mirror of
https://github.com/lua/lua
synced 2024-09-30 05:39:22 +02:00
395 lines
9.2 KiB
C
395 lines
9.2 KiB
C
/*
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** $Id: lgc.c,v 1.88 2001/02/07 18:13:49 roberto Exp roberto $
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** Garbage Collector
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** See Copyright Notice in lua.h
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*/
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#include "lua.h"
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#include "ldo.h"
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#include "lfunc.h"
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#include "lgc.h"
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#include "lmem.h"
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#include "lobject.h"
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#include "lstate.h"
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#include "lstring.h"
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#include "ltable.h"
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#include "ltm.h"
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/*
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** optional "lock" for GC
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** (when Lua calls GC tag methods it unlocks the regular lock)
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*/
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#ifndef LUA_LOCKGC
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#define LUA_LOCKGC(L) {
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#endif
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#ifndef LUA_UNLOCKGC
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#define LUA_UNLOCKGC(L) }
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#endif
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typedef struct GCState {
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Hash *tmark; /* list of marked tables to be visited */
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Closure *cmark; /* list of marked closures to be visited */
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} GCState;
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static void markobject (GCState *st, TObject *o);
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/* mark a string; marks larger than 1 cannot be changed */
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#define strmark(s) {if ((s)->marked == 0) (s)->marked = 1;}
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static void protomark (Proto *f) {
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if (!f->marked) {
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int i;
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f->marked = 1;
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strmark(f->source);
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for (i=0; i<f->sizekstr; i++)
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strmark(f->kstr[i]);
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for (i=0; i<f->sizekproto; i++)
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protomark(f->kproto[i]);
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for (i=0; i<f->sizelocvars; i++) /* mark local-variable names */
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strmark(f->locvars[i].varname);
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}
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}
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static void markclosure (GCState *st, Closure *cl) {
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if (!ismarked(cl)) {
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if (!cl->isC)
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protomark(cl->f.l);
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cl->mark = st->cmark; /* chain it for later traversal */
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st->cmark = cl;
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}
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}
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static void marktable (GCState *st, Hash *h) {
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if (!ismarked(h)) {
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h->mark = st->tmark; /* chain it in list of marked */
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st->tmark = h;
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}
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}
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static void markobject (GCState *st, TObject *o) {
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switch (ttype(o)) {
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case LUA_TUSERDATA: case LUA_TSTRING:
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strmark(tsvalue(o));
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break;
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case LUA_TMARK:
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markclosure(st, infovalue(o)->func);
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break;
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case LUA_TFUNCTION:
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markclosure(st, clvalue(o));
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break;
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case LUA_TTABLE: {
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marktable(st, hvalue(o));
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break;
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}
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default: break; /* numbers, etc */
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}
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}
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static void markstacks (lua_State *L, GCState *st) {
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lua_State *L1 = L;
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do { /* for each thread */
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StkId o, lim;
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marktable(st, L1->gt); /* mark table of globals */
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for (o=L1->stack; o<L1->top; o++)
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markobject(st, o);
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lim = (L1->stack_last - L1->top > MAXSTACK) ? L1->top+MAXSTACK
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: L1->stack_last;
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for (; o<=lim; o++) setnilvalue(o);
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lua_assert(L1->previous->next == L1 && L1->next->previous == L1);
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L1 = L1->next;
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} while (L1 != L);
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}
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static void marklock (global_State *G, GCState *st) {
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int i;
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for (i=0; i<G->nref; i++) {
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if (G->refArray[i].st == LOCK)
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markobject(st, &G->refArray[i].o);
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}
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}
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static void marktagmethods (global_State *G, GCState *st) {
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int t;
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for (t=0; t<G->ntag; t++) {
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struct TM *tm = &G->TMtable[t];
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int e;
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if (tm->name) strmark(tm->name);
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for (e=0; e<TM_N; e++) {
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Closure *cl = tm->method[e];
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if (cl) markclosure(st, cl);
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}
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}
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}
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static void traverseclosure (GCState *st, Closure *f) {
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int i;
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for (i=0; i<f->nupvalues; i++) /* mark its upvalues */
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markobject(st, &f->upvalue[i]);
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}
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static void traversetable (GCState *st, Hash *h) {
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int i;
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for (i=0; i<h->size; i++) {
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Node *n = node(h, i);
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if (ttype(val(n)) == LUA_TNIL) {
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if (ttype_key(n) != LUA_TNIL)
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n->key_value.ts = NULL; /* dead key; remove it */
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}
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else {
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lua_assert(ttype_key(n) != LUA_TNIL);
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if (ttype_key(n) != LUA_TNUMBER) {
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TObject o;
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setkey2obj(&o, n);
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markobject(st, &o);
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}
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markobject(st, &n->val);
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}
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}
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}
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static void markall (lua_State *L) {
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GCState st;
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st.cmark = NULL;
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st.tmark = NULL;
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marktagmethods(G(L), &st); /* mark tag methods */
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markstacks(L, &st); /* mark all stacks */
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marklock(G(L), &st); /* mark locked objects */
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marktable(&st, G(L)->type2tag);
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for (;;) { /* mark tables and closures */
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if (st.cmark) {
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Closure *f = st.cmark; /* get first closure from list */
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st.cmark = f->mark; /* remove it from list */
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traverseclosure(&st, f);
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}
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else if (st.tmark) {
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Hash *h = st.tmark; /* get first table from list */
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st.tmark = h->mark; /* remove it from list */
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traversetable(&st, h);
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}
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else break; /* nothing else to mark */
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}
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}
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static int hasmark (const TObject *o) {
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/* valid only for locked objects */
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switch (ttype(o)) {
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case LUA_TSTRING: case LUA_TUSERDATA:
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return tsvalue(o)->marked;
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case LUA_TTABLE:
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return ismarked(hvalue(o));
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case LUA_TFUNCTION:
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return ismarked(clvalue(o));
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default: /* number */
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return 1;
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}
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}
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/* macro for internal debugging; check if a link of free refs is valid */
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#define VALIDLINK(L, st,n) (NONEXT <= (st) && (st) < (n))
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static void invalidaterefs (global_State *G) {
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int n = G->nref;
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int i;
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for (i=0; i<n; i++) {
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struct Ref *r = &G->refArray[i];
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if (r->st == HOLD && !hasmark(&r->o))
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r->st = COLLECTED;
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lua_assert((r->st == LOCK && hasmark(&r->o)) ||
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(r->st == HOLD && hasmark(&r->o)) ||
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r->st == COLLECTED ||
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r->st == NONEXT ||
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(r->st < n && VALIDLINK(L, G->refArray[r->st].st, n)));
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}
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lua_assert(VALIDLINK(L, G->refFree, n));
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}
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static void collectproto (lua_State *L) {
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Proto **p = &G(L)->rootproto;
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Proto *next;
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while ((next = *p) != NULL) {
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if (next->marked) {
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next->marked = 0;
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p = &next->next;
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}
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else {
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*p = next->next;
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luaF_freeproto(L, next);
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}
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}
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}
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static void collectclosure (lua_State *L) {
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Closure **p = &G(L)->rootcl;
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Closure *next;
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while ((next = *p) != NULL) {
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if (ismarked(next)) {
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next->mark = next; /* unmark */
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p = &next->next;
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}
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else {
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*p = next->next;
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luaF_freeclosure(L, next);
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}
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}
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}
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static void collecttable (lua_State *L) {
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Hash **p = &G(L)->roottable;
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Hash *next;
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while ((next = *p) != NULL) {
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if (ismarked(next)) {
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next->mark = next; /* unmark */
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p = &next->next;
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}
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else {
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*p = next->next;
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luaH_free(L, next);
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}
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}
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}
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static void checktab (lua_State *L, stringtable *tb) {
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if (tb->nuse < (ls_nstr)(tb->size/4) && tb->size > MINPOWER2)
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luaS_resize(L, tb, tb->size/2); /* table is too big */
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}
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static void collectstrings (lua_State *L, int all) {
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int i;
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for (i=0; i<G(L)->strt.size; i++) { /* for each list */
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TString **p = &G(L)->strt.hash[i];
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TString *next;
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while ((next = *p) != NULL) {
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if (next->marked && !all) { /* preserve? */
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if (next->marked < FIXMARK) /* does not change FIXMARKs */
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next->marked = 0;
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p = &next->nexthash;
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}
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else { /* collect */
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*p = next->nexthash;
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G(L)->strt.nuse--;
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luaM_free(L, next, sizestring(next->len));
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}
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}
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}
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checktab(L, &G(L)->strt);
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}
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static void collectudata (lua_State *L, int all) {
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int i;
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for (i=0; i<G(L)->udt.size; i++) { /* for each list */
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TString **p = &G(L)->udt.hash[i];
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TString *next;
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while ((next = *p) != NULL) {
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lua_assert(next->marked <= 1);
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if (next->marked && !all) { /* preserve? */
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next->marked = 0;
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p = &next->nexthash;
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}
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else { /* collect */
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int tag = next->u.d.tag;
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*p = next->nexthash;
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next->nexthash = G(L)->TMtable[tag].collected; /* chain udata */
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G(L)->TMtable[tag].collected = next;
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G(L)->udt.nuse--;
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}
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}
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}
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checktab(L, &G(L)->udt);
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}
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#define MINBUFFER 256
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static void checkMbuffer (lua_State *L) {
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if (G(L)->Mbuffsize > MINBUFFER*2) { /* is buffer too big? */
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size_t newsize = G(L)->Mbuffsize/2; /* still larger than MINBUFFER */
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luaM_reallocvector(L, G(L)->Mbuffer, G(L)->Mbuffsize, newsize, char);
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G(L)->Mbuffsize = newsize;
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}
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}
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static void callgcTM (lua_State *L, const TObject *obj) {
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Closure *tm = luaT_gettmbyObj(G(L), obj, TM_GC);
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if (tm != NULL) {
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int oldah = L->allowhooks;
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L->allowhooks = 0; /* stop debug hooks during GC tag methods */
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luaD_checkstack(L, 2);
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setclvalue(L->top, tm);
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setobj(L->top+1, obj);
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L->top += 2;
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luaD_call(L, L->top-2, 0);
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L->allowhooks = oldah; /* restore hooks */
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}
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}
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static void callgcTMudata (lua_State *L) {
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int tag;
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G(L)->GCthreshold = 2*G(L)->nblocks; /* avoid GC during tag methods */
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for (tag=G(L)->ntag-1; tag>=0; tag--) { /* for each tag (in reverse order) */
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TString *udata;
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while ((udata = G(L)->TMtable[tag].collected) != NULL) {
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TObject obj;
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G(L)->TMtable[tag].collected = udata->nexthash; /* remove it from list */
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setuvalue(&obj, udata);
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callgcTM(L, &obj);
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luaM_free(L, udata, sizeudata(udata->len));
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}
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}
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}
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void luaC_collect (lua_State *L, int all) {
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LUA_LOCKGC(L);
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collectudata(L, all);
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callgcTMudata(L);
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collectstrings(L, all);
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collecttable(L);
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collectproto(L);
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collectclosure(L);
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LUA_UNLOCKGC(L);
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}
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void luaC_collectgarbage (lua_State *L) {
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markall(L);
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invalidaterefs(G(L)); /* check unlocked references */
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luaC_collect(L, 0);
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checkMbuffer(L);
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G(L)->GCthreshold = 2*G(L)->nblocks; /* set new threshold */
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callgcTM(L, &luaO_nilobject);
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}
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void luaC_checkGC (lua_State *L) {
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if (G(L)->nblocks >= G(L)->GCthreshold)
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luaC_collectgarbage(L);
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}
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