lisp.h

/* Fundamental definitions for GNU Emacs Lisp interpreter.
   Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 1998, 1999, 2000,
                 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
                 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef EMACS_LISP_H
#define EMACS_LISP_H

#include <stdarg.h>

/* Use the configure flag --enable-checking[=LIST] to enable various
   types of run time checks for Lisp objects.  */

#ifdef GC_CHECK_CONS_LIST
#define CHECK_CONS_LIST() check_cons_list()
#else
#define CHECK_CONS_LIST() ((void)0)
#endif

/* These are default choices for the types to use.  */
#ifdef _LP64
#ifndef EMACS_INT
#define EMACS_INT long
#define BITS_PER_EMACS_INT BITS_PER_LONG
#endif
#ifndef EMACS_UINT
#define EMACS_UINT unsigned long
#endif
#else /* not _LP64 */
#ifndef EMACS_INT
#define EMACS_INT int
#define BITS_PER_EMACS_INT BITS_PER_INT
#endif
#ifndef EMACS_UINT
#define EMACS_UINT unsigned int
#endif
#endif

/* Extra internal type checking?  */
extern int suppress_checking;
extern void die (const char *, const char *, int) NO_RETURN;

#ifdef ENABLE_CHECKING

/* The suppress_checking variable is initialized to 0 in alloc.c.  Set
   it to 1 using a debugger to temporarily disable aborting on
   detected internal inconsistencies or error conditions.

   Testing suppress_checking after the supplied condition ensures that
   the side effects produced by CHECK will be consistent, independent
   of whether ENABLE_CHECKING is defined, or whether the checks are
   suppressed at run time.

   In some cases, a good compiler may be able to optimize away the
   CHECK macro altogether, e.g., if XSTRING (x) uses CHECK to test
   STRINGP (x), but a particular use of XSTRING is invoked only after
   testing that STRINGP (x) is true, making the test redundant.  */

#define CHECK(check,msg) (((check) || suppress_checking		\
			   ? (void) 0				\
			   : die ((msg), __FILE__, __LINE__)),	\
			  0)
#else

/* Produce same side effects and result, but don't complain.  */
#define CHECK(check,msg) ((check),0)

#endif

/* Define an Emacs version of "assert", since some system ones are
   flaky.  */
#ifndef ENABLE_CHECKING
#define eassert(X)	(void) 0
#else /* ENABLE_CHECKING */
#if defined (__GNUC__) && __GNUC__ >= 2 && defined (__STDC__)
#define eassert(cond) CHECK(cond,"assertion failed: " #cond)
#else
#define eassert(cond) CHECK(cond,"assertion failed")
#endif
#endif /* ENABLE_CHECKING */

/* Use the configure flag --enable-use-lisp-union-type to make
   Lisp_Object use a union type instead of the default int.  The flag
   causes USE_LISP_UNION_TYPE to be defined.  */

/***** Select the tagging scheme.  *****/
/* There are basically two options that control the tagging scheme:
   - USE_LISP_UNION_TYPE says that Lisp_Object should be a union instead
     of an integer.
   - USE_LSB_TAG means that we can assume the least 3 bits of pointers are
     always 0, and we can thus use them to hold tag bits, without
     restricting our addressing space.

   If USE_LSB_TAG is not set, then we use the top 3 bits for tagging, thus
   restricting our possible address range.  Currently USE_LSB_TAG is not
   allowed together with a union.  This is not due to any fundamental
   technical (or political ;-) problem: nobody wrote the code to do it yet.

   USE_LSB_TAG not only requires the least 3 bits of pointers returned by
   malloc to be 0 but also needs to be able to impose a mult-of-8 alignment
   on the few static Lisp_Objects used: all the defsubr as well
   as the two special buffers buffer_defaults and buffer_local_symbols.  */

/* First, try and define DECL_ALIGN(type,var) which declares a static
   variable VAR of type TYPE with the added requirement that it be
   TYPEBITS-aligned. */
#ifndef NO_DECL_ALIGN
# ifndef DECL_ALIGN
/* What compiler directive should we use for non-gcc compilers?  -stef  */
#  if defined (__GNUC__)
#   define DECL_ALIGN(type, var) \
     type __attribute__ ((__aligned__ (1 << GCTYPEBITS))) var
#  endif
# endif
#endif

/* Let's USE_LSB_TAG on systems where we know malloc returns mult-of-8.  */
#if defined GNU_MALLOC || defined DOUG_LEA_MALLOC || defined __GLIBC__ || defined DARWIN_OS
/* We also need to be able to specify mult-of-8 alignment on static vars.  */
# if defined DECL_ALIGN
#  define USE_LSB_TAG
# endif
#endif

/* If we cannot use 8-byte alignment, make DECL_ALIGN a no-op.  */
#ifndef DECL_ALIGN
# ifdef USE_LSB_TAG
#  error "USE_LSB_TAG used without defining DECL_ALIGN"
# endif
# define DECL_ALIGN(type, var) type var
#endif


/* Define the fundamental Lisp data structures.  */

/* If USE_2_TAGBITS_FOR_INTS is defined, then Lisp integers use
   2 tags, to give them one extra bit, thus extending their range from
   e.g -2^28..2^28-1 to -2^29..2^29-1.  */
#define USE_2_TAGS_FOR_INTS

/* Making it work for the union case is too much trouble.  */
#ifdef USE_LISP_UNION_TYPE
# undef USE_2_TAGS_FOR_INTS
#endif

/* This is the set of Lisp data types.  */

#if !defined USE_2_TAGS_FOR_INTS
# define LISP_INT_TAG Lisp_Int
# define case_Lisp_Int case Lisp_Int
# define LISP_STRING_TAG 4
# define LISP_INT_TAG_P(x) ((x) == Lisp_Int)
#else
# define LISP_INT_TAG Lisp_Int0
# define case_Lisp_Int case Lisp_Int0: case Lisp_Int1
# ifdef USE_LSB_TAG
#  define LISP_INT1_TAG 4
#  define LISP_STRING_TAG 1
#  define LISP_INT_TAG_P(x) (((x) & 3) == 0)
# else
#  define LISP_INT1_TAG 1
#  define LISP_STRING_TAG 4
#  define LISP_INT_TAG_P(x) (((x) & 6) == 0)
# endif
#endif

enum Lisp_Type
  {
    /* Integer.  XINT (obj) is the integer value.  */
#ifdef USE_2_TAGS_FOR_INTS
    Lisp_Int0 = 0,
    Lisp_Int1 = LISP_INT1_TAG,
#else
    Lisp_Int = 0,
#endif

    /* Symbol.  XSYMBOL (object) points to a struct Lisp_Symbol.  */
    Lisp_Symbol = 2,

    /* Miscellaneous.  XMISC (object) points to a union Lisp_Misc,
       whose first member indicates the subtype.  */
    Lisp_Misc = 3,

    /* String.  XSTRING (object) points to a struct Lisp_String.
       The length of the string, and its contents, are stored therein.  */
    Lisp_String = LISP_STRING_TAG,

    /* Vector of Lisp objects, or something resembling it.
       XVECTOR (object) points to a struct Lisp_Vector, which contains
       the size and contents.  The size field also contains the type
       information, if it's not a real vector object.  */
    Lisp_Vectorlike = 5,

    /* Cons.  XCONS (object) points to a struct Lisp_Cons.  */
    Lisp_Cons = 6,

    Lisp_Float = 7,
  };

/* This is the set of data types that share a common structure.
   The first member of the structure is a type code from this set.
   The enum values are arbitrary, but we'll use large numbers to make it
   more likely that we'll spot the error if a random word in memory is
   mistakenly interpreted as a Lisp_Misc.  */
enum Lisp_Misc_Type
  {
    Lisp_Misc_Free = 0x5eab,
    Lisp_Misc_Marker,
    Lisp_Misc_Overlay,
    Lisp_Misc_Save_Value,
    /* Currently floats are not a misc type,
       but let's define this in case we want to change that.  */
    Lisp_Misc_Float,
    /* This is not a type code.  It is for range checking.  */
    Lisp_Misc_Limit
  };

/* These are the types of forwarding objects used in the value slot
   of symbols for special built-in variables whose value is stored in
   C variables.  */
enum Lisp_Fwd_Type
  {
    Lisp_Fwd_Int,		/* Fwd to a C `int' variable.  */
    Lisp_Fwd_Bool,		/* Fwd to a C boolean var.  */
    Lisp_Fwd_Obj,		/* Fwd to a C Lisp_Object variable.  */
    Lisp_Fwd_Buffer_Obj,	/* Fwd to a Lisp_Object field of buffers.  */
    Lisp_Fwd_Kboard_Obj,	/* Fwd to a Lisp_Object field of kboards.  */
  };

#ifndef GCTYPEBITS
#define GCTYPEBITS 3
#endif

/* These values are overridden by the m- file on some machines.  */
#ifndef VALBITS
#define VALBITS (BITS_PER_EMACS_INT - GCTYPEBITS)
#endif

#ifdef USE_LISP_UNION_TYPE

#ifndef WORDS_BIG_ENDIAN

/* Definition of Lisp_Object for little-endian machines.  */

typedef
union Lisp_Object
  {
    /* Used for comparing two Lisp_Objects;
       also, positive integers can be accessed fast this way.  */
    EMACS_UINT i;

    struct
      {
	EMACS_INT val  : VALBITS;
	enum Lisp_Type type : GCTYPEBITS;
      } s;
    struct
      {
	EMACS_UINT val : VALBITS;
	enum Lisp_Type type : GCTYPEBITS;
      } u;
  }
Lisp_Object;

#else /* If WORDS_BIG_ENDIAN */

typedef
union Lisp_Object
  {
    /* Used for comparing two Lisp_Objects;
       also, positive integers can be accessed fast this way.  */
    EMACS_UINT i;

    struct
      {
	enum Lisp_Type type : GCTYPEBITS;
	EMACS_INT val  : VALBITS;
      } s;
    struct
      {
	enum Lisp_Type type : GCTYPEBITS;
	EMACS_UINT val : VALBITS;
      } u;
  }
Lisp_Object;

#endif /* WORDS_BIG_ENDIAN */

#ifdef __GNUC__
static __inline__ Lisp_Object
LISP_MAKE_RVALUE (Lisp_Object o)
{
    return o;
}
#else
/* This is more portable to pre-C99 non-GCC compilers, but for
   backwards compatibility GCC still accepts an old GNU extension
   which caused this to only generate a warning.  */
#define LISP_MAKE_RVALUE(o) (0 ? (o) : (o))
#endif

#else /* USE_LISP_UNION_TYPE */

/* If union type is not wanted, define Lisp_Object as just a number.  */

typedef EMACS_INT Lisp_Object;
#define LISP_MAKE_RVALUE(o) (0+(o))
#endif /* USE_LISP_UNION_TYPE */

/* In the size word of a vector, this bit means the vector has been marked.  */

#define ARRAY_MARK_FLAG ((EMACS_UINT) 1 << (BITS_PER_EMACS_INT - 1))

/* In the size word of a struct Lisp_Vector, this bit means it's really
   some other vector-like object.  */
#define PSEUDOVECTOR_FLAG ((ARRAY_MARK_FLAG >> 1))

/* In a pseudovector, the size field actually contains a word with one
   PSEUDOVECTOR_FLAG bit set, and exactly one of the following bits to
   indicate the actual type.
   We use a bitset, even tho only one of the bits can be set at any
   particular time just so as to be able to use micro-optimizations such as
   testing membership of a particular subset of pseudovectors in Fequal.
   It is not crucial, but there are plenty of bits here, so why not do it?  */
enum pvec_type
{
  PVEC_NORMAL_VECTOR = 0,
  PVEC_PROCESS = 0x200,
  PVEC_FRAME = 0x400,
  PVEC_COMPILED = 0x800,
  PVEC_WINDOW = 0x1000,
  PVEC_WINDOW_CONFIGURATION = 0x2000,
  PVEC_SUBR = 0x4000,
  PVEC_CHAR_TABLE = 0x8000,
  PVEC_BOOL_VECTOR = 0x10000,
  PVEC_BUFFER = 0x20000,
  PVEC_HASH_TABLE = 0x40000,
  PVEC_TERMINAL = 0x80000,
  PVEC_SUB_CHAR_TABLE = 0x100000,
  PVEC_FONT = 0x200000,
  PVEC_OTHER = 0x400000,
  PVEC_TYPE_MASK = 0x7ffe00

#if 0 /* This is used to make the value of PSEUDOVECTOR_FLAG available to
	 GDB.  It doesn't work on OS Alpha.  Moved to a variable in
	 emacs.c.  */
  PVEC_FLAG = PSEUDOVECTOR_FLAG
#endif
};

/* For convenience, we also store the number of elements in these bits.
   Note that this size is not necessarily the memory-footprint size, but
   only the number of Lisp_Object fields (that need to be traced by the GC).
   The distinction is used e.g. by Lisp_Process which places extra
   non-Lisp_Object fields at the end of the structure.  */
#define PSEUDOVECTOR_SIZE_MASK 0x1ff

/* Number of bits to put in each character in the internal representation
   of bool vectors.  This should not vary across implementations.  */
#define BOOL_VECTOR_BITS_PER_CHAR 8

/* These macros extract various sorts of values from a Lisp_Object.
 For example, if tem is a Lisp_Object whose type is Lisp_Cons,
 XCONS (tem) is the struct Lisp_Cons * pointing to the memory for that cons.  */

#ifndef USE_LISP_UNION_TYPE

/* Return a perfect hash of the Lisp_Object representation.  */
#define XHASH(a) (a)

#ifdef USE_LSB_TAG

#define TYPEMASK ((((EMACS_INT) 1) << GCTYPEBITS) - 1)
#define XTYPE(a) ((enum Lisp_Type) (((EMACS_UINT) (a)) & TYPEMASK))
#ifdef USE_2_TAGS_FOR_INTS
# define XINT(a) (((EMACS_INT) (a)) >> (GCTYPEBITS - 1))
# define XUINT(a) (((EMACS_UINT) (a)) >> (GCTYPEBITS - 1))
# define make_number(N) (((EMACS_INT) (N)) << (GCTYPEBITS - 1))
#else
# define XINT(a) (((EMACS_INT) (a)) >> GCTYPEBITS)
# define XUINT(a) (((EMACS_UINT) (a)) >> GCTYPEBITS)
# define make_number(N) (((EMACS_INT) (N)) << GCTYPEBITS)
#endif
#define XSET(var, type, ptr)					\
    (eassert (XTYPE (ptr) == 0), /* Check alignment.  */	\
     (var) = ((EMACS_INT) (type)) | ((EMACS_INT) (ptr)))

#define XPNTR(a) ((EMACS_INT) ((a) & ~TYPEMASK))

#else  /* not USE_LSB_TAG */

#define VALMASK ((((EMACS_INT) 1) << VALBITS) - 1)

/* One need to override this if there must be high bits set in data space
   (doing the result of the below & ((1 << (GCTYPE + 1)) - 1) would work
    on all machines, but would penalize machines which don't need it)
 */
#define XTYPE(a) ((enum Lisp_Type) (((EMACS_UINT) (a)) >> VALBITS))

/* For integers known to be positive, XFASTINT provides fast retrieval
   and XSETFASTINT provides fast storage.  This takes advantage of the
   fact that Lisp_Int is 0.  */
#define XFASTINT(a) ((a) + 0)
#define XSETFASTINT(a, b) ((a) = (b))

/* Extract the value of a Lisp_Object as a (un)signed integer.  */

#ifdef USE_2_TAGS_FOR_INTS
# define XINT(a) ((((EMACS_INT) (a)) << (GCTYPEBITS - 1)) >> (GCTYPEBITS - 1))
# define XUINT(a) ((EMACS_UINT) ((a) & (1 + (VALMASK << 1))))
# define make_number(N) ((((EMACS_INT) (N)) & (1 + (VALMASK << 1))))
#else
# define XINT(a) ((((EMACS_INT) (a)) << (BITS_PER_EMACS_INT - VALBITS))	\
		 >> (BITS_PER_EMACS_INT - VALBITS))
# define XUINT(a) ((EMACS_UINT) ((a) & VALMASK))
# define make_number(N)		\
  ((((EMACS_INT) (N)) & VALMASK) | ((EMACS_INT) Lisp_Int) << VALBITS)
#endif

#define XSET(var, type, ptr) \
   ((var) = ((EMACS_INT)(type) << VALBITS) + ((EMACS_INT) (ptr) & VALMASK))

#define XPNTR(a) ((EMACS_UINT) ((a) & VALMASK))

#endif /* not USE_LSB_TAG */

#else /* USE_LISP_UNION_TYPE */

#ifdef USE_2_TAGS_FOR_INTS
# error "USE_2_TAGS_FOR_INTS is not supported with USE_LISP_UNION_TYPE"
#endif

#define XHASH(a) ((a).i)

#define XTYPE(a) ((enum Lisp_Type) (a).u.type)

#ifdef EXPLICIT_SIGN_EXTEND
/* Make sure we sign-extend; compilers have been known to fail to do so.
   We additionally cast to EMACS_INT since it seems that some compilers
   have been known to fail to do so, even though the bitfield is declared
   as EMACS_INT already.  */
#define XINT(a) ((((EMACS_INT) (a).s.val) << (BITS_PER_EMACS_INT - VALBITS)) \
		 >> (BITS_PER_EMACS_INT - VALBITS))
#else
#define XINT(a) ((a).s.val)
#endif /* EXPLICIT_SIGN_EXTEND */

#define XUINT(a) ((a).u.val)

#ifdef USE_LSB_TAG

# define XSET(var, vartype, ptr) \
  (eassert ((((EMACS_UINT) (ptr)) & ((1 << GCTYPEBITS) - 1)) == 0),	\
   (var).u.val = ((EMACS_UINT) (ptr)) >> GCTYPEBITS,			\
   (var).u.type = ((char) (vartype)))

/* Some versions of gcc seem to consider the bitfield width when issuing
   the "cast to pointer from integer of different size" warning, so the
   cast is here to widen the value back to its natural size.  */
# define XPNTR(v) ((EMACS_INT)((v).s.val) << GCTYPEBITS)

#else  /* !USE_LSB_TAG */

/* For integers known to be positive, XFASTINT provides fast retrieval
   and XSETFASTINT provides fast storage.  This takes advantage of the
   fact that Lisp_Int is 0.  */
# define XFASTINT(a) ((a).i + 0)
# define XSETFASTINT(a, b) ((a).i = (b))

# define XSET(var, vartype, ptr) \
   (((var).s.val = ((EMACS_INT) (ptr))), ((var).s.type = ((char) (vartype))))

#endif	/* !USE_LSB_TAG */

#if __GNUC__ >= 2 && defined (__OPTIMIZE__)
#define make_number(N) \
  (__extension__ ({ Lisp_Object _l; _l.s.val = (N); _l.s.type = Lisp_Int; _l; }))
#else
extern Lisp_Object make_number (EMACS_INT);
#endif

#endif /* USE_LISP_UNION_TYPE */

/* For integers known to be positive, XFASTINT sometimes provides
   faster retrieval and XSETFASTINT provides faster storage.
   If not, fallback on the non-accelerated path.  */
#ifndef XFASTINT
# define XFASTINT(a) (XINT (a))
# define XSETFASTINT(a, b) (XSETINT (a, b))
#endif

#define EQ(x, y) (XHASH (x) == XHASH (y))

#ifndef XPNTR
#ifdef HAVE_SHM
/* In this representation, data is found in two widely separated segments.  */
extern size_t pure_size;
#define XPNTR(a) \
  (XUINT (a) | (XUINT (a) > pure_size ? DATA_SEG_BITS : PURE_SEG_BITS))
#else /* not HAVE_SHM */
#ifdef DATA_SEG_BITS
/* This case is used for the rt-pc.
   In the diffs I was given, it checked for ptr = 0
   and did not adjust it in that case.
   But I don't think that zero should ever be found
   in a Lisp object whose data type says it points to something.  */
#define XPNTR(a) (XUINT (a) | DATA_SEG_BITS)
#else
/* Some versions of gcc seem to consider the bitfield width when
   issuing the "cast to pointer from integer of different size"
   warning, so the cast is here to widen the value back to its natural
   size.  */
#define XPNTR(a) ((EMACS_INT) XUINT (a))
#endif
#endif /* not HAVE_SHM */
#endif /* no XPNTR */

/* Largest and smallest representable fixnum values.  These are the C
   values.  */

#ifdef USE_2_TAGS_FOR_INTS
# define MOST_NEGATIVE_FIXNUM	- ((EMACS_INT) 1 << VALBITS)
# define MOST_POSITIVE_FIXNUM	(((EMACS_INT) 1 << VALBITS) - 1)
/* Mask indicating the significant bits of a Lisp_Int.
   I.e. (x & INTMASK) == XUINT (make_number (x)).  */
# define INTMASK ((((EMACS_INT) 1) << (VALBITS + 1)) - 1)
#else
# define MOST_NEGATIVE_FIXNUM	- ((EMACS_INT) 1 << (VALBITS - 1))
# define MOST_POSITIVE_FIXNUM	(((EMACS_INT) 1 << (VALBITS - 1)) - 1)
/* Mask indicating the significant bits of a Lisp_Int.
   I.e. (x & INTMASK) == XUINT (make_number (x)).  */
# define INTMASK ((((EMACS_INT) 1) << VALBITS) - 1)
#endif

/* Value is non-zero if I doesn't fit into a Lisp fixnum.  It is
   written this way so that it also works if I is of unsigned
   type.  */

#define FIXNUM_OVERFLOW_P(i) \
  ((i) > MOST_POSITIVE_FIXNUM \
   || ((i) < 0 && (i) < MOST_NEGATIVE_FIXNUM))

/* Extract a value or address from a Lisp_Object.  */

#define XCONS(a) (eassert (CONSP(a)),(struct Lisp_Cons *) XPNTR(a))
#define XVECTOR(a) (eassert (VECTORLIKEP(a)),(struct Lisp_Vector *) XPNTR(a))
#define XSTRING(a) (eassert (STRINGP(a)),(struct Lisp_String *) XPNTR(a))
#define XSYMBOL(a) (eassert (SYMBOLP(a)),(struct Lisp_Symbol *) XPNTR(a))
#define XFLOAT(a) (eassert (FLOATP(a)),(struct Lisp_Float *) XPNTR(a))

/* Misc types.  */

#define XMISC(a)   ((union Lisp_Misc *) XPNTR(a))
#define XMISCANY(a)	(eassert (MISCP (a)), &(XMISC(a)->u_any))
#define XMISCTYPE(a)   (XMISCANY (a)->type)
#define XMARKER(a)	(eassert (MARKERP (a)), &(XMISC(a)->u_marker))
#define XOVERLAY(a)	(eassert (OVERLAYP (a)), &(XMISC(a)->u_overlay))
#define XSAVE_VALUE(a)	(eassert (SAVE_VALUEP (a)), &(XMISC(a)->u_save_value))

/* Forwarding object types.  */

#define XFWDTYPE(a)     (a->u_intfwd.type)
#define XINTFWD(a)	(eassert (INTFWDP (a)), &((a)->u_intfwd))
#define XBOOLFWD(a)	(eassert (BOOLFWDP (a)), &((a)->u_boolfwd))
#define XOBJFWD(a)	(eassert (OBJFWDP (a)), &((a)->u_objfwd))
#define XBUFFER_OBJFWD(a) \
  (eassert (BUFFER_OBJFWDP (a)), &((a)->u_buffer_objfwd))
#define XKBOARD_OBJFWD(a) \
  (eassert (KBOARD_OBJFWDP (a)), &((a)->u_kboard_objfwd))

/* Pseudovector types.  */

#define XPROCESS(a) (eassert (PROCESSP(a)),(struct Lisp_Process *) XPNTR(a))
#define XWINDOW(a) (eassert (WINDOWP(a)),(struct window *) XPNTR(a))
#define XTERMINAL(a) (eassert (TERMINALP(a)),(struct terminal *) XPNTR(a))
#define XSUBR(a) (eassert (SUBRP(a)),(struct Lisp_Subr *) XPNTR(a))
#define XBUFFER(a) (eassert (BUFFERP(a)),(struct buffer *) XPNTR(a))
#define XCHAR_TABLE(a) (eassert (CHAR_TABLE_P (a)), (struct Lisp_Char_Table *) XPNTR(a))
#define XSUB_CHAR_TABLE(a) (eassert (SUB_CHAR_TABLE_P (a)), (struct Lisp_Sub_Char_Table *) XPNTR(a))
#define XBOOL_VECTOR(a) (eassert (BOOL_VECTOR_P (a)), (struct Lisp_Bool_Vector *) XPNTR(a))

/* Construct a Lisp_Object from a value or address.  */

#define XSETINT(a, b) (a) = make_number (b)
#define XSETCONS(a, b) XSET (a, Lisp_Cons, b)
#define XSETVECTOR(a, b) XSET (a, Lisp_Vectorlike, b)
#define XSETSTRING(a, b) XSET (a, Lisp_String, b)
#define XSETSYMBOL(a, b) XSET (a, Lisp_Symbol, b)
#define XSETFLOAT(a, b) XSET (a, Lisp_Float, b)

/* Misc types.  */

#define XSETMISC(a, b) XSET (a, Lisp_Misc, b)
#define XSETMARKER(a, b) (XSETMISC (a, b), XMISCTYPE (a) = Lisp_Misc_Marker)

/* Pseudovector types.  */

#define XSETPVECTYPE(v,code) ((v)->size |= PSEUDOVECTOR_FLAG | (code))
#define XSETPSEUDOVECTOR(a, b, code) \
  (XSETVECTOR (a, b),							\
   eassert ((XVECTOR (a)->size & (PSEUDOVECTOR_FLAG | PVEC_TYPE_MASK))	\
	    == (PSEUDOVECTOR_FLAG | (code))))
#define XSETWINDOW_CONFIGURATION(a, b) \
  (XSETPSEUDOVECTOR (a, b, PVEC_WINDOW_CONFIGURATION))
#define XSETPROCESS(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_PROCESS))
#define XSETWINDOW(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_WINDOW))
#define XSETTERMINAL(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_TERMINAL))
#define XSETSUBR(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_SUBR))
#define XSETCOMPILED(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_COMPILED))
#define XSETBUFFER(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_BUFFER))
#define XSETCHAR_TABLE(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_CHAR_TABLE))
#define XSETBOOL_VECTOR(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_BOOL_VECTOR))
#define XSETSUB_CHAR_TABLE(a, b) (XSETPSEUDOVECTOR (a, b, PVEC_SUB_CHAR_TABLE))

/* Convenience macros for dealing with Lisp arrays.  */

#define AREF(ARRAY, IDX)	XVECTOR ((ARRAY))->contents[IDX]
#define ASIZE(ARRAY)		XVECTOR ((ARRAY))->size
/* The IDX==IDX tries to detect when the macro argument is side-effecting.  */
#define ASET(ARRAY, IDX, VAL)	\
  (eassert ((IDX) == (IDX)),				\
   eassert ((IDX) >= 0 && (IDX) < ASIZE (ARRAY)),	\
   AREF ((ARRAY), (IDX)) = (VAL))

/* Convenience macros for dealing with Lisp strings.  */

#define SDATA(string)		(XSTRING (string)->data + 0)
#define SREF(string, index)	(SDATA (string)[index] + 0)
#define SSET(string, index, new) (SDATA (string)[index] = (new))
#define SCHARS(string)		(XSTRING (string)->size + 0)
#define SBYTES(string)		(STRING_BYTES (XSTRING (string)) + 0)

#define STRING_SET_CHARS(string, newsize) \
    (XSTRING (string)->size = (newsize))

#define STRING_COPYIN(string, index, new, count) \
    memcpy (SDATA (string) + index, new, count)

/* Type checking.  */

#define CHECK_TYPE(ok, Qxxxp, x) \
  do { if (!(ok)) wrong_type_argument (Qxxxp, (x)); } while (0)



/* See the macros in intervals.h.  */

typedef struct interval *INTERVAL;

/* Complain if object is not string or buffer type */
#define CHECK_STRING_OR_BUFFER(x) \
  CHECK_TYPE (STRINGP (x) || BUFFERP (x), Qbuffer_or_string_p, x)


/* In a cons, the markbit of the car is the gc mark bit */

struct Lisp_Cons
  {
    /* Please do not use the names of these elements in code other
       than the core lisp implementation.  Use XCAR and XCDR below.  */
#ifdef HIDE_LISP_IMPLEMENTATION
    Lisp_Object car_;
    union
    {
      Lisp_Object cdr_;
      struct Lisp_Cons *chain;
    } u;
#else
    Lisp_Object car;
    union
    {
      Lisp_Object cdr;
      struct Lisp_Cons *chain;
    } u;
#endif
  };

/* Take the car or cdr of something known to be a cons cell.  */
/* The _AS_LVALUE macros shouldn't be used outside of the minimal set
   of code that has to know what a cons cell looks like.  Other code not
   part of the basic lisp implementation should assume that the car and cdr
   fields are not accessible as lvalues.  (What if we want to switch to
   a copying collector someday?  Cached cons cell field addresses may be
   invalidated at arbitrary points.)  */
#ifdef HIDE_LISP_IMPLEMENTATION
#define XCAR_AS_LVALUE(c) (XCONS ((c))->car_)
#define XCDR_AS_LVALUE(c) (XCONS ((c))->u.cdr_)
#else
#define XCAR_AS_LVALUE(c) (XCONS ((c))->car)
#define XCDR_AS_LVALUE(c) (XCONS ((c))->u.cdr)
#endif

/* Use these from normal code.  */
#define XCAR(c)	LISP_MAKE_RVALUE(XCAR_AS_LVALUE(c))
#define XCDR(c) LISP_MAKE_RVALUE(XCDR_AS_LVALUE(c))

/* Use these to set the fields of a cons cell.

   Note that both arguments may refer to the same object, so 'n'
   should not be read after 'c' is first modified.  Also, neither
   argument should be evaluated more than once; side effects are
   especially common in the second argument.  */
#define XSETCAR(c,n) (XCAR_AS_LVALUE(c) = (n))
#define XSETCDR(c,n) (XCDR_AS_LVALUE(c) = (n))

/* Take the car or cdr of something whose type is not known.  */
#define CAR(c)					\
 (CONSP ((c)) ? XCAR ((c))			\
  : NILP ((c)) ? Qnil				\
  : wrong_type_argument (Qlistp, (c)))

#define CDR(c)					\
 (CONSP ((c)) ? XCDR ((c))			\
  : NILP ((c)) ? Qnil				\
  : wrong_type_argument (Qlistp, (c)))

/* Take the car or cdr of something whose type is not known.  */
#define CAR_SAFE(c)				\
  (CONSP ((c)) ? XCAR ((c)) : Qnil)

#define CDR_SAFE(c)				\
  (CONSP ((c)) ? XCDR ((c)) : Qnil)

/* Nonzero if STR is a multibyte string.  */
#define STRING_MULTIBYTE(STR)  \
  (XSTRING (STR)->size_byte >= 0)

/* Return the length in bytes of STR.  */

#ifdef GC_CHECK_STRING_BYTES

struct Lisp_String;
extern int string_bytes (struct Lisp_String *);
#define STRING_BYTES(S) string_bytes ((S))

#else /* not GC_CHECK_STRING_BYTES */

#define STRING_BYTES(STR)  \
  ((STR)->size_byte < 0 ? (STR)->size : (STR)->size_byte)

#endif /* not GC_CHECK_STRING_BYTES */

/* Mark STR as a unibyte string.  */
#define STRING_SET_UNIBYTE(STR)  \
  do { if (EQ (STR, empty_multibyte_string))  \
      (STR) = empty_unibyte_string;  \
    else XSTRING (STR)->size_byte = -1; } while (0)

/* Mark STR as a multibyte string.  Assure that STR contains only
   ASCII characters in advance.  */
#define STRING_SET_MULTIBYTE(STR)  \
  do { if (EQ (STR, empty_unibyte_string))  \
      (STR) = empty_multibyte_string;  \
    else XSTRING (STR)->size_byte = XSTRING (STR)->size; } while (0)

/* Get text properties.  */
#define STRING_INTERVALS(STR)  (XSTRING (STR)->intervals + 0)

/* Set text properties.  */
#define STRING_SET_INTERVALS(STR, INT) (XSTRING (STR)->intervals = (INT))

/* In a string or vector, the sign bit of the `size' is the gc mark bit */

struct Lisp_String
  {
    EMACS_INT size;
    EMACS_INT size_byte;
    INTERVAL intervals;		/* text properties in this string */
    unsigned char *data;
  };

#ifdef offsetof
#define OFFSETOF(type,field) offsetof(type,field)
#else
#define OFFSETOF(type,field) \
  ((int)((char*)&((type*)0)->field - (char*)0))
#endif

struct Lisp_Vector
  {
    EMACS_UINT size;
    struct Lisp_Vector *next;
    Lisp_Object contents[1];
  };

/* If a struct is made to look like a vector, this macro returns the length
   of the shortest vector that would hold that struct.  */
#define VECSIZE(type) ((sizeof (type)					  \
			- OFFSETOF (struct Lisp_Vector, contents[0])      \
                        + sizeof(Lisp_Object) - 1) /* round up */	  \
		       / sizeof (Lisp_Object))

/* Like VECSIZE, but used when the pseudo-vector has non-Lisp_Object fields
   at the end and we need to compute the number of Lisp_Object fields (the
   ones that the GC needs to trace).  */
#define PSEUDOVECSIZE(type, nonlispfield) \
  ((OFFSETOF(type, nonlispfield) - OFFSETOF(struct Lisp_Vector, contents[0])) \
   / sizeof (Lisp_Object))

/* A char-table is a kind of vectorlike, with contents are like a
   vector but with a few other slots.  For some purposes, it makes
   sense to handle a char-table with type struct Lisp_Vector.  An
   element of a char table can be any Lisp objects, but if it is a sub
   char-table, we treat it a table that contains information of a
   specific range of characters.  A sub char-table has the same
   structure as a vector.  A sub char table appears only in an element
   of a char-table, and there's no way to access it directly from
   Emacs Lisp program.  */

/* This is the number of slots that every char table must have.  This
   counts the ordinary slots and the top, defalt, parent, and purpose
   slots.  */
#define CHAR_TABLE_STANDARD_SLOTS (VECSIZE (struct Lisp_Char_Table) - 1)

/* Return the number of "extra" slots in the char table CT.  */

#define CHAR_TABLE_EXTRA_SLOTS(CT)	\
  (((CT)->size & PSEUDOVECTOR_SIZE_MASK) - CHAR_TABLE_STANDARD_SLOTS)

#ifdef __GNUC__

#define CHAR_TABLE_REF_ASCII(CT, IDX)					\
  ({struct Lisp_Char_Table *_tbl = NULL;				\
    Lisp_Object _val;							\
    do {								\
      _tbl = _tbl ? XCHAR_TABLE (_tbl->parent) : XCHAR_TABLE (CT);	\
      _val = (! SUB_CHAR_TABLE_P (_tbl->ascii) ? _tbl->ascii		\
	      : XSUB_CHAR_TABLE (_tbl->ascii)->contents[IDX]);		\
      if (NILP (_val))							\
	_val = _tbl->defalt;						\
    } while (NILP (_val) && ! NILP (_tbl->parent));			\
    _val; })

#else  /* not __GNUC__ */

#define CHAR_TABLE_REF_ASCII(CT, IDX)					  \
  (! NILP (XCHAR_TABLE (CT)->ascii)					  \
   ? (! SUB_CHAR_TABLE_P (XCHAR_TABLE (CT)->ascii)			  \
      ? XCHAR_TABLE (CT)->ascii						  \
      : ! NILP (XSUB_CHAR_TABLE (XCHAR_TABLE (CT)->ascii)->contents[IDX]) \
      ? XSUB_CHAR_TABLE (XCHAR_TABLE (CT)->ascii)->contents[IDX]	  \
      : char_table_ref ((CT), (IDX)))					  \
   :  char_table_ref ((CT), (IDX)))

#endif	/* not __GNUC__ */

/* Almost equivalent to Faref (CT, IDX) with optimization for ASCII
   characters.  Do not check validity of CT.  */
#define CHAR_TABLE_REF(CT, IDX)					\
  (ASCII_CHAR_P (IDX) ? CHAR_TABLE_REF_ASCII ((CT), (IDX))	\
   : char_table_ref ((CT), (IDX)))

/* Almost equivalent to Faref (CT, IDX).  However, if the result is
   not a character, return IDX.

   For these characters, do not check validity of CT
   and do not follow parent.  */
#define CHAR_TABLE_TRANSLATE(CT, IDX)	\
  char_table_translate (CT, IDX)

/* Equivalent to Faset (CT, IDX, VAL) with optimization for ASCII and
   8-bit European characters.  Do not check validity of CT.  */
#define CHAR_TABLE_SET(CT, IDX, VAL)					\
  (((IDX) >= 0 && ASCII_CHAR_P (IDX)					\
    && SUB_CHAR_TABLE_P (XCHAR_TABLE (CT)->ascii))			\
   ? XSUB_CHAR_TABLE (XCHAR_TABLE (CT)->ascii)->contents[IDX] = VAL	\
   : char_table_set (CT, IDX, VAL))

#define CHARTAB_SIZE_BITS_0 6
#define CHARTAB_SIZE_BITS_1 4
#define CHARTAB_SIZE_BITS_2 5
#define CHARTAB_SIZE_BITS_3 7

extern const int chartab_size[4];

struct Lisp_Sub_Char_Table;

struct Lisp_Char_Table
  {
    /* This is the vector's size field, which also holds the
       pseudovector type information.  It holds the size, too.
       The size counts the defalt, parent, purpose, ascii,
       contents, and extras slots.  */
    EMACS_UINT size;
    struct Lisp_Vector *next;

    /* This holds a default value,
       which is used whenever the value for a specific character is nil.  */
    Lisp_Object defalt;

    /* This points to another char table, which we inherit from when the
       value for a specific character is nil.  The `defalt' slot takes
       precedence over this.  */
    Lisp_Object parent;

    /* This is a symbol which says what kind of use this char-table is
       meant for.  */
    Lisp_Object purpose;

    /* The bottom sub char-table for characters of the range 0..127.  It
       is nil if none of ASCII character has a specific value.  */
    Lisp_Object ascii;

    Lisp_Object contents[(1 << CHARTAB_SIZE_BITS_0)];

    /* These hold additional data.  It is a vector.  */
    Lisp_Object extras[1];
  };

struct Lisp_Sub_Char_Table
  {
    /* This is the vector's size field, which also holds the
       pseudovector type information.  It holds the size, too.  */
    EMACS_INT size;
    struct Lisp_Vector *next;

    /* Depth of this sub char-table.  It should be 1, 2, or 3.  A sub
       char-table of depth 1 contains 16 elements, and each element
       covers 4096 (128*32) characters.  A sub char-table of depth 2
       contains 32 elements, and each element covers 128 characters.  A
       sub char-table of depth 3 contains 128 elements, and each element
       is for one character.  */
    Lisp_Object depth;

    /* Minimum character covered by the sub char-table.  */
    Lisp_Object min_char;

    Lisp_Object contents[1];
  };

/* A boolvector is a kind of vectorlike, with contents are like a string.  */
struct Lisp_Bool_Vector
  {
    /* This is the vector's size field.  It doesn't have the real size,
       just the subtype information.  */
    EMACS_UINT vector_size;
    struct Lisp_Vector *next;
    /* This is the size in bits.  */
    EMACS_UINT size;
    /* This contains the actual bits, packed into bytes.  */
    unsigned char data[1];
  };

/* This structure describes a built-in function.
   It is generated by the DEFUN macro only.
   defsubr makes it into a Lisp object.

   This type is treated in most respects as a pseudovector,
   but since we never dynamically allocate or free them,
   we don't need a next-vector field.  */

struct Lisp_Subr
  {