mirror of
https://github.com/lua/lua
synced 2024-11-21 20:31:22 +03:00
55ac40f859
Several definitions that don't need to be "global" (that is, that concerns only specific parts of the code) moved out of llimits.h, to more appropriate places.
258 lines
8.5 KiB
C
258 lines
8.5 KiB
C
/*
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** $Id: lgc.h $
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** Garbage Collector
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** See Copyright Notice in lua.h
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*/
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#ifndef lgc_h
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#define lgc_h
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#include <stddef.h>
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#include "lobject.h"
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#include "lstate.h"
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/*
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** Collectable objects may have one of three colors: white, which means
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** the object is not marked; gray, which means the object is marked, but
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** its references may be not marked; and black, which means that the
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** object and all its references are marked. The main invariant of the
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** garbage collector, while marking objects, is that a black object can
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** never point to a white one. Moreover, any gray object must be in a
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** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
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** can be visited again before finishing the collection cycle. (Open
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** upvalues are an exception to this rule.) These lists have no meaning
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** when the invariant is not being enforced (e.g., sweep phase).
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*/
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/*
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** Possible states of the Garbage Collector
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*/
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#define GCSpropagate 0
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#define GCSenteratomic 1
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#define GCSatomic 2
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#define GCSswpallgc 3
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#define GCSswpfinobj 4
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#define GCSswptobefnz 5
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#define GCSswpend 6
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#define GCScallfin 7
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#define GCSpause 8
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#define issweepphase(g) \
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(GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
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/*
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** macro to tell when main invariant (white objects cannot point to black
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** ones) must be kept. During a collection, the sweep
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** phase may break the invariant, as objects turned white may point to
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** still-black objects. The invariant is restored when sweep ends and
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** all objects are white again.
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*/
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#define keepinvariant(g) ((g)->gcstate <= GCSatomic)
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/*
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** some useful bit tricks
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*/
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#define resetbits(x,m) ((x) &= cast_byte(~(m)))
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#define setbits(x,m) ((x) |= (m))
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#define testbits(x,m) ((x) & (m))
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#define bitmask(b) (1<<(b))
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#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
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#define l_setbit(x,b) setbits(x, bitmask(b))
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#define resetbit(x,b) resetbits(x, bitmask(b))
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#define testbit(x,b) testbits(x, bitmask(b))
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/*
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** Layout for bit use in 'marked' field. First three bits are
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** used for object "age" in generational mode. Last bit is used
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** by tests.
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*/
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#define WHITE0BIT 3 /* object is white (type 0) */
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#define WHITE1BIT 4 /* object is white (type 1) */
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#define BLACKBIT 5 /* object is black */
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#define FINALIZEDBIT 6 /* object has been marked for finalization */
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#define TESTBIT 7
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#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
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#define iswhite(x) testbits((x)->marked, WHITEBITS)
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#define isblack(x) testbit((x)->marked, BLACKBIT)
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#define isgray(x) /* neither white nor black */ \
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(!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
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#define tofinalize(x) testbit((x)->marked, FINALIZEDBIT)
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#define otherwhite(g) ((g)->currentwhite ^ WHITEBITS)
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#define isdeadm(ow,m) ((m) & (ow))
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#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
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#define changewhite(x) ((x)->marked ^= WHITEBITS)
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#define nw2black(x) \
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check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
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#define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS)
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/* object age in generational mode */
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#define G_NEW 0 /* created in current cycle */
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#define G_SURVIVAL 1 /* created in previous cycle */
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#define G_OLD0 2 /* marked old by frw. barrier in this cycle */
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#define G_OLD1 3 /* first full cycle as old */
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#define G_OLD 4 /* really old object (not to be visited) */
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#define G_TOUCHED1 5 /* old object touched this cycle */
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#define G_TOUCHED2 6 /* old object touched in previous cycle */
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#define AGEBITS 7 /* all age bits (111) */
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#define getage(o) ((o)->marked & AGEBITS)
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#define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
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#define isold(o) (getage(o) > G_SURVIVAL)
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/*
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** In generational mode, objects are created 'new'. After surviving one
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** cycle, they become 'survival'. Both 'new' and 'survival' can point
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** to any other object, as they are traversed at the end of the cycle.
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** We call them both 'young' objects.
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** If a survival object survives another cycle, it becomes 'old1'.
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** 'old1' objects can still point to survival objects (but not to
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** new objects), so they still must be traversed. After another cycle
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** (that, being old, 'old1' objects will "survive" no matter what)
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** finally the 'old1' object becomes really 'old', and then they
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** are no more traversed.
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**
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** To keep its invariants, the generational mode uses the same barriers
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** also used by the incremental mode. If a young object is caught in a
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** forward barrier, it cannot become old immediately, because it can
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** still point to other young objects. Instead, it becomes 'old0',
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** which in the next cycle becomes 'old1'. So, 'old0' objects is
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** old but can point to new and survival objects; 'old1' is old
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** but cannot point to new objects; and 'old' cannot point to any
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** young object.
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**
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** If any old object ('old0', 'old1', 'old') is caught in a back
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** barrier, it becomes 'touched1' and goes into a gray list, to be
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** visited at the end of the cycle. There it evolves to 'touched2',
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** which can point to survivals but not to new objects. In yet another
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** cycle then it becomes 'old' again.
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**
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** The generational mode must also control the colors of objects,
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** because of the barriers. While the mutator is running, young objects
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** are kept white. 'old', 'old1', and 'touched2' objects are kept black,
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** as they cannot point to new objects; exceptions are threads and open
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** upvalues, which age to 'old1' and 'old' but are kept gray. 'old0'
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** objects may be gray or black, as in the incremental mode. 'touched1'
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** objects are kept gray, as they must be visited again at the end of
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** the cycle.
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*/
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/* Default Values for GC parameters */
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/*
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** Minor collections will shift to major ones after LUAI_MINORMAJOR%
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** objects become old.
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*/
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#define LUAI_MINORMAJOR 100
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/*
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** Major collections will shift to minor ones after a collection
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** collects at least LUAI_MAJORMINOR% of the new objects.
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*/
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#define LUAI_MAJORMINOR 50
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/*
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** A young (minor) collection will run after creating LUAI_GENMINORMUL%
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** new objects.
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*/
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#define LUAI_GENMINORMUL 25
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/* incremental */
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/* Number of objects must be LUAI_GCPAUSE% before starting new cycle */
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#define LUAI_GCPAUSE 200
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/* Step multiplier. (Roughly, the collector handles LUAI_GCMUL% objects
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for each new allocated object.) */
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#define LUAI_GCMUL 200
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/* How many objects to allocate before next GC step */
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#define LUAI_GCSTEPSIZE 250
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#define setgcparam(g,p,v) (g->gcparams[LUA_GCP##p] = luaO_codeparam(v))
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#define applygcparam(g,p,x) luaO_applyparam(g->gcparams[LUA_GCP##p], x)
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/*
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** Control when GC is running:
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*/
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#define GCSTPUSR 1 /* bit true when GC stopped by user */
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#define GCSTPGC 2 /* bit true when GC stopped by itself */
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#define GCSTPCLS 4 /* bit true when closing Lua state */
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#define gcrunning(g) ((g)->gcstp == 0)
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/*
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** Does one step of collection when debt becomes zero. 'pre'/'pos'
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** allows some adjustments to be done only when needed. macro
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** 'condchangemem' is used only for heavy tests (forcing a full
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** GC cycle on every opportunity)
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*/
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#if !defined(HARDMEMTESTS)
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#define condchangemem(L,pre,pos) ((void)0)
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#else
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#define condchangemem(L,pre,pos) \
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{ if (gcrunning(G(L))) { pre; luaC_fullgc(L, 0); pos; } }
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#endif
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#define luaC_condGC(L,pre,pos) \
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{ if (G(L)->GCdebt <= 0) { pre; luaC_step(L); pos;}; \
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condchangemem(L,pre,pos); }
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/* more often than not, 'pre'/'pos' are empty */
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#define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
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#define luaC_objbarrier(L,p,o) ( \
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(isblack(p) && iswhite(o)) ? \
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luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
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#define luaC_barrier(L,p,v) ( \
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iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0))
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#define luaC_objbarrierback(L,p,o) ( \
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(isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0))
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#define luaC_barrierback(L,p,v) ( \
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iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : cast_void(0))
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LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
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LUAI_FUNC void luaC_freeallobjects (lua_State *L);
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LUAI_FUNC void luaC_step (lua_State *L);
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LUAI_FUNC void luaC_runtilstate (lua_State *L, int state, int fast);
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LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
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LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
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LUAI_FUNC GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz,
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size_t offset);
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LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
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LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
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LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
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LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
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#endif
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