lua/lstate.h

/*
** $Id: lstate.h $
** Global State
** See Copyright Notice in lua.h
*/

#ifndef lstate_h
#define lstate_h

#include "lua.h"

#include "lobject.h"
#include "ltm.h"
#include "lzio.h"


/*
** Some notes about garbage-collected objects: All objects in Lua must
** be kept somehow accessible until being freed, so all objects always
** belong to one (and only one) of these lists, using field 'next' of
** the 'CommonHeader' for the link:
**
** 'allgc': all objects not marked for finalization;
** 'finobj': all objects marked for finalization;
** 'tobefnz': all objects ready to be finalized;
** 'fixedgc': all objects that are not to be collected (currently
** only small strings, such as reserved words).
**
** For the generational collector, some of these lists have marks for
** generations. Each mark points to the first element in the list for
** that particular generation; that generation goes until the next mark.
**
** 'allgc' -> 'survival': new objects;
** 'survival' -> 'old': objects that survived one collection;
** 'old1' -> 'reallyold': objects that became old in last collection;
** 'reallyold' -> NULL: objects old for more than one cycle.
**
** 'finobj' -> 'finobjsur': new objects marked for finalization;
** 'finobjsur' -> 'finobjold1': survived   """";
** 'finobjold1' -> 'finobjrold': just old  """";
** 'finobjrold' -> NULL: really old       """".
**
** All lists can contain elements older than their main ages, due
** to 'luaC_checkfinalizer' and 'udata2finalize', which move
** objects between the normal lists and the "marked for finalization"
** lists. Moreover, barriers can age young objects in young lists as
** OLD0, which then become OLD1. However, a list never contains
** elements younger than their main ages.
**
** The generational collector also uses a pointer 'firstold1', which
** points to the first OLD1 object in the list. It is used to optimize
** 'markold'. (Potentially OLD1 objects can be anywhere between 'allgc'
** and 'reallyold', but often the list has no OLD1 objects or they are
** after 'old1'.) Note the difference between it and 'old1':
** 'firstold1': no OLD1 objects before this point; there can be all
**   ages after it.
** 'old1': no objects younger than OLD1 after this point.
*/

/*
** Moreover, there is another set of lists that control gray objects.
** These lists are linked by fields 'gclist'. (All objects that
** can become gray have such a field. The field is not the same
** in all objects, but it always has this name.)  Any gray object
** must belong to one of these lists, and all objects in these lists
** must be gray (with one exception explained below):
**
** 'gray': regular gray objects, still waiting to be visited.
** 'grayagain': objects that must be revisited at the atomic phase.
**   That includes
**   - black objects got in a write barrier;
**   - all kinds of weak tables during propagation phase;
**   - all threads.
** 'weak': tables with weak values to be cleared;
** 'ephemeron': ephemeron tables with white->white entries;
** 'allweak': tables with weak keys and/or weak values to be cleared.
**
** The exception to that "gray rule" is the TOUCHED2 objects in
** generational mode. Those objects stay in a gray list (because they
** must be visited again at the end of the cycle), but they are marked
** black (because assignments to them must activate barriers, to move
** them back to TOUCHED1).
*/



/*
** About 'nCcalls': each thread in Lua (a lua_State) keeps a count of
** how many "C calls" it still can do in the C stack, to avoid C-stack
** overflow.  This count is very rough approximation; it considers only
** recursive functions inside the interpreter, as non-recursive calls
** can be considered using a fixed (although unknown) amount of stack
** space.
**
** The count has two parts: the lower part is the count itself; the
** higher part counts the number of non-yieldable calls in the stack.
** (They are together so that we can change both with one instruction.)
**
** Because calls to external C functions can use an unknown amount
** of space (e.g., functions using an auxiliary buffer), calls
** to these functions add more than one to the count (see CSTACKCF).
**
** The proper count excludes the number of CallInfo structures allocated
** by Lua, as a kind of "potential" calls. So, when Lua calls a function
** (and "consumes" one CallInfo), it needs neither to decrement nor to
** check 'nCcalls', as its use of C stack is already accounted for.
*/

/* number of "C stack slots" used by an external C function */
#define CSTACKCF	10


/*
** The C-stack size is sliced in the following zones:
** - larger than CSTACKERR: normal stack;
** - [CSTACKMARK, CSTACKERR]: buffer zone to signal a stack overflow;
** - [CSTACKCF, CSTACKERRMARK]: error-handling zone;
** - below CSTACKERRMARK: buffer zone to signal overflow during overflow;
** (Because the counter can be decremented CSTACKCF at once, we need
** the so called "buffer zones", with at least that size, to properly
** detect a change from one zone to the next.)
*/
#define CSTACKERR	(8 * CSTACKCF)
#define CSTACKMARK	(CSTACKERR - (CSTACKCF + 2))
#define CSTACKERRMARK	(CSTACKCF + 2)


/* initial limit for the C-stack of threads */
#define CSTACKTHREAD	(2 * CSTACKERR)


/* true if this thread does not have non-yieldable calls in the stack */
#define yieldable(L)		(((L)->nCcalls & 0xffff0000) == 0)

/* real number of C calls */
#define getCcalls(L)	((L)->nCcalls & 0xffff)


/* Increment the number of non-yieldable calls */
#define incnny(L)	((L)->nCcalls += 0x10000)

/* Decrement the number of non-yieldable calls */
#define decnny(L)	((L)->nCcalls -= 0x10000)

/* Increment the number of non-yieldable calls and decrement nCcalls */
#define incXCcalls(L)	((L)->nCcalls += 0x10000 - CSTACKCF)

/* Decrement the number of non-yieldable calls and increment nCcalls */
#define decXCcalls(L)	((L)->nCcalls -= 0x10000 - CSTACKCF)






struct lua_longjmp;  /* defined in ldo.c */


/*
** Atomic type (relative to signals) to better ensure that 'lua_sethook'
** is thread safe
*/
#if !defined(l_signalT)
#include <signal.h>
#define l_signalT	sig_atomic_t
#endif


/* extra stack space to handle TM calls and some other extras */
#define EXTRA_STACK   5


#define BASIC_STACK_SIZE        (2*LUA_MINSTACK)


/* kinds of Garbage Collection */
#define KGC_INC		0	/* incremental gc */
#define KGC_GEN		1	/* generational gc */


typedef struct stringtable {
  TString **hash;
  int nuse;  /* number of elements */
  int size;
} stringtable;


/*
** Information about a call.
*/
typedef struct CallInfo {
  StkId func;  /* function index in the stack */
  StkId	top;  /* top for this function */
  struct CallInfo *previous, *next;  /* dynamic call link */
  union {
    struct {  /* only for Lua functions */
      const Instruction *savedpc;
      volatile l_signalT trap;
      int nextraargs;  /* # of extra arguments in vararg functions */
    } l;
    struct {  /* only for C functions */
      lua_KFunction k;  /* continuation in case of yields */
      ptrdiff_t old_errfunc;
      lua_KContext ctx;  /* context info. in case of yields */
    } c;
  } u;
  union {
    int funcidx;  /* called-function index */
    int nyield;  /* number of values yielded */
    struct {  /* info about transferred values (for call/return hooks) */
      unsigned short ftransfer;  /* offset of first value transferred */
      unsigned short ntransfer;  /* number of values transferred */
    } transferinfo;
  } u2;
  short nresults;  /* expected number of results from this function */
  unsigned short callstatus;
} CallInfo;


/*
** Bits in CallInfo status
*/
#define CIST_OAH	(1<<0)	/* original value of 'allowhook' */
#define CIST_C		(1<<1)	/* call is running a C function */
#define CIST_HOOKED	(1<<2)	/* call is running a debug hook */
#define CIST_YPCALL	(1<<3)	/* call is a yieldable protected call */
#define CIST_TAIL	(1<<4)	/* call was tail called */
#define CIST_HOOKYIELD	(1<<5)	/* last hook called yielded */
#define CIST_FIN	(1<<6)  /* call is running a finalizer */
#define CIST_TRAN	(1<<7)	/* 'ci' has transfer information */
#if defined(LUA_COMPAT_LT_LE)
#define CIST_LEQ	(1<<8)  /* using __lt for __le */
#endif

/* active function is a Lua function */
#define isLua(ci)	(!((ci)->callstatus & CIST_C))

/* call is running Lua code (not a hook) */
#define isLuacode(ci)	(!((ci)->callstatus & (CIST_C | CIST_HOOKED)))

/* assume that CIST_OAH has offset 0 and that 'v' is strictly 0/1 */
#define setoah(st,v)	((st) = ((st) & ~CIST_OAH) | (v))
#define getoah(st)	((st) & CIST_OAH)


/*
** 'global state', shared by all threads of this state
*/
typedef struct global_State {
  lua_Alloc frealloc;  /* function to reallocate memory */
  void *ud;         /* auxiliary data to 'frealloc' */
  l_mem totalbytes;  /* number of bytes currently allocated - GCdebt */
  l_mem GCdebt;  /* bytes allocated not yet compensated by the collector */
  lu_mem GCestimate;  /* an estimate of the non-garbage memory in use */
  lu_mem lastatomic;  /* see function 'genstep' in file 'lgc.c' */
  stringtable strt;  /* hash table for strings */
  TValue l_registry;
  TValue nilvalue;  /* a nil value */
  unsigned int seed;  /* randomized seed for hashes */
  lu_byte currentwhite;
  lu_byte gcstate;  /* state of garbage collector */
  lu_byte gckind;  /* kind of GC running */
  lu_byte genminormul;  /* control for minor generational collections */
  lu_byte genmajormul;  /* control for major generational collections */
  lu_byte gcrunning;  /* true if GC is running */
  lu_byte gcemergency;  /* true if this is an emergency collection */
  lu_byte gcpause;  /* size of pause between successive GCs */
  lu_byte gcstepmul;  /* GC "speed" */
  lu_byte gcstepsize;  /* (log2 of) GC granularity */
  GCObject *allgc;  /* list of all collectable objects */
  GCObject **sweepgc;  /* current position of sweep in list */
  GCObject *finobj;  /* list of collectable objects with finalizers */
  GCObject *gray;  /* list of gray objects */
  GCObject *grayagain;  /* list of objects to be traversed atomically */
  GCObject *weak;  /* list of tables with weak values */
  GCObject *ephemeron;  /* list of ephemeron tables (weak keys) */
  GCObject *allweak;  /* list of all-weak tables */
  GCObject *tobefnz;  /* list of userdata to be GC */
  GCObject *fixedgc;  /* list of objects not to be collected */
  /* fields for generational collector */
  GCObject *survival;  /* start of objects that survived one GC cycle */
  GCObject *old1;  /* start of old1 objects */
  GCObject *reallyold;  /* objects more than one cycle old ("really old") */
  GCObject *firstold1;  /* first OLD1 object in the list (if any) */
  GCObject *finobjsur;  /* list of survival objects with finalizers */
  GCObject *finobjold1;  /* list of old1 objects with finalizers */
  GCObject *finobjrold;  /* list of really old objects with finalizers */
  struct lua_State *twups;  /* list of threads with open upvalues */
  lua_CFunction panic;  /* to be called in unprotected errors */
  struct lua_State *mainthread;
  TString *memerrmsg;  /* message for memory-allocation errors */
  TString *tmname[TM_N];  /* array with tag-method names */
  struct Table *mt[LUA_NUMTAGS];  /* metatables for basic types */
  TString *strcache[STRCACHE_N][STRCACHE_M];  /* cache for strings in API */
  lua_WarnFunction warnf;  /* warning function */
  void *ud_warn;         /* auxiliary data to 'warnf' */
  unsigned int Cstacklimit;  /* current limit for the C stack */
} global_State;


/*
** 'per thread' state
*/
struct lua_State {
  CommonHeader;
  lu_byte status;
  lu_byte allowhook;
  unsigned short nci;  /* number of items in 'ci' list */
  StkId top;  /* first free slot in the stack */
  global_State *l_G;
  CallInfo *ci;  /* call info for current function */
  StkId stack_last;  /* last free slot in the stack */
  StkId stack;  /* stack base */
  UpVal *openupval;  /* list of open upvalues in this stack */
  GCObject *gclist;
  struct lua_State *twups;  /* list of threads with open upvalues */
  struct lua_longjmp *errorJmp;  /* current error recover point */
  CallInfo base_ci;  /* CallInfo for first level (C calling Lua) */
  volatile lua_Hook hook;
  ptrdiff_t errfunc;  /* current error handling function (stack index) */
  l_uint32 nCcalls;  /* number of allowed nested C calls - 'nci' */
  int oldpc;  /* last pc traced */
  int stacksize;
  int basehookcount;
  int hookcount;
  volatile l_signalT hookmask;
};


#define G(L)	(L->l_G)


/*
** Union of all collectable objects (only for conversions)
*/
union GCUnion {
  GCObject gc;  /* common header */
  struct TString ts;
  struct Udata u;
  union Closure cl;
  struct Table h;
  struct Proto p;
  struct lua_State th;  /* thread */
  struct UpVal upv;
};


#define cast_u(o)	cast(union GCUnion *, (o))

/* macros to convert a GCObject into a specific value */
#define gco2ts(o)  \
	check_exp(novariant((o)->tt) == LUA_TSTRING, &((cast_u(o))->ts))
#define gco2u(o)  check_exp((o)->tt == LUA_VUSERDATA, &((cast_u(o))->u))
#define gco2lcl(o)  check_exp((o)->tt == LUA_VLCL, &((cast_u(o))->cl.l))
#define gco2ccl(o)  check_exp((o)->tt == LUA_VCCL, &((cast_u(o))->cl.c))
#define gco2cl(o)  \
	check_exp(novariant((o)->tt) == LUA_TFUNCTION, &((cast_u(o))->cl))
#define gco2t(o)  check_exp((o)->tt == LUA_VTABLE, &((cast_u(o))->h))
#define gco2p(o)  check_exp((o)->tt == LUA_VPROTO, &((cast_u(o))->p))
#define gco2th(o)  check_exp((o)->tt == LUA_VTHREAD, &((cast_u(o))->th))
#define gco2upv(o)	check_exp((o)->tt == LUA_VUPVAL, &((cast_u(o))->upv))


/*
** macro to convert a Lua object into a GCObject
** (The access to 'tt' tries to ensure that 'v' is actually a Lua object.)
*/
#define obj2gco(v)	check_exp((v)->tt >= LUA_TSTRING, &(cast_u(v)->gc))


/* actual number of total bytes allocated */
#define gettotalbytes(g)	cast(lu_mem, (g)->totalbytes + (g)->GCdebt)

LUAI_FUNC void luaE_setdebt (global_State *g, l_mem debt);
LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
LUAI_FUNC void luaE_freeCI (lua_State *L);
LUAI_FUNC void luaE_shrinkCI (lua_State *L);
LUAI_FUNC void luaE_enterCcall (lua_State *L);
LUAI_FUNC void luaE_warning (lua_State *L, const char *msg, int tocont);
LUAI_FUNC void luaE_warnerror (lua_State *L, const char *where);


#define luaE_exitCcall(L)	((L)->nCcalls++)

#endif