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https://github.com/lua/lua
synced 2024-11-22 04:41:23 +03:00
Better control of gray objects
Avoid turning an object to gray except at the moment it is inserted in a gray list or in the explicit exceptional cases such as open upvalues and fixed strings.
This commit is contained in:
Roberto Ierusalimschy
parent
f849885a4b
commit
8a89da07ba
94
lgc.c
94
lgc.c
@ -75,6 +75,11 @@
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#define set2gray(x) resetbits(x->marked, maskcolors)
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/* make an object black (coming from any color) */
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#define set2black(x) \
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(x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT)))
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#define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x)))
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#define keyiswhite(n) (keyiscollectable(n) && iswhite(gckey(n)))
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@ -135,15 +140,23 @@ static GCObject **getgclist (GCObject *o) {
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/*
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** Link a collectable object 'o' with a known type into list pointed by 'p'.
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** Link a collectable object 'o' with a known type into the list 'p'.
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** (Must be a macro to access the 'gclist' field in different types.)
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*/
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#define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o))
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#define linkgclist(o,p) linkgclist_(obj2gco(o), &(o)->gclist, &(p))
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static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) {
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lua_assert(!isgray(o)); /* cannot be in a gray list */
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*pnext = *list;
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*list = o;
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set2gray(o); /* now it is */
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}
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/*
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** Link a generic collectable object 'o' into list pointed by 'p'.
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** Link a generic collectable object 'o' into the list 'p'.
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*/
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#define linkobjgclist(o,p) (*getgclist(o) = (p), (p) = obj2gco(o))
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#define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p))
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@ -219,9 +232,10 @@ void luaC_barrierback_ (lua_State *L, GCObject *o) {
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global_State *g = G(L);
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lua_assert(isblack(o) && !isdead(g, o));
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lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1));
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if (getage(o) != G_TOUCHED2) /* not already in gray list? */
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linkobjgclist(o, g->grayagain); /* link it in 'grayagain' */
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set2gray(o); /* make object gray (again) */
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if (getage(o) == G_TOUCHED2) /* already in gray list? */
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set2gray(o); /* make it gray to become touched1 */
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else /* link it in 'grayagain' and paint it gray */
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linkobjgclist(o, g->grayagain);
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if (isold(o)) /* generational mode? */
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setage(o, G_TOUCHED1); /* touched in current cycle */
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}
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@ -264,25 +278,30 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
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/*
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** Mark an object. Userdata, strings, and closed upvalues are visited
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** and turned black here. Other objects are marked gray and added
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** to appropriate list to be visited (and turned black) later. (Open
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** upvalues are already indirectly linked through the 'twups' list. They
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** are kept gray to avoid barriers, as their values will be revisited by
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** the thread or by 'remarkupvals'.)
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** Mark an object. Userdata with no user values, strings, and closed
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** upvalues are visited and turned black here. Open upvalues are
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** already indirectly linked through their respective threads in the
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** 'twups' list, so they don't go to the gray list; nevertheless, they
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** are kept gray to avoid barriers, as their values will be revisited
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** by the thread or by 'remarkupvals'. Other objects are added to the
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** gray list to be visited (and turned black) later. Both userdata and
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** upvalues can call this function recursively, but this recursion goes
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** for at most two levels: An upvalue cannot refer to another upvalue
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** (only closures can), and a userdata's metatable must be a table.
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*/
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static void reallymarkobject (global_State *g, GCObject *o) {
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set2gray(o);
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switch (o->tt) {
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case LUA_VSHRSTR:
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case LUA_VLNGSTR: {
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nw2black(o); /* nothing to visit */
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set2black(o); /* nothing to visit */
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break;
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}
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case LUA_VUPVAL: {
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UpVal *uv = gco2upv(o);
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if (!upisopen(uv)) /* open upvalues are kept gray */
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nw2black(o); /* closed upvalues are visited here */
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if (upisopen(uv))
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set2gray(uv); /* open upvalues are kept gray */
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else
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set2black(o); /* closed upvalues are visited here */
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markvalue(g, uv->v); /* mark its content */
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break;
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}
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@ -290,7 +309,7 @@ static void reallymarkobject (global_State *g, GCObject *o) {
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Udata *u = gco2u(o);
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if (u->nuvalue == 0) { /* no user values? */
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markobjectN(g, u->metatable); /* mark its metatable */
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nw2black(o); /* nothing else to mark */
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set2black(o); /* nothing else to mark */
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break;
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}
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/* else... */
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@ -402,17 +421,11 @@ static void restartcollection (global_State *g) {
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** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go
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** back to a gray list, but then it must become OLD. (That is what
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** 'correctgraylist' does when it finds a TOUCHED2 object.)
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** It is defined as a macro because 'gclist' is not a unique field in
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** different collectable objects.
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*/
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#define genlink(g,o) genlink_(g, obj2gco(o), &(o)->gclist)
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static void genlink_ (global_State *g, GCObject *o, GCObject **pnext) {
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static void genlink (global_State *g, GCObject *o) {
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lua_assert(isblack(o));
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if (getage(o) == G_TOUCHED1) { /* touched in this cycle? */
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*pnext = g->grayagain; /* link it back in 'grayagain' */
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g->grayagain = o;
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set2gray(o);
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linkobjgclist(o, g->grayagain); /* link it back in 'grayagain' */
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} /* everything else do not need to be linked back */
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else if (getage(o) == G_TOUCHED2)
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changeage(o, G_TOUCHED2, G_OLD); /* advance age */
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@ -496,10 +509,8 @@ static int traverseephemeron (global_State *g, Table *h, int inv) {
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linkgclist(h, g->ephemeron); /* have to propagate again */
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else if (hasclears) /* table has white keys? */
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linkgclist(h, g->allweak); /* may have to clean white keys */
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else {
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nw2black(h); /* 'genlink' expects black objects */
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genlink(g, h); /* check whether collector still needs to see it */
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}
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else
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genlink(g, obj2gco(h)); /* check whether collector still needs to see it */
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return marked;
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}
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@ -519,7 +530,7 @@ static void traversestrongtable (global_State *g, Table *h) {
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markvalue(g, gval(n));
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}
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}
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genlink(g, h);
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genlink(g, obj2gco(h));
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}
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@ -531,7 +542,6 @@ static lu_mem traversetable (global_State *g, Table *h) {
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(cast_void(weakkey = strchr(svalue(mode), 'k')),
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cast_void(weakvalue = strchr(svalue(mode), 'v')),
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(weakkey || weakvalue))) { /* is really weak? */
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set2gray(h); /* turn it back to gray, as it probably goes to a list */
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if (!weakkey) /* strong keys? */
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traverseweakvalue(g, h);
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else if (!weakvalue) /* strong values? */
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@ -550,7 +560,7 @@ static int traverseudata (global_State *g, Udata *u) {
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markobjectN(g, u->metatable); /* mark its metatable */
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for (i = 0; i < u->nuvalue; i++)
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markvalue(g, &u->uv[i].uv);
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genlink(g, u);
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genlink(g, obj2gco(u));
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return 1 + u->nuvalue;
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}
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@ -612,10 +622,8 @@ static int traverseLclosure (global_State *g, LClosure *cl) {
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static int traversethread (global_State *g, lua_State *th) {
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UpVal *uv;
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StkId o = th->stack;
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if (isold(th) || g->gcstate == GCSpropagate) {
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if (isold(th) || g->gcstate == GCSpropagate)
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linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
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set2gray(th);
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}
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if (o == NULL)
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return 1; /* stack not completely built yet */
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lua_assert(g->gcstate == GCSatomic ||
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@ -641,8 +649,7 @@ static int traversethread (global_State *g, lua_State *th) {
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/*
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** traverse one gray object, turning it to black (except for threads,
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** which are always gray).
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** traverse one gray object, turning it to black.
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*/
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static lu_mem propagatemark (global_State *g) {
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GCObject *o = g->gray;
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@ -684,8 +691,10 @@ static void convergeephemerons (global_State *g) {
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g->ephemeron = NULL; /* tables may return to this list when traversed */
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changed = 0;
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while ((w = next) != NULL) { /* for each ephemeron table */
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next = gco2t(w)->gclist; /* list is rebuilt during loop */
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if (traverseephemeron(g, gco2t(w), dir)) { /* marked some value? */
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Table *h = gco2t(w);
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next = h->gclist; /* list is rebuilt during loop */
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nw2black(h); /* out of the list (for now) */
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if (traverseephemeron(g, h, dir)) { /* marked some value? */
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propagateall(g); /* propagate changes */
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changed = 1; /* will have to revisit all ephemeron tables */
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}
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@ -1048,7 +1057,6 @@ static void sweep2old (lua_State *L, GCObject **p) {
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if (curr->tt == LUA_VTHREAD) { /* threads must be watched */
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lua_State *th = gco2th(curr);
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linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
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set2gray(th);
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}
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else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr)))
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set2gray(curr); /* open upvalues are always gray */
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@ -1183,10 +1191,8 @@ static void markold (global_State *g, GCObject *from, GCObject *to) {
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if (getage(p) == G_OLD1) {
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lua_assert(!iswhite(p));
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changeage(p, G_OLD1, G_OLD); /* now they are old */
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if (isblack(p)) {
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set2gray(p); /* should be '2white', but gray works too */
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if (isblack(p))
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reallymarkobject(g, p);
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}
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}
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}
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}
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