Details

The fields 'old' and 'finobjold' were renamed 'old1' and 'finobjold1',
respectively, to make clearer the main ages of their elements.

lgc.c

@@ -932,15 +932,15 @@ static GCObject **findlast (GCObject **p) {
 /*
 ** Move all unreachable objects (or 'all' objects) that need
 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized).
-** (Note that objects after 'finobjold' cannot be white, so they
-** don't need to be traversed. In incremental mode, 'finobjold' is NULL,
+** (Note that objects after 'finobjold1' cannot be white, so they
+** don't need to be traversed. In incremental mode, 'finobjold1' is NULL,
 ** so the whole list is traversed.)
 */
 static void separatetobefnz (global_State *g, int all) {
   GCObject *curr;
   GCObject **p = &g->finobj;
   GCObject **lastnext = findlast(&g->tobefnz);
-  while ((curr = *p) != g->finobjold) {  /* traverse all finalizable objects */
+  while ((curr = *p) != g->finobjold1) {  /* traverse all finalizable objects */
     lua_assert(tofinalize(curr));
     if (!(iswhite(curr) || all))  /* not being collected? */
       p = &curr->next;  /* don't bother with it */
@@ -975,8 +975,8 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
     else {  /* correct pointers into 'allgc' list, if needed */
       if (o == g->survival)
         g->survival = o->next;
-      if (o == g->old)
-        g->old = o->next;
+      if (o == g->old1)
+        g->old1 = o->next;
       if (o == g->reallyold)
         g->reallyold = o->next;
     }
@@ -1178,17 +1178,17 @@ static void youngcollection (lua_State *L, global_State *g) {
   g->gcstate = GCSswpallgc;
   psurvival = sweepgen(L, g, &g->allgc, g->survival);
   /* sweep 'survival' */
-  sweepgen(L, g, psurvival, g->old);
-  g->reallyold = g->old;
-  g->old = *psurvival;  /* 'survival' survivals are old now */
+  sweepgen(L, g, psurvival, g->old1);
+  g->reallyold = g->old1;
+  g->old1 = *psurvival;  /* 'survival' survivals are old now */
   g->survival = g->allgc;  /* all news are survivals */
 
   /* repeat for 'finobj' lists */
   psurvival = sweepgen(L, g, &g->finobj, g->finobjsur);
   /* sweep 'survival' */
-  sweepgen(L, g, psurvival, g->finobjold);
-  g->finobjrold = g->finobjold;
-  g->finobjold = *psurvival;  /* 'survival' survivals are old now */
+  sweepgen(L, g, psurvival, g->finobjold1);
+  g->finobjrold = g->finobjold1;
+  g->finobjold1 = *psurvival;  /* 'survival' survivals are old now */
   g->finobjsur = g->finobj;  /* all news are survivals */
 
   sweepgen(L, g, &g->tobefnz, NULL);
@@ -1202,11 +1202,11 @@ static void atomic2gen (lua_State *L, global_State *g) {
   g->gcstate = GCSswpallgc;
   sweep2old(L, &g->allgc);
   /* everything alive now is old */
-  g->reallyold = g->old = g->survival = g->allgc;
+  g->reallyold = g->old1 = g->survival = g->allgc;
 
   /* repeat for 'finobj' lists */
   sweep2old(L, &g->finobj);
-  g->finobjrold = g->finobjold = g->finobjsur = g->finobj;
+  g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj;
 
   sweep2old(L, &g->tobefnz);
 
@@ -1239,10 +1239,10 @@ static lu_mem entergen (lua_State *L, global_State *g) {
 */
 static void enterinc (global_State *g) {
   whitelist(g, g->allgc);
-  g->reallyold = g->old = g->survival = NULL;
+  g->reallyold = g->old1 = g->survival = NULL;
   whitelist(g, g->finobj);
   whitelist(g, g->tobefnz);
-  g->finobjrold = g->finobjold = g->finobjsur = NULL;
+  g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
   g->gcstate = GCSpause;
   g->gckind = KGC_INC;
   g->lastatomic = 0;

lstate.c

@@ -413,8 +413,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->gckind = KGC_INC;
   g->gcemergency = 0;
   g->finobj = g->tobefnz = g->fixedgc = NULL;
-  g->survival = g->old = g->reallyold = NULL;
-  g->finobjsur = g->finobjold = g->finobjrold = NULL;
+  g->survival = g->old1 = g->reallyold = NULL;
+  g->finobjsur = g->finobjold1 = g->finobjrold = NULL;
   g->sweepgc = NULL;
   g->gray = g->grayagain = NULL;
   g->weak = g->ephemeron = g->allweak = NULL;

lstate.h

@@ -32,13 +32,20 @@
 **
 ** 'allgc' -> 'survival': new objects;
 ** 'survival' -> 'old': objects that survived one collection;
-** 'old' -> 'reallyold': objects that became old in last collection;
+** 'old1' -> 'reallyold': objects that became old in last collection;
 ** 'reallyold' -> NULL: objects old for more than one cycle.
 **
 ** 'finobj' -> 'finobjsur': new objects marked for finalization;
-** 'finobjsur' -> 'finobjold': survived   """";
-** 'finobjold' -> 'finobjrold': just old  """";
+** 'finobjsur' -> 'finobjold1': survived   """";
+** 'finobjold1' -> 'finobjrold': just old  """";
 ** 'finobjrold' -> NULL: really old       """".
+**
+** All lists can contain elements older than their main ages, due
+** to 'luaC_checkfinalizer' and 'udata2finalize', which move
+** objects between the normal lists and the "marked for finalization"
+** lists. Moreover, barriers can age young objects in young lists as
+** OLD0, which then become OLD1. However, a list never contains
+** elements younger than their main ages.
 */
 
 /*
@@ -257,10 +264,10 @@ typedef struct global_State {
   GCObject *fixedgc;  /* list of objects not to be collected */
   /* fields for generational collector */
   GCObject *survival;  /* start of objects that survived one GC cycle */
-  GCObject *old;  /* start of old objects */
-  GCObject *reallyold;  /* old objects with more than one cycle */
+  GCObject *old1;  /* start of old1 objects */
+  GCObject *reallyold;  /* objects more than one cycle old ("really old") */
   GCObject *finobjsur;  /* list of survival objects with finalizers */
-  GCObject *finobjold;  /* list of old objects with finalizers */
+  GCObject *finobjold1;  /* list of old1 objects with finalizers */
   GCObject *finobjrold;  /* list of really old objects with finalizers */
   struct lua_State *twups;  /* list of threads with open upvalues */
   lua_CFunction panic;  /* to be called in unprotected errors */

ltests.c

@@ -586,10 +586,10 @@ int lua_checkmemory (lua_State *L) {
 
   /* check 'allgc' list */
   maybedead = (GCSatomic < g->gcstate && g->gcstate <= GCSswpallgc);
-  checklist(g, maybedead, 0, g->allgc, g->survival, g->old, g->reallyold);
+  checklist(g, maybedead, 0, g->allgc, g->survival, g->old1, g->reallyold);
 
   /* check 'finobj' list */
-  checklist(g, 0, 1, g->finobj, g->finobjsur, g->finobjold, g->finobjrold);
+  checklist(g, 0, 1, g->finobj, g->finobjsur, g->finobjold1, g->finobjrold);
 
   /* check 'tobefnz' list */
   for (o = g->tobefnz; o != NULL; o = o->next) {