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| 1 /* |
| 2 ** $Id: lgc.h,v 2.58 2012/09/11 12:53:08 roberto Exp $ |
| 3 ** Garbage Collector |
| 4 ** See Copyright Notice in lua.h |
| 5 */ |
| 6 |
| 7 #ifndef lgc_h |
| 8 #define lgc_h |
| 9 |
| 10 |
| 11 #include "lobject.h" |
| 12 #include "lstate.h" |
| 13 |
| 14 /* |
| 15 ** Collectable objects may have one of three colors: white, which |
| 16 ** means the object is not marked; gray, which means the |
| 17 ** object is marked, but its references may be not marked; and |
| 18 ** black, which means that the object and all its references are marked. |
| 19 ** The main invariant of the garbage collector, while marking objects, |
| 20 ** is that a black object can never point to a white one. Moreover, |
| 21 ** any gray object must be in a "gray list" (gray, grayagain, weak, |
| 22 ** allweak, ephemeron) so that it can be visited again before finishing |
| 23 ** the collection cycle. These lists have no meaning when the invariant |
| 24 ** is not being enforced (e.g., sweep phase). |
| 25 */ |
| 26 |
| 27 |
| 28 |
| 29 /* how much to allocate before next GC step */ |
| 30 #if !defined(GCSTEPSIZE) |
| 31 /* ~100 small strings */ |
| 32 #define GCSTEPSIZE (cast_int(100 * sizeof(TString))) |
| 33 #endif |
| 34 |
| 35 |
| 36 /* |
| 37 ** Possible states of the Garbage Collector |
| 38 */ |
| 39 #define GCSpropagate 0 |
| 40 #define GCSatomic 1 |
| 41 #define GCSsweepstring 2 |
| 42 #define GCSsweepudata 3 |
| 43 #define GCSsweep 4 |
| 44 #define GCSpause 5 |
| 45 |
| 46 |
| 47 #define issweepphase(g) \ |
| 48 (GCSsweepstring <= (g)->gcstate && (g)->gcstate <= GCSsweep) |
| 49 |
| 50 #define isgenerational(g) ((g)->gckind == KGC_GEN) |
| 51 |
| 52 /* |
| 53 ** macros to tell when main invariant (white objects cannot point to black |
| 54 ** ones) must be kept. During a non-generational collection, the sweep |
| 55 ** phase may break the invariant, as objects turned white may point to |
| 56 ** still-black objects. The invariant is restored when sweep ends and |
| 57 ** all objects are white again. During a generational collection, the |
| 58 ** invariant must be kept all times. |
| 59 */ |
| 60 |
| 61 #define keepinvariant(g) (isgenerational(g) || g->gcstate <= GCSatomic) |
| 62 |
| 63 |
| 64 /* |
| 65 ** Outside the collector, the state in generational mode is kept in |
| 66 ** 'propagate', so 'keepinvariant' is always true. |
| 67 */ |
| 68 #define keepinvariantout(g) \ |
| 69 check_exp(g->gcstate == GCSpropagate || !isgenerational(g), \ |
| 70 g->gcstate <= GCSatomic) |
| 71 |
| 72 |
| 73 /* |
| 74 ** some useful bit tricks |
| 75 */ |
| 76 #define resetbits(x,m) ((x) &= cast(lu_byte, ~(m))) |
| 77 #define setbits(x,m) ((x) |= (m)) |
| 78 #define testbits(x,m) ((x) & (m)) |
| 79 #define bitmask(b) (1<<(b)) |
| 80 #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) |
| 81 #define l_setbit(x,b) setbits(x, bitmask(b)) |
| 82 #define resetbit(x,b) resetbits(x, bitmask(b)) |
| 83 #define testbit(x,b) testbits(x, bitmask(b)) |
| 84 |
| 85 |
| 86 /* Layout for bit use in `marked' field: */ |
| 87 #define WHITE0BIT 0 /* object is white (type 0) */ |
| 88 #define WHITE1BIT 1 /* object is white (type 1) */ |
| 89 #define BLACKBIT 2 /* object is black */ |
| 90 #define FINALIZEDBIT 3 /* object has been separated for finalization */ |
| 91 #define SEPARATED 4 /* object is in 'finobj' list or in 'tobefnz' */ |
| 92 #define FIXEDBIT 5 /* object is fixed (should not be collected) */ |
| 93 #define OLDBIT 6 /* object is old (only in generational mode) */ |
| 94 /* bit 7 is currently used by tests (luaL_checkmemory) */ |
| 95 |
| 96 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) |
| 97 |
| 98 |
| 99 #define iswhite(x) testbits((x)->gch.marked, WHITEBITS) |
| 100 #define isblack(x) testbit((x)->gch.marked, BLACKBIT) |
| 101 #define isgray(x) /* neither white nor black */ \ |
| 102 (!testbits((x)->gch.marked, WHITEBITS | bitmask(BLACKBIT))) |
| 103 |
| 104 #define isold(x) testbit((x)->gch.marked, OLDBIT) |
| 105 |
| 106 /* MOVE OLD rule: whenever an object is moved to the beginning of |
| 107 a GC list, its old bit must be cleared */ |
| 108 #define resetoldbit(o) resetbit((o)->gch.marked, OLDBIT) |
| 109 |
| 110 #define otherwhite(g) (g->currentwhite ^ WHITEBITS) |
| 111 #define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow))) |
| 112 #define isdead(g,v) isdeadm(otherwhite(g), (v)->gch.marked) |
| 113 |
| 114 #define changewhite(x) ((x)->gch.marked ^= WHITEBITS) |
| 115 #define gray2black(x) l_setbit((x)->gch.marked, BLACKBIT) |
| 116 |
| 117 #define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x))) |
| 118 |
| 119 #define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS) |
| 120 |
| 121 |
| 122 #define luaC_condGC(L,c) \ |
| 123 {if (G(L)->GCdebt > 0) {c;}; condchangemem(L);} |
| 124 #define luaC_checkGC(L) luaC_condGC(L, luaC_step(L);) |
| 125 |
| 126 |
| 127 #define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \ |
| 128 luaC_barrier_(L,obj2gco(p),gcvalue(v)); } |
| 129 |
| 130 #define luaC_barrierback(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \ |
| 131 luaC_barrierback_(L,p); } |
| 132 |
| 133 #define luaC_objbarrier(L,p,o) \ |
| 134 { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \ |
| 135 luaC_barrier_(L,obj2gco(p),obj2gco(o)); } |
| 136 |
| 137 #define luaC_objbarrierback(L,p,o) \ |
| 138 { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) luaC_barrierback_(L,p); } |
| 139 |
| 140 #define luaC_barrierproto(L,p,c) \ |
| 141 { if (isblack(obj2gco(p))) luaC_barrierproto_(L,p,c); } |
| 142 |
| 143 LUAI_FUNC void luaC_freeallobjects (lua_State *L); |
| 144 LUAI_FUNC void luaC_step (lua_State *L); |
| 145 LUAI_FUNC void luaC_forcestep (lua_State *L); |
| 146 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); |
| 147 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); |
| 148 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, |
| 149 GCObject **list, int offset); |
| 150 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); |
| 151 LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o); |
| 152 LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c); |
| 153 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); |
| 154 LUAI_FUNC void luaC_checkupvalcolor (global_State *g, UpVal *uv); |
| 155 LUAI_FUNC void luaC_changemode (lua_State *L, int mode); |
| 156 |
| 157 #endif |
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