lisp.h

/* Fundamental definitions for GNU Emacs Lisp interpreter.

Copyright (C) 1985-1987, 1993-1995, 1997-2012 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 <stdalign.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <inttypes.h>
#include <limits.h>

#include <intprops.h>

INLINE_HEADER_BEGIN
#ifndef LISP_INLINE
# define LISP_INLINE INLINE
#endif

/* The ubiquitous max and min macros.  */
#undef min
#undef max
#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) < (b) ? (a) : (b))

/* EMACS_INT - signed integer wide enough to hold an Emacs value
   EMACS_INT_MAX - maximum value of EMACS_INT; can be used in #if
   pI - printf length modifier for EMACS_INT
   EMACS_UINT - unsigned variant of EMACS_INT */
#ifndef EMACS_INT_MAX
# if LONG_MAX < LLONG_MAX && defined WIDE_EMACS_INT
typedef long long int EMACS_INT;
typedef unsigned long long int EMACS_UINT;
#  define EMACS_INT_MAX LLONG_MAX
#  define pI "ll"
# elif INT_MAX < LONG_MAX
typedef long int EMACS_INT;
typedef unsigned long int EMACS_UINT;
#  define EMACS_INT_MAX LONG_MAX
#  define pI "l"
# else
typedef int EMACS_INT;
typedef unsigned int EMACS_UINT;
#  define EMACS_INT_MAX INT_MAX
#  define pI ""
# endif
#endif

/* Number of bits in some machine integer types.  */
enum
  {
    BITS_PER_CHAR      = CHAR_BIT,
    BITS_PER_SHORT     = CHAR_BIT * sizeof (short),
    BITS_PER_INT       = CHAR_BIT * sizeof (int),
    BITS_PER_LONG      = CHAR_BIT * sizeof (long int),
    BITS_PER_EMACS_INT = CHAR_BIT * sizeof (EMACS_INT)
  };

/* printmax_t and uprintmax_t are types for printing large integers.
   These are the widest integers that are supported for printing.
   pMd etc. are conversions for printing them.
   On C99 hosts, there's no problem, as even the widest integers work.
   Fall back on EMACS_INT on pre-C99 hosts.  */
#ifdef PRIdMAX
typedef intmax_t printmax_t;
typedef uintmax_t uprintmax_t;
# define pMd PRIdMAX
# define pMu PRIuMAX
#else
typedef EMACS_INT printmax_t;
typedef EMACS_UINT uprintmax_t;
# define pMd pI"d"
# define pMu pI"u"
#endif

/* Use pD to format ptrdiff_t values, which suffice for indexes into
   buffers and strings.  Emacs never allocates objects larger than
   PTRDIFF_MAX bytes, as they cause problems with pointer subtraction.
   In C99, pD can always be "t"; configure it here for the sake of
   pre-C99 libraries such as glibc 2.0 and Solaris 8.  */
#if PTRDIFF_MAX == INT_MAX
# define pD ""
#elif PTRDIFF_MAX == LONG_MAX
# define pD "l"
#elif PTRDIFF_MAX == LLONG_MAX
# define pD "ll"
#else
# define pD "t"
#endif

/* Extra internal type checking?  */

/* Define an Emacs version of 'assert (COND)', since some
   system-defined 'assert's are flaky.  COND should be free of side
   effects; it may or may not be evaluated.  */
#ifndef ENABLE_CHECKING
# define eassert(X) ((void) (0 && (X))) /* Check that X compiles.  */
#else /* ENABLE_CHECKING */

extern _Noreturn void die (const char *, const char *, int);

/* 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.

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

# define eassert(cond)						\
   ((cond) || suppress_checking					\
    ? (void) 0							\
    : die ("assertion failed: " # cond, __FILE__, __LINE__))
#endif /* ENABLE_CHECKING */

/* Use the configure flag --enable-check-lisp-object-type to make
   Lisp_Object use a struct type instead of the default int.  The flag
   causes CHECK_LISP_OBJECT_TYPE to be defined.  */

/***** Select the tagging scheme.  *****/
/* The following option controls the tagging scheme:
   - 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, then use the top 3 bits for tagging, thus
   restricting our possible address range.

   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.  */

enum Lisp_Bits
  {
    /* Number of bits in a Lisp_Object tag.  This can be used in #if,
       and for GDB's sake also as a regular symbol.  */
    GCTYPEBITS =
#define GCTYPEBITS 3
	GCTYPEBITS,

    /* 2**GCTYPEBITS.  This must also be a macro that expands to a
       literal integer constant, for MSVC.  */
    GCALIGNMENT =
#define GCALIGNMENT 8
	GCALIGNMENT,

    /* Number of bits in a Lisp_Object value, not counting the tag.  */
    VALBITS = BITS_PER_EMACS_INT - GCTYPEBITS,

    /* Number of bits in a Lisp fixnum tag.  */
    INTTYPEBITS = GCTYPEBITS - 1,

    /* Number of bits in a Lisp fixnum value, not counting the tag.  */
    FIXNUM_BITS = VALBITS + 1
  };

#if GCALIGNMENT != 1 << GCTYPEBITS
# error "GCALIGNMENT and GCTYPEBITS are inconsistent"
#endif

/* The maximum value that can be stored in a EMACS_INT, assuming all
   bits other than the type bits contribute to a nonnegative signed value.
   This can be used in #if, e.g., '#if VAL_MAX < UINTPTR_MAX' below.  */
#define VAL_MAX (EMACS_INT_MAX >> (GCTYPEBITS - 1))

/* Unless otherwise specified, use USE_LSB_TAG on systems where:  */
#ifndef USE_LSB_TAG
/* 1.  We know malloc returns a multiple of 8.  */
# if (defined GNU_MALLOC || defined DOUG_LEA_MALLOC || defined __GLIBC__ \
      || defined DARWIN_OS || defined __sun)
/* 2.  We can specify multiple-of-8 alignment on static variables.  */
#  ifdef alignas
/* 3.  Pointers-as-ints exceed VAL_MAX.
   On hosts where pointers-as-ints do not exceed VAL_MAX, USE_LSB_TAG is:
    a. unnecessary, because the top bits of an EMACS_INT are unused, and
    b. slower, because it typically requires extra masking.
   So, default USE_LSB_TAG to 1 only on hosts where it might be useful.  */
#   if VAL_MAX < UINTPTR_MAX
#    define USE_LSB_TAG 1
#   endif
#  endif
# endif
#endif
#ifdef USE_LSB_TAG
# undef USE_LSB_TAG
enum enum_USE_LSB_TAG { USE_LSB_TAG = 1 };
# define USE_LSB_TAG 1
#else
enum enum_USE_LSB_TAG { USE_LSB_TAG = 0 };
# define USE_LSB_TAG 0
#endif

#ifndef alignas
# define alignas(alignment) /* empty */
# if USE_LSB_TAG
#  error "USE_LSB_TAG requires alignas"
# endif
#endif


/* Define the fundamental Lisp data structures.  */

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

/* 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.  */
static EMACS_INT const INTMASK = EMACS_INT_MAX >> (INTTYPEBITS - 1);
#define case_Lisp_Int case Lisp_Int0: case Lisp_Int1
#define LISP_INT_TAG_P(x) (((x) & ~Lisp_Int1) == 0)

/* Stolen from GDB.  The only known compiler that doesn't support
   enums in bitfields is MSVC.  */
#ifdef _MSC_VER
#define ENUM_BF(TYPE) unsigned int
#else
#define ENUM_BF(TYPE) enum TYPE
#endif


enum Lisp_Type
  {
    /* Integer.  XINT (obj) is the integer value.  */
    Lisp_Int0 = 0,
    Lisp_Int1 = USE_LSB_TAG ? 1 << INTTYPEBITS : 1,

    /* 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 = USE_LSB_TAG ? 1 : 1 << INTTYPEBITS,

    /* 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.  */
  };

#ifdef CHECK_LISP_OBJECT_TYPE

typedef struct { EMACS_INT i; } Lisp_Object;

#define XLI(o) (o).i
LISP_INLINE Lisp_Object
XIL (EMACS_INT i)
{
  Lisp_Object o = { i };
  return o;
}

LISP_INLINE Lisp_Object
LISP_MAKE_RVALUE (Lisp_Object o)
{
    return o;
}

#define LISP_INITIALLY_ZERO {0}

#undef CHECK_LISP_OBJECT_TYPE
enum CHECK_LISP_OBJECT_TYPE { CHECK_LISP_OBJECT_TYPE = 1 };
#else /* CHECK_LISP_OBJECT_TYPE */

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

typedef EMACS_INT Lisp_Object;
#define XLI(o) (o)
#define XIL(i) (i)
#define LISP_MAKE_RVALUE(o) (0+(o))
#define LISP_INITIALLY_ZERO 0
enum CHECK_LISP_OBJECT_TYPE { CHECK_LISP_OBJECT_TYPE = 0 };
#endif /* CHECK_LISP_OBJECT_TYPE */

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

static ptrdiff_t const ARRAY_MARK_FLAG
#define ARRAY_MARK_FLAG PTRDIFF_MIN
      = ARRAY_MARK_FLAG;

/* In the size word of a struct Lisp_Vector, this bit means it's really
   some other vector-like object.  */
static ptrdiff_t const PSEUDOVECTOR_FLAG
#define PSEUDOVECTOR_FLAG (PTRDIFF_MAX - PTRDIFF_MAX / 2)
      = PSEUDOVECTOR_FLAG;

/* 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,	/* Unused!  */
  PVEC_FREE,
  PVEC_PROCESS,
  PVEC_FRAME,
  PVEC_WINDOW,
  PVEC_BOOL_VECTOR,
  PVEC_BUFFER,
  PVEC_HASH_TABLE,
  PVEC_TERMINAL,
  PVEC_WINDOW_CONFIGURATION,
  PVEC_SUBR,
  PVEC_OTHER,
  /* These last 4 are special because we OR them in fns.c:internal_equal,
     so they have to use a disjoint bit pattern:
     if (!(size & (PVEC_COMPILED | PVEC_CHAR_TABLE
                   | PVEC_SUB_CHAR_TABLE | PVEC_FONT))) */
  PVEC_COMPILED			= 0x10,
  PVEC_CHAR_TABLE		= 0x20,
  PVEC_SUB_CHAR_TABLE		= 0x30,
  PVEC_FONT			= 0x40
};

/* DATA_SEG_BITS forces extra bits to be or'd in with any pointers
   which were stored in a Lisp_Object.  */
#ifndef DATA_SEG_BITS
# define DATA_SEG_BITS 0
#endif
enum { gdb_DATA_SEG_BITS = DATA_SEG_BITS };
#undef DATA_SEG_BITS

enum More_Lisp_Bits
  {
    DATA_SEG_BITS = gdb_DATA_SEG_BITS,

    /* 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 GC).
       The distinction is used, e.g., by Lisp_Process, which places extra
       non-Lisp_Object fields at the end of the structure.  */
    PSEUDOVECTOR_SIZE_BITS = 16,
    PSEUDOVECTOR_SIZE_MASK = (1 << PSEUDOVECTOR_SIZE_BITS) - 1,
    PVEC_TYPE_MASK = 0x0fff << PSEUDOVECTOR_SIZE_BITS,

    /* Number of bits to put in each character in the internal representation
       of bool vectors.  This should not vary across implementations.  */
    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.  */

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

#if USE_LSB_TAG

enum lsb_bits
  {
    TYPEMASK = (1 << GCTYPEBITS) - 1,
    VALMASK = ~ TYPEMASK
  };
#define XTYPE(a) ((enum Lisp_Type) (XLI (a) & TYPEMASK))
#define XINT(a) (XLI (a) >> INTTYPEBITS)
#define XUINT(a) ((EMACS_UINT) XLI (a) >> INTTYPEBITS)
#define make_number(N) XIL ((EMACS_INT) (N) << INTTYPEBITS)
#define XSET(var, type, ptr)						   \
  (eassert (XTYPE (XIL ((intptr_t) (ptr))) == 0), /* Check alignment.  */  \
   (var) = XIL ((type) | (intptr_t) (ptr)))

#define XPNTR(a) ((intptr_t) (XLI (a) & ~TYPEMASK))
#define XUNTAG(a, type) ((intptr_t) (XLI (a) - (type)))

#else  /* not USE_LSB_TAG */

static EMACS_INT const VALMASK
#define VALMASK VAL_MAX
      = VALMASK;

#define XTYPE(a) ((enum Lisp_Type) ((EMACS_UINT) XLI (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 integers have zero-bits in their tags.  */
#define XFASTINT(a) (XLI (a) + 0)
#define XSETFASTINT(a, b) ((a) = XIL (b))

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

#define XINT(a) (XLI (a) << INTTYPEBITS >> INTTYPEBITS)
#define XUINT(a) ((EMACS_UINT) (XLI (a) & INTMASK))
#define make_number(N) XIL ((EMACS_INT) (N) & INTMASK)

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

#if DATA_SEG_BITS
/* DATA_SEG_BITS forces extra bits to be or'd in with any pointers
   which were stored in a Lisp_Object */
#define XPNTR(a) ((uintptr_t) ((XLI (a) & VALMASK)) | DATA_SEG_BITS))
#else
#define XPNTR(a) ((uintptr_t) (XLI (a) & VALMASK))
#endif

#endif /* not USE_LSB_TAG */

/* 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

/* Extract the pointer value of the Lisp object A, under the
   assumption that A's type is TYPE.  This is a fallback
   implementation if nothing faster is available.  */
#ifndef XUNTAG
# define XUNTAG(a, type) XPNTR (a)
#endif

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

/* Largest and smallest representable fixnum values.  These are the C
   values.  They are macros for use in static initializers, and
   constants for visibility to GDB.  */
static EMACS_INT const MOST_POSITIVE_FIXNUM =
#define MOST_POSITIVE_FIXNUM (EMACS_INT_MAX >> INTTYPEBITS)
	MOST_POSITIVE_FIXNUM;
static EMACS_INT const MOST_NEGATIVE_FIXNUM =
#define MOST_NEGATIVE_FIXNUM (-1 - MOST_POSITIVE_FIXNUM)
	MOST_NEGATIVE_FIXNUM;

/* 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 or if I is a NaN.  */

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

LISP_INLINE ptrdiff_t
clip_to_bounds (ptrdiff_t lower, EMACS_INT num, ptrdiff_t upper)
{
  return num < lower ? lower : num <= upper ? num : upper;
}

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

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

/* Misc types.  */

#define XMISC(a)	((union Lisp_Misc *) XUNTAG (a, Lisp_Misc))
#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 *) XUNTAG (a, Lisp_Vectorlike))
#define XWINDOW(a) (eassert (WINDOWP (a)), \
		    (struct window *) XUNTAG (a, Lisp_Vectorlike))
#define XTERMINAL(a) (eassert (TERMINALP (a)), \
		      (struct terminal *) XUNTAG (a, Lisp_Vectorlike))
#define XSUBR(a) (eassert (SUBRP (a)), \
		  (struct Lisp_Subr *) XUNTAG (a, Lisp_Vectorlike))
#define XBUFFER(a) (eassert (BUFFERP (a)), \
		    (struct buffer *) XUNTAG (a, Lisp_Vectorlike))
#define XCHAR_TABLE(a) (eassert (CHAR_TABLE_P (a)), \
			(struct Lisp_Char_Table *) XUNTAG (a, Lisp_Vectorlike))
#define XSUB_CHAR_TABLE(a) (eassert (SUB_CHAR_TABLE_P (a)), \
			    ((struct Lisp_Sub_Char_Table *) \
			     XUNTAG (a, Lisp_Vectorlike)))
#define XBOOL_VECTOR(a) (eassert (BOOL_VECTOR_P (a)), \
			 ((struct Lisp_Bool_Vector *) \
			  XUNTAG (a, Lisp_Vectorlike)))

/* 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) XSETTYPED_PVECTYPE (v, header.size, code)
#define XSETTYPED_PVECTYPE(v, size_member, code) \
  ((v)->size_member |= PSEUDOVECTOR_FLAG | ((code) << PSEUDOVECTOR_SIZE_BITS))
#define XSETPVECTYPESIZE(v, code, sizeval) \
  ((v)->header.size = (PSEUDOVECTOR_FLAG			\
		       | ((code) << PSEUDOVECTOR_SIZE_BITS)	\
		       | (sizeval)))

/* The cast to struct vectorlike_header * avoids aliasing issues.  */
#define XSETPSEUDOVECTOR(a, b, code) \
  XSETTYPED_PSEUDOVECTOR (a, b,					\
			  (((struct vectorlike_header *)	\
			    XUNTAG (a, Lisp_Vectorlike))	\
			   ->size),				\
			  code)
#define XSETTYPED_PSEUDOVECTOR(a, b, size, code)			\
  (XSETVECTOR (a, b),							\
   eassert ((size & (PSEUDOVECTOR_FLAG | PVEC_TYPE_MASK))		\
	    == (PSEUDOVECTOR_FLAG | (code << PSEUDOVECTOR_SIZE_BITS))))

#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))
/* XSETSUBR is special since Lisp_Subr lacks struct vectorlike_header.  */
#define XSETSUBR(a, b) \
  XSETTYPED_PSEUDOVECTOR (a, b, XSUBR (a)->size, 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))->header.size
#define ASET(ARRAY, IDX, VAL)	\
  (eassert (0 <= (IDX) && (IDX) < ASIZE (ARRAY)),	\
   XVECTOR (ARRAY)->contents[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)

/* Avoid "differ in sign" warnings.  */
#define SSDATA(x)  ((char *) SDATA (x))

#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)

/* Deprecated and will be removed soon.  */

#define INTERNAL_FIELD(field) field ## _

/* 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)

struct Lisp_Cons
  {
    /* Car of this cons cell.  */
    Lisp_Object car;

    union
    {
      /* Cdr of this cons cell.  */
      Lisp_Object cdr;

      /* Used to chain conses on a free list.  */
      struct Lisp_Cons *chain;
    } u;
  };

/* 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.)  */
#define XCAR_AS_LVALUE(c) (XCONS (c)->car)
#define XCDR_AS_LVALUE(c) (XCONS (c)->u.cdr)

/* 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)

/* True 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 ptrdiff_t 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 */

/* An upper bound on the number of bytes in a Lisp string, not
   counting the terminating null.  This a tight enough bound to
   prevent integer overflow errors that would otherwise occur during
   string size calculations.  A string cannot contain more bytes than
   a fixnum can represent, nor can it be so long that C pointer
   arithmetic stops working on the string plus its terminating null.
   Although the actual size limit (see STRING_BYTES_MAX in alloc.c)
   may be a bit smaller than STRING_BYTES_BOUND, calculating it here
   would expose alloc.c internal details that we'd rather keep
   private.

   This is a macro for use in static initializers, and a constant for
   visibility to GDB.  The cast to ptrdiff_t ensures that
   the macro is signed.  */
static ptrdiff_t const STRING_BYTES_BOUND =
#define STRING_BYTES_BOUND  \
  ((ptrdiff_t) min (MOST_POSITIVE_FIXNUM, min (SIZE_MAX, PTRDIFF_MAX) - 1))
	STRING_BYTES_BOUND;

/* 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)

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

struct Lisp_String
  {
    ptrdiff_t size;
    ptrdiff_t size_byte;
    INTERVAL intervals;		/* Text properties in this string.  */
    unsigned char *data;
  };

/* Header of vector-like objects.  This documents the layout constraints on
   vectors and pseudovectors other than struct Lisp_Subr.  It also prevents
   compilers from being fooled by Emacs's type punning: the XSETPSEUDOVECTOR
   and PSEUDOVECTORP macros cast their pointers to struct vectorlike_header *,
   because when two such pointers potentially alias, a compiler won't
   incorrectly reorder loads and stores to their size fields.  See
   <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=8546>.  */
struct vectorlike_header
  {
    /* This field contains various pieces of information:
       - The MSB (ARRAY_MARK_FLAG) holds the gcmarkbit.
       - The next bit (PSEUDOVECTOR_FLAG) indicates whether this is a plain
         vector (0) or a pseudovector (1).
       - If PSEUDOVECTOR_FLAG is 0, the rest holds the size (number
         of slots) of the vector.
       - If PSEUDOVECTOR_FLAG is 1, the rest is subdivided into
         a "pvec type" tag held in PVEC_TYPE_MASK and a size held in the lowest
         PSEUDOVECTOR_SIZE_BITS.  That size normally indicates the number of
         Lisp_Object slots at the beginning of the object that need to be
         traced by the GC, tho some types use it slightly differently.
       - E.g. if the pvec type is PVEC_FREE it means this is an unallocated
         vector on a free-list and PSEUDOVECTOR_SIZE_BITS indicates its size
         in bytes.  */
    ptrdiff_t size;

    /* When the vector is allocated from a vector block, NBYTES is used
       if the vector is not on a free list, and VECTOR is used otherwise.
       For large vector-like objects, BUFFER or VECTOR is used as a pointer
       to the next vector-like object.  It is generally a buffer or a
       Lisp_Vector alias, so for convenience it is a union instead of a
       pointer: this way, one can write P->next.vector instead of ((struct
       Lisp_Vector *) P->next).  */
    union {
      /* This is only needed for small vectors that are not free because the
	 `size' field only gives us the number of Lisp_Object slots, whereas we
	 need to know the total size, including non-Lisp_Object data.
	 FIXME: figure out a way to store this info elsewhere so we can
	 finally get rid of this extra word of overhead.  */
      ptrdiff_t nbytes;
      struct buffer *buffer;
      /* FIXME: This can be removed: For large vectors, this field could be
	 placed *before* the vector itself.  And for small vectors on a free
	 list, this field could be stored in the vector's bytes, since the
	 empty vector is handled specially anyway.  */
      struct Lisp_Vector *vector;
    } next;
  };

/* Regular vector is just a header plus array of Lisp_Objects.  */

struct Lisp_Vector
  {
    struct vectorlike_header header;
    Lisp_Object contents[1];
  };

/* A boolvector is a kind of vectorlike, with contents are like a string.  */

struct Lisp_Bool_Vector
  {
    /* HEADER.SIZE is the vector's size field.  It doesn't have the real size,
       just the subtype information.  */
    struct vectorlike_header header;
    /* This is the size in bits.  */
    EMACS_INT size;
    /* This contains the actual bits, packed into bytes.  */
    unsigned char data[1];
  };

/* Some handy constants for calculating sizes
   and offsets, mostly of vectorlike objects.   */

enum
  {
    header_size = offsetof (struct Lisp_Vector, contents),
    bool_header_size = offsetof (struct Lisp_Bool_Vector, data),
    word_size = sizeof (Lisp_Object)
  };

/* 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) - header_size + word_size - 1) / word_size)

/* 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) - header_size) / word_size)

/* 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.  */

#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__ */

/* Compute A OP B, using the unsigned comparison operator OP.  A and B
   should be integer expressions.  This is not the same as
   mathematical comparison; for example, UNSIGNED_CMP (0, <, -1)
   returns 1.  For efficiency, prefer plain unsigned comparison if A
   and B's sizes both fit (after integer promotion).  */
#define UNSIGNED_CMP(a, op, b)						\
  (max (sizeof ((a) + 0), sizeof ((b) + 0)) <= sizeof (unsigned)	\
   ? ((a) + (unsigned) 0) op ((b) + (unsigned) 0)			\
   : ((a) + (uintmax_t) 0) op ((b) + (uintmax_t) 0))

/* Nonzero iff C is an ASCII character.  */
#define ASCII_CHAR_P(c) UNSIGNED_CMP (c, <, 0x80)

/* 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)					\
  (ASCII_CHAR_P (IDX) && SUB_CHAR_TABLE_P (XCHAR_TABLE (CT)->ascii)	\
   ? set_sub_char_table_contents (XCHAR_TABLE (CT)->ascii, IDX, VAL)	\
   : char_table_set (CT, IDX, VAL))

enum CHARTAB_SIZE_BITS
  {
    CHARTAB_SIZE_BITS_0 = 6,
    CHARTAB_SIZE_BITS_1 = 4,
    CHARTAB_SIZE_BITS_2 = 5,
    CHARTAB_SIZE_BITS_3 = 7
  };

extern const int chartab_size[4];

struct Lisp_Char_Table
  {
    /* HEADER.SIZE 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.  */
    struct vectorlike_header header;

    /* 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;