mirror of
https://github.com/lua/lua
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167 lines
5.2 KiB
C
167 lines
5.2 KiB
C
/*
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** $Id: lgc.h,v 2.95 2017/04/10 13:33:04 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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#ifndef lgc_h
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#define lgc_h
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#include "lobject.h"
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#include "lstate.h"
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/*
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** Collectable objects may have one of three colors: white, which
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** means the object is not marked; gray, which means the
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** object is marked, but its references may be not marked; and
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** black, which means that the object and all its references are marked.
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** The main invariant of the garbage collector, while marking objects,
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** is that a black object can never point to a white one. Moreover,
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** any gray object must be in a "gray list" (gray, grayagain, weak,
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** allweak, ephemeron) so that it can be visited again before finishing
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** the collection cycle. These lists have no meaning when the invariant
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** is not being enforced (e.g., sweep phase).
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*/
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/* how much to allocate before next GC step */
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#if !defined(GCSTEPSIZE)
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/* ~100 small strings */
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#define GCSTEPSIZE (cast_int(100 * sizeof(TString)))
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#endif
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/*
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** Possible states of the Garbage Collector
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*/
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#define GCSpropagate 0
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#define GCSenteratomic 1
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#define GCSatomic 2
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#define GCSswpallgc 3
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#define GCSswpfinobj 4
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#define GCSswptobefnz 5
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#define GCSswpend 6
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#define GCScallfin 7
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#define GCSpause 8
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#define issweepphase(g) \
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(GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
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/*
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** macro to tell when main invariant (white objects cannot point to black
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** ones) must be kept. During a collection, the sweep
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** phase may break the invariant, as objects turned white may point to
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** still-black objects. The invariant is restored when sweep ends and
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** all objects are white again.
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*/
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#define keepinvariant(g) ((g)->gcstate <= GCSatomic)
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/*
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** some useful bit tricks
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*/
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#define resetbits(x,m) ((x) &= cast(lu_byte, ~(m)))
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#define setbits(x,m) ((x) |= (m))
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#define testbits(x,m) ((x) & (m))
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#define bitmask(b) (1<<(b))
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#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
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#define l_setbit(x,b) setbits(x, bitmask(b))
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#define resetbit(x,b) resetbits(x, bitmask(b))
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#define testbit(x,b) testbits(x, bitmask(b))
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/*
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** Layout for bit use in 'marked' field. First three bits are
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** used for object "age" in generational mode.
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*/
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#define WHITE0BIT 3 /* object is white (type 0) */
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#define WHITE1BIT 4 /* object is white (type 1) */
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#define BLACKBIT 5 /* object is black */
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#define FINALIZEDBIT 6 /* object has been marked for finalization */
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#define TESTGRAYBIT 7 /* used by tests (luaL_checkmemory) */
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#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
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#define iswhite(x) testbits((x)->marked, WHITEBITS)
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#define isblack(x) testbit((x)->marked, BLACKBIT)
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#define isgray(x) /* neither white nor black */ \
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(!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
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#define tofinalize(x) testbit((x)->marked, FINALIZEDBIT)
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#define otherwhite(g) ((g)->currentwhite ^ WHITEBITS)
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#define isdeadm(ow,m) ((m) & (ow))
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#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
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#define changewhite(x) ((x)->marked ^= WHITEBITS)
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#define gray2black(x) l_setbit((x)->marked, BLACKBIT)
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#define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS)
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/* object age in generational mode */
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#define G_NEW 0 /* created in current cycle */
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#define G_SURVIVAL 1 /* created in previous cycle */
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#define G_OLD0 2 /* marked old by frw. barrier in this cycle */
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#define G_OLD1 3 /* first full cycle as old */
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#define G_OLD 4 /* really old object (not to be visited) */
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#define G_TOUCHED1 5 /* old object touched this cycle */
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#define G_TOUCHED2 6 /* old object touched in previous cycle */
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#define AGEBITS 7 /* all age bits (111) */
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#define getage(o) ((o)->marked & AGEBITS)
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#define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
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#define isold(o) (getage(o) > G_SURVIVAL)
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#define changeage(o,f,t) \
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check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))
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/*
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** Does one step of collection when debt becomes positive. 'pre'/'pos'
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** allows some adjustments to be done only when needed. macro
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** 'condchangemem' is used only for heavy tests (forcing a full
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** GC cycle on every opportunity)
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*/
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#define luaC_condGC(L,pre,pos) \
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{ if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
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condchangemem(L,pre,pos); }
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/* more often than not, 'pre'/'pos' are empty */
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#define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
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#define luaC_barrier(L,p,v) ( \
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(iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
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luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
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#define luaC_barrierback(L,p,v) ( \
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(iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
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luaC_barrierback_(L,p) : cast_void(0))
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#define luaC_objbarrier(L,p,o) ( \
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(isblack(p) && iswhite(o)) ? \
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luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
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LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
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LUAI_FUNC void luaC_freeallobjects (lua_State *L);
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LUAI_FUNC void luaC_step (lua_State *L);
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LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
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LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
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LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
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LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
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LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o);
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LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
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LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
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#endif
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