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better(?) scheme for cleaning weak tables; all ressurected objects

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are removed from weak values before finalization
This commit is contained in:
Roberto Ierusalimschy 2011-09-24 18:00:40 -03:00
parent 12ab78aca6
commit 95ed6c1127
1 changed files with 44 additions and 18 deletions
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62
lgc.c
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@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.109 2011/05/05 19:42:25 roberto Exp roberto $
** $Id: lgc.c,v 2.110 2011/09/19 17:03:38 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -116,13 +116,13 @@ static void removeentry (Node *n) {
** other objects: if really collected, cannot keep them; for objects
** being finalized, keep them in keys, but not in values
*/
static int iscleared (const TValue *o, int iskey) {
static int iscleared (const TValue *o) {
if (!iscollectable(o)) return 0;
else if (ttisstring(o)) {
stringmark(rawtsvalue(o)); /* strings are `values', so are never weak */
return 0;
}
else return iswhite(gcvalue(o)) || (!iskey && isfinalized(gcvalue(o)));
else return iswhite(gcvalue(o));
}
@ -373,14 +373,14 @@ static int traverseephemeron (global_State *g, Table *h) {
checkdeadkey(n);
if (ttisnil(gval(n))) /* entry is empty? */
removeentry(n); /* remove it */
else if (iscleared(gkey(n), 1)) { /* key is not marked (yet)? */
hasclears = 1; /* table still have white keys */
else if (iscleared(gkey(n))) { /* key is not marked (yet)? */
hasclears = 1; /* table must be cleared */
if (valiswhite(gval(n))) /* value not marked yet? */
prop = 1;
prop = 1; /* must propagate again */
}
else if (valiswhite(gval(n))) { /* value not marked yet? */
marked = 1; /* mark it now */
reallymarkobject(g, gcvalue(gval(n)));
marked = 1;
reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
}
}
if (prop)
@ -566,21 +566,39 @@ static void convergeephemerons (global_State *g) {
/*
** clear collected entries from all weaktables in list 'l'
** clear entries with unmarked keys from all weaktables in list 'l' up
** to element 'f'
*/
static void cleartable (GCObject *l) {
for (; l != NULL; l = gco2t(l)->gclist) {
static void clearkeys (GCObject *l, GCObject *f) {
for (; l != f; l = gco2t(l)->gclist) {
Table *h = gco2t(l);
Node *n, *limit = gnode(h, sizenode(h));
for (n = gnode(h, 0); n < limit; n++) {
if (!ttisnil(gval(n)) && (iscleared(gkey(n)))) {
setnilvalue(gval(n)); /* remove value ... */
removeentry(n); /* and remove entry from table */
}
}
}
}
/*
** clear entries with unmarked values from all weaktables in list 'l' up
** to element 'f'
*/
static void clearvalues (GCObject *l, GCObject *f) {
for (; l != f; l = gco2t(l)->gclist) {
Table *h = gco2t(l);
Node *n, *limit = gnode(h, sizenode(h));
int i;
for (i = 0; i < h->sizearray; i++) {
TValue *o = &h->array[i];
if (iscleared(o, 0)) /* value was collected? */
if (iscleared(o)) /* value was collected? */
setnilvalue(o); /* remove value */
}
for (n = gnode(h, 0); n < limit; n++) {
if (!ttisnil(gval(n)) && /* non-empty entry? */
(iscleared(gkey(n), 1) || iscleared(gval(n), 0))) {
if (!ttisnil(gval(n)) && iscleared(gval(n))) {
setnilvalue(gval(n)); /* remove value ... */
removeentry(n); /* and remove entry from table */
}
@ -862,6 +880,7 @@ void luaC_freeallobjects (lua_State *L) {
static void atomic (lua_State *L) {
global_State *g = G(L);
GCObject *origweak, *origall;
lua_assert(!iswhite(obj2gco(g->mainthread)));
markobject(g, L); /* mark running thread */
/* registry and global metatables may be changed by API */
@ -876,14 +895,21 @@ static void atomic (lua_State *L) {
traverselistofgrays(g, &g->ephemeron); /* remark ephemeron tables */
convergeephemerons(g);
/* at this point, all strongly accessible objects are marked. */
luaC_separateudata(L, 0); /* separate userdata to be finalized */
/* clear values from weak tables, before checking finalizers */
clearvalues(g->weak, NULL);
clearvalues(g->allweak, NULL);
origweak = g->weak; origall = g->allweak;
luaC_separateudata(L, 0); /* separate objects to be finalized */
markbeingfnz(g); /* mark userdata that will be finalized */
propagateall(g); /* remark, to propagate `preserveness' */
convergeephemerons(g);
/* at this point, all accessible objects are marked. */
/* remove collected objects from weak tables */
cleartable(g->weak);
cleartable(g->ephemeron);
cleartable(g->allweak);
clearkeys(g->ephemeron, NULL); /* clear keys from all ephemeron tables */
clearkeys(g->allweak, NULL); /* clear keys from all allweak tables */
/* clear values from weak tables accessible from separated objects */
clearvalues(g->weak, origweak);
clearvalues(g->allweak, origall);
g->sweepstrgc = 0; /* prepare to sweep strings */
g->gcstate = GCSsweepstring;
g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */