bitmask(OLDBIT);  /* do not sweep old generation */
-  }
-  else {  /* normal mode */
-    toclear = maskcolors;  /* clear all color bits + old bit */
-    toset = luaC_white(g);  /* make object white */
-    tostop = 0;  /* do not stop */
-  }
-  while (*p != NULL && count-- > 0) {
-    GCObject *curr = *p;
-    int marked = gch(curr)->marked;
-    if (isdeadm(ow, marked)) {  /* is 'curr' dead? */
-      *p = gch(curr)->next;  /* remove 'curr' from list */
-      freeobj(L, curr);  /* erase 'curr' */
-    }
-    else {
-      if (testbits(marked, tostop))
-        return NULL;  /* stop sweeping this list */
-      if (gch(curr)->tt == LUA_TTHREAD)
-        sweepthread(L, gco2th(curr));  /* sweep thread's upvalues */
-      /* update marks */
-      gch(curr)->marked = cast_byte((marked & toclear) | toset);
-      p = &gch(curr)->next;  /* go to next element */
+  int deadmask = otherwhite(g);
+  while ((curr = *p) != NULL && count-- > 0) {
+    if (curr->gch.tt == LUA_TTHREAD)  /* sweep open upvalues of each thread */
+      sweepwholelist(L, &gco2th(curr)->openupval);
+    if ((curr->gch.marked ^ WHITEBITS) & deadmask) {  /* not dead? */
+      lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
+      makewhite(g, curr);  /* make it white (for next cycle) */
+      p = &curr->gch.next;
+    }
+    else {  /* must erase `curr' */
+      lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
+      *p = curr->gch.next;
+      if (curr == g->rootgc)  /* is the first element of the list? */
+        g->rootgc = curr->gch.next;  /* adjust first */
+      freeobj(L, curr);
     }
   }
-  return (*p == NULL) ? NULL : p;
-}
-
-
-/*
-** sweep a list until a live object (or end of list)
-*/
-static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
-  GCObject ** old = p;
-  int i = 0;
-  do {
-    i++;
-    p = sweeplist(L, p, 1);
-  } while (p == old);
-  if (n) *n += i;
   return p;
 }
 
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** Finalization
-** =======================================================
-*/
 
 static void checkSizes (lua_State *L) {
   global_State *g = G(L);
-  if (g->gckind != KGC_EMERGENCY) {  /* do not change sizes in emergency */
-    int hs = g->strt.size / 2;  /* half the size of the string table */
-    if (g->strt.nuse < cast(lu_int32, hs))  /* using less than that half? */
-      luaS_resize(L, hs);  /* halve its size */
-    luaZ_freebuffer(L, &g->buff);  /* free concatenation buffer */
+  /* check size of string hash */
+  if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
+      g->strt.size > MINSTRTABSIZE*2)
+    luaS_resize(L, g->strt.size/2);  /* table is too big */
+  /* check size of buffer */
+  if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) {  /* buffer too big? */
+    size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
+    luaZ_resizebuffer(L, &g->buff, newsize);
   }
 }
 
 
-static GCObject *udata2finalize (global_State *g) {
-  GCObject *o = g->tobefnz;  /* get first element */
-  lua_assert(isfinalized(o));
-  g->tobefnz = gch(o)->next;  /* remove it from 'tobefnz' list */
-  gch(o)->next = g->allgc;  /* return it to 'allgc' list */
-  g->allgc = o;
-  resetbit(gch(o)->marked, SEPARATED);  /* mark that it is not in 'tobefnz' */
-  lua_assert(!isold(o));  /* see MOVE OLD rule */
-  if (!keepinvariantout(g))  /* not keeping invariant? */
-    makewhite(g, o);  /* "sweep" object */
-  return o;
-}
-
-
-static void dothecall (lua_State *L, void *ud) {
-  UNUSED(ud);
-  luaD_call(L, L->top - 2, 0, 0);
-}
-
-
-static void GCTM (lua_State *L, int propagateerrors) {
+static void GCTM (lua_State *L) {
   global_State *g = G(L);
+  GCObject *o = g->tmudata->gch.next;  /* get first element */
+  Udata *udata = rawgco2u(o);
   const TValue *tm;
-  TValue v;
-  setgcovalue(L, &v, udata2finalize(g));
-  tm = luaT_gettmbyobj(L, &v, TM_GC);
-  if (tm != NULL && ttisfunction(tm)) {  /* is there a finalizer? */
-    int status;
+  /* remove udata from `tmudata' */
+  if (o == g->tmudata)  /* last element? */
+    g->tmudata = NULL;
+  else
+    g->tmudata->gch.next = udata->uv.next;
+  udata->uv.next = g->mainthread->next;  /* return it to `root' list */
+  g->mainthread->next = o;
+  makewhite(g, o);
+  tm = fasttm(L, udata->uv.metatable, TM_GC);
+  if (tm != NULL) {
     lu_byte oldah = L->allowhook;
-    int running  = g->gcrunning;
-    L->allowhook = 0;  /* stop debug hooks during GC metamethod */
-    g->gcrunning = 0;  /* avoid GC steps */
-    setobj2s(L, L->top, tm);  /* push finalizer... */
-    setobj2s(L, L->top + 1, &v);  /* ... and its argument */
-    L->top += 2;  /* and (next line) call the finalizer */
-    status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
+    lu_mem oldt = g->GCthreshold;
+    L->allowhook = 0;  /* stop debug hooks during GC tag method */
+    g->GCthreshold = 2*g->totalbytes;  /* avoid GC steps */
+    setobj2s(L, L->top, tm);
+    setuvalue(L, L->top+1, udata);
+    L->top += 2;
+    luaD_call(L, L->top - 2, 0);
     L->allowhook = oldah;  /* restore hooks */
-    g->gcrunning = running;  /* restore state */
-    if (status != LUA_OK && propagateerrors) {  /* error while running __gc? */
-      if (status == LUA_ERRRUN) {  /* is there an error object? */
-        const char *msg = (ttisstring(L->top - 1))
-                            ? svalue(L->top - 1)
-                            : "no message";
-        luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
-        status = LUA_ERRGCMM;  /* error in __gc metamethod */
-      }
-      luaD_throw(L, status);  /* re-throw error */
-    }
+    g->GCthreshold = oldt;  /* restore threshold */
   }
 }
 
 
 /*
-** move all unreachable objects (or 'all' objects) that need
-** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
+** Call all GC tag methods
 */
-static void separatetobefnz (lua_State *L, int all) {
-  global_State *g = G(L);
-  GCObject **p = &g->finobj;
-  GCObject *curr;
-  GCObject **lastnext = &g->tobefnz;
-  /* find last 'next' field in 'tobefnz' list (to add elements in its end) */
-  while (*lastnext != NULL)
-    lastnext = &gch(*lastnext)->next;
-  while ((curr = *p) != NULL) {  /* traverse all finalizable objects */
-    lua_assert(!isfinalized(curr));
-    lua_assert(testbit(gch(curr)->marked, SEPARATED));
-    if (!(iswhite(curr) || all))  /* not being collected? */
-      p = &gch(curr)->next;  /* don't bother with it */
-    else {
-      l_setbit(gch(curr)->marked, FINALIZEDBIT); /* won't be finalized again */
-      *p = gch(curr)->next;  /* remove 'curr' from 'finobj' list */
-      gch(curr)->next = *lastnext;  /* link at the end of 'tobefnz' list */
-      *lastnext = curr;
-      lastnext = &gch(curr)->next;
-    }
-  }
+void luaC_callGCTM (lua_State *L) {
+  while (G(L)->tmudata)
+    GCTM(L);
 }
 
 
-/*
-** if object 'o' has a finalizer, remove it from 'allgc' list (must
-** search the list to find it) and link it in 'finobj' list.
-*/
-void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
+void luaC_freeall (lua_State *L) {
   global_State *g = G(L);
-  if (testbit(gch(o)->marked, SEPARATED) || /* obj. is already separated... */
-      isfinalized(o) ||                           /* ... or is finalized... */
-      gfasttm(g, mt, TM_GC) == NULL)                /* or has no finalizer? */
-    return;  /* nothing to be done */
-  else {  /* move 'o' to 'finobj' list */
-    GCObject **p;
-    GCheader *ho = gch(o);
-    if (g->sweepgc == &ho->next) {  /* avoid removing current sweep object */
-      lua_assert(issweepphase(g));
-      g->sweepgc = sweeptolive(L, g->sweepgc, NULL);
-    }
-    /* search for pointer pointing to 'o' */
-    for (p = &g->allgc; *p != o; p = &gch(*p)->next) { /* empty */ }
-    *p = ho->next;  /* remove 'o' from root list */
-    ho->next = g->finobj;  /* link it in list 'finobj' */
-    g->finobj = o;
-    l_setbit(ho->marked, SEPARATED);  /* mark it as such */
-    if (!keepinvariantout(g))  /* not keeping invariant? */
-      makewhite(g, o);  /* "sweep" object */
-    else
-      resetoldbit(o);  /* see MOVE OLD rule */
-  }
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** GC control
-** =======================================================
-*/
-
-
-/*
-** set a reasonable "time" to wait before starting a new GC cycle;
-** cycle will start when memory use hits threshold
-*/
-static void setpause (global_State *g, l_mem estimate) {
-  l_mem debt, threshold;
-  estimate = estimate / PAUSEADJ;  /* adjust 'estimate' */
-  threshold = (g->gcpause < MAX_LMEM / estimate)  /* overflow? */
-            ? estimate * g->gcpause  /* no overflow */
-            : MAX_LMEM;  /* overflow; truncate to maximum */
-  debt = -cast(l_mem, threshold - gettotalbytes(g));
-  luaE_setdebt(g, debt);
+  int i;
+  g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT);  /* mask to collect all elements */
+  sweepwholelist(L, &g->rootgc);
+  for (i = 0; i < g->strt.size; i++)  /* free all string lists */
+    sweepwholelist(L, &g->strt.hash[i]);
 }
 
 
-#define sweepphases  \
-        (bitmask(GCSsweepstring) | bitmask(GCSsweepudata) | bitmask(GCSsweep))
-
-
-/*
-** enter first sweep phase (strings) and prepare pointers for other
-** sweep phases.  The calls to 'sweeptolive' make pointers point to an
-** object inside the list (instead of to the header), so that the real
-** sweep do not need to skip objects created between "now" and the start
-** of the real sweep.
-** Returns how many objects it swept.
-*/
-static int entersweep (lua_State *L) {
-  global_State *g = G(L);
-  int n = 0;
-  g->gcstate = GCSsweepstring;
-  lua_assert(g->sweepgc == NULL && g->sweepfin == NULL);
-  /* prepare to sweep strings, finalizable objects, and regular objects */
-  g->sweepstrgc = 0;
-  g->sweepfin = sweeptolive(L, &g->finobj, &n);
-  g->sweepgc = sweeptolive(L, &g->allgc, &n);
-  return n;
+static void markmt (global_State *g) {
+  int i;
+  for (i=0; i<NUM_TAGS; i++)
+    if (g->mt[i]) markobject(g, g->mt[i]);
 }
 
 
-/*
-** change GC mode
-*/
-void luaC_changemode (lua_State *L, int mode) {
+/* mark root set */
+static void markroot (lua_State *L) {
   global_State *g = G(L);
-  if (mode == g->gckind) return;  /* nothing to change */
-  if (mode == KGC_GEN) {  /* change to generational mode */
-    /* make sure gray lists are consistent */
-    luaC_runtilstate(L, bitmask(GCSpropagate));
-    g->GCestimate = gettotalbytes(g);
-    g->gckind = KGC_GEN;
-  }
-  else {  /* change to incremental mode */
-    /* sweep all objects to turn them back to white
-       (as white has not changed, nothing extra will be collected) */
-    g->gckind = KGC_NORMAL;
-    entersweep(L);
-    luaC_runtilstate(L, ~sweepphases);
-  }
+  g->gray = NULL;
+  g->grayagain = NULL;
+  g->weak = NULL;
+  markobject(g, g->mainthread);
+  /* make global table be traversed before main stack */
+  markvalue(g, gt(g->mainthread));
+  markvalue(g, registry(L));
+  markmt(g);
+  g->gcstate = GCSpropagate;
 }
 
 
-/*
-** call all pending finalizers
-*/
-static void callallpendingfinalizers (lua_State *L, int propagateerrors) {
-  global_State *g = G(L);
-  while (g->tobefnz) {
-    resetoldbit(g->tobefnz);
-    GCTM(L, propagateerrors);
+static void remarkupvals (global_State *g) {
+  UpVal *uv;
+  for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
+    lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
+    if (isgray(obj2gco(uv)))
+      markvalue(g, uv->v);
   }
 }
 
 
-void luaC_freeallobjects (lua_State *L) {
-  global_State *g = G(L);
-  int i;
-  separatetobefnz(L, 1);  /* separate all objects with finalizers */
-  lua_assert(g->finobj == NULL);
-  callallpendingfinalizers(L, 0);
-  g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
-  g->gckind = KGC_NORMAL;
-  sweepwholelist(L, &g->finobj);  /* finalizers can create objs. in 'finobj' */
-  sweepwholelist(L, &g->allgc);
-  for (i = 0; i < g->strt.size; i++)  /* free all string lists */
-    sweepwholelist(L, &g->strt.hash[i]);
-  lua_assert(g->strt.nuse == 0);
-}
-
-
-static l_mem atomic (lua_State *L) {
+static void atomic (lua_State *L) {
   global_State *g = G(L);
-  l_mem work = -cast(l_mem, g->GCmemtrav);  /* start counting work */
-  GCObject *origweak, *origall;
-  lua_assert(!iswhite(obj2gco(g->mainthread)));
-  markobject(g, L);  /* mark running thread */
-  /* registry and global metatables may be changed by API */
-  markvalue(g, &g->l_registry);
-  markmt(g);  /* mark basic metatables */
+  size_t udsize;  /* total size of userdata to be finalized */
   /* remark occasional upvalues of (maybe) dead threads */
   remarkupvals(g);
-  propagateall(g);  /* propagate changes */
-  work += g->GCmemtrav;  /* stop counting (do not (re)count grays) */
-  /* traverse objects caught by write barrier and by 'remarkupvals' */
-  retraversegrays(g);
-  work -= g->GCmemtrav;  /* restart counting */
-  convergeephemerons(g);
-  /* at this point, all strongly accessible objects are marked. */
-  /* clear values from weak tables, before checking finalizers */
-  clearvalues(g, g->weak, NULL);
-  clearvalues(g, g->allweak, NULL);
-  origweak = g->weak; origall = g->allweak;
-  work += g->GCmemtrav;  /* stop counting (objects being finalized) */
-  separatetobefnz(L, 0);  /* separate objects to be finalized */
-  markbeingfnz(g);  /* mark objects that will be finalized */
-  propagateall(g);  /* remark, to propagate `preserveness' */
-  work -= g->GCmemtrav;  /* restart counting */
-  convergeephemerons(g);
-  /* at this point, all resurrected objects are marked. */
-  /* remove dead objects from weak tables */
-  clearkeys(g, g->ephemeron, NULL);  /* clear keys from all ephemeron tables */
-  clearkeys(g, g->allweak, NULL);  /* clear keys from all allweak tables */
-  /* clear values from resurrected weak tables */
-  clearvalues(g, g->weak, origweak);
-  clearvalues(g, g->allweak, origall);
-  g->currentwhite = cast_byte(otherwhite(g));  /* flip current white */
-  work += g->GCmemtrav;  /* complete counting */
-  return work;  /* estimate of memory marked by 'atomic' */
+  /* traverse objects cautch by write barrier and by 'remarkupvals' */
+  propagateall(g);
+  /* remark weak tables */
+  g->gray = g->weak;
+  g->weak = NULL;
+  lua_assert(!iswhite(obj2gco(g->mainthread)));
+  markobject(g, L);  /* mark running thread */
+  markmt(g);  /* mark basic metatables (again) */
+  propagateall(g);
+  /* remark gray again */
+  g->gray = g->grayagain;
+  g->grayagain = NULL;
+  propagateall(g);
+  udsize = luaC_separateudata(L, 0);  /* separate userdata to be finalized */
+  marktmu(g);  /* mark `preserved' userdata */
+  udsize += propagateall(g);  /* remark, to propagate `preserveness' */
+  cleartable(g->weak);  /* remove collected objects from weak tables */
+  /* flip current white */
+  g->currentwhite = cast_byte(otherwhite(g));
+  g->sweepstrgc = 0;
+  g->sweepgc = &g->rootgc;
+  g->gcstate = GCSsweepstring;
+  g->estimate = g->totalbytes - udsize;  /* first estimate */
 }
 
 
-static lu_mem singlestep (lua_State *L) {
+static l_mem singlestep (lua_State *L) {
   global_State *g = G(L);
+  /*lua_checkmemory(L);*/
   switch (g->gcstate) {
     case GCSpause: {
-      /* start to count memory traversed */
-      g->GCmemtrav = g->strt.size * sizeof(GCObject*);
-      lua_assert(!isgenerational(g));
-      restartcollection(g);
-      g->gcstate = GCSpropagate;
-      return g->GCmemtrav;
+      markroot(L);  /* start a new collection */
+      return 0;
     }
     case GCSpropagate: {
-      if (g->gray) {
-        lu_mem oldtrav = g->GCmemtrav;
-        propagatemark(g);
-        return g->GCmemtrav - oldtrav;  /* memory traversed in this step */
-      }
+      if (g->gray)
+        return propagatemark(g);
       else {  /* no more `gray' objects */
-        lu_mem work;
-        int sw;
-        g->gcstate = GCSatomic;  /* finish mark phase */
-        g->GCestimate = g->GCmemtrav;  /* save what was counted */;
-        work = atomic(L);  /* add what was traversed by 'atomic' */
-        g->GCestimate += work;  /* estimate of total memory traversed */ 
-        sw = entersweep(L);
-        return work + sw * GCSWEEPCOST;
+        atomic(L);  /* finish mark phase */
+        return 0;
       }
     }
     case GCSsweepstring: {
-      int i;
-      for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++)
-        sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]);
-      g->sweepstrgc += i;
-      if (g->sweepstrgc >= g->strt.size)  /* no more strings to sweep? */
-        g->gcstate = GCSsweepudata;
-      return i * GCSWEEPCOST;
-    }
-    case GCSsweepudata: {
-      if (g->sweepfin) {
-        g->sweepfin = sweeplist(L, g->sweepfin, GCSWEEPMAX);
-        return GCSWEEPMAX*GCSWEEPCOST;
-      }
-      else {
-        g->gcstate = GCSsweep;
-        return 0;
-      }
+      lu_mem old = g->totalbytes;
+      sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
+      if (g->sweepstrgc >= g->strt.size)  /* nothing more to sweep? */
+        g->gcstate = GCSsweep;  /* end sweep-string phase */
+      lua_assert(old >= g->totalbytes);
+      g->estimate -= old - g->totalbytes;
+      return GCSWEEPCOST;
     }
     case GCSsweep: {
-      if (g->sweepgc) {
-        g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
-        return GCSWEEPMAX*GCSWEEPCOST;
+      lu_mem old = g->totalbytes;
+      g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
+      if (*g->sweepgc == NULL) {  /* nothing more to sweep? */
+        checkSizes(L);
+        g->gcstate = GCSfinalize;  /* end sweep phase */
+      }
+      lua_assert(old >= g->totalbytes);
+      g->estimate -= old - g->totalbytes;
+      return GCSWEEPMAX*GCSWEEPCOST;
+    }
+    case GCSfinalize: {
+      if (g->tmudata) {
+        GCTM(L);
+        if (g->estimate > GCFINALIZECOST)
+          g->estimate -= GCFINALIZECOST;
+        return GCFINALIZECOST;
       }
       else {
-        /* sweep main thread */
-        GCObject *mt = obj2gco(g->mainthread);
-        sweeplist(L, &mt, 1);
-        checkSizes(L);
-        g->gcstate = GCSpause;  /* finish collection */
-        return GCSWEEPCOST;
+        g->gcstate = GCSpause;  /* end collection */
+        g->gcdept = 0;
+        return 0;
       }
     }
     default: lua_assert(0); return 0;
@@ -1103,118 +607,105 @@ static lu_mem singlestep (lua_State *L) {
 }
 
 
-/*
-** advances the garbage collector until it reaches a state allowed
-** by 'statemask'
-*/
-void luaC_runtilstate (lua_State *L, int statesmask) {
+void luaC_step (lua_State *L) {
   global_State *g = G(L);
-  while (!testbit(statesmask, g->gcstate))
-    singlestep(L);
+  l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
+  if (lim == 0)
+    lim = (MAX_LUMEM-1)/2;  /* no limit */
+  g->gcdept += g->totalbytes - g->GCthreshold;
+  do {
+    lim -= singlestep(L);
+    if (g->gcstate == GCSpause)
+      break;
+  } while (lim > 0);
+  if (g->gcstate != GCSpause) {
+    if (g->gcdept < GCSTEPSIZE)
+      g->GCthreshold = g->totalbytes + GCSTEPSIZE;  /* - lim/g->gcstepmul;*/
+    else {
+      g->gcdept -= GCSTEPSIZE;
+      g->GCthreshold = g->totalbytes;
+    }
+  }
+  else {
+    lua_assert(g->totalbytes >= g->estimate);
+    setthreshold(g);
+  }
 }
 
 
-static void generationalcollection (lua_State *L) {
+void luaC_fullgc (lua_State *L) {
   global_State *g = G(L);
-  lua_assert(g->gcstate == GCSpropagate);
-  if (g->GCestimate == 0) {  /* signal for another major collection? */
-    luaC_fullgc(L, 0);  /* perform a full regular collection */
-    g->GCestimate = gettotalbytes(g);  /* update control */
+  if (g->gcstate <= GCSpropagate) {
+    /* reset sweep marks to sweep all elements (returning them to white) */
+    g->sweepstrgc = 0;
+    g->sweepgc = &g->rootgc;
+    /* reset other collector lists */
+    g->gray = NULL;
+    g->grayagain = NULL;
+    g->weak = NULL;
+    g->gcstate = GCSsweepstring;
+  }
+  lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
+  /* finish any pending sweep phase */
+  while (g->gcstate != GCSfinalize) {
+    lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
+    singlestep(L);
   }
-  else {
-    lu_mem estimate = g->GCestimate;
-    luaC_runtilstate(L, bitmask(GCSpause));  /* run complete (minor) cycle */
-    g->gcstate = GCSpropagate;  /* skip restart */
-    if (gettotalbytes(g) > (estimate / 100) * g->gcmajorinc)
-      g->GCestimate = 0;  /* signal for a major collection */
-    else
-      g->GCestimate = estimate;  /* keep estimate from last major coll. */
-
+  markroot(L);
+  while (g->gcstate != GCSpause) {
+    singlestep(L);
   }
-  setpause(g, gettotalbytes(g));
-  lua_assert(g->gcstate == GCSpropagate);
+  setthreshold(g);
 }
 
 
-static void incstep (lua_State *L) {
+void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
   global_State *g = G(L);
-  l_mem debt = g->GCdebt;
-  int stepmul = g->gcstepmul;
-  if (stepmul < 40) stepmul = 40;  /* avoid ridiculous low values (and 0) */
-  /* convert debt from Kb to 'work units' (avoid zero debt and overflows) */
-  debt = (debt / STEPMULADJ) + 1;
-  debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
-  do {  /* always perform at least one single step */
-    lu_mem work = singlestep(L);  /* do some work */
-    debt -= work;
-  } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
-  if (g->gcstate == GCSpause)
-    setpause(g, g->GCestimate);  /* pause until next cycle */
-  else {
-    debt = (debt / stepmul) * STEPMULADJ;  /* convert 'work units' to Kb */
-    luaE_setdebt(g, debt);
-  }
+  lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
+  lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
+  lua_assert(ttype(&o->gch) != LUA_TTABLE);
+  /* must keep invariant? */
+  if (g->gcstate == GCSpropagate)
+    reallymarkobject(g, v);  /* restore invariant */
+  else  /* don't mind */
+    makewhite(g, o);  /* mark as white just to avoid other barriers */
 }
 
 
-/*
-** performs a basic GC step
-*/
-void luaC_forcestep (lua_State *L) {
+void luaC_barrierback (lua_State *L, Table *t) {
   global_State *g = G(L);
-  int i;
-  if (isgenerational(g)) generationalcollection(L);
-  else incstep(L);
-  /* run a few finalizers (or all of them at the end of a collect cycle) */
-  for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++)
-    GCTM(L, 1);  /* call one finalizer */
+  GCObject *o = obj2gco(t);
+  lua_assert(isblack(o) && !isdead(g, o));
+  lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
+  black2gray(o);  /* make table gray (again) */
+  t->gclist = g->grayagain;
+  g->grayagain = o;
 }
 
 
-/*
-** performs a basic GC step only if collector is running
-*/
-void luaC_step (lua_State *L) {
+void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
   global_State *g = G(L);
-  if (g->gcrunning) luaC_forcestep(L);
-  else luaE_setdebt(g, -GCSTEPSIZE);  /* avoid being called too often */
+  o->gch.next = g->rootgc;
+  g->rootgc = o;
+  o->gch.marked = luaC_white(g);
+  o->gch.tt = tt;
 }
 
 
-
-/*
-** performs a full GC cycle; if "isemergency", does not call
-** finalizers (which could change stack positions)
-*/
-void luaC_fullgc (lua_State *L, int isemergency) {
+void luaC_linkupval (lua_State *L, UpVal *uv) {
   global_State *g = G(L);
-  int origkind = g->gckind;
-  lua_assert(origkind != KGC_EMERGENCY);
-  if (isemergency)  /* do not run finalizers during emergency GC */
-    g->gckind = KGC_EMERGENCY;
-  else {
-    g->gckind = KGC_NORMAL;
-    callallpendingfinalizers(L, 1);
-  }
-  if (keepinvariant(g)) {  /* may there be some black objects? */
-    /* must sweep all objects to turn them back to white
-       (as white has not changed, nothing will be collected) */
-    entersweep(L);
-  }
-  /* finish any pending sweep phase to start a new cycle */
-  luaC_runtilstate(L, bitmask(GCSpause));
-  luaC_runtilstate(L, ~bitmask(GCSpause));  /* start new collection */
-  luaC_runtilstate(L, bitmask(GCSpause));  /* run entire collection */
-  if (origkind == KGC_GEN) {  /* generational mode? */
-    /* generational mode must be kept in propagate phase */
-    luaC_runtilstate(L, bitmask(GCSpropagate));
+  GCObject *o = obj2gco(uv);
+  o->gch.next = g->rootgc;  /* link upvalue into `rootgc' list */
+  g->rootgc = o;
+  if (isgray(o)) { 
+    if (g->gcstate == GCSpropagate) {
+      gray2black(o);  /* closed upvalues need barrier */
+      luaC_barrier(L, uv, uv->v);
+    }
+    else {  /* sweep phase: sweep it (turning it into white) */
+      makewhite(g, o);
+      lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
+    }
   }
-  g->gckind = origkind;
-  setpause(g, gettotalbytes(g));
-  if (!isemergency)   /* do not run finalizers during emergency GC */
-    callallpendingfinalizers(L, 1);
 }
 
-/* }====================================================== */
-
-