The Battle for Wesnoth  1.15.1+dev
lgc.h
Go to the documentation of this file.
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 
134 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
136 LUAI_FUNC void luaC_step (lua_State *L);
137 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
138 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
139 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
145 
146 
147 #endif
Definition: lobject.h:497
#define LUAI_FUNC
Definition: luaconf.h:282
LUAI_FUNC void luaC_runtilstate(lua_State *L, int statesmask)
Definition: lgc.cpp:1104
LUAI_FUNC void luaC_fix(lua_State *L, GCObject *o)
Definition: lgc.cpp:194
LUAI_FUNC GCObject * luaC_newobj(lua_State *L, int tt, size_t sz)
Definition: lgc.cpp:208
LUAI_FUNC void luaC_step(lua_State *L)
Definition: lgc.cpp:1129
LUAI_FUNC void luaC_upvdeccount(lua_State *L, UpVal *uv)
Definition: lgc.cpp:678
LUAI_FUNC void luaC_checkfinalizer(lua_State *L, GCObject *o, Table *mt)
Definition: lgc.cpp:902
Definition: lfunc.h:35
LUAI_FUNC void luaC_freeallobjects(lua_State *L)
Definition: lgc.cpp:967
LUAI_FUNC void luaC_fullgc(lua_State *L, int isemergency)
Definition: lgc.cpp:1159
LUAI_FUNC void luaC_upvalbarrier_(lua_State *L, UpVal *uv)
Definition: lgc.cpp:185
LUAI_FUNC void luaC_barrierback_(lua_State *L, Table *o)
Definition: lgc.cpp:171
LUAI_FUNC void luaC_barrier_(lua_State *L, GCObject *o, GCObject *v)
Definition: lgc.cpp:155