/* ** $Id: lgc.h,v 2.91.1.1 2017/04/19 17:39:34 roberto Exp $ ** Garbage Collector ** See Copyright Notice in lua.h */ #ifndef lgc_h #define lgc_h #include "lobject.h" #include "lstate.h" /* ** Collectable objects may have one of three colors: white, which ** means the object is not marked; gray, which means the ** object is marked, but its references may be not marked; and ** black, which means that the object and all its references are marked. ** The main invariant of the garbage collector, while marking objects, ** is that a black object can never point to a white one. Moreover, ** any gray object must be in a "gray list" (gray, grayagain, weak, ** allweak, ephemeron) so that it can be visited again before finishing ** the collection cycle. These lists have no meaning when the invariant ** is not being enforced (e.g., sweep phase). */ /* how much to allocate before next GC step */ #if !defined(GCSTEPSIZE) /* ~100 small strings */ #define GCSTEPSIZE (cast_int(100 * sizeof(TString))) #endif /* ** Possible states of the Garbage Collector */ #define GCSpropagate 0 #define GCSatomic 1 #define GCSswpallgc 2 #define GCSswpfinobj 3 #define GCSswptobefnz 4 #define GCSswpend 5 #define GCScallfin 6 #define GCSpause 7 #define issweepphase(g) \ (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend) /* ** macro to tell when main invariant (white objects cannot point to black ** ones) must be kept. During a collection, the sweep ** phase may break the invariant, as objects turned white may point to ** still-black objects. The invariant is restored when sweep ends and ** all objects are white again. */ #define keepinvariant(g) ((g)->gcstate <= GCSatomic) /* ** some useful bit tricks */ #define resetbits(x,m) ((x) &= cast(lu_byte, ~(m))) #define setbits(x,m) ((x) |= (m)) #define testbits(x,m) ((x) & (m)) #define bitmask(b) (1<<(b)) #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) #define l_setbit(x,b) setbits(x, bitmask(b)) #define resetbit(x,b) resetbits(x, bitmask(b)) #define testbit(x,b) testbits(x, bitmask(b)) /* Layout for bit use in 'marked' field: */ #define WHITE0BIT 0 /* object is white (type 0) */ #define WHITE1BIT 1 /* object is white (type 1) */ #define BLACKBIT 2 /* object is black */ #define FINALIZEDBIT 3 /* object has been marked for finalization */ /* bit 7 is currently used by tests (luaL_checkmemory) */ #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) #define iswhite(x) testbits((x)->marked, WHITEBITS) #define isblack(x) testbit((x)->marked, BLACKBIT) #define isgray(x) /* neither white nor black */ \ (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT))) #define tofinalize(x) testbit((x)->marked, FINALIZEDBIT) #define otherwhite(g) ((g)->currentwhite ^ WHITEBITS) #define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow))) #define isdead(g,v) isdeadm(otherwhite(g), (v)->marked) #define changewhite(x) ((x)->marked ^= WHITEBITS) #define gray2black(x) l_setbit((x)->marked, BLACKBIT) #define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS) /* ** Does one step of collection when debt becomes positive. 'pre'/'pos' ** allows some adjustments to be done only when needed. macro ** 'condchangemem' is used only for heavy tests (forcing a full ** GC cycle on every opportunity) */ #define luaC_condGC(L,pre,pos) \ { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \ condchangemem(L,pre,pos); } /* more often than not, 'pre'/'pos' are empty */ #define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0) #define luaC_barrier(L,p,v) ( \ (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0)) #define luaC_barrierback(L,p,v) ( \ (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ luaC_barrierback_(L,p) : cast_void(0)) #define luaC_objbarrier(L,p,o) ( \ (isblack(p) && iswhite(o)) ? \ luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0)) #define luaC_upvalbarrier(L,uv) ( \ (iscollectable((uv)->v) && !upisopen(uv)) ? \ luaC_upvalbarrier_(L,uv) : cast_void(0)) LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o); LUAI_FUNC void luaC_freeallobjects (lua_State *L); LUAI_FUNC void luaC_step (lua_State *L); LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz); LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o); LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv); LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv); #endif