aboutsummaryrefslogtreecommitdiff
path: root/lua-5.3.5/lgc.h
blob: 425cd7cef34cba62df9067f7b0933c19826e6038 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
/*
** $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