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-rw-r--r--lua-5.3.5/lgc.c1179
1 files changed, 1179 insertions, 0 deletions
diff --git a/lua-5.3.5/lgc.c b/lua-5.3.5/lgc.c
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+++ b/lua-5.3.5/lgc.c
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+/*
+** $Id: lgc.c,v 2.215.1.2 2017/08/31 16:15:27 roberto Exp $
+** Garbage Collector
+** See Copyright Notice in lua.h
+*/
+
+#define lgc_c
+#define LUA_CORE
+
+#include "lprefix.h"
+
+
+#include <string.h>
+
+#include "lua.h"
+
+#include "ldebug.h"
+#include "ldo.h"
+#include "lfunc.h"
+#include "lgc.h"
+#include "lmem.h"
+#include "lobject.h"
+#include "lstate.h"
+#include "lstring.h"
+#include "ltable.h"
+#include "ltm.h"
+
+
+/*
+** internal state for collector while inside the atomic phase. The
+** collector should never be in this state while running regular code.
+*/
+#define GCSinsideatomic (GCSpause + 1)
+
+/*
+** 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))
+
+/* cost of calling one finalizer */
+#define GCFINALIZECOST GCSWEEPCOST
+
+
+/*
+** 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
+
+
+/*
+** 'makewhite' erases all color bits then sets only the current white
+** bit
+*/
+#define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS))
+#define makewhite(g,x) \
+ (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g)))
+
+#define white2gray(x) resetbits(x->marked, WHITEBITS)
+#define black2gray(x) resetbit(x->marked, BLACKBIT)
+
+
+#define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x)))
+
+#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
+
+
+#define checkconsistency(obj) \
+ lua_longassert(!iscollectable(obj) || righttt(obj))
+
+
+#define markvalue(g,o) { checkconsistency(o); \
+ if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
+
+#define markobject(g,t) { if (iswhite(t)) reallymarkobject(g, obj2gco(t)); }
+
+/*
+** mark an object that can be NULL (either because it is really optional,
+** or it was stripped as debug info, or inside an uncompleted structure)
+*/
+#define markobjectN(g,t) { if (t) markobject(g,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 collectable object 'o' into list pointed by 'p'
+*/
+#define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o))
+
+
+/*
+** If key is not marked, mark its entry as dead. This allows key to be
+** collected, but keeps its entry in the table. A dead node is needed
+** when Lua looks up for a key (it may be part of a chain) and when
+** traversing a weak table (key might be removed from the table during
+** traversal). Other places never manipulate dead keys, because its
+** associated nil value is enough to signal that the entry is logically
+** empty.
+*/
+static void removeentry (Node *n) {
+ lua_assert(ttisnil(gval(n)));
+ if (valiswhite(gkey(n)))
+ setdeadvalue(wgkey(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, tsvalue(o)); /* strings are 'values', so are never weak */
+ return 0;
+ }
+ else return iswhite(gcvalue(o));
+}
+
+
+/*
+** barrier that moves collector forward, that is, mark the white object
+** being pointed by a black object. (If in sweep phase, clear the black
+** object to white [sweep it] to avoid other barrier calls for this
+** same 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));
+ if (keepinvariant(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.
+*/
+void luaC_barrierback_ (lua_State *L, Table *t) {
+ global_State *g = G(L);
+ lua_assert(isblack(t) && !isdead(g, t));
+ black2gray(t); /* make table gray (again) */
+ linkgclist(t, g->grayagain);
+}
+
+
+/*
+** barrier for assignments to closed upvalues. Because upvalues are
+** shared among closures, it is impossible to know the color of all
+** closures pointing to it. So, we assume that the object being assigned
+** must be marked.
+*/
+void luaC_upvalbarrier_ (lua_State *L, UpVal *uv) {
+ global_State *g = G(L);
+ GCObject *o = gcvalue(uv->v);
+ lua_assert(!upisopen(uv)); /* ensured by macro luaC_upvalbarrier */
+ if (keepinvariant(g))
+ markobject(g, o);
+}
+
+
+void luaC_fix (lua_State *L, GCObject *o) {
+ global_State *g = G(L);
+ lua_assert(g->allgc == o); /* object must be 1st in 'allgc' list! */
+ white2gray(o); /* they will be gray forever */
+ g->allgc = o->next; /* remove object from 'allgc' list */
+ o->next = g->fixedgc; /* link it to 'fixedgc' list */
+ g->fixedgc = o;
+}
+
+
+/*
+** create a new collectable object (with given type and size) and link
+** it to 'allgc' list.
+*/
+GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
+ global_State *g = G(L);
+ GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz));
+ o->marked = luaC_white(g);
+ o->tt = tt;
+ o->next = g->allgc;
+ g->allgc = 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) {
+ reentry:
+ white2gray(o);
+ switch (o->tt) {
+ case LUA_TSHRSTR: {
+ gray2black(o);
+ g->GCmemtrav += sizelstring(gco2ts(o)->shrlen);
+ break;
+ }
+ case LUA_TLNGSTR: {
+ gray2black(o);
+ g->GCmemtrav += sizelstring(gco2ts(o)->u.lnglen);
+ break;
+ }
+ case LUA_TUSERDATA: {
+ TValue uvalue;
+ markobjectN(g, gco2u(o)->metatable); /* mark its metatable */
+ gray2black(o);
+ g->GCmemtrav += sizeudata(gco2u(o));
+ getuservalue(g->mainthread, gco2u(o), &uvalue);
+ if (valiswhite(&uvalue)) { /* markvalue(g, &uvalue); */
+ o = gcvalue(&uvalue);
+ goto reentry;
+ }
+ break;
+ }
+ case LUA_TLCL: {
+ linkgclist(gco2lcl(o), g->gray);
+ break;
+ }
+ case LUA_TCCL: {
+ linkgclist(gco2ccl(o), g->gray);
+ break;
+ }
+ case LUA_TTABLE: {
+ linkgclist(gco2t(o), g->gray);
+ break;
+ }
+ case LUA_TTHREAD: {
+ linkgclist(gco2th(o), g->gray);
+ break;
+ }
+ case LUA_TPROTO: {
+ linkgclist(gco2p(o), g->gray);
+ break;
+ }
+ default: lua_assert(0); break;
+ }
+}
+
+
+/*
+** mark metamethods for basic types
+*/
+static void markmt (global_State *g) {
+ int i;
+ for (i=0; i < LUA_NUMTAGS; i++)
+ markobjectN(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 = o->next)
+ markobject(g, o);
+}
+
+
+/*
+** Mark all values stored in marked open upvalues from non-marked threads.
+** (Values from marked threads were already marked when traversing the
+** thread.) Remove from the list threads that no longer have upvalues and
+** not-marked threads.
+*/
+static void remarkupvals (global_State *g) {
+ lua_State *thread;
+ lua_State **p = &g->twups;
+ while ((thread = *p) != NULL) {
+ lua_assert(!isblack(thread)); /* threads are never black */
+ if (isgray(thread) && thread->openupval != NULL)
+ p = &thread->twups; /* keep marked thread with upvalues in the list */
+ else { /* thread is not marked or without upvalues */
+ UpVal *uv;
+ *p = thread->twups; /* remove thread from the list */
+ thread->twups = thread; /* mark that it is out of list */
+ for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
+ if (uv->u.open.touched) {
+ markvalue(g, uv->v); /* remark upvalue's value */
+ uv->u.open.touched = 0;
+ }
+ }
+ }
+ }
+}
+
+
+/*
+** mark root set and reset all gray lists, to start a new 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
+** =======================================================
+*/
+
+/*
+** Traverse a table with weak values and link it to proper list. During
+** propagate phase, keep it in 'grayagain' list, to be revisited in the
+** atomic phase. In the atomic phase, if table has any white value,
+** put it in 'weak' list, to be cleared.
+*/
+static void traverseweakvalue (global_State *g, Table *h) {
+ Node *n, *limit = gnodelast(h);
+ /* if there is array part, assume it may have white values (it is not
+ worth traversing it now just to check) */
+ int hasclears = (h->sizearray > 0);
+ 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 */
+ if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */
+ hasclears = 1; /* table will have to be cleared */
+ }
+ }
+ if (g->gcstate == GCSpropagate)
+ linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */
+ else if (hasclears)
+ linkgclist(h, g->weak); /* has to be cleared later */
+}
+
+
+/*
+** Traverse an ephemeron table and link it to proper list. Returns true
+** iff any object was marked during this traversal (which implies that
+** convergence has to continue). During propagation phase, keep table
+** in 'grayagain' list, to be visited again in the atomic phase. In
+** the atomic phase, if table has any white->white entry, it has to
+** be revisited during ephemeron convergence (as that key may turn
+** black). Otherwise, if it has any white key, table has to be cleared
+** (in the atomic phase).
+*/
+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 hasww = 0; /* true if table has entry "white-key -> white-value" */
+ Node *n, *limit = gnodelast(h);
+ unsigned int i;
+ /* traverse array part */
+ for (i = 0; i < h->sizearray; i++) {
+ if (valiswhite(&h->array[i])) {
+ marked = 1;
+ reallymarkobject(g, gcvalue(&h->array[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? */
+ hasww = 1; /* white-white entry */
+ }
+ else if (valiswhite(gval(n))) { /* value not marked yet? */
+ marked = 1;
+ reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
+ }
+ }
+ /* link table into proper list */
+ if (g->gcstate == GCSpropagate)
+ linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */
+ else if (hasww) /* table has white->white entries? */
+ linkgclist(h, g->ephemeron); /* have to propagate again */
+ else if (hasclears) /* table has white keys? */
+ linkgclist(h, g->allweak); /* may have to clean white keys */
+ return marked;
+}
+
+
+static void traversestrongtable (global_State *g, Table *h) {
+ Node *n, *limit = gnodelast(h);
+ unsigned 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 */
+ }
+ }
+}
+
+
+static lu_mem traversetable (global_State *g, Table *h) {
+ const char *weakkey, *weakvalue;
+ const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
+ markobjectN(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(h); /* keep table gray */
+ if (!weakkey) /* strong keys? */
+ traverseweakvalue(g, h);
+ else if (!weakvalue) /* strong values? */
+ traverseephemeron(g, h);
+ else /* all weak */
+ linkgclist(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, allocsizenode(h));
+}
+
+
+/*
+** Traverse a prototype. (While a prototype is being build, its
+** arrays can be larger than needed; the extra slots are filled with
+** NULL, so the use of 'markobjectN')
+*/
+static int traverseproto (global_State *g, Proto *f) {
+ int i;
+ if (f->cache && iswhite(f->cache))
+ f->cache = NULL; /* allow cache to be collected */
+ markobjectN(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 */
+ markobjectN(g, f->upvalues[i].name);
+ for (i = 0; i < f->sizep; i++) /* mark nested protos */
+ markobjectN(g, f->p[i]);
+ for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
+ markobjectN(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 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);
+}
+
+/*
+** open upvalues point to values in a thread, so those values should
+** be marked when the thread is traversed except in the atomic phase
+** (because then the value cannot be changed by the thread and the
+** thread may not be traversed again)
+*/
+static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
+ int i;
+ markobjectN(g, cl->p); /* mark its prototype */
+ for (i = 0; i < cl->nupvalues; i++) { /* mark its upvalues */
+ UpVal *uv = cl->upvals[i];
+ if (uv != NULL) {
+ if (upisopen(uv) && g->gcstate != GCSinsideatomic)
+ uv->u.open.touched = 1; /* can be marked in 'remarkupvals' */
+ else
+ markvalue(g, uv->v);
+ }
+ }
+ return sizeLclosure(cl->nupvalues);
+}
+
+
+static lu_mem traversethread (global_State *g, lua_State *th) {
+ StkId o = th->stack;
+ if (o == NULL)
+ return 1; /* stack not completely built yet */
+ lua_assert(g->gcstate == GCSinsideatomic ||
+ th->openupval == NULL || isintwups(th));
+ for (; o < th->top; o++) /* mark live elements in the stack */
+ markvalue(g, o);
+ if (g->gcstate == GCSinsideatomic) { /* final traversal? */
+ StkId lim = th->stack + th->stacksize; /* real end of stack */
+ for (; o < lim; o++) /* clear not-marked stack slice */
+ setnilvalue(o);
+ /* 'remarkupvals' may have removed thread from 'twups' list */
+ if (!isintwups(th) && th->openupval != NULL) {
+ th->twups = g->twups; /* link it back to the list */
+ g->twups = th;
+ }
+ }
+ else if (g->gckind != KGC_EMERGENCY)
+ luaD_shrinkstack(th); /* do not change stack in emergency cycle */
+ return (sizeof(lua_State) + sizeof(TValue) * th->stacksize +
+ sizeof(CallInfo) * th->nci);
+}
+
+
+/*
+** traverse one gray object, turning it to black (except for threads,
+** which are always gray).
+*/
+static void propagatemark (global_State *g) {
+ lu_mem size;
+ GCObject *o = g->gray;
+ lua_assert(isgray(o));
+ gray2black(o);
+ switch (o->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;
+ }
+ case LUA_TTHREAD: {
+ lua_State *th = gco2th(o);
+ g->gray = th->gclist; /* remove from 'gray' list */
+ linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
+ black2gray(o);
+ size = traversethread(g, th);
+ break;
+ }
+ case LUA_TPROTO: {
+ Proto *p = gco2p(o);
+ g->gray = p->gclist; /* remove from 'gray' list */
+ size = traverseproto(g, p);
+ break;
+ }
+ default: lua_assert(0); return;
+ }
+ g->GCmemtrav += size;
+}
+
+
+static void propagateall (global_State *g) {
+ while (g->gray) propagatemark(g);
+}
+
+
+static void convergeephemerons (global_State *g) {
+ int changed;
+ do {
+ GCObject *w;
+ GCObject *next = g->ephemeron; /* get ephemeron list */
+ g->ephemeron = NULL; /* tables may 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);
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Sweep Functions
+** =======================================================
+*/
+
+
+/*
+** clear entries with unmarked keys from all weaktables in list 'l' up
+** to element 'f'
+*/
+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 ... */
+ }
+ if (ttisnil(gval(n))) /* is entry empty? */
+ removeentry(n); /* remove entry from table */
+ }
+ }
+}
+
+
+/*
+** clear entries with unmarked values from all weaktables in list 'l' up
+** to element 'f'
+*/
+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);
+ unsigned 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 */
+ }
+ for (n = gnode(h, 0); n < limit; n++) {
+ if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
+ setnilvalue(gval(n)); /* remove value ... */
+ removeentry(n); /* and remove entry from table */
+ }
+ }
+ }
+}
+
+
+void luaC_upvdeccount (lua_State *L, UpVal *uv) {
+ lua_assert(uv->refcount > 0);
+ uv->refcount--;
+ if (uv->refcount == 0 && !upisopen(uv))
+ luaM_free(L, uv);
+}
+
+
+static void freeLclosure (lua_State *L, LClosure *cl) {
+ int i;
+ for (i = 0; i < cl->nupvalues; i++) {
+ UpVal *uv = cl->upvals[i];
+ if (uv)
+ luaC_upvdeccount(L, uv);
+ }
+ luaM_freemem(L, cl, sizeLclosure(cl->nupvalues));
+}
+
+
+static void freeobj (lua_State *L, GCObject *o) {
+ switch (o->tt) {
+ case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
+ case LUA_TLCL: {
+ freeLclosure(L, gco2lcl(o));
+ break;
+ }
+ case LUA_TCCL: {
+ luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
+ 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:
+ luaS_remove(L, gco2ts(o)); /* remove it from hash table */
+ luaM_freemem(L, o, sizelstring(gco2ts(o)->shrlen));
+ break;
+ case LUA_TLNGSTR: {
+ luaM_freemem(L, o, sizelstring(gco2ts(o)->u.lnglen));
+ 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 at most 'count' elements from a list of GCObjects erasing dead
+** objects, where a dead object is one marked with the old (non current)
+** white; change all non-dead objects back to white, preparing for next
+** collection cycle. Return where to continue the traversal or NULL if
+** list is finished.
+*/
+static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
+ global_State *g = G(L);
+ int ow = otherwhite(g);
+ int white = luaC_white(g); /* current white */
+ while (*p != NULL && count-- > 0) {
+ GCObject *curr = *p;
+ int marked = curr->marked;
+ if (isdeadm(ow, marked)) { /* is 'curr' dead? */
+ *p = curr->next; /* remove 'curr' from list */
+ freeobj(L, curr); /* erase 'curr' */
+ }
+ else { /* change mark to 'white' */
+ curr->marked = cast_byte((marked & maskcolors) | white);
+ p = &curr->next; /* go to next element */
+ }
+ }
+ return (*p == NULL) ? NULL : p;
+}
+
+
+/*
+** sweep a list until a live object (or end of list)
+*/
+static GCObject **sweeptolive (lua_State *L, GCObject **p) {
+ GCObject **old = p;
+ do {
+ p = sweeplist(L, p, 1);
+ } while (p == old);
+ return p;
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Finalization
+** =======================================================
+*/
+
+/*
+** If possible, shrink string table
+*/
+static void checkSizes (lua_State *L, global_State *g) {
+ if (g->gckind != KGC_EMERGENCY) {
+ l_mem olddebt = g->GCdebt;
+ if (g->strt.nuse < g->strt.size / 4) /* string table too big? */
+ luaS_resize(L, g->strt.size / 2); /* shrink it a little */
+ g->GCestimate += g->GCdebt - olddebt; /* update estimate */
+ }
+}
+
+
+static GCObject *udata2finalize (global_State *g) {
+ GCObject *o = g->tobefnz; /* get first element */
+ lua_assert(tofinalize(o));
+ g->tobefnz = o->next; /* remove it from 'tobefnz' list */
+ o->next = g->allgc; /* return it to 'allgc' list */
+ g->allgc = o;
+ resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */
+ if (issweepphase(g))
+ makewhite(g, o); /* "sweep" object */
+ return o;
+}
+
+
+static void dothecall (lua_State *L, void *ud) {
+ UNUSED(ud);
+ luaD_callnoyield(L, L->top - 2, 0);
+}
+
+
+static void GCTM (lua_State *L, int propagateerrors) {
+ global_State *g = G(L);
+ 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;
+ 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 */
+ L->ci->callstatus |= CIST_FIN; /* will run a finalizer */
+ status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
+ L->ci->callstatus &= ~CIST_FIN; /* not running a finalizer anymore */
+ 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 */
+ }
+ }
+}
+
+
+/*
+** call a few (up to 'g->gcfinnum') finalizers
+*/
+static int runafewfinalizers (lua_State *L) {
+ global_State *g = G(L);
+ unsigned int i;
+ lua_assert(!g->tobefnz || g->gcfinnum > 0);
+ for (i = 0; g->tobefnz && i < g->gcfinnum; i++)
+ GCTM(L, 1); /* call one finalizer */
+ g->gcfinnum = (!g->tobefnz) ? 0 /* nothing more to finalize? */
+ : g->gcfinnum * 2; /* else call a few more next time */
+ return i;
+}
+
+
+/*
+** call all pending finalizers
+*/
+static void callallpendingfinalizers (lua_State *L) {
+ global_State *g = G(L);
+ while (g->tobefnz)
+ GCTM(L, 0);
+}
+
+
+/*
+** find last 'next' field in list 'p' list (to add elements in its end)
+*/
+static GCObject **findlast (GCObject **p) {
+ while (*p != NULL)
+ p = &(*p)->next;
+ return p;
+}
+
+
+/*
+** move all unreachable objects (or 'all' objects) that need
+** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
+*/
+static void separatetobefnz (global_State *g, int all) {
+ GCObject *curr;
+ GCObject **p = &g->finobj;
+ GCObject **lastnext = findlast(&g->tobefnz);
+ while ((curr = *p) != NULL) { /* traverse all finalizable objects */
+ lua_assert(tofinalize(curr));
+ if (!(iswhite(curr) || all)) /* not being collected? */
+ p = &curr->next; /* don't bother with it */
+ else {
+ *p = curr->next; /* remove 'curr' from 'finobj' list */
+ curr->next = *lastnext; /* link at the end of 'tobefnz' list */
+ *lastnext = curr;
+ lastnext = &curr->next;
+ }
+ }
+}
+
+
+/*
+** 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) {
+ global_State *g = G(L);
+ if (tofinalize(o) || /* obj. is already marked... */
+ gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */
+ return; /* nothing to be done */
+ else { /* move 'o' to 'finobj' list */
+ GCObject **p;
+ if (issweepphase(g)) {
+ makewhite(g, o); /* "sweep" object 'o' */
+ if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */
+ g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */
+ }
+ /* search for pointer pointing to 'o' */
+ for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
+ *p = o->next; /* remove 'o' from 'allgc' list */
+ o->next = g->finobj; /* link it in 'finobj' list */
+ g->finobj = o;
+ l_setbit(o->marked, FINALIZEDBIT); /* mark it as such */
+ }
+}
+
+/* }====================================================== */
+
+
+
+/*
+** {======================================================
+** GC control
+** =======================================================
+*/
+
+
+/*
+** Set a reasonable "time" to wait before starting a new GC cycle; cycle
+** will start when memory use hits threshold. (Division by 'estimate'
+** should be OK: it cannot be zero (because Lua cannot even start with
+** less than PAUSEADJ bytes).
+*/
+static void setpause (global_State *g) {
+ l_mem threshold, debt;
+ l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */
+ lua_assert(estimate > 0);
+ threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */
+ ? estimate * g->gcpause /* no overflow */
+ : MAX_LMEM; /* overflow; truncate to maximum */
+ debt = gettotalbytes(g) - threshold;
+ luaE_setdebt(g, debt);
+}
+
+
+/*
+** Enter first sweep phase.
+** The call to 'sweeplist' tries to make pointer 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.
+*/
+static void entersweep (lua_State *L) {
+ global_State *g = G(L);
+ g->gcstate = GCSswpallgc;
+ lua_assert(g->sweepgc == NULL);
+ g->sweepgc = sweeplist(L, &g->allgc, 1);
+}
+
+
+void luaC_freeallobjects (lua_State *L) {
+ global_State *g = G(L);
+ separatetobefnz(g, 1); /* separate all objects with finalizers */
+ lua_assert(g->finobj == NULL);
+ callallpendingfinalizers(L);
+ lua_assert(g->tobefnz == NULL);
+ g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
+ g->gckind = KGC_NORMAL;
+ sweepwholelist(L, &g->finobj);
+ sweepwholelist(L, &g->allgc);
+ sweepwholelist(L, &g->fixedgc); /* collect fixed objects */
+ lua_assert(g->strt.nuse == 0);
+}
+
+
+static l_mem atomic (lua_State *L) {
+ global_State *g = G(L);
+ l_mem work;
+ GCObject *origweak, *origall;
+ GCObject *grayagain = g->grayagain; /* save original list */
+ lua_assert(g->ephemeron == NULL && g->weak == NULL);
+ lua_assert(!iswhite(g->mainthread));
+ g->gcstate = GCSinsideatomic;
+ g->GCmemtrav = 0; /* start counting work */
+ markobject(g, L); /* mark running thread */
+ /* registry and global metatables may be changed by API */
+ markvalue(g, &g->l_registry);
+ markmt(g); /* mark global metatables */
+ /* remark occasional upvalues of (maybe) dead threads */
+ remarkupvals(g);
+ propagateall(g); /* propagate changes */
+ work = g->GCmemtrav; /* stop counting (do not recount 'grayagain') */
+ g->gray = grayagain;
+ propagateall(g); /* traverse 'grayagain' list */
+ g->GCmemtrav = 0; /* 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(g, 0); /* separate objects to be finalized */
+ g->gcfinnum = 1; /* there may be objects to be finalized */
+ markbeingfnz(g); /* mark objects that will be finalized */
+ propagateall(g); /* remark, to propagate 'resurrection' */
+ g->GCmemtrav = 0; /* 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);
+ luaS_clearcache(g);
+ g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
+ work += g->GCmemtrav; /* complete counting */
+ return work; /* estimate of memory marked by 'atomic' */
+}
+
+
+static lu_mem sweepstep (lua_State *L, global_State *g,
+ int nextstate, GCObject **nextlist) {
+ if (g->sweepgc) {
+ l_mem olddebt = g->GCdebt;
+ g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
+ g->GCestimate += g->GCdebt - olddebt; /* update estimate */
+ if (g->sweepgc) /* is there still something to sweep? */
+ return (GCSWEEPMAX * GCSWEEPCOST);
+ }
+ /* else enter next state */
+ g->gcstate = nextstate;
+ g->sweepgc = nextlist;
+ return 0;
+}
+
+
+static lu_mem singlestep (lua_State *L) {
+ global_State *g = G(L);
+ switch (g->gcstate) {
+ case GCSpause: {
+ g->GCmemtrav = g->strt.size * sizeof(GCObject*);
+ restartcollection(g);
+ g->gcstate = GCSpropagate;
+ return g->GCmemtrav;
+ }
+ case GCSpropagate: {
+ g->GCmemtrav = 0;
+ lua_assert(g->gray);
+ propagatemark(g);
+ if (g->gray == NULL) /* no more gray objects? */
+ g->gcstate = GCSatomic; /* finish propagate phase */
+ return g->GCmemtrav; /* memory traversed in this step */
+ }
+ case GCSatomic: {
+ lu_mem work;
+ propagateall(g); /* make sure gray list is empty */
+ work = atomic(L); /* work is what was traversed by 'atomic' */
+ entersweep(L);
+ g->GCestimate = gettotalbytes(g); /* first estimate */;
+ return work;
+ }
+ case GCSswpallgc: { /* sweep "regular" objects */
+ return sweepstep(L, g, GCSswpfinobj, &g->finobj);
+ }
+ case GCSswpfinobj: { /* sweep objects with finalizers */
+ return sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
+ }
+ case GCSswptobefnz: { /* sweep objects to be finalized */
+ return sweepstep(L, g, GCSswpend, NULL);
+ }
+ case GCSswpend: { /* finish sweeps */
+ makewhite(g, g->mainthread); /* sweep main thread */
+ checkSizes(L, g);
+ g->gcstate = GCScallfin;
+ return 0;
+ }
+ case GCScallfin: { /* call remaining finalizers */
+ if (g->tobefnz && g->gckind != KGC_EMERGENCY) {
+ int n = runafewfinalizers(L);
+ return (n * GCFINALIZECOST);
+ }
+ else { /* emergency mode or no more finalizers */
+ g->gcstate = GCSpause; /* finish collection */
+ return 0;
+ }
+ }
+ default: lua_assert(0); return 0;
+ }
+}
+
+
+/*
+** advances the garbage collector until it reaches a state allowed
+** by 'statemask'
+*/
+void luaC_runtilstate (lua_State *L, int statesmask) {
+ global_State *g = G(L);
+ while (!testbit(statesmask, g->gcstate))
+ singlestep(L);
+}
+
+
+/*
+** get GC debt and convert it from Kb to 'work units' (avoid zero debt
+** and overflows)
+*/
+static l_mem getdebt (global_State *g) {
+ l_mem debt = g->GCdebt;
+ int stepmul = g->gcstepmul;
+ if (debt <= 0) return 0; /* minimal debt */
+ else {
+ debt = (debt / STEPMULADJ) + 1;
+ debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
+ return debt;
+ }
+}
+
+/*
+** performs a basic GC step when collector is running
+*/
+void luaC_step (lua_State *L) {
+ global_State *g = G(L);
+ l_mem debt = getdebt(g); /* GC deficit (be paid now) */
+ if (!g->gcrunning) { /* not running? */
+ luaE_setdebt(g, -GCSTEPSIZE * 10); /* avoid being called too often */
+ return;
+ }
+ do { /* repeat until pause or enough "credit" (negative debt) */
+ lu_mem work = singlestep(L); /* perform one single step */
+ debt -= work;
+ } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
+ if (g->gcstate == GCSpause)
+ setpause(g); /* pause until next cycle */
+ else {
+ debt = (debt / g->gcstepmul) * STEPMULADJ; /* convert 'work units' to Kb */
+ luaE_setdebt(g, debt);
+ runafewfinalizers(L);
+ }
+}
+
+
+/*
+** Performs a full GC cycle; if 'isemergency', set a flag to avoid
+** some operations which could change the interpreter state in some
+** unexpected ways (running finalizers and shrinking some structures).
+** Before running the collection, check 'keepinvariant'; if it is true,
+** there may be some objects marked as black, so the collector has
+** to sweep all objects to turn them back to white (as white has not
+** changed, nothing will be collected).
+*/
+void luaC_fullgc (lua_State *L, int isemergency) {
+ global_State *g = G(L);
+ lua_assert(g->gckind == KGC_NORMAL);
+ if (isemergency) g->gckind = KGC_EMERGENCY; /* set flag */
+ if (keepinvariant(g)) { /* black objects? */
+ entersweep(L); /* sweep everything to turn them back to white */
+ }
+ /* 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(GCScallfin)); /* run up to finalizers */
+ /* estimate must be correct after a full GC cycle */
+ lua_assert(g->GCestimate == gettotalbytes(g));
+ luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */
+ g->gckind = KGC_NORMAL;
+ setpause(g);
+}
+
+/* }====================================================== */
+
+