1/*
2** $Id: lgc.h,v 2.91.1.1 2017/04/19 17:39:34 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 GCSswpallgc 2
42#define GCSswpfinobj 3
43#define GCSswptobefnz 4
44#define GCSswpend 5
45#define GCScallfin 6
46#define GCSpause 7
47
48
49#define issweepphase(g) \
50 (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
51
52
53/*
54** macro to tell when main invariant (white objects cannot point to black
55** ones) must be kept. During a collection, the sweep
56** phase may break the invariant, as objects turned white may point to
57** still-black objects. The invariant is restored when sweep ends and
58** all objects are white again.
59*/
60
61#define keepinvariant(g) ((g)->gcstate <= GCSatomic)
62
63
64/*
65** some useful bit tricks
66*/
67#define resetbits(x,m) ((x) &= cast(lu_byte, ~(m)))
68#define setbits(x,m) ((x) |= (m))
69#define testbits(x,m) ((x) & (m))
70#define bitmask(b) (1<<(b))
71#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
72#define l_setbit(x,b) setbits(x, bitmask(b))
73#define resetbit(x,b) resetbits(x, bitmask(b))
74#define testbit(x,b) testbits(x, bitmask(b))
75
76
77/* Layout for bit use in 'marked' field: */
78#define WHITE0BIT 0 /* object is white (type 0) */
79#define WHITE1BIT 1 /* object is white (type 1) */
80#define BLACKBIT 2 /* object is black */
81#define FINALIZEDBIT 3 /* object has been marked for finalization */
82/* bit 7 is currently used by tests (luaL_checkmemory) */
83
84#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
85
86
87#define iswhite(x) testbits((x)->marked, WHITEBITS)
88#define isblack(x) testbit((x)->marked, BLACKBIT)
89#define isgray(x) /* neither white nor black */ \
90 (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
91
92#define tofinalize(x) testbit((x)->marked, FINALIZEDBIT)
93
94#define otherwhite(g) ((g)->currentwhite ^ WHITEBITS)
95#define isdeadm(ow,m) (!(((m) ^ WHITEBITS) & (ow)))
96#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
97
98#define changewhite(x) ((x)->marked ^= WHITEBITS)
99#define gray2black(x) l_setbit((x)->marked, BLACKBIT)
100
101#define luaC_white(g) cast(lu_byte, (g)->currentwhite & WHITEBITS)
102
103
104/*
105** Does one step of collection when debt becomes positive. 'pre'/'pos'
106** allows some adjustments to be done only when needed. macro
107** 'condchangemem' is used only for heavy tests (forcing a full
108** GC cycle on every opportunity)
109*/
110#define luaC_condGC(L,pre,pos) \
111 { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
112 condchangemem(L,pre,pos); }
113
114/* more often than not, 'pre'/'pos' are empty */
115#define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
116
117
118#define luaC_barrier(L,p,v) ( \
119 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
120 luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
121
122#define luaC_barrierback(L,p,v) ( \
123 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
124 luaC_barrierback_(L,p) : cast_void(0))
125
126#define luaC_objbarrier(L,p,o) ( \
127 (isblack(p) && iswhite(o)) ? \
128 luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
129
130#define luaC_upvalbarrier(L,uv) ( \
131 (iscollectable((uv)->v) && !upisopen(uv)) ? \
132 luaC_upvalbarrier_(L,uv) : cast_void(0))
133
134LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
135LUAI_FUNC void luaC_freeallobjects (lua_State *L);
136LUAI_FUNC void luaC_step (lua_State *L);
137LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
138LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
139LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
140LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
141LUAI_FUNC void luaC_barrierback_ (lua_State *L, Table *o);
142LUAI_FUNC void luaC_upvalbarrier_ (lua_State *L, UpVal *uv);
143LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
144LUAI_FUNC void luaC_upvdeccount (lua_State *L, UpVal *uv);
145
146
147#endif
148