/********************************************
 ** Do not edit this file!
 ** This file is generated from foreign.rktc,
 ** to make changes, edit that file and
 ** run it to generate an updated version
 ** of this file.
 ********************************************/

#include "schpriv.h"

#ifndef DONT_USE_FOREIGN

#include <errno.h>

#ifndef WINDOWS_DYNAMIC_LOAD

# include <dlfcn.h>

# if SIZEOF_CHAR == 1
   typedef   signed char Tsint8;
   typedef unsigned char Tuint8;
# else
#  error "configuration error, please contact PLT (int8)"
# endif

# if SIZEOF_SHORT == 2
   typedef   signed short Tsint16;
   typedef unsigned short Tuint16;
# elif SIZEOF_INT == 2
   typedef   signed int Tsint16;
   typedef unsigned int Tuint16;
# else
#  error "configuration error, please contact PLT (int16)"
# endif

# if SIZEOF_INT == 4
   typedef   signed int Tsint32;
   typedef unsigned int Tuint32;
# elif SIZEOF_LONG == 4
   typedef   signed long Tsint32;
   typedef unsigned long Tuint32;
# else
#  error "configuration error, please contact PLT (int32)"
# endif

# if SIZEOF_LONG == 8
   typedef   signed long Tsint64;
   typedef unsigned long Tuint64;
# elif SIZEOF_LONG_LONG == 8
   typedef   signed long long Tsint64;
   typedef unsigned long long Tuint64;
# else
#  error "configuration error, please contact PLT (int64)"
# endif

#else /* WINDOWS_DYNAMIC_LOAD defined */

# include <windows.h>
# ifndef __CYGWIN32__
#  include <wtypes.h>
   typedef          _int8  Tsint8;
   typedef unsigned _int8  Tuint8;
   typedef          _int16 Tsint16;
   typedef unsigned _int16 Tuint16;
   typedef          _int32 Tsint32;
   typedef unsigned _int32 Tuint32;
   typedef          _int64 Tsint64;
   typedef unsigned _int64 Tuint64;
# endif

#endif /* WINDOWS_DYNAMIC_LOAD */

#include "ffi.h"

#ifndef MZ_PRECISE_GC
# define XFORM_OK_PLUS +
# define GC_CAN_IGNORE /* empty */
#endif

#define W_OFFSET(src, delta) ((char *)(src) XFORM_OK_PLUS (delta))

/* same as the macro in file.c */
#define TO_PATH(x) (SCHEME_PATHP(x) ? (x) : scheme_char_string_to_path(x))

static void save_errno_values(int kind);

/*****************************************************************************/
/* Defining EnumProcessModules for openning `self' as an ffi-lib */

/* We'd like to use EnumProcessModules to find all loaded DLLs, but it's
   only available in NT 4.0 and later. The alternative, Module32{First,Next},
   is available *except* for NT 4.0! So we try EnumProcessModules first. */

#ifdef WINDOWS_DYNAMIC_LOAD
#ifdef MZ_PRECISE_GC
START_XFORM_SKIP;
#endif

int epm_tried = 0;
typedef BOOL (WINAPI *EnumProcessModules_t)(HANDLE hProcess,
                                            HMODULE* lphModule,
                                            DWORD cb,
                                            LPDWORD lpcbNeeded);
EnumProcessModules_t _EnumProcessModules;
#include <tlhelp32.h>

BOOL mzEnumProcessModules(HANDLE hProcess, HMODULE* lphModule,
                          DWORD cb, LPDWORD lpcbNeeded)
{
  if (!epm_tried) {
    HMODULE hm;
    hm = LoadLibrary("psapi.dll");
    if (hm) {
      _EnumProcessModules =
        (EnumProcessModules_t)GetProcAddress(hm, "EnumProcessModules");
    }
    epm_tried = 1;
  }

  if (_EnumProcessModules)
    return _EnumProcessModules(hProcess, lphModule, cb, lpcbNeeded);
  else {
    HANDLE snapshot;
    MODULEENTRY32 mod;
    int i, ok;

    snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPMODULE,
                                        GetCurrentProcessId());
    if (snapshot == INVALID_HANDLE_VALUE)
      return FALSE;

    for (i = 0; 1; i++) {
      mod.dwSize = sizeof(mod);
      if (!i)
        ok = Module32First(snapshot, &mod);
      else
        ok = Module32Next(snapshot, &mod);
      if (!ok)
        break;
      if (cb >= sizeof(HMODULE)) {
        lphModule[i] = mod.hModule;
        cb -= sizeof(HMODULE);
      }
    }

    CloseHandle(snapshot);
    *lpcbNeeded = i * sizeof(HMODULE);
    return GetLastError() == ERROR_NO_MORE_FILES;
  }
}

#ifdef MZ_PRECISE_GC
END_XFORM_SKIP;
#endif
#endif /* WINDOWS_DYNAMIC_LOAD */

/*****************************************************************************/
/* Library objects */

/* ffi-lib structure definition */
static Scheme_Type ffi_lib_tag;
typedef struct ffi_lib_struct {
  Scheme_Object so;
  void* handle;
  Scheme_Object* name;
  Scheme_Hash_Table* objects;
} ffi_lib_struct;
#define SCHEME_FFILIBP(x) (SCHEME_TYPE(x)==ffi_lib_tag)
#define MYNAME "ffi-lib?"
static Scheme_Object *foreign_ffi_lib_p(int argc, Scheme_Object *argv[])
{
  return SCHEME_FFILIBP(argv[0]) ? scheme_true : scheme_false;
}
#undef MYNAME
/* 3m stuff for ffi_lib */
#ifdef MZ_PRECISE_GC
START_XFORM_SKIP;
int ffi_lib_SIZE(void *p) {
  return gcBYTES_TO_WORDS(sizeof(ffi_lib_struct));
}
int ffi_lib_MARK(void *p) {
  ffi_lib_struct *s = (ffi_lib_struct *)p;
  gcMARK(s->handle);
  gcMARK(s->name);
  gcMARK(s->objects);
  return gcBYTES_TO_WORDS(sizeof(ffi_lib_struct));
}
int ffi_lib_FIXUP(void *p) {
  ffi_lib_struct *s = (ffi_lib_struct *)p;
  gcFIXUP(s->handle);
  gcFIXUP(s->name);
  gcFIXUP(s->objects);
  return gcBYTES_TO_WORDS(sizeof(ffi_lib_struct));
}
END_XFORM_SKIP;
#endif

THREAD_LOCAL_DECL(static Scheme_Hash_Table *opened_libs);

/* (ffi-lib filename no-error?) -> ffi-lib */
#define MYNAME "ffi-lib"
static Scheme_Object *foreign_ffi_lib(int argc, Scheme_Object *argv[])
{
  char *name;
  Scheme_Object *path, *hashname;
  void *handle;
  int null_ok = 0;
  ffi_lib_struct *lib;
  if (!(SCHEME_PATH_STRINGP(argv[0]) || SCHEME_FALSEP(argv[0])))
    scheme_wrong_type(MYNAME, "string-or-false", 0, argc, argv);
  /* leave the filename as given, the system will look for it */
  /* (`#f' means open the executable) */
  path = SCHEME_FALSEP(argv[0]) ? NULL : TO_PATH(argv[0]);
  name = (path==NULL) ? NULL : SCHEME_PATH_VAL(path);
  hashname = (Scheme_Object*)((name==NULL) ? "" : name);
  lib = (ffi_lib_struct*)scheme_hash_get(opened_libs, hashname);
  if (!lib) {
    Scheme_Hash_Table *ht;
#   ifdef WINDOWS_DYNAMIC_LOAD
    if (name==NULL) {
      /* openning the executable is marked by a NULL handle */
      handle = NULL;
      null_ok = 1;
    } else
      handle = LoadLibrary(name);
#   else /* WINDOWS_DYNAMIC_LOAD undefined */
    handle = dlopen(name, RTLD_NOW | RTLD_GLOBAL);
#   endif /* WINDOWS_DYNAMIC_LOAD */
    if (handle == NULL && !null_ok) {
      if (argc > 1 && SCHEME_TRUEP(argv[1])) return scheme_false;
      else {
#       ifdef WINDOWS_DYNAMIC_LOAD
        long err;
        err = GetLastError();
        scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                         MYNAME": couldn't open %V (%E)", argv[0], err);
#       else /* WINDOWS_DYNAMIC_LOAD undefined */
        scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                         MYNAME": couldn't open %V (%s)", argv[0], dlerror());
#       endif /* WINDOWS_DYNAMIC_LOAD */
      }
    }
    ht = scheme_make_hash_table(SCHEME_hash_string);
    lib = (ffi_lib_struct*)scheme_malloc_tagged(sizeof(ffi_lib_struct));
    lib->so.type = ffi_lib_tag;
    lib->handle = (handle);
    lib->name = (argv[0]);
    lib->objects = (ht);
    scheme_hash_set(opened_libs, hashname, (Scheme_Object*)lib);
    /* no dlclose finalizer - since the hash table always keeps a reference */
    /* maybe add some explicit unload at some point */
  }
  return (Scheme_Object*)lib;
}
#undef MYNAME

/* (ffi-lib-name ffi-lib) -> string */
#define MYNAME "ffi-lib-name"
static Scheme_Object *foreign_ffi_lib_name(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FFILIBP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-lib", 0, argc, argv);
  return ((ffi_lib_struct*)argv[0])->name;
}
#undef MYNAME

/*****************************************************************************/
/* Pull pointers (mostly functions) out of ffi-lib objects */

/* ffi-obj structure definition */
static Scheme_Type ffi_obj_tag;
typedef struct ffi_obj_struct {
  Scheme_Object so;
  void* obj;
  char* name;
  ffi_lib_struct* lib;
} ffi_obj_struct;
#define SCHEME_FFIOBJP(x) (SCHEME_TYPE(x)==ffi_obj_tag)
#define MYNAME "ffi-obj?"
static Scheme_Object *foreign_ffi_obj_p(int argc, Scheme_Object *argv[])
{
  return SCHEME_FFIOBJP(argv[0]) ? scheme_true : scheme_false;
}
#undef MYNAME
/* 3m stuff for ffi_obj */
#ifdef MZ_PRECISE_GC
START_XFORM_SKIP;
int ffi_obj_SIZE(void *p) {
  return gcBYTES_TO_WORDS(sizeof(ffi_obj_struct));
}
int ffi_obj_MARK(void *p) {
  ffi_obj_struct *s = (ffi_obj_struct *)p;
  gcMARK(s->obj);
  gcMARK(s->name);
  gcMARK(s->lib);
  return gcBYTES_TO_WORDS(sizeof(ffi_obj_struct));
}
int ffi_obj_FIXUP(void *p) {
  ffi_obj_struct *s = (ffi_obj_struct *)p;
  gcFIXUP(s->obj);
  gcFIXUP(s->name);
  gcFIXUP(s->lib);
  return gcBYTES_TO_WORDS(sizeof(ffi_obj_struct));
}
END_XFORM_SKIP;
#endif

/* (ffi-obj objname ffi-lib-or-libname) -> ffi-obj */
#define MYNAME "ffi-obj"
static Scheme_Object *foreign_ffi_obj(int argc, Scheme_Object *argv[])
{
  ffi_obj_struct *obj;
  void *dlobj;
  ffi_lib_struct *lib = NULL;
  char *dlname;
  if (SCHEME_FFILIBP(argv[1]))
    lib = (ffi_lib_struct*)argv[1];
  else if (SCHEME_PATH_STRINGP(argv[1]) || SCHEME_FALSEP(argv[1]))
    lib = (ffi_lib_struct*)(foreign_ffi_lib(1,&argv[1]));
  else
    scheme_wrong_type(MYNAME, "ffi-lib", 1, argc, argv);
  if (!SCHEME_BYTE_STRINGP(argv[0]))
    scheme_wrong_type(MYNAME, "bytes", 0, argc, argv);
  dlname = SCHEME_BYTE_STR_VAL(argv[0]);
  obj = (ffi_obj_struct*)scheme_hash_get(lib->objects, (Scheme_Object*)dlname);
  if (!obj) {
#   ifdef WINDOWS_DYNAMIC_LOAD
    if (lib->handle) {
      dlobj = GetProcAddress(lib->handle, dlname);
    } else {
      /* this is for the executable-open case, which was marked by a NULL
       * handle, deal with it by searching all current modules */
#     define NUM_QUICK_MODS 16
      HMODULE *mods, me, quick_mods[NUM_QUICK_MODS];
      DWORD cnt = NUM_QUICK_MODS * sizeof(HMODULE), actual_cnt, i;
      me = GetCurrentProcess();
      mods = quick_mods;
      if (mzEnumProcessModules(me, mods, cnt, &actual_cnt)) {
        if (actual_cnt > cnt) {
          cnt = actual_cnt;
          mods = (HMODULE *)scheme_malloc_atomic(cnt);
          if (!mzEnumProcessModules(me, mods, cnt, &actual_cnt))
            mods = NULL;
        } else
          cnt = actual_cnt;
      } else
        mods = NULL;
      if (mods) {
        cnt /= sizeof(HMODULE);
        for (i = 0; i < cnt; i++) {
          dlobj = GetProcAddress(mods[i], dlname);
          if (dlobj) break;
        }
      } else
        dlobj = NULL;
    }
    if (!dlobj) {
      long err;
      err = GetLastError();
      scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                       MYNAME": couldn't get \"%s\" from %V (%E)",
                       dlname, lib->name, err);
    }
#   else /* WINDOWS_DYNAMIC_LOAD undefined */
    dlobj = dlsym(lib->handle, dlname);
    if (!dlobj) {
      const char *err;
      err = dlerror();
      if (err != NULL)
        scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                         MYNAME": couldn't get \"%s\" from %V (%s)",
                         dlname, lib->name, err);
    }
#   endif /* WINDOWS_DYNAMIC_LOAD */
    obj = (ffi_obj_struct*)scheme_malloc_tagged(sizeof(ffi_obj_struct));
    obj->so.type = ffi_obj_tag;
    obj->obj = (dlobj);
    obj->name = (dlname);
    obj->lib = (lib);
    scheme_hash_set(lib->objects, (Scheme_Object*)dlname, (Scheme_Object*)obj);
  }
  return (obj == NULL) ? scheme_false : (Scheme_Object*)obj;
}
#undef MYNAME

/* (ffi-obj-lib ffi-obj) -> ffi-lib */
#define MYNAME "ffi-obj-lib"
static Scheme_Object *foreign_ffi_obj_lib(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FFIOBJP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj", 0, argc, argv);
  return (Scheme_Object*)(((ffi_obj_struct*)argv[0])->lib);
}
#undef MYNAME

/* (ffi-obj-name ffi-obj) -> string */
#define MYNAME "ffi-obj-name"
static Scheme_Object *foreign_ffi_obj_name(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FFIOBJP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj", 0, argc, argv);
  return scheme_make_byte_string(((ffi_obj_struct*)argv[0])->name);
}
#undef MYNAME

/*****************************************************************************/
/* Type helpers */

/* These are not defined in Racket because:
 * - SCHEME_UINT_VAL is not really a simple accessor like other SCHEME_X_VALs
 * - scheme_make_integer_from_unsigned behaves the same as the signed version
 */
#define SCHEME_UINT_VAL(obj) ((unsigned)(SCHEME_INT_VAL(obj)))
#define scheme_make_integer_from_unsigned(i) \
  ((Scheme_Object *)((((unsigned long)i) << 1) | 0x1))

#ifndef SIXTY_FOUR_BIT_INTEGERS

/* longs and ints are really the same */
#define scheme_get_realint_val(x,y) \
  scheme_get_int_val(x,(long*)(y))
#define scheme_get_unsigned_realint_val(x,y) \
  scheme_get_unsigned_int_val(x,(unsigned long*)(y))
#define scheme_make_realinteger_value \
  scheme_make_integer_value
#define scheme_make_realinteger_value_from_unsigned \
  scheme_make_integer_value_from_unsigned

#else /* SIXTY_FOUR_BIT_INTEGERS defined */

/* These will make sense in Racket when longs are longer than ints (needed
 * for libffi's int32 types).  There is no need to deal with bignums because
 * mzscheme's fixnums are longs. */
inline int scheme_get_realint_val(Scheme_Object *o, int *v)
{
  if (SCHEME_INTP(o)) {
    unsigned long lv = SCHEME_INT_VAL(o);
    int i = (int)lv;
    if (i != lv)
      return 0;
    *v = i;
    return 1;
  } else return 0;
}
inline int scheme_get_unsigned_realint_val(Scheme_Object *o, unsigned int *v)
{
  if (SCHEME_INTP(o)) {
    unsigned long lv = SCHEME_INT_VAL(o);
    unsigned int i = (unsigned int)lv;
    if (i != lv)
      return 0;
    *v = i;
    return 1;
  } else return 0;
}
#define scheme_make_realinteger_value(ri) \
  scheme_make_integer((long)(ri))
#define scheme_make_realinteger_value_from_unsigned(ri) \
  scheme_make_integer((unsigned long)(ri))

#endif /* SIXTY_FOUR_BIT_INTEGERS */

/* This is related to the section of scheme.h that defines mzlonglong. */
#ifndef INT64_AS_LONG_LONG
#ifdef  NO_LONG_LONG_TYPE
#ifndef SIXTY_FOUR_BIT_INTEGERS
#error foreign requires a 64-bit integer type type.
#endif
#endif
#endif

#define SCHEME_FALSEP_OR_CHAR_STRINGP(o) (SCHEME_FALSEP(o) || SCHEME_CHAR_STRINGP(o))

static mzchar *ucs4_string_or_null_to_ucs4_pointer(Scheme_Object *ucs)
{
  if (SCHEME_FALSEP(ucs)) return NULL;
  return SCHEME_CHAR_STR_VAL(ucs);
}

static unsigned short *ucs4_string_to_utf16_pointer(Scheme_Object *ucs)
{
  long ulen;
  unsigned short *res;
  res = scheme_ucs4_to_utf16
          (SCHEME_CHAR_STR_VAL(ucs), 0, 1+SCHEME_CHAR_STRLEN_VAL(ucs),
           NULL, -1, &ulen, 0);
  return res;
}

static unsigned short *ucs4_string_or_null_to_utf16_pointer(Scheme_Object *ucs)
{
  if (SCHEME_FALSEP(ucs)) return NULL;
  return ucs4_string_to_utf16_pointer(ucs);
}

Scheme_Object *utf16_pointer_to_ucs4_string(unsigned short *utf)
{
  long ulen;
  mzchar *res;
  int end;
  if (!utf) return scheme_false;
  for (end=0; utf[end] != 0; end++) { /**/ }
  res = scheme_utf16_to_ucs4(utf, 0, end, NULL, -1, &ulen, 0);
  return scheme_make_sized_char_string(res, ulen, 0);
}

/*****************************************************************************/
/* Types */

/***********************************************************************
 * The following are the only primitive types.
 * The tricky part is figuring out what width-ed types correspond to
 * what internal types.  Matthew says:
 *   Racket expects to be compiled such that sizeof(int) == 4,
 *   sizeof(long) == sizeof(void*), sizeof(short) >= 2,
 *   sizeof(char) == 1, sizeof(float) == 4, and sizeof(double) == 8.
 *   So, on a 64-bit OS, Racket expects only `long' to change.
 **********************************************************************/

/* returns #<void> when used as output type, not for input types. */
#define FOREIGN_void (1)
/* Type Name:   void
 * LibFfi type: ffi_type_void
 * C type:      -none-
 * Predicate:   -none-
 * Scheme->C:   -none-
 * S->C offset: 0
 * C->Scheme:   scheme_void
 */

#define FOREIGN_int8 (2)
/* Type Name:   int8
 * LibFfi type: ffi_type_sint8
 * C type:      Tsint8
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_INT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer(<C>)
 */

#define FOREIGN_uint8 (3)
/* Type Name:   uint8
 * LibFfi type: ffi_type_uint8
 * C type:      Tuint8
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_UINT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_from_unsigned(<C>)
 */

#define FOREIGN_int16 (4)
/* Type Name:   int16
 * LibFfi type: ffi_type_sint16
 * C type:      Tsint16
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_INT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer(<C>)
 */

#define FOREIGN_uint16 (5)
/* Type Name:   uint16
 * LibFfi type: ffi_type_uint16
 * C type:      Tuint16
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_UINT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_from_unsigned(<C>)
 */

/* Treats integers properly: */
#define FOREIGN_int32 (6)
/* Type Name:   int32
 * LibFfi type: ffi_type_sint32
 * C type:      Tsint32
 * Predicate:   scheme_get_realint_val(<Scheme>,&aux)
 * Scheme->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Scheme:   scheme_make_realinteger_value(<C>)
 */

/* Treats integers properly: */
#define FOREIGN_uint32 (7)
/* Type Name:   uint32
 * LibFfi type: ffi_type_uint32
 * C type:      Tuint32
 * Predicate:   scheme_get_unsigned_realint_val(<Scheme>,&aux)
 * Scheme->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Scheme:   scheme_make_realinteger_value_from_unsigned(<C>)
 */

#define FOREIGN_int64 (8)
/* Type Name:   int64
 * LibFfi type: ffi_type_sint64
 * C type:      Tsint64
 * Predicate:   scheme_get_long_long_val(<Scheme>,&aux)
 * Scheme->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_value_from_long_long(<C>)
 */

#define FOREIGN_uint64 (9)
/* Type Name:   uint64
 * LibFfi type: ffi_type_uint64
 * C type:      Tuint64
 * Predicate:   scheme_get_unsigned_long_long_val(<Scheme>,&aux)
 * Scheme->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_value_from_unsigned_long_long(<C>)
 */

/* This is like int32, but always assumes fixnum: */
#define FOREIGN_fixint (10)
/* Type Name:   fixint
 * LibFfi type: ffi_type_sint32
 * C type:      Tsint32
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_INT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer(<C>)
 */

/* This is like uint32, but always assumes fixnum: */
#define FOREIGN_ufixint (11)
/* Type Name:   ufixint
 * LibFfi type: ffi_type_uint32
 * C type:      Tuint32
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_UINT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_from_unsigned(<C>)
 */

/* This is what mzscheme defines as long: */
#ifndef SIXTY_FOUR_BIT_INTEGERS
#define ffi_type_smzlong ffi_type_sint32
#define ffi_type_umzlong ffi_type_uint32
#else /* SIXTY_FOUR_BIT_INTEGERS defined */
#define ffi_type_smzlong ffi_type_sint64
#define ffi_type_umzlong ffi_type_uint64
#endif /* SIXTY_FOUR_BIT_INTEGERS */

/* This is what mzscheme defines as long, assuming fixnums: */
#define FOREIGN_fixnum (12)
/* Type Name:   fixnum
 * LibFfi type: ffi_type_smzlong
 * C type:      long
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_INT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer(<C>)
 */

/* This is what mzscheme defines as ulong, assuming fixnums: */
#define FOREIGN_ufixnum (13)
/* Type Name:   ufixnum
 * LibFfi type: ffi_type_umzlong
 * C type:      unsigned long
 * Predicate:   SCHEME_INTP(<Scheme>)
 * Scheme->C:   SCHEME_UINT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_integer_from_unsigned(<C>)
 */

#define FOREIGN_float (14)
/* Type Name:   float
 * LibFfi type: ffi_type_float
 * C type:      float
 * Predicate:   SCHEME_FLTP(<Scheme>)
 * Scheme->C:   SCHEME_FLT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_float(<C>)
 */

#define FOREIGN_double (15)
/* Type Name:   double
 * LibFfi type: ffi_type_double
 * C type:      double
 * Predicate:   SCHEME_DBLP(<Scheme>)
 * Scheme->C:   SCHEME_DBL_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_double(<C>)
 */

/* A double that will coerce numbers to doubles: */
#define FOREIGN_doubleS (16)
/* Type Name:   double* (doubleS)
 * LibFfi type: ffi_type_double
 * C type:      double
 * Predicate:   SCHEME_REALP(<Scheme>)
 * Scheme->C:   scheme_real_to_double(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_double(<C>)
 */

/* Booleans -- implemented as an int which is 1 or 0: */
#define FOREIGN_bool (17)
/* Type Name:   bool
 * LibFfi type: ffi_type_sint
 * C type:      int
 * Predicate:   1
 * Scheme->C:   SCHEME_TRUEP(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   (<C>?scheme_true:scheme_false)
 */

/* Strings -- no copying is done (when possible).
 * #f is not NULL only for byte-strings, for other strings it is
 * meaningless to use NULL. */

#define FOREIGN_string_ucs_4 (18)
/* Type Name:   string/ucs-4 (string_ucs_4)
 * LibFfi type: ffi_type_pointer
 * C type:      mzchar*
 * Predicate:   SCHEME_FALSEP_OR_CHAR_STRINGP(<Scheme>)
 * Scheme->C:   ucs4_string_or_null_to_ucs4_pointer(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_make_char_string_without_copying(<C>)
 */

#define FOREIGN_string_utf_16 (19)
/* Type Name:   string/utf-16 (string_utf_16)
 * LibFfi type: ffi_type_pointer
 * C type:      unsigned short*
 * Predicate:   SCHEME_FALSEP_OR_CHAR_STRINGP(<Scheme>)
 * Scheme->C:   ucs4_string_or_null_to_utf16_pointer(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   utf16_pointer_to_ucs4_string(<C>)
 */

/* Byte strings -- not copying C strings, #f is NULL.
 * (note: these are not like char* which is just a pointer) */

#define FOREIGN_bytes (20)
/* Type Name:   bytes
 * LibFfi type: ffi_type_pointer
 * C type:      char*
 * Predicate:   SCHEME_FALSEP(<Scheme>)||SCHEME_BYTE_STRINGP(<Scheme>)
 * Scheme->C:   SCHEME_FALSEP(<Scheme>)?NULL:SCHEME_BYTE_STR_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   (<C>==NULL)?scheme_false:scheme_make_byte_string_without_copying(<C>)
 */

#define FOREIGN_path (21)
/* Type Name:   path
 * LibFfi type: ffi_type_pointer
 * C type:      char*
 * Predicate:   SCHEME_FALSEP(<Scheme>)||SCHEME_PATH_STRINGP(<Scheme>)
 * Scheme->C:   SCHEME_FALSEP(<Scheme>)?NULL:SCHEME_PATH_VAL(TO_PATH(<Scheme>))
 * S->C offset: 0
 * C->Scheme:   (<C>==NULL)?scheme_false:scheme_make_path_without_copying(<C>)
 */

#define FOREIGN_symbol (22)
/* Type Name:   symbol
 * LibFfi type: ffi_type_pointer
 * C type:      char*
 * Predicate:   SCHEME_SYMBOLP(<Scheme>)
 * Scheme->C:   SCHEME_SYM_VAL(<Scheme>)
 * S->C offset: 0
 * C->Scheme:   scheme_intern_symbol(<C>)
 */

/* This is for any C pointer: #f is NULL, cpointer values as well as
 * ffi-obj and string values pass their pointer.  When used as a return
 * value, either a cpointer object or #f is returned. */
#define FOREIGN_pointer (23)
/* Type Name:   pointer
 * LibFfi type: ffi_type_pointer
 * C type:      void*
 * Predicate:   SCHEME_FFIANYPTRP(<Scheme>)
 * Scheme->C:   SCHEME_FFIANYPTR_VAL(<Scheme>)
 * S->C offset: FFIANYPTR
 * C->Scheme:   scheme_make_foreign_external_cpointer(<C>)
 */

#define FOREIGN_gcpointer (24)
/* Type Name:   gcpointer
 * LibFfi type: ffi_type_gcpointer
 * C type:      void*
 * Predicate:   SCHEME_FFIANYPTRP(<Scheme>)
 * Scheme->C:   SCHEME_FFIANYPTR_VAL(<Scheme>)
 * S->C offset: FFIANYPTR
 * C->Scheme:   scheme_make_foreign_cpointer(<C>)
 */

/* This is used for passing and Scheme_Object* value as is.  Useful for
 * functions that know about Scheme_Object*s, like Racket's. */
#define FOREIGN_scheme (25)
/* Type Name:   scheme
 * LibFfi type: ffi_type_gcpointer
 * C type:      Scheme_Object*
 * Predicate:   1
 * Scheme->C:   <Scheme>
 * S->C offset: 0
 * C->Scheme:   <C>
 */

/* Special type, not actually used for anything except to mark values
 * that are treated like pointers but not referenced.  Used for
 * creating function types. */
#define FOREIGN_fpointer (26)
/* Type Name:   fpointer
 * LibFfi type: ffi_type_pointer
 * C type:      void*
 * Predicate:   -none-
 * Scheme->C:   -none-
 * S->C offset: 0
 * C->Scheme:   -none-
 */

typedef union _ForeignAny {
  Tsint8 x_int8;
  Tuint8 x_uint8;
  Tsint16 x_int16;
  Tuint16 x_uint16;
  Tsint32 x_int32;
  Tuint32 x_uint32;
  Tsint64 x_int64;
  Tuint64 x_uint64;
  Tsint32 x_fixint;
  Tuint32 x_ufixint;
  long x_fixnum;
  unsigned long x_ufixnum;
  float x_float;
  double x_double;
  double x_doubleS;
  int x_bool;
  mzchar* x_string_ucs_4;
  unsigned short* x_string_utf_16;
  char* x_bytes;
  char* x_path;
  char* x_symbol;
  void* x_pointer;
  void* x_gcpointer;
  Scheme_Object* x_scheme;
  void* x_fpointer;
} ForeignAny;

/* This is a tag that is used to identify user-made struct types. */
#define FOREIGN_struct (27)

/*****************************************************************************/
/* Type objects */

/* This struct is used for both user types and primitive types (including
 * struct types).  If it is a user type then basetype will be another ctype,
 * otherwise,
 * - if it's a primitive type, then basetype will be a symbol naming that type
 * - if it's a struct, then basetype will be the list of ctypes that
 *   made this struct
 * scheme_to_c will have the &ffi_type pointer, and c_to_scheme will have an
 * integer (a label value) for non-struct type.  (Note that the
 * integer is not really needed, since it is possible to identify the
 * type by the basetype field.)
 */
/* ctype structure definition */
static Scheme_Type ctype_tag;
typedef struct ctype_struct {
  Scheme_Object so;
  Scheme_Object* basetype;
  Scheme_Object* scheme_to_c;
  Scheme_Object* c_to_scheme;
} ctype_struct;
#define SCHEME_CTYPEP(x) (SCHEME_TYPE(x)==ctype_tag)
#define MYNAME "ctype?"
static Scheme_Object *foreign_ctype_p(int argc, Scheme_Object *argv[])
{
  return SCHEME_CTYPEP(argv[0]) ? scheme_true : scheme_false;
}
#undef MYNAME
/* 3m stuff for ctype */
#ifdef MZ_PRECISE_GC
START_XFORM_SKIP;
int ctype_SIZE(void *p) {
  return gcBYTES_TO_WORDS(sizeof(ctype_struct));
}
int ctype_MARK(void *p) {
  ctype_struct *s = (ctype_struct *)p;
  gcMARK(s->basetype);
  gcMARK(s->scheme_to_c);
  gcMARK(s->c_to_scheme);
  return gcBYTES_TO_WORDS(sizeof(ctype_struct));
}
int ctype_FIXUP(void *p) {
  ctype_struct *s = (ctype_struct *)p;
  gcFIXUP(s->basetype);
  gcFIXUP(s->scheme_to_c);
  gcFIXUP(s->c_to_scheme);
  return gcBYTES_TO_WORDS(sizeof(ctype_struct));
}
END_XFORM_SKIP;
#endif

static ffi_type ffi_type_gcpointer;

#define CTYPE_BASETYPE(x)  (((ctype_struct*)(x))->basetype)
#define CTYPE_USERP(x)     (CTYPE_BASETYPE(x) != NULL && SCHEME_CTYPEP(CTYPE_BASETYPE(x)))
#define CTYPE_PRIMP(x)     (!CTYPE_USERP(x))
#define CTYPE_PRIMTYPE(x)  ((ffi_type*)(((ctype_struct*)(x))->scheme_to_c))
#define CTYPE_PRIMLABEL(x) ((long)(((ctype_struct*)(x))->c_to_scheme))
#define CTYPE_USER_S2C(x)  (((ctype_struct*)(x))->scheme_to_c)
#define CTYPE_USER_C2S(x)  (((ctype_struct*)(x))->c_to_scheme)

/* Returns #f for primitive types. */
#define MYNAME "ctype-basetype"
static Scheme_Object *foreign_ctype_basetype(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return CTYPE_BASETYPE(argv[0]);
}
#undef MYNAME

#define MYNAME "ctype-scheme->c"
static Scheme_Object *foreign_ctype_scheme_to_c(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return (CTYPE_PRIMP(argv[0])) ? scheme_false :
           ((ctype_struct*)(argv[0]))->scheme_to_c;
}
#undef MYNAME

#define MYNAME "ctype-c->scheme"
static Scheme_Object *foreign_ctype_c_to_scheme(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return (CTYPE_PRIMP(argv[0])) ? scheme_false :
           ((ctype_struct*)(argv[0]))->c_to_scheme;
}
#undef MYNAME

/* Returns a primitive type, or NULL if not a type */
static Scheme_Object *get_ctype_base(Scheme_Object *type)
{
  if (!SCHEME_CTYPEP(type)) return NULL;
  while (CTYPE_USERP(type)) { type = CTYPE_BASETYPE(type); }
  return type;
}

/* Returns the size, 0 for void, -1 if no such type */
static int ctype_sizeof(Scheme_Object *type)
{
  type = get_ctype_base(type);
  if (type == NULL) return -1;
  switch (CTYPE_PRIMLABEL(type)) {
  case FOREIGN_void: return 0;
  case FOREIGN_int8: return sizeof(Tsint8);
  case FOREIGN_uint8: return sizeof(Tuint8);
  case FOREIGN_int16: return sizeof(Tsint16);
  case FOREIGN_uint16: return sizeof(Tuint16);
  case FOREIGN_int32: return sizeof(Tsint32);
  case FOREIGN_uint32: return sizeof(Tuint32);
  case FOREIGN_int64: return sizeof(Tsint64);
  case FOREIGN_uint64: return sizeof(Tuint64);
  case FOREIGN_fixint: return sizeof(Tsint32);
  case FOREIGN_ufixint: return sizeof(Tuint32);
  case FOREIGN_fixnum: return sizeof(long);
  case FOREIGN_ufixnum: return sizeof(unsigned long);
  case FOREIGN_float: return sizeof(float);
  case FOREIGN_double: return sizeof(double);
  case FOREIGN_doubleS: return sizeof(double);
  case FOREIGN_bool: return sizeof(int);
  case FOREIGN_string_ucs_4: return sizeof(mzchar*);
  case FOREIGN_string_utf_16: return sizeof(unsigned short*);
  case FOREIGN_bytes: return sizeof(char*);
  case FOREIGN_path: return sizeof(char*);
  case FOREIGN_symbol: return sizeof(char*);
  case FOREIGN_pointer: return sizeof(void*);
  case FOREIGN_gcpointer: return sizeof(void*);
  case FOREIGN_scheme: return sizeof(Scheme_Object*);
  case FOREIGN_fpointer: return sizeof(void*);
  /* for structs */
  default: return CTYPE_PRIMTYPE(type)->size;
  }
}

/* (make-ctype basetype scheme->c c->scheme) -> ctype */
/* The scheme->c can throw type errors to check for valid arguments */
/* a #f means no conversion function, if both are #f -- then just return the */
/* basetype. */
#define MYNAME "make-ctype"
static Scheme_Object *foreign_make_ctype(int argc, Scheme_Object *argv[])
{
  ctype_struct *type;
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  else if (!(SCHEME_FALSEP(argv[1]) || SCHEME_PROCP(argv[1])))
    scheme_wrong_type(MYNAME, "procedure-or-false", 1, argc, argv);
  else if (!(SCHEME_FALSEP(argv[2]) || SCHEME_PROCP(argv[2])))
    scheme_wrong_type(MYNAME, "procedure-or-false", 2, argc, argv);
  else if (SCHEME_FALSEP(argv[1]) && SCHEME_FALSEP(argv[2]))
    return argv[0];
  else {
    type = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
    type->so.type = ctype_tag;
    type->basetype = (argv[0]);
    type->scheme_to_c = (argv[1]);
    type->c_to_scheme = (argv[2]);
    return (Scheme_Object*)type;
  }
  return NULL; /* hush the compiler */
}
#undef MYNAME

/* see below */
void free_libffi_type(void *ignored, void *p)
{
  free(((ffi_type*)p)->elements);
  free(p);
}

/*****************************************************************************/
/* ABI spec */

static Scheme_Object *default_sym;
static Scheme_Object *stdcall_sym;
static Scheme_Object *sysv_sym;

ffi_abi sym_to_abi(char *who, Scheme_Object *sym)
{
  if (SCHEME_FALSEP(sym) || SAME_OBJ(sym, default_sym))
    return FFI_DEFAULT_ABI;
  else if (SAME_OBJ(sym, sysv_sym)) {
#ifdef WINDOWS_DYNAMIC_LOAD
    return FFI_SYSV;
#else
    scheme_signal_error("%s: ABI not implemented: %V", who, sym);
#endif
  } else if (SAME_OBJ(sym, stdcall_sym)) {
#ifdef WINDOWS_DYNAMIC_LOAD
    return FFI_STDCALL;
#else
    scheme_signal_error("%s: ABI not implemented: %V", who, sym);
#endif
  } else {
    scheme_signal_error("%s: unknown ABI: %V", who, sym);
  }
  return 0; /* hush the compiler */
}

/* helper macro */
#define GET_ABI(name,n) \
  ((argc > (n)) ? sym_to_abi((name),argv[n]) : FFI_DEFAULT_ABI)

/*****************************************************************************/
/* cstruct types */

/* (make-cstruct-type types [abi]) -> ctype */
/* This creates a new primitive type that is a struct.  This type can be used
 * with cpointer objects, except that the contents is used rather than the
 * pointer value.  Marshaling to lists or whatever should be done in Scheme. */
#define MYNAME "make-cstruct-type"
static Scheme_Object *foreign_make_cstruct_type(int argc, Scheme_Object *argv[])
{
  Scheme_Object *p, *base;
  /* since ffi_type objects can be used in callbacks, they are allocated using
   * malloc so they don't move, and they are freed when the Scheme object is
   * GCed. */
  GC_CAN_IGNORE ffi_type **elements, *libffi_type, **dummy;
  ctype_struct *type;
  ffi_cif cif;
  int i, nargs;
  ffi_abi abi;
  nargs = scheme_proper_list_length(argv[0]);
  if (nargs < 0) scheme_wrong_type(MYNAME, "proper list", 0, argc, argv);
  abi = GET_ABI(MYNAME,1);
  /* allocate the type elements */
  elements = malloc((nargs+1) * sizeof(ffi_type*));
  elements[nargs] = NULL;
  for (i=0, p=argv[0]; i<nargs; i++, p=SCHEME_CDR(p)) {
    if (NULL == (base = get_ctype_base(SCHEME_CAR(p))))
      scheme_wrong_type(MYNAME, "list-of-C-types", 0, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 0, argc, argv);
    elements[i] = CTYPE_PRIMTYPE(base);
  }
  /* allocate the new libffi type object */
  libffi_type = malloc(sizeof(ffi_type));
  libffi_type->size      = 0;
  libffi_type->alignment = 0;
  libffi_type->type      = FFI_TYPE_STRUCT;
  libffi_type->elements  = elements;
  /* use ffi_prep_cif to set the size and alignment information */
  dummy = &libffi_type;
  if (ffi_prep_cif(&cif, abi, 1, &ffi_type_void, dummy) != FFI_OK)
    scheme_signal_error("internal error: ffi_prep_cif did not return FFI_OK");
  type = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  type->so.type = ctype_tag;
  type->basetype = (argv[0]);
  type->scheme_to_c = ((Scheme_Object*)libffi_type);
  type->c_to_scheme = ((Scheme_Object*)FOREIGN_struct);
  scheme_register_finalizer(type, free_libffi_type, libffi_type, NULL, NULL);
  return (Scheme_Object*)type;
}
#undef MYNAME

/*****************************************************************************/
/* Callback type */

/* ffi-callback structure definition */
static Scheme_Type ffi_callback_tag;
typedef struct ffi_callback_struct {
  Scheme_Object so;
  void* callback;
  Scheme_Object* proc;
  Scheme_Object* itypes;
  Scheme_Object* otype;
  Scheme_Object* sync;
} ffi_callback_struct;
#define SCHEME_FFICALLBACKP(x) (SCHEME_TYPE(x)==ffi_callback_tag)
#define MYNAME "ffi-callback?"
static Scheme_Object *foreign_ffi_callback_p(int argc, Scheme_Object *argv[])
{
  return SCHEME_FFICALLBACKP(argv[0]) ? scheme_true : scheme_false;
}
#undef MYNAME
/* 3m stuff for ffi_callback */
#ifdef MZ_PRECISE_GC
START_XFORM_SKIP;
int ffi_callback_SIZE(void *p) {
  return gcBYTES_TO_WORDS(sizeof(ffi_callback_struct));
}
int ffi_callback_MARK(void *p) {
  ffi_callback_struct *s = (ffi_callback_struct *)p;
  gcMARK(s->callback);
  gcMARK(s->proc);
  gcMARK(s->itypes);
  gcMARK(s->otype);
  gcMARK(s->sync);
  return gcBYTES_TO_WORDS(sizeof(ffi_callback_struct));
}
int ffi_callback_FIXUP(void *p) {
  ffi_callback_struct *s = (ffi_callback_struct *)p;
  gcFIXUP(s->callback);
  gcFIXUP(s->proc);
  gcFIXUP(s->itypes);
  gcFIXUP(s->otype);
  gcFIXUP(s->sync);
  return gcBYTES_TO_WORDS(sizeof(ffi_callback_struct));
}
END_XFORM_SKIP;
#endif

/* The sync field:
     NULL => non-atomic mode, no sync proc
     #t => atomic mode, no sync proc
     (rcons queue proc) => non-atomic mode, sync proc
     (box (rcons queue proc)) => atomic mode, sync proc */

/*****************************************************************************/
/* Pointer objects */
/* use cpointer (with a NULL tag when creating), #f for NULL */

#define SCHEME_FFIANYPTRP(x) \
  (SCHEME_FALSEP(x) || SCHEME_CPTRP(x) || SCHEME_FFIOBJP(x) || \
   SCHEME_BYTE_STRINGP(x) || SCHEME_FFICALLBACKP(x))
#define SCHEME_FFIANYPTR_VAL(x) \
  (SCHEME_CPTRP(x) ? SCHEME_CPTR_VAL(x) : \
    (SCHEME_FALSEP(x) ? NULL : \
      (SCHEME_FFIOBJP(x) ? (((ffi_obj_struct*)x)->obj) : \
       (SCHEME_BYTE_STRINGP(x) ? SCHEME_BYTE_STR_VAL(x) : \
         (SCHEME_FFICALLBACKP(x) ? ((ffi_callback_struct *)x)->callback : \
          NULL)))))
#define SCHEME_FFIANYPTR_OFFSET(x) \
  (SCHEME_CPTRP(x) ? SCHEME_CPTR_OFFSET(x) : 0)
#define SCHEME_FFIANYPTR_OFFSETVAL(x) \
  W_OFFSET(SCHEME_FFIANYPTR_VAL(x), SCHEME_FFIANYPTR_OFFSET(x))

#define SCHEME_CPOINTER_W_OFFSET_P(x) \
  SAME_TYPE(SCHEME_TYPE(x), scheme_offset_cpointer_type)

#define scheme_make_foreign_cpointer(x) \
  ((x==NULL)?scheme_false:scheme_make_cptr(x,NULL))

#define scheme_make_foreign_external_cpointer(x) \
  ((x==NULL)?scheme_false:scheme_make_external_cptr(x,NULL))

#define MYNAME "cpointer?"
static Scheme_Object *foreign_cpointer_p(int argc, Scheme_Object *argv[])
{
  return SCHEME_FFIANYPTRP(argv[0]) ? scheme_true : scheme_false;
}
#undef MYNAME

#define MYNAME "cpointer-tag"
static Scheme_Object *foreign_cpointer_tag(int argc, Scheme_Object *argv[])
{
  Scheme_Object *tag = NULL;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (SCHEME_CPTRP(argv[0])) tag = SCHEME_CPTR_TYPE(argv[0]);
  return (tag == NULL) ? scheme_false : tag;
}
#undef MYNAME

#define MYNAME "set-cpointer-tag!"
static Scheme_Object *foreign_set_cpointer_tag_bang(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_CPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "proper-cpointer", 0, argc, argv);
  SCHEME_CPTR_TYPE(argv[0]) = argv[1];
  return scheme_void;
}
#undef MYNAME

/*****************************************************************************/
/* Scheme<-->C conversions */

/* On big endian machines we need to know whether we're pulling a value from an
 * argument location where it always takes a whole word or straight from a
 * memory location -- deal with it via a C2SCHEME macro wrapper that is used
 * for both the function definition and calls */
#ifdef SCHEME_BIG_ENDIAN
#define C2SCHEME(typ,src,delta,argsloc) c_to_scheme(typ,src,delta,argsloc)
#define REF_CTYPE(ctype) (((sizeof(ctype)<sizeof(int)) && args_loc) \
  ? ((ctype)(((int*)W_OFFSET(src,delta))[0])) \
  : (((ctype *)W_OFFSET(src,delta))[0]))
#else
#define C2SCHEME(typ,src,delta,argsloc) c_to_scheme(typ,src,delta)
#define REF_CTYPE(ctype) (((ctype *)W_OFFSET(src,delta))[0])
#endif

static Scheme_Object *C2SCHEME(Scheme_Object *type, void *src,
                               int delta, int args_loc)
{
  Scheme_Object *res;
  if (!SCHEME_CTYPEP(type))
    scheme_wrong_type("C->Scheme", "C-type", 0, 1, &type);
  if (CTYPE_USERP(type)) {
    res = C2SCHEME(CTYPE_BASETYPE(type), src, delta, args_loc);
    if (SCHEME_FALSEP(CTYPE_USER_C2S(type)))
      return res;
    else
      return _scheme_apply(CTYPE_USER_C2S(type), 1, (Scheme_Object**)(&res));
  } else if (CTYPE_PRIMLABEL(type) == FOREIGN_fpointer) {
    return scheme_make_foreign_external_cpointer(*(void **)W_OFFSET(src, delta));
  } else switch (CTYPE_PRIMLABEL(type)) {
    case FOREIGN_void: return scheme_void;
    case FOREIGN_int8: return scheme_make_integer(REF_CTYPE(Tsint8));
    case FOREIGN_uint8: return scheme_make_integer_from_unsigned(REF_CTYPE(Tuint8));
    case FOREIGN_int16: return scheme_make_integer(REF_CTYPE(Tsint16));
    case FOREIGN_uint16: return scheme_make_integer_from_unsigned(REF_CTYPE(Tuint16));
    case FOREIGN_int32: return scheme_make_realinteger_value(REF_CTYPE(Tsint32));
    case FOREIGN_uint32: return scheme_make_realinteger_value_from_unsigned(REF_CTYPE(Tuint32));
    case FOREIGN_int64: return scheme_make_integer_value_from_long_long(REF_CTYPE(Tsint64));
    case FOREIGN_uint64: return scheme_make_integer_value_from_unsigned_long_long(REF_CTYPE(Tuint64));
    case FOREIGN_fixint: return scheme_make_integer(REF_CTYPE(Tsint32));
    case FOREIGN_ufixint: return scheme_make_integer_from_unsigned(REF_CTYPE(Tuint32));
    case FOREIGN_fixnum: return scheme_make_integer(REF_CTYPE(long));
    case FOREIGN_ufixnum: return scheme_make_integer_from_unsigned(REF_CTYPE(unsigned long));
    case FOREIGN_float: return scheme_make_float(REF_CTYPE(float));
    case FOREIGN_double: return scheme_make_double(REF_CTYPE(double));
    case FOREIGN_doubleS: return scheme_make_double(REF_CTYPE(double));
    case FOREIGN_bool: return (REF_CTYPE(int)?scheme_true:scheme_false);
    case FOREIGN_string_ucs_4: return scheme_make_char_string_without_copying(REF_CTYPE(mzchar*));
    case FOREIGN_string_utf_16: return utf16_pointer_to_ucs4_string(REF_CTYPE(unsigned short*));
    case FOREIGN_bytes: return (REF_CTYPE(char*)==NULL)?scheme_false:scheme_make_byte_string_without_copying(REF_CTYPE(char*));
    case FOREIGN_path: return (REF_CTYPE(char*)==NULL)?scheme_false:scheme_make_path_without_copying(REF_CTYPE(char*));
    case FOREIGN_symbol: return scheme_intern_symbol(REF_CTYPE(char*));
    case FOREIGN_pointer: return scheme_make_foreign_external_cpointer(REF_CTYPE(void*));
    case FOREIGN_gcpointer: return scheme_make_foreign_cpointer(REF_CTYPE(void*));
    case FOREIGN_scheme: return REF_CTYPE(Scheme_Object*);
    case FOREIGN_fpointer: return (REF_CTYPE(void*));
    case FOREIGN_struct:
           return scheme_make_foreign_cpointer(W_OFFSET(src, delta));
    default: scheme_signal_error("corrupt foreign type: %V", type);
  }
  return NULL; /* hush the compiler */
}
#undef REF_CTYPE

/* On big endian machines we need to know whether we're pulling a value from an
 * argument location where it always takes a whole word or straight from a
 * memory location -- deal with it as above, via a SCHEME2C macro wrapper that
 * is used for both the function definition and calls, but the actual code in
 * the function is different: in the relevant cases zero an int and offset the
 * ptr */

/* Usually writes the C object to dst and returns NULL.  When basetype_p is not
 * NULL, then any pointer value (any pointer or a struct) is returned, and the
 * basetype_p is set to the corrsponding number tag.  If basetype_p is NULL,
 * then a struct value will be *copied* into dst. */
static void* SCHEME2C(Scheme_Object *type, void *dst, long delta,
                      Scheme_Object *val, long *basetype_p, long *_offset,
                      int ret_loc)
{
  if (!SCHEME_CTYPEP(type))
    scheme_wrong_type("Scheme->C", "C-type", 0, 1, &type);
  while (CTYPE_USERP(type)) {
    if (!SCHEME_FALSEP(CTYPE_USER_S2C(type)))
      val = _scheme_apply(CTYPE_USER_S2C(type), 1, (Scheme_Object**)(&val));
    type = CTYPE_BASETYPE(type);
  }
  if (CTYPE_PRIMLABEL(type) == FOREIGN_fpointer) {
    /* No need for the SET_CTYPE trick for pointers. */
    if (SCHEME_FFICALLBACKP(val))
      ((void**)W_OFFSET(dst,delta))[0] = ((ffi_callback_struct*)val)->callback;
    else if (SCHEME_CPTRP(val))
      ((void**)W_OFFSET(dst,delta))[0] = SCHEME_CPTR_VAL(val);
    else if (SCHEME_FFIOBJP(val))
      ((void**)W_OFFSET(dst,delta))[0] = ((ffi_obj_struct*)val)->obj;
    else if (SCHEME_FALSEP(val))
      ((void**)W_OFFSET(dst,delta))[0] = NULL;
    else /* ((void**)W_OFFSET(dst,delta))[0] = val; */
         scheme_wrong_type("Scheme->C", "cpointer", 0, 1, &val);
  } else switch (CTYPE_PRIMLABEL(type)) {
    case FOREIGN_void:
      if (!ret_loc) scheme_wrong_type("Scheme->C","non-void-C-type",0,1,&(type));
      break;
    case FOREIGN_int8:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint8)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tsint8));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tsint8 tmp;
        tmp = (Tsint8)(SCHEME_INT_VAL(val));
        (((Tsint8*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","int8",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_uint8:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint8)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tuint8));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tuint8 tmp;
        tmp = (Tuint8)(SCHEME_UINT_VAL(val));
        (((Tuint8*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","uint8",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_int16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint16)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tsint16));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tsint16 tmp;
        tmp = (Tsint16)(SCHEME_INT_VAL(val));
        (((Tsint16*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","int16",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_uint16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint16)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tuint16));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tuint16 tmp;
        tmp = (Tuint16)(SCHEME_UINT_VAL(val));
        (((Tuint16*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","uint16",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_int32:
      if (!(scheme_get_realint_val(val,&(((Tsint32*)W_OFFSET(dst,delta))[0])))) scheme_wrong_type("Scheme->C","int32",0,1,&(val));
      return NULL;
    case FOREIGN_uint32:
      if (!(scheme_get_unsigned_realint_val(val,&(((Tuint32*)W_OFFSET(dst,delta))[0])))) scheme_wrong_type("Scheme->C","uint32",0,1,&(val));
      return NULL;
    case FOREIGN_int64:
      if (!(scheme_get_long_long_val(val,&(((Tsint64*)W_OFFSET(dst,delta))[0])))) scheme_wrong_type("Scheme->C","int64",0,1,&(val));
      return NULL;
    case FOREIGN_uint64:
      if (!(scheme_get_unsigned_long_long_val(val,&(((Tuint64*)W_OFFSET(dst,delta))[0])))) scheme_wrong_type("Scheme->C","uint64",0,1,&(val));
      return NULL;
    case FOREIGN_fixint:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint32)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tsint32));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tsint32 tmp;
        tmp = (Tsint32)(SCHEME_INT_VAL(val));
        (((Tsint32*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","fixint",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_ufixint:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint32)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Tuint32));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        Tuint32 tmp;
        tmp = (Tuint32)(SCHEME_UINT_VAL(val));
        (((Tuint32*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","ufixint",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_fixnum:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(long)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(long));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        long tmp;
        tmp = (long)(SCHEME_INT_VAL(val));
        (((long*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","fixnum",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_ufixnum:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(unsigned long)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(unsigned long));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        unsigned long tmp;
        tmp = (unsigned long)(SCHEME_UINT_VAL(val));
        (((unsigned long*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","ufixnum",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_float:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(float)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(float));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FLTP(val)) {
        float tmp;
        tmp = (float)(SCHEME_FLT_VAL(val));
        (((float*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","float",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_double:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(double)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(double));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_DBLP(val)) {
        double tmp;
        tmp = (double)(SCHEME_DBL_VAL(val));
        (((double*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","double",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_doubleS:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(double)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(double));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_REALP(val)) {
        double tmp;
        tmp = (double)(scheme_real_to_double(val));
        (((double*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","double*",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_bool:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(int)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(int));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (1) {
        int tmp;
        tmp = (int)(SCHEME_TRUEP(val));
        (((int*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        scheme_wrong_type("Scheme->C","bool",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_string_ucs_4:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(mzchar*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(mzchar*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FALSEP_OR_CHAR_STRINGP(val)) {
        mzchar* tmp;
        tmp = (mzchar*)(ucs4_string_or_null_to_ucs4_pointer(val));
        if (basetype_p == NULL || tmp == NULL) {
          (((mzchar**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_string_ucs_4;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","string/ucs-4",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_string_utf_16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(unsigned short*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(unsigned short*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FALSEP_OR_CHAR_STRINGP(val)) {
        unsigned short* tmp;
        tmp = (unsigned short*)(ucs4_string_or_null_to_utf16_pointer(val));
        if (basetype_p == NULL || tmp == NULL) {
          (((unsigned short**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_string_utf_16;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","string/utf-16",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_bytes:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(char*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FALSEP(val)||SCHEME_BYTE_STRINGP(val)) {
        char* tmp;
        tmp = (char*)(SCHEME_FALSEP(val)?NULL:SCHEME_BYTE_STR_VAL(val));
        if (basetype_p == NULL || tmp == NULL) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_bytes;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","bytes",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_path:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(char*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FALSEP(val)||SCHEME_PATH_STRINGP(val)) {
        char* tmp;
        tmp = (char*)(SCHEME_FALSEP(val)?NULL:SCHEME_PATH_VAL(TO_PATH(val)));
        if (basetype_p == NULL || tmp == NULL) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_path;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","path",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_symbol:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(char*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_SYMBOLP(val)) {
        char* tmp;
        tmp = (char*)(SCHEME_SYM_VAL(val));
        if (basetype_p == NULL || tmp == NULL) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_symbol;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","symbol",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_pointer:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(void*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(void*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FFIANYPTRP(val)) {
        void* tmp; long toff;
        tmp = (void*)(SCHEME_FFIANYPTR_VAL(val));
        toff = SCHEME_FFIANYPTR_OFFSET(val);
        if (_offset) *_offset = toff;
        if (basetype_p == NULL || (tmp == NULL && toff == 0)) {
          (((void**)W_OFFSET(dst,delta))[0]) = (_offset ? tmp : (void*)W_OFFSET(tmp, toff));
          return NULL;
        } else {
          *basetype_p = FOREIGN_pointer;
          return _offset ? tmp : (void*)W_OFFSET(tmp, toff);
        }
      } else {
        scheme_wrong_type("Scheme->C","pointer",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_gcpointer:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(void*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(void*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FFIANYPTRP(val)) {
        void* tmp; long toff;
        tmp = (void*)(SCHEME_FFIANYPTR_VAL(val));
        toff = SCHEME_FFIANYPTR_OFFSET(val);
        if (_offset) *_offset = toff;
        if (basetype_p == NULL || (tmp == NULL && toff == 0)) {
          (((void**)W_OFFSET(dst,delta))[0]) = (_offset ? tmp : (void*)W_OFFSET(tmp, toff));
          return NULL;
        } else {
          *basetype_p = FOREIGN_gcpointer;
          return _offset ? tmp : (void*)W_OFFSET(tmp, toff);
        }
      } else {
        scheme_wrong_type("Scheme->C","gcpointer",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_scheme:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Scheme_Object*)<sizeof(int) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(int)-sizeof(Scheme_Object*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (1) {
        Scheme_Object* tmp;
        tmp = (Scheme_Object*)(val);
        if (basetype_p == NULL || tmp == NULL) {
          (((Scheme_Object**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_scheme;
          return tmp;
        }
      } else {
        scheme_wrong_type("Scheme->C","scheme",0,1,&(val));
        return NULL; /* hush the compiler */
      }
    case FOREIGN_fpointer:
      if (!(ret_loc)) scheme_wrong_type("Scheme->C","fpointer",0,1,&(val));
      break;
    case FOREIGN_struct:
      if (!SCHEME_FFIANYPTRP(val))
        scheme_wrong_type("Scheme->C", "pointer", 0, 1, &val);
      {
        void* p = SCHEME_FFIANYPTR_VAL(val);
        long poff = SCHEME_FFIANYPTR_OFFSET(val);
        if (basetype_p == NULL) {
          if (p == NULL && poff == 0)
            scheme_signal_error("FFI pointer value was NULL");
          memcpy(W_OFFSET(dst, delta), W_OFFSET(p, poff),
                 CTYPE_PRIMTYPE(type)->size);
          return NULL;
        } else {
          *basetype_p = FOREIGN_struct;
          if (_offset) {
            *_offset = poff;
            return p;
          } else {
            return W_OFFSET(p, poff);
          }
        }
      }
    default: scheme_signal_error("corrupt foreign type: %V", type);
  }
  return NULL; /* hush the compiler */
}
#undef SET_CTYPE

/*****************************************************************************/
/* C type information */

/* (ctype-sizeof type) -> int, returns 0 for void, error if not a C type */
#define MYNAME "ctype-sizeof"
static Scheme_Object *foreign_ctype_sizeof(int argc, Scheme_Object *argv[])
{
  int size;
  size = ctype_sizeof(argv[0]);
  if (size >= 0) return scheme_make_integer(size);
  else scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  return NULL; /* hush the compiler */
}
#undef MYNAME

/* (ctype-alignof type) -> int, returns 0 for void, error if not a C type */
#define MYNAME "ctype-alignof"
static Scheme_Object *foreign_ctype_alignof(int argc, Scheme_Object *argv[])
{
  Scheme_Object *type;
  type = get_ctype_base(argv[0]);
  if (type == NULL) scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  else return scheme_make_integer(CTYPE_PRIMTYPE(type)->alignment);
  return NULL; /* hush the compiler */
}
#undef MYNAME

/* (compiler-sizeof symbols) -> int, where symbols name some C type.
 * The symbols are in 'int 'char 'void 'short 'long '*, order does not matter,
 * when a single symbol is used, a list is not needed.
 * (This is about actual C types, not C type objects.) */
#define MYNAME "compiler-sizeof"
static Scheme_Object *foreign_compiler_sizeof(int argc, Scheme_Object *argv[])
{
  int res=0;
  int basetype = 0; /* 1=int, 2=char, 3=void, 4=float, 5=double */
  int intsize = 0;  /* "short" => decrement, "long" => increment */
  int stars = 0;    /* number of "*"s */
  Scheme_Object *l = argv[0], *p;
  while (!SAME_OBJ(l, scheme_null)) {
    if (SCHEME_PAIRP(l)) { p = SCHEME_CAR(l); l = SCHEME_CDR(l); }
    else { p = l; l = scheme_null; }
    if (!SCHEME_SYMBOLP(p)) {
      scheme_wrong_type(MYNAME, "list of symbols", 0, argc, argv);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"int")) {
      if (basetype==0) basetype=1;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"char")) {
      if (basetype==0) basetype=2;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"void")) {
      if (basetype==0) basetype=3;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"float")) {
      if (basetype==0) basetype=4;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"double")) {
      if (basetype==0 || basetype==4) basetype=5;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"short")) {
      if (intsize>0)
        scheme_signal_error(MYNAME": cannot use both 'short and 'long");
      else intsize--;
    } else if (!strcmp(SCHEME_SYM_VAL(p),"long")) {
      if (intsize<0)
        scheme_signal_error(MYNAME": cannot use both 'short and 'long");
      else intsize++;
    } else if (!strcmp(SCHEME_SYM_VAL(p),"*")) {
      stars++;
    } else {
      scheme_wrong_type(MYNAME, "list of C type symbols", 0, argc, argv);
    }
  }
  if (stars > 1)
    scheme_signal_error(MYNAME": cannot handle more than one '*");
  if (intsize < -1)
    scheme_signal_error(MYNAME": cannot handle more than one 'short");
  if (intsize > 2)
    scheme_signal_error(MYNAME": cannot handle more than two 'long");
  if (basetype == 0) basetype = 1; /* int is the default type */
  /* don't assume anything, so it can be used to verify compiler assumptions */
  /* (only forbid stuff that the compiler doesn't allow) */
# define RETSIZE(t) res=((stars==0)?sizeof(t):sizeof(t *))
  switch (basetype) {
  case 1: /* int */
    switch (intsize) {
    case 0:  RETSIZE(int); break;
    case 1:  RETSIZE(long int); break;
#   ifdef INT64_AS_LONG_LONG
    case 2:  RETSIZE(_int64); break; /* MSVC doesn't allow long long */
#   else /* INT64_AS_LONG_LONG undefined */
    case 2:  RETSIZE(long long int); break;
#   endif /* INT64_AS_LONG_LONG */
    case -1: RETSIZE(short int); break;
    }
    break;
  case 2: /* char */
    if (intsize==0) RETSIZE(char);
    else scheme_signal_error(MYNAME": cannot qualify 'char");
    break;
  case 3: /* void */
    if (intsize==0 && stars>0) RETSIZE(int); /* avoid sizeof(void) */
    else if (stars==0)
      scheme_signal_error(MYNAME": cannot use 'void without a '*");
    else scheme_signal_error(MYNAME": cannot qualify 'void");
    break;
  case 4: /* float */
    if (intsize==0) RETSIZE(float);
    else scheme_signal_error(MYNAME": bad qualifiers for 'float");
    break;
  case 5: /* double */
    if (intsize==0) RETSIZE(double);
    else if (intsize==1) RETSIZE(long double);
    else scheme_signal_error(MYNAME": bad qualifiers for 'double");
    break;
  default:
    scheme_signal_error(MYNAME": internal error (unexpected type %d)",
                        basetype);
  }
# undef RETSIZE
  return scheme_make_integer(res);
}
#undef MYNAME

/*****************************************************************************/
/* Pointer type user functions */

static Scheme_Object *nonatomic_sym;
static Scheme_Object *atomic_sym;
static Scheme_Object *stubborn_sym;
static Scheme_Object *uncollectable_sym;
static Scheme_Object *eternal_sym;
static Scheme_Object *interior_sym;
static Scheme_Object *atomic_interior_sym;
static Scheme_Object *raw_sym;
static Scheme_Object *fail_ok_sym;

/* (malloc num type cpointer mode) -> pointer */
/* The arguments for this function are:
 * - num: bytes to allocate, or the number of instances of type when given,
 * - type: malloc the size of this type (or num instances of it),
 * - cpointer: a source pointer to copy contents from,
 * - mode: a symbol for different allocation functions to use - one of
 *   'nonatomic, 'atomic, 'stubborn, 'uncollectable, 'eternal, 'raw (the last
 *   one is for using the real malloc)
 * - if an additional 'fail-ok flag is given, then scheme_malloc_fail_ok is
 *   used with the chosen malloc function
 * The arguments can be specified in any order at all since they are all
 * different types, the only requirement is for a size, either a number of
 * bytes or a type.  If no mode is specified, then scheme_malloc will be used
 * when the type is any pointer, otherwise scheme_malloc_atomic is used. */
#define MYNAME "malloc"
static Scheme_Object *foreign_malloc(int argc, Scheme_Object *argv[])
{
  int i, size=0, num=0, failok=0;
  void *from = NULL, *res = NULL;
  long foff = 0;
  Scheme_Object *mode = NULL, *a, *base = NULL;
  void *(*mf)(size_t);
  for (i=0; i<argc; i++) {
    a = argv[i];
    if (SCHEME_INTP(a)) {
      if (num != 0)
        scheme_signal_error(MYNAME": specifying a second integer size: %V", a);
      num = SCHEME_INT_VAL(a);
      if (num <= 0)
        scheme_wrong_type(MYNAME, "positive-integer", 0, argc, argv);
    } else if (SCHEME_CTYPEP(a)) {
      if (size != 0)
        scheme_signal_error(MYNAME": specifying a second type: %V", a);
      if (NULL == (base = get_ctype_base(a)))
        scheme_wrong_type(MYNAME, "C-type", i, argc, argv);
      size = ctype_sizeof(a);
      if (size <= 0)
        scheme_wrong_type(MYNAME, "non-void-C-type", i, argc, argv);
    } else if (SAME_OBJ(a, fail_ok_sym)) {
      failok = 1;
    } else if (SCHEME_SYMBOLP(a)) {
      if (mode != NULL)
        scheme_signal_error(MYNAME": specifying a second mode symbol: %V", a);
      mode = a;
    } else if (SCHEME_FFIANYPTRP(a) && !SCHEME_FALSEP(a)) {
      if (from != NULL)
        scheme_signal_error(MYNAME": specifying a second source pointer: %V",
                            a);
      from = SCHEME_FFIANYPTR_VAL(a);
      foff = SCHEME_FFIANYPTR_OFFSET(a);
    } else {
      scheme_wrong_type(MYNAME, "malloc-argument", i, argc, argv);
    }
  }
  if ((num == 0) && (size == 0)) scheme_signal_error(MYNAME": no size given");
  size = ((size==0) ? 1 : size) * ((num==0) ? 1 : num);
  if (mode == NULL)
    mf = (base != NULL && CTYPE_PRIMTYPE(base) == &ffi_type_gcpointer)
      ? scheme_malloc : scheme_malloc_atomic;
  else if (SAME_OBJ(mode, nonatomic_sym))     mf = scheme_malloc;
  else if (SAME_OBJ(mode, atomic_sym))        mf = scheme_malloc_atomic;
  else if (SAME_OBJ(mode, stubborn_sym))      mf = scheme_malloc_stubborn;
  else if (SAME_OBJ(mode, eternal_sym))       mf = scheme_malloc_eternal;
  else if (SAME_OBJ(mode, uncollectable_sym)) mf = scheme_malloc_uncollectable;
  else if (SAME_OBJ(mode, interior_sym))      mf = scheme_malloc_atomic_allow_interior;
  else if (SAME_OBJ(mode, atomic_interior_sym)) mf = scheme_malloc_atomic_allow_interior;
  else if (SAME_OBJ(mode, raw_sym))           mf = malloc;
  else {
    scheme_signal_error(MYNAME": bad allocation mode: %V", mode);
    return NULL; /* hush the compiler */
  }
  if (failok) res = scheme_malloc_fail_ok(mf,size); else res = mf(size);
  if (((from != NULL) || (foff != 0)) && (res != NULL))
    memcpy(res, W_OFFSET(from, foff), size);
  if (SAME_OBJ(mode, raw_sym))
    return scheme_make_foreign_external_cpointer(res);
  else
    return scheme_make_foreign_cpointer(res);
}
#undef MYNAME

/* (end-stubborn-change ptr) */
#define MYNAME "end-stubborn-change"
static Scheme_Object *foreign_end_stubborn_change(int argc, Scheme_Object *argv[])
{
  void *ptr;
  long poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  scheme_end_stubborn_change(W_OFFSET(ptr, poff));
  return scheme_void;
}
#undef MYNAME

/* (free ptr) */
/* This is useful for raw-malloced objects, including objects from C libraries
 * that the library is mallocing itself. */
#define MYNAME "free"
static Scheme_Object *foreign_free(int argc, Scheme_Object *argv[])
{
  void *ptr;
  long poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  free(W_OFFSET(ptr, poff));
  return scheme_void;
}
#undef MYNAME

/* (malloc-immobile-cell v) */
#define MYNAME "malloc-immobile-cell"
static Scheme_Object *foreign_malloc_immobile_cell(int argc, Scheme_Object *argv[])
{
  return scheme_make_foreign_external_cpointer(scheme_malloc_immobile_box(argv[0]));
}
#undef MYNAME

/* (free-immobile-cell b) */
#define MYNAME "free-immobile-cell"
static Scheme_Object *foreign_free_immobile_cell(int argc, Scheme_Object *argv[])
{
  void *ptr;
  long poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  scheme_free_immobile_box((void **)W_OFFSET(ptr, poff));
  return scheme_void;
}
#undef MYNAME

#define C_LONG_TYPE_STR "exact integer that fits a C long"

/* (ptr-add cptr offset-k [type])
 *   Adds an offset to a pointer, returning an offset_cpointer value
 * (ptr-add! cptr offset-k [type])
 *   Modifies an existing offset_cpointer value by adjusting its offset field,
 *   returns void
 */
static Scheme_Object *do_ptr_add(const char *who, int is_bang,
                                 int argc, Scheme_Object **argv)
{
  long noff;
  if (is_bang) {
    if (!SCHEME_CPOINTER_W_OFFSET_P(argv[0]))
      scheme_wrong_type(who, "offset-cpointer", 0, argc, argv);
  } else {
    if (!SCHEME_FFIANYPTRP(argv[0]))
      scheme_wrong_type(who, "cpointer", 0, argc, argv);
  }
  if (!scheme_get_int_val(argv[1], &noff))
    scheme_wrong_type(who, C_LONG_TYPE_STR, 1, argc, argv);
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      long size;
      size = ctype_sizeof(argv[2]);
      if (size <= 0) scheme_wrong_type(who, "non-void-C-type", 2, argc, argv);
      noff = noff * size;
    } else
      scheme_wrong_type(who, "C-type", 2, argc, argv);
  }
  if (is_bang) {
    ((Scheme_Offset_Cptr*)(argv[0]))->offset += noff;
    return scheme_void;
  } else {
    if (SCHEME_CPTRP(argv[0]) && (SCHEME_CPTR_FLAGS(argv[0]) & 0x1))
      return scheme_make_offset_external_cptr
        (SCHEME_FFIANYPTR_VAL(argv[0]),
         SCHEME_FFIANYPTR_OFFSET(argv[0]) + noff,
         (SCHEME_CPTRP(argv[0])) ? SCHEME_CPTR_TYPE(argv[0]) : NULL);
    else
      return scheme_make_offset_cptr
        (SCHEME_FFIANYPTR_VAL(argv[0]),
         SCHEME_FFIANYPTR_OFFSET(argv[0]) + noff,
         (SCHEME_CPTRP(argv[0])) ? SCHEME_CPTR_TYPE(argv[0]) : NULL);
  }
}

/* (ptr-add cptr offset-k [type]) */
#define MYNAME "ptr-add"
static Scheme_Object *foreign_ptr_add(int argc, Scheme_Object *argv[])
{
  return do_ptr_add(MYNAME, 0, argc, argv);
}
#undef MYNAME
/* (ptr-add! cptr offset-k [type]) */
#define MYNAME "ptr-add!"
static Scheme_Object *foreign_ptr_add_bang(int argc, Scheme_Object *argv[])
{
  return do_ptr_add(MYNAME, 1, argc, argv);
}
#undef MYNAME

/* (offset-ptr? x) */
/* Returns #t if the argument is a cpointer with an offset */
#define MYNAME "offset-ptr?"
static Scheme_Object *foreign_offset_ptr_p(int argc, Scheme_Object *argv[])
{
  return (SCHEME_CPOINTER_W_OFFSET_P(argv[0])) ? scheme_true : scheme_false;
}
#undef MYNAME

/* (ptr-offset ptr) */
/* Returns the offset of a cpointer (0 if it's not an offset pointer) */
#define MYNAME "ptr-offset"
static Scheme_Object *foreign_ptr_offset(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  return scheme_make_integer_value(SCHEME_FFIANYPTR_OFFSET(argv[0]));
}
#undef MYNAME

/* (set-ptr-offset! ptr offset [type]) */
/* Sets the offset of an offset-cpointer (possibly multiplied by the size of
 * the given ctype) */
#define MYNAME "set-ptr-offset!"
static Scheme_Object *foreign_set_ptr_offset_bang(int argc, Scheme_Object *argv[])
{
  long noff;
  if (!SCHEME_CPOINTER_W_OFFSET_P(argv[0]))
    scheme_wrong_type(MYNAME, "offset-cpointer", 0, argc, argv);
  if (!scheme_get_int_val(argv[1], &noff)) {
    scheme_wrong_type(MYNAME, C_LONG_TYPE_STR, 1, argc, argv);
  }
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      long size;
      if (NULL == get_ctype_base(argv[2]))
        scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
      size = ctype_sizeof(argv[2]);
      if (size <= 0)
        scheme_wrong_type(MYNAME, "non-void-C-type", 2, argc, argv);
      noff = noff * size;
    } else
      scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
  }
  ((Scheme_Offset_Cptr*)(argv[0]))->offset = noff;
  return scheme_void;
}
#undef MYNAME

/* (mem{move,cpy} dest-ptr [dest-offset] src-ptr [src-offset] count [ctype])
 *   Copies count * sizeof(ctype) bytes
 *   from src-ptr + src-offset * sizeof(ctype)
 *   to dest-ptr + dest-offset * sizeof(ctype).
 * --or--
 * (memset dest-ptr [dest-offset] byte count [ctype])
 *   Sets count * sizeof(ctype) bytes to byte
 *   at dest-ptr + dest-offset * sizeof(ctype) */
static Scheme_Object *do_memop(const char *who, int mode,
                               int argc, Scheme_Object **argv)
/* mode 0=>memset, 1=>memmove, 2=>memcpy */
{
  void *src = NULL, *dest = NULL;
  long soff = 0, doff = 0, count, v, mult = 0;
  int i, j, ch = 0, argc1 = argc;

  /* arg parsing: last optional ctype, then count, then fill byte for memset,
   * then the first and second pointer+offset pair. */

  /* get the optional last ctype multiplier */
  if (SCHEME_CTYPEP(argv[argc1-1])) {
    argc1--;
    mult = ctype_sizeof(argv[argc1]);
    if (mult <= 0)
      scheme_wrong_type(who, "non-void-C-type", argc1, argc, argv);
  }

  /* get the count argument */
  argc1--;
  if ((!scheme_get_int_val(argv[argc1], &count)) || (count < 0))
    scheme_wrong_type(who, "count as " C_LONG_TYPE_STR, argc1, argc, argv);
  if (mult) count *= mult;

  /* get the fill byte for memset */
  if (!mode) {
    argc1--;
    ch = SCHEME_INTP(argv[argc1]) ? SCHEME_INT_VAL(argv[argc1]) : -1;
    if ((ch < 0) || (ch > 255))
      scheme_wrong_type(who, "byte", argc1, argc, argv);
  }

  /* get the two pointers + offsets */
  i = 0;
  for (j=0; j<2; j++) {
    if (!mode && j==1) break; /* memset needs only a dest argument */
    if (!(i<argc1))
      scheme_raise_exn(MZEXN_FAIL_CONTRACT,
                       "%s: missing a pointer argument for %s",
                       who, (j == 0 ? "destination" : "source"));
    if (!SCHEME_FFIANYPTRP(argv[i]))
      scheme_wrong_type(who, "cpointer", i, argc, argv);
    switch (j) {
    case 0: dest = SCHEME_FFIANYPTR_VAL(argv[i]);
            doff = SCHEME_FFIANYPTR_OFFSET(argv[i]);
            break;
    case 1: src  = SCHEME_FFIANYPTR_VAL(argv[i]);
            soff = SCHEME_FFIANYPTR_OFFSET(argv[i]);
            break;
    }
    i++;
    if ((i<argc1) && SCHEME_EXACT_INTEGERP(argv[i])) {
      if (!scheme_get_int_val(argv[i], &v))
        scheme_wrong_type(who, C_LONG_TYPE_STR, i, argc, argv);
      if (mult) v *= mult;
      switch (j) {
      case 0: doff += v; break;
      case 1: soff += v; break;
      }
      i++;
    }
  }

  /* verify that there are no unused leftovers */
  if (!(i==argc1))
    scheme_arg_mismatch(who, "unexpected extra argument: ", argv[i]);

  switch (mode) {
  case 0: memset (W_OFFSET(dest, doff), ch, count); break;
  case 1: memmove(W_OFFSET(dest, doff), W_OFFSET(src, soff), count); break;
  case 2: memcpy (W_OFFSET(dest, doff), W_OFFSET(src, soff), count); break;
  }

  return scheme_void;
}

#define MYNAME "vector->cpointer"
static Scheme_Object *foreign_vector_to_cpointer(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_VECTORP(argv[0]))
    scheme_wrong_type(MYNAME, "vector", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (long)SCHEME_VEC_ELS((Scheme_Object *)0x0), NULL);
}
#undef MYNAME

#define MYNAME "flvector->cpointer"
static Scheme_Object *foreign_flvector_to_cpointer(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FLVECTORP(argv[0]))
    scheme_wrong_type(MYNAME, "flvector", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (long)SCHEME_FLVEC_ELS((Scheme_Object *)0x0), NULL);
}
#undef MYNAME

#define MYNAME "memset"
static Scheme_Object *foreign_memset(int argc, Scheme_Object *argv[])
{
  return do_memop(MYNAME, 0, argc, argv);
}
#undef MYNAME
#define MYNAME "memmove"
static Scheme_Object *foreign_memmove(int argc, Scheme_Object *argv[])
{
  return do_memop(MYNAME, 1, argc, argv);
}
#undef MYNAME
#define MYNAME "memcpy"
static Scheme_Object *foreign_memcpy(int argc, Scheme_Object *argv[])
{
  return do_memop(MYNAME, 2, argc, argv);
}
#undef MYNAME

static Scheme_Object *abs_sym;

/* (ptr-ref cpointer type [['abs] n]) -> the object at the given location */
/* n defaults to 0 which is the only value that should be used with ffi_objs */
/* if n is given, an 'abs flag can precede it to make n be a byte offset */
/* rather than some multiple of sizeof(type). */
/* WARNING: there are *NO* checks at all, this is raw C level code. */
#define MYNAME "ptr-ref"
static Scheme_Object *foreign_ptr_ref(int argc, Scheme_Object *argv[])
{
  int size=0; void *ptr; Scheme_Object *base;
  long delta;

  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  delta = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (delta == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  if (NULL == (base = get_ctype_base(argv[1])))
    scheme_wrong_type(MYNAME, "C-type", 1, argc, argv);
  size = ctype_sizeof(base);

  if (CTYPE_PRIMLABEL(base) == FOREIGN_fpointer) {
    if (SCHEME_FFIOBJP(argv[0])) {
      /* The ffiobj pointer is the function pointer. */
      ptr = argv[0];
      delta = (long)&(((ffi_obj_struct*)0x0)->obj);
    }
  }

  if (size < 0) {
    /* should not happen */
    scheme_wrong_type(MYNAME, "C-type", 1, argc, argv);
  } else if (size == 0) {
    scheme_wrong_type(MYNAME, "non-void-C-type", 1, argc, argv);
  }

  if (argc > 3) {
    if (!SAME_OBJ(argv[2],abs_sym))
      scheme_wrong_type(MYNAME, "abs-flag", 2, argc, argv);
    if (!SCHEME_INTP(argv[3]))
      scheme_wrong_type(MYNAME, "integer", 3, argc, argv);
    delta += SCHEME_INT_VAL(argv[3]);
  } else if (argc > 2) {
    if (!SCHEME_INTP(argv[2]))
      scheme_wrong_type(MYNAME, "integer", 2, argc, argv);
    if (!size)
      scheme_signal_error(MYNAME": cannot multiply fpointer type by offset");
    delta += (size * SCHEME_INT_VAL(argv[2]));
  }
  return C2SCHEME(argv[1], ptr, delta, 0);
}
#undef MYNAME

/* (ptr-set! cpointer type [['abs] n] value) -> void */
/* n defaults to 0 which is the only value that should be used with ffi_objs */
/* if n is given, an 'abs flag can precede it to make n be a byte offset */
/* rather than some multiple of sizeof(type). */
/* WARNING: there are *NO* checks at all, this is raw C level code. */
#define MYNAME "ptr-set!"
static Scheme_Object *foreign_ptr_set_bang(int argc, Scheme_Object *argv[])
{
  int size=0; void *ptr;
  long delta;
  Scheme_Object *val = argv[argc-1], *base;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  delta = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (delta == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  if (NULL == (base = get_ctype_base(argv[1])))
    scheme_wrong_type(MYNAME, "C-type", 1, argc, argv);
  size = ctype_sizeof(base);

  if (size < 0) {
    /* should not happen */
    scheme_wrong_type(MYNAME, "C-type", 1, argc, argv);
  } else if (size == 0) {
    scheme_wrong_type(MYNAME, "non-void-C-type", 1, argc, argv);
  }

  if (argc > 4) {
    if (!SAME_OBJ(argv[2],abs_sym))
      scheme_wrong_type(MYNAME, "'abs", 2, argc, argv);
    if (!SCHEME_INTP(argv[3]))
      scheme_wrong_type(MYNAME, "integer", 3, argc, argv);
    delta += SCHEME_INT_VAL(argv[3]);
  } else if (argc > 3) {
    if (!SCHEME_INTP(argv[2]))
      scheme_wrong_type(MYNAME, "integer", 2, argc, argv);
    if (!size)
      scheme_signal_error(MYNAME": cannot multiply fpointer type by offset");
    delta += (size * SCHEME_INT_VAL(argv[2]));
  }
  SCHEME2C(argv[1], ptr, delta, val, NULL, NULL, 0);
  return scheme_void;
}
#undef MYNAME

/* (ptr-equal? cpointer cpointer) -> boolean */
#define MYNAME "ptr-equal?"
static Scheme_Object *foreign_ptr_equal_p(int argc, Scheme_Object *argv[])
{
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (!SCHEME_FFIANYPTRP(argv[1]))
    scheme_wrong_type(MYNAME, "cpointer", 1, argc, argv);
  return (SAME_OBJ(argv[0],argv[1]) ||
          (SCHEME_FFIANYPTR_OFFSETVAL(argv[0])
           == SCHEME_FFIANYPTR_OFFSETVAL(argv[1])))
         ? scheme_true : scheme_false;
}
#undef MYNAME

/* (make-sized-byte-string cpointer len) */
#define MYNAME "make-sized-byte-string"
static Scheme_Object *foreign_make_sized_byte_string(int argc, Scheme_Object *argv[])
{
  /* Warning: no copying is done so it is possible to share string contents. */
  /* Warning: if source ptr has a offset, resulting string object uses shifted
   * pointer.
   * (Should use real byte-strings with new version.) */
  long len;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (!scheme_get_int_val(argv[1],&len))
    scheme_wrong_type(MYNAME, "integer in a C long range", 1, argc, argv);
  if (SCHEME_FALSEP(argv[0])) return scheme_false;
  else return
         scheme_make_sized_byte_string(SCHEME_FFIANYPTR_OFFSETVAL(argv[0]),
                                       len, 0);
}
#undef MYNAME

/* *** Calling Scheme code while the GC is working leads to subtle bugs, so
   *** this is implemented now in Scheme using will executors. */

/* internal: apply Scheme finalizer */
void do_scm_finalizer(void *p, void *finalizer)
{
  Scheme_Object *f = (Scheme_Object*)finalizer;
  if (!SCHEME_FALSEP(f)) _scheme_apply(f, 1, (Scheme_Object**)(void*)(&p));
}
void do_ptr_finalizer(void *p, void *finalizer)
{
  Scheme_Object *f = (Scheme_Object*)finalizer;
  Scheme_Object *ptr;
  if (p == NULL) return;
  ptr = scheme_make_cptr(p,NULL);
  if (!SCHEME_FALSEP(f)) _scheme_apply(f, 1, (Scheme_Object**)(&ptr));
  /* don't leave dangling references! */
  SCHEME_CPTR_VAL(ptr) = NULL;
  ptr = NULL;
}

/* (register-finalizer ptrobj finalizer ['pointer]) -> old-finalizer */
/* The finalizer is called by the primitive finalizer mechanism, make sure */
/* no references to the object are recreated.  #f means erase existing */
/* finalizer if any.*/
/* If no 'pointer argument is given, this is can be used with any Scheme */
/* object, and the finalizer will be called with it.  If an additional */
/* 'pointer argument of 'pointer is given, the object must be a cpointer */
/* object, the finalizer will be invoked when the pointer itself is */
/* unreachable, and it will get a new cpointer object that points to it. */
/* (Only needed in cases where pointer aliases might be created.) */
/*
 * defsymbols[pointer]
 * cdefine[register-finalizer 2 3]{
 *   void *ptr, *old = NULL;
 *   int ptrsym = (argc == 3 && argv[2] == pointer_sym);
 *   if (ptrsym) {
 *     if (!SCHEME_FFIANYPTRP(argv[0]))
 *       scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
 *     ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
 *     if (ptr == NULL)
 *       scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
 *   } else {
 *     if (argc == 3)
 *       scheme_wrong_type(MYNAME, "pointer-mode", 2, argc, argv);
 *     ptr = argv[0];
 *   }
 *   if (!(SCHEME_FALSEP(argv[1]) || SCHEME_PROCP(argv[1])))
 *     scheme_wrong_type(MYNAME, "procedure-or-false", 1, argc, argv);
 *   scheme_register_finalizer
 *     (ptr, (ptrsym ? do_ptr_finalizer : do_scm_finalizer),
 *      argv[1], NULL, &old);
 *   return (old == NULL) ? scheme_false : (Scheme_Object*)old;
 * }
 */

/*****************************************************************************/
/* Calling foreign function objects */

#define MAX_QUICK_ARGS 16

typedef void(*VoidFun)();

Scheme_Object *ffi_do_call(void *data, int argc, Scheme_Object *argv[])
/* data := {name, c-function, itypes, otype, cif} */
{
  /* The name is not currently used */
  /* char *name = SCHEME_BYTE_STR_VAL(SCHEME_VEC_ELS(data)[0]); */
  void          *c_func = (void*)(SCHEME_VEC_ELS(data)[1]);
  Scheme_Object *itypes = SCHEME_VEC_ELS(data)[2];
  Scheme_Object *otype  = SCHEME_VEC_ELS(data)[3];
  Scheme_Object *base;
  ffi_cif       *cif    = (ffi_cif*)(SCHEME_VEC_ELS(data)[4]);
  long          cfoff   = SCHEME_INT_VAL(SCHEME_VEC_ELS(data)[5]);
  int           save_errno = SCHEME_INT_VAL(SCHEME_VEC_ELS(data)[6]);
  int           nargs   = cif->nargs;
  /* When the foreign function is called, we need an array (ivals) of nargs
   * ForeignAny objects to store the actual C values that are created, and we
   * need another array (avalues) for the pointers to these values (this is
   * what libffi actually uses).  To make things more fun, ForeignAny is
   * problematic for the precise GC, since it is sometimes a pointer and
   * sometime not.  To deal with this, while converting argv objects into
   * ivals, scheme_to_c will save pointer values in avalues, so the GC can,
   * ignore ivals -- just before we reach the actual call, avalues is
   * overwritten, but from that point on it is all C code so there is no
   * problem.  Hopefully.
   * (Things get complicated if the C call can involve GC (usually due to a
   * Scheme callback), but then the programmer need to arrange for pointers
   * that cannot move.  Because of all this, the *only* array that should not
   * be ignored by the GC is avalues.)
   */
  GC_CAN_IGNORE ForeignAny *ivals, oval;
  void **avalues, *p, *newp, *tmp;
  GC_CAN_IGNORE ForeignAny stack_ivals[MAX_QUICK_ARGS];
  void *stack_avalues[MAX_QUICK_ARGS];
  long stack_offsets[MAX_QUICK_ARGS];
  int i;
  long basetype, offset, *offsets;
  if (nargs <= MAX_QUICK_ARGS) {
    ivals   = stack_ivals;
    avalues = stack_avalues;
    offsets = stack_offsets;
  } else {
    ivals   = malloc(nargs * sizeof(ForeignAny));
    avalues = scheme_malloc(nargs * sizeof(void*));
    offsets = scheme_malloc_atomic(nargs * sizeof(long));
  }
  /* iterate on input values and types */
  for (i=0; i<nargs; i++, itypes=SCHEME_CDR(itypes)) {
    /* convert argv[i] according to current itype */
    offset = 0;
    p = SCHEME2C(SCHEME_CAR(itypes), &(ivals[i]), 0, argv[i], &basetype,
                 &offset, 0);
    if ((p != NULL) || offset) {
      avalues[i] = p;
      ivals[i].x_fixnum = basetype; /* remember the base type */
    } else {
      avalues[i] = NULL;
    }
    offsets[i] = offset;
  }
  base = get_ctype_base(otype); /* verified below, so cannot be NULL */
  /* If this is a struct return value, then need to malloc in any case, even if
   * the size is smaller than ForeignAny, because this value will be
   * returned. */
  if (CTYPE_PRIMLABEL(base) == FOREIGN_struct) {
    /* need to have p be a pointer that is invisible to the GC */
    p = malloc(CTYPE_PRIMTYPE(base)->size);
    newp = scheme_malloc_atomic(CTYPE_PRIMTYPE(base)->size);
  } else {
    p = &oval;
    newp = NULL;
  }
  /* We finished with all possible mallocs, clear up the avalues and offsets
   * mess */
  for (i=0; i<nargs; i++) {
    if ((avalues[i] == NULL) && !offsets[i]) /* if this was a non-pointer... */
      avalues[i] = &(ivals[i]); /* ... set the avalues pointer */
    else if (ivals[i].x_fixnum != FOREIGN_struct) { /* if *not* a struct... */
      /* ... set the ivals pointer (pointer type doesn't matter) and avalues */
      ivals[i].x_pointer = avalues[i];
      avalues[i] = &(ivals[i]);
    }
    /* Otherwise it was a struct pointer, and avalues[i] is already fine. */
    /* Add offset, if any: */
    if (offsets[i] != 0) {
      ivals[i].x_pointer = (char *)ivals[i].x_pointer + offsets[i];
    }
  }
  /* Finally, call the function */
  ffi_call(cif, (VoidFun)W_OFFSET(c_func, cfoff), p, avalues);
  if (save_errno != 0) save_errno_values(save_errno);
  if (ivals != stack_ivals) free(ivals);
  ivals = NULL; /* no need now to hold on to this */
  for (i=0; i<nargs; i++) { avalues[i] = NULL; } /* no need for these refs */
  avalues = NULL;
  switch (CTYPE_PRIMLABEL(base)) {
  case FOREIGN_struct:
    memcpy(newp, p, CTYPE_PRIMTYPE(base)->size);
    free(p);
    p = newp;
    break;
  default:
    /* not sure why this code is here, looks fine to remove this case */
    if (CTYPE_PRIMTYPE(base) == &ffi_type_pointer) {
      tmp = ((void**)p)[0];
      p = &tmp;
    }
    break;
  }
  return C2SCHEME(otype, p, 0, 1);
}

/* see below */
void free_fficall_data(void *ignored, void *p)
{
  free(((ffi_cif*)p)->arg_types);
  free(p);
}

/* (ffi-call ffi-obj in-types out-type [abi save-errno?]) -> (in-types -> out-value) */
/* the real work is done by ffi_do_call above */
#define MYNAME "ffi-call"
static Scheme_Object *foreign_ffi_call(int argc, Scheme_Object *argv[])
{
  static Scheme_Object *ffi_name_prefix = NULL;
  Scheme_Object *itypes = argv[1];
  Scheme_Object *otype  = argv[2];
  Scheme_Object *obj, *data, *p, *base;
  ffi_abi abi;
  long ooff;
  GC_CAN_IGNORE ffi_type *rtype, **atypes;
  GC_CAN_IGNORE ffi_cif *cif;
  int i, nargs, save_errno;
  MZ_REGISTER_STATIC(ffi_name_prefix);
  if (!ffi_name_prefix)
    ffi_name_prefix = scheme_make_byte_string_without_copying("ffi:");
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj-or-cpointer", 0, argc, argv);
  obj = SCHEME_FFIANYPTR_VAL(argv[0]);
  ooff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((obj == NULL) && (ooff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  nargs = scheme_proper_list_length(itypes);
  if (nargs < 0)
    scheme_wrong_type(MYNAME, "proper list", 1, argc, argv);
  if (NULL == (base = get_ctype_base(otype)))
    scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
  rtype = CTYPE_PRIMTYPE(base);
  abi = GET_ABI(MYNAME,3);
  if (argc > 4) {
    save_errno = -1;
    if (SCHEME_FALSEP(argv[4]))
      save_errno = 0;
    else if (SCHEME_SYMBOLP(argv[4])
             && !SCHEME_SYM_WEIRDP(argv[4])) {
      if (!strcmp(SCHEME_SYM_VAL(argv[4]), "posix"))
        save_errno = 1;
      else if (!strcmp(SCHEME_SYM_VAL(argv[4]), "windows"))
        save_errno = 2;
    }
    if (save_errno == -1) {
      scheme_wrong_type(MYNAME, "'posix, 'windows, or #f", 4, argc, argv);
    }
  } else
    save_errno = 0;
  atypes = malloc(nargs * sizeof(ffi_type*));
  for (i=0, p=itypes; i<nargs; i++, p=SCHEME_CDR(p)) {
    if (NULL == (base = get_ctype_base(SCHEME_CAR(p))))
      scheme_wrong_type(MYNAME, "list-of-C-types", 1, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 1, argc, argv);
    atypes[i] = CTYPE_PRIMTYPE(base);
  }
  cif = malloc(sizeof(ffi_cif));
  if (ffi_prep_cif(cif, abi, nargs, rtype, atypes) != FFI_OK)
    scheme_signal_error("internal error: ffi_prep_cif did not return FFI_OK");
  data = scheme_make_vector(7, NULL);
  p = scheme_append_byte_string
        (ffi_name_prefix,
         scheme_make_byte_string_without_copying
           (SCHEME_FFIOBJP(argv[0]) ?
             ((ffi_obj_struct*)(argv[0]))->name : "proc"));
  SCHEME_VEC_ELS(data)[0] = p;
  SCHEME_VEC_ELS(data)[1] = obj;
  SCHEME_VEC_ELS(data)[2] = itypes;
  SCHEME_VEC_ELS(data)[3] = otype;
  SCHEME_VEC_ELS(data)[4] = (Scheme_Object*)cif;
  SCHEME_VEC_ELS(data)[5] = scheme_make_integer(ooff);
  SCHEME_VEC_ELS(data)[6] = scheme_make_integer(save_errno);
  scheme_register_finalizer(data, free_fficall_data, cif, NULL, NULL);
  return scheme_make_closed_prim_w_arity
           (ffi_do_call, (void*)data, SCHEME_BYTE_STR_VAL(p),
            nargs, nargs);
}
#undef MYNAME

/*****************************************************************************/
/* Scheme callbacks */

typedef void (*ffi_callback_t)(ffi_cif* cif, void* resultp, void** args, void *userdata);

static ffi_callback_struct *extract_ffi_callback(void *userdata)
  XFORM_SKIP_PROC
{
  ffi_callback_struct *data;

#ifdef MZ_PRECISE_GC
  {
    void *tmp;
    tmp  = *((void**)userdata);
    data = (ffi_callback_struct*)(SCHEME_WEAK_BOX_VAL(tmp));
    if (data == NULL) scheme_signal_error("callback lost");
  }
#else
  data = (ffi_callback_struct*)userdata;
#endif

  return data;
}

void ffi_do_callback(ffi_cif* cif, void* resultp, void** args, void *userdata)
{
  ffi_callback_struct *data;
  Scheme_Object *argv_stack[MAX_QUICK_ARGS];
  int argc = cif->nargs, i;
  Scheme_Object **argv, *p, *v;

  data = extract_ffi_callback(userdata);

  if (argc <= MAX_QUICK_ARGS)
    argv = argv_stack;
  else
    argv = scheme_malloc(argc * sizeof(Scheme_Object*));
  if (data->sync && !SCHEME_RPAIRP(data->sync))
    scheme_start_in_scheduler();
  for (i=0, p=data->itypes; i<argc; i++, p=SCHEME_CDR(p)) {
    v = C2SCHEME(SCHEME_CAR(p), args[i], 0, 0);
    argv[i] = v;
  }
  p = _scheme_apply(data->proc, argc, argv);
  SCHEME2C(data->otype, resultp, 0, p, NULL, NULL, 1);
  if (data->sync && !SCHEME_RPAIRP(data->sync))
    scheme_end_in_scheduler();
}

#ifdef MZ_USE_MZRT

/* When OS-level thread support is avaiable, support callbacks
   in foreign threads that are executed on the main Scheme thread. */

typedef struct Queued_Callback {
  ffi_cif* cif;
  void* resultp;
  void** args;
  void *userdata;
  mzrt_sema *sema;
  int called;
  struct Queued_Callback *next;
} Queued_Callback;

typedef struct FFI_Sync_Queue {
  Queued_Callback *callbacks; /* malloc()ed list */
  mzrt_mutex *lock;
  mzrt_thread_id orig_thread;
  void *sig_hand;
} FFI_Sync_Queue;

THREAD_LOCAL_DECL(static struct FFI_Sync_Queue *ffi_sync_queue);

static Scheme_Object *callback_thunk(void *_qc, int argc, Scheme_Object *argv[])
{
  Queued_Callback *qc = (Queued_Callback *)_qc;

  if (qc->called)
    scheme_raise_exn(MZEXN_FAIL_CONTRACT,
                     "callback thunk for synchronization has already been called");
  qc->called = 1;

  ffi_do_callback(qc->cif, qc->resultp, qc->args, qc->userdata);

  mzrt_sema_post(qc->sema);

  return scheme_void;
}

void scheme_check_foreign_work(void)
{
  GC_CAN_IGNORE Queued_Callback *qc;
  ffi_callback_struct *data;
  Scheme_Object *a[1], *proc;

  if (ffi_sync_queue) {
    do {
      mzrt_mutex_lock(ffi_sync_queue->lock);
      qc = ffi_sync_queue->callbacks;
      if (qc)
        ffi_sync_queue->callbacks = qc->next;
      mzrt_mutex_unlock(ffi_sync_queue->lock);

      if (qc) {
        qc->next = NULL;

        data = extract_ffi_callback(qc->userdata);

        proc = scheme_make_closed_prim_w_arity(callback_thunk, (void *)qc,
                                               "callback-thunk", 0, 0);
        a[0] = proc;

        proc = data->sync;
        if (SCHEME_BOXP(proc)) proc = SCHEME_BOX_VAL(proc);
        proc = SCHEME_CDR(proc);

        scheme_start_in_scheduler();
        _scheme_apply(proc, 1, a);
        scheme_end_in_scheduler();
      }

    } while (qc);
  }
}

#endif

void ffi_queue_callback(ffi_cif* cif, void* resultp, void** args, void *userdata)
  XFORM_SKIP_PROC
{
  ffi_callback_struct *data;

  data = extract_ffi_callback(userdata);

#ifdef MZ_USE_MZRT
  {
    FFI_Sync_Queue *queue;
    Scheme_Object *o;

    o = data->sync;
    if (SCHEME_BOXP(o)) o = SCHEME_BOX_VAL(o);

    queue = (FFI_Sync_Queue *)SCHEME_CAR(o);

    if (queue->orig_thread != mz_proc_thread_self()) {
      Queued_Callback *qc;
      mzrt_sema *sema;

      mzrt_sema_create(&sema, 0);

      qc = (Queued_Callback *)malloc(sizeof(Queued_Callback));
      qc->cif = cif;
      qc->resultp = resultp;
      qc->args = args;
      qc->userdata = userdata;
      qc->sema = sema;
      qc->called = 0;

      mzrt_mutex_lock(queue->lock);
      qc->next = queue->callbacks;
      queue->callbacks = qc;
      mzrt_mutex_unlock(queue->lock);
      scheme_signal_received_at(queue->sig_hand);

      /* wait for the callback to be invoked in the main thread */
      mzrt_sema_wait(sema);

      mzrt_sema_destroy(sema);
      free(qc);
      return;
    }
  }
#endif
  ffi_do_callback(cif, resultp, args, userdata);
}

/* see ffi-callback below */
typedef struct closure_and_cif_struct {
  ffi_closure          closure;
  ffi_cif              cif;
#ifdef MZ_PRECISE_GC
  struct immobile_box *data;
#else
  void                *data;
#endif
} closure_and_cif;
/* free the above */
void free_cl_cif_args(void *ignored, void *p)
{
  /*
  scheme_warning("Releasing cl+cif+args %V %V (%d)",
                 ignored,
                 (((closure_and_cif*)p)->data),
                 SAME_OBJ(ignored,(((closure_and_cif*)p)->data)));
  */
#ifdef MZ_PRECISE_GC
  GC_free_immobile_box((void**)(((closure_and_cif*)p)->data));
#endif
  scheme_free_code(p);
}

/* (ffi-callback scheme-proc in-types out-type [abi atomic? sync]) -> ffi-callback */
/* the treatment of in-types and out-types is similar to that in ffi-call */
/* the real work is done by ffi_do_callback above */
#define MYNAME "ffi-callback"
static Scheme_Object *foreign_ffi_callback(int argc, Scheme_Object *argv[])
{
    ffi_callback_struct *data;
    Scheme_Object *itypes = argv[1];
    Scheme_Object *otype = argv[2];
    Scheme_Object *sync;
    Scheme_Object *p, *base;
    ffi_abi abi;
    int is_atomic;
    int nargs, i;
    /* ffi_closure objects are problematic when used with a moving GC.  The
     * problem is that memory that is GC-visible can move at any time.  The
     * solution is to use an immobile-box, which an immobile pointer (in a simple
     * malloced block), which points to the ffi_callback_struct that contains the
     * relevant Scheme call details.  Another minor complexity is that an
     * immobile box serves as a reference for the GC, which means that nothing
     * will ever get collected: and the solution for this is to stick a weak-box
     * in the chain.  Users need to be aware of GC issues, and need to keep a
     * reference to the callback object to avoid releasing the whole thing --
     * when that reference is lost, the ffi_callback_struct will be GCed, and a
     * finalizer will free() the malloced memory.  Everything on the malloced
     * part is allocated in one block, to make it easy to free.  The final layout
     * of the various objects is:
     *
     * <<======malloc======>> : <<===========scheme_malloc===============>>
     *                        :
     *    ffi_closure <------------------------\
     *      |  |              :                |
     *      |  |              :                |
     *      |  \--> immobile ----> weak        |
     *      |         box     :    box         |
     *      |                 :     |          |
     *      |                 :     |          |
     *      |                 :     \--> ffi_callback_struct
     *      |                 :               |  |
     *      V                 :               |  \-----> Scheme Closure
     *     cif ---> atypes    :               |
     *                        :               \--------> input/output types
     */
    GC_CAN_IGNORE ffi_type *rtype, **atypes;
    GC_CAN_IGNORE ffi_cif *cif;
    GC_CAN_IGNORE ffi_closure *cl;
    GC_CAN_IGNORE closure_and_cif *cl_cif_args;
    GC_CAN_IGNORE ffi_callback_t do_callback;
    if (!SCHEME_PROCP(argv[0]))
      scheme_wrong_type(MYNAME, "procedure", 0, argc, argv);
    nargs = scheme_proper_list_length(itypes);
    if (nargs < 0)
      scheme_wrong_type(MYNAME, "proper list", 1, argc, argv);
    if (NULL == (base = get_ctype_base(otype)))
      scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
    rtype = CTYPE_PRIMTYPE(base);
    abi = GET_ABI(MYNAME,3);
    is_atomic = ((argc > 4) && SCHEME_TRUEP(argv[4]));
    sync = (is_atomic ? scheme_true : NULL);
    if (argc > 5)
      (void)scheme_check_proc_arity2(MYNAME, 1, 5, argc, argv, 1);
    if (((argc > 5) && SCHEME_TRUEP(argv[5]))) {
  #ifdef MZ_USE_MZRT
      if (!ffi_sync_queue) {
        mzrt_thread_id tid;
        void *sig_hand;

        ffi_sync_queue = (FFI_Sync_Queue *)malloc(sizeof(FFI_Sync_Queue));
        tid = mz_proc_thread_self();
        ffi_sync_queue->orig_thread = tid;
        mzrt_mutex_create(&ffi_sync_queue->lock);
        sig_hand = scheme_get_signal_handle();
        ffi_sync_queue->sig_hand = sig_hand;
        ffi_sync_queue->callbacks = NULL;
      }
      sync = scheme_make_raw_pair((Scheme_Object *)ffi_sync_queue,
                                  argv[5]);
      if (is_atomic) sync = scheme_box(sync);
  #endif
      do_callback = ffi_queue_callback;
    } else
      do_callback = ffi_do_callback;
    /* malloc space for everything needed, so a single free gets rid of this */
    cl_cif_args = scheme_malloc_code(sizeof(closure_and_cif) + nargs*sizeof(ffi_cif*));
    cl = &(cl_cif_args->closure); /* cl is the same as cl_cif_args */
    cif = &(cl_cif_args->cif);
    atypes = (ffi_type **)(((char*)cl_cif_args) + sizeof(closure_and_cif));
    for (i=0, p=itypes; i<nargs; i++, p=SCHEME_CDR(p)) {
      if (NULL == (base = get_ctype_base(SCHEME_CAR(p))))
        scheme_wrong_type(MYNAME, "list-of-C-types", 1, argc, argv);
      if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
        scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 1, argc, argv);
      atypes[i] = CTYPE_PRIMTYPE(base);
    }
    if (ffi_prep_cif(cif, abi, nargs, rtype, atypes) != FFI_OK)
      scheme_signal_error("internal error: ffi_prep_cif did not return FFI_OK");
    data = (ffi_callback_struct*)scheme_malloc_tagged(sizeof(ffi_callback_struct));
    data->so.type = ffi_callback_tag;
    data->callback = (cl_cif_args);
    data->proc = (argv[0]);
    data->itypes = (argv[1]);
    data->otype = (argv[2]);
    data->sync = (sync);
#   ifdef MZ_PRECISE_GC
    {
      /* put data in immobile, weak box */
      void **tmp;
      tmp = GC_malloc_immobile_box(GC_malloc_weak_box(data, NULL, 0));
      cl_cif_args->data = (struct immobile_box*)tmp;
    }
#   else /* MZ_PRECISE_GC undefined */
    cl_cif_args->data = (void*)data;
#   endif /* MZ_PRECISE_GC */
    if (ffi_prep_closure(cl, cif, do_callback, (void*)(cl_cif_args->data))
        != FFI_OK)
      scheme_signal_error
        ("internal error: ffi_prep_closure did not return FFI_OK");
    scheme_register_finalizer(data, free_cl_cif_args, cl_cif_args, NULL, NULL);
    return (Scheme_Object*)data;
}
#undef MYNAME

/*****************************************************************************/

static void save_errno_values(int kind)
{
  Scheme_Thread *p = scheme_current_thread;

  if (kind == 2) {
    long v = 0;
#   ifdef WINDOWS_DYNAMIC_LOAD
    v = GetLastError();
#   endif /* WINDOWS_DYNAMIC_LOAD */
    p->saved_errno = v;
    return;
  }

  p->saved_errno = errno;
}

#define MYNAME "saved-errno"
static Scheme_Object *foreign_saved_errno(int argc, Scheme_Object *argv[])
{
  Scheme_Thread *p = scheme_current_thread;
  return scheme_make_integer_value(p->saved_errno);
}
#undef MYNAME

#define MYNAME "lookup-errno"
static Scheme_Object *foreign_lookup_errno(int argc, Scheme_Object *argv[])
{
  Scheme_Object *v = argv[0];
  if (SCHEME_SYMBOLP(v) && !SCHEME_SYM_WEIRDP(v)) {
    if (!strcmp("EINTR", SCHEME_SYM_VAL(v)))
      return scheme_make_integer(EINTR);
    if (!strcmp("EEXIST", SCHEME_SYM_VAL(v)))
      return scheme_make_integer(EEXIST);
    if (!strcmp("EAGAIN", SCHEME_SYM_VAL(v)))
      return scheme_make_integer(EAGAIN);
  }
  scheme_wrong_type(MYNAME, "'EINTR, 'EEXIST, or 'EAGAIN",0, argc, argv);
  return NULL;
}
#undef MYNAME

/*****************************************************************************/

void ctype_printer(Scheme_Object *ctype, int dis, Scheme_Print_Params *pp)
{
  char *str;
  if (!SCHEME_CTYPEP(ctype))
    scheme_wrong_type("Scheme->C", "C-type", 0, 1, &ctype);
  if (CTYPE_PRIMP(ctype)) {
    scheme_print_bytes(pp, "#<ctype:", 0, 8);
    ctype = CTYPE_BASETYPE(ctype);
    if (SCHEME_SYMBOLP(ctype)) {
      str = SCHEME_SYM_VAL(ctype);
      scheme_print_bytes(pp, str, 0, strlen(str));
    } else {
      scheme_print_bytes(pp, "cstruct", 0, 7);
    }
    scheme_print_bytes(pp, ">", 0, 1);
  } else {
    scheme_print_bytes(pp, "#<ctype>", 0, 8);
  }
}

/*****************************************************************************/
/* Initialization */

/* types need to be initialized before places can spawn
 * types become entries in the GC mark and fixup tables
 * this function should initialize read-only globals that can be
 * shared without locking */
void scheme_init_foreign_globals()
{
  ffi_lib_tag = scheme_make_type("<ffi-lib>");
  ffi_obj_tag = scheme_make_type("<ffi-obj>");
  ctype_tag = scheme_make_type("<ctype>");
  ffi_callback_tag = scheme_make_type("<ffi-callback>");
# ifdef MZ_PRECISE_GC
  GC_register_traversers(ffi_lib_tag, ffi_lib_SIZE, ffi_lib_MARK, ffi_lib_FIXUP, 1, 0);
  GC_register_traversers(ffi_obj_tag, ffi_obj_SIZE, ffi_obj_MARK, ffi_obj_FIXUP, 1, 0);
  GC_register_traversers(ctype_tag, ctype_SIZE, ctype_MARK, ctype_FIXUP, 1, 0);
  GC_register_traversers(ffi_callback_tag, ffi_callback_SIZE, ffi_callback_MARK, ffi_callback_FIXUP, 1, 0);
# endif /* MZ_PRECISE_GC */
  scheme_set_type_printer(ctype_tag, ctype_printer);
  MZ_REGISTER_STATIC(default_sym);
  default_sym = scheme_intern_symbol("default");
  MZ_REGISTER_STATIC(stdcall_sym);
  stdcall_sym = scheme_intern_symbol("stdcall");
  MZ_REGISTER_STATIC(sysv_sym);
  sysv_sym = scheme_intern_symbol("sysv");
  MZ_REGISTER_STATIC(nonatomic_sym);
  nonatomic_sym = scheme_intern_symbol("nonatomic");
  MZ_REGISTER_STATIC(atomic_sym);
  atomic_sym = scheme_intern_symbol("atomic");
  MZ_REGISTER_STATIC(stubborn_sym);
  stubborn_sym = scheme_intern_symbol("stubborn");
  MZ_REGISTER_STATIC(uncollectable_sym);
  uncollectable_sym = scheme_intern_symbol("uncollectable");
  MZ_REGISTER_STATIC(eternal_sym);
  eternal_sym = scheme_intern_symbol("eternal");
  MZ_REGISTER_STATIC(interior_sym);
  interior_sym = scheme_intern_symbol("interior");
  MZ_REGISTER_STATIC(atomic_interior_sym);
  atomic_interior_sym = scheme_intern_symbol("atomic-interior");
  MZ_REGISTER_STATIC(raw_sym);
  raw_sym = scheme_intern_symbol("raw");
  MZ_REGISTER_STATIC(fail_ok_sym);
  fail_ok_sym = scheme_intern_symbol("fail-ok");
  MZ_REGISTER_STATIC(abs_sym);
  abs_sym = scheme_intern_symbol("abs");
}

void scheme_init_foreign_places() {
  MZ_REGISTER_STATIC(opened_libs);
  opened_libs = scheme_make_hash_table(SCHEME_hash_string);
}

void scheme_init_foreign(Scheme_Env *env)
{
  Scheme_Env *menv;
  ctype_struct *t;
  Scheme_Object *s;
  memcpy(&ffi_type_gcpointer, &ffi_type_pointer, sizeof(ffi_type_pointer));
  menv = scheme_primitive_module(scheme_intern_symbol("#%foreign"), env);
  scheme_add_global("ffi-lib?",
    scheme_make_prim_w_arity(foreign_ffi_lib_p, "ffi-lib?", 1, 1), menv);
  scheme_add_global("ffi-lib",
    scheme_make_prim_w_arity(foreign_ffi_lib, "ffi-lib", 1, 2), menv);
  scheme_add_global("ffi-lib-name",
    scheme_make_prim_w_arity(foreign_ffi_lib_name, "ffi-lib-name", 1, 1), menv);
  scheme_add_global("ffi-obj?",
    scheme_make_prim_w_arity(foreign_ffi_obj_p, "ffi-obj?", 1, 1), menv);
  scheme_add_global("ffi-obj",
    scheme_make_prim_w_arity(foreign_ffi_obj, "ffi-obj", 2, 2), menv);
  scheme_add_global("ffi-obj-lib",
    scheme_make_prim_w_arity(foreign_ffi_obj_lib, "ffi-obj-lib", 1, 1), menv);
  scheme_add_global("ffi-obj-name",
    scheme_make_prim_w_arity(foreign_ffi_obj_name, "ffi-obj-name", 1, 1), menv);
  scheme_add_global("ctype?",
    scheme_make_prim_w_arity(foreign_ctype_p, "ctype?", 1, 1), menv);
  scheme_add_global("ctype-basetype",
    scheme_make_prim_w_arity(foreign_ctype_basetype, "ctype-basetype", 1, 1), menv);
  scheme_add_global("ctype-scheme->c",
    scheme_make_prim_w_arity(foreign_ctype_scheme_to_c, "ctype-scheme->c", 1, 1), menv);
  scheme_add_global("ctype-c->scheme",
    scheme_make_prim_w_arity(foreign_ctype_c_to_scheme, "ctype-c->scheme", 1, 1), menv);
  scheme_add_global("make-ctype",
    scheme_make_prim_w_arity(foreign_make_ctype, "make-ctype", 3, 3), menv);
  scheme_add_global("make-cstruct-type",
    scheme_make_prim_w_arity(foreign_make_cstruct_type, "make-cstruct-type", 1, 2), menv);
  scheme_add_global("ffi-callback?",
    scheme_make_prim_w_arity(foreign_ffi_callback_p, "ffi-callback?", 1, 1), menv);
  scheme_add_global("cpointer?",
    scheme_make_prim_w_arity(foreign_cpointer_p, "cpointer?", 1, 1), menv);
  scheme_add_global("cpointer-tag",
    scheme_make_prim_w_arity(foreign_cpointer_tag, "cpointer-tag", 1, 1), menv);
  scheme_add_global("set-cpointer-tag!",
    scheme_make_prim_w_arity(foreign_set_cpointer_tag_bang, "set-cpointer-tag!", 2, 2), menv);
  scheme_add_global("ctype-sizeof",
    scheme_make_prim_w_arity(foreign_ctype_sizeof, "ctype-sizeof", 1, 1), menv);
  scheme_add_global("ctype-alignof",
    scheme_make_prim_w_arity(foreign_ctype_alignof, "ctype-alignof", 1, 1), menv);
  scheme_add_global("compiler-sizeof",
    scheme_make_prim_w_arity(foreign_compiler_sizeof, "compiler-sizeof", 1, 1), menv);
  scheme_add_global("malloc",
    scheme_make_prim_w_arity(foreign_malloc, "malloc", 1, 5), menv);
  scheme_add_global("end-stubborn-change",
    scheme_make_prim_w_arity(foreign_end_stubborn_change, "end-stubborn-change", 1, 1), menv);
  scheme_add_global("free",
    scheme_make_prim_w_arity(foreign_free, "free", 1, 1), menv);
  scheme_add_global("malloc-immobile-cell",
    scheme_make_prim_w_arity(foreign_malloc_immobile_cell, "malloc-immobile-cell", 1, 1), menv);
  scheme_add_global("free-immobile-cell",
    scheme_make_prim_w_arity(foreign_free_immobile_cell, "free-immobile-cell", 1, 1), menv);
  scheme_add_global("ptr-add",
    scheme_make_prim_w_arity(foreign_ptr_add, "ptr-add", 2, 3), menv);
  scheme_add_global("ptr-add!",
    scheme_make_prim_w_arity(foreign_ptr_add_bang, "ptr-add!", 2, 3), menv);
  scheme_add_global("offset-ptr?",
    scheme_make_prim_w_arity(foreign_offset_ptr_p, "offset-ptr?", 1, 1), menv);
  scheme_add_global("ptr-offset",
    scheme_make_prim_w_arity(foreign_ptr_offset, "ptr-offset", 1, 1), menv);
  scheme_add_global("set-ptr-offset!",
    scheme_make_prim_w_arity(foreign_set_ptr_offset_bang, "set-ptr-offset!", 2, 3), menv);
  scheme_add_global("vector->cpointer",
    scheme_make_prim_w_arity(foreign_vector_to_cpointer, "vector->cpointer", 1, 1), menv);
  scheme_add_global("flvector->cpointer",
    scheme_make_prim_w_arity(foreign_flvector_to_cpointer, "flvector->cpointer", 1, 1), menv);
  scheme_add_global("memset",
    scheme_make_prim_w_arity(foreign_memset, "memset", 3, 5), menv);
  scheme_add_global("memmove",
    scheme_make_prim_w_arity(foreign_memmove, "memmove", 3, 6), menv);
  scheme_add_global("memcpy",
    scheme_make_prim_w_arity(foreign_memcpy, "memcpy", 3, 6), menv);
  scheme_add_global("ptr-ref",
    scheme_make_prim_w_arity(foreign_ptr_ref, "ptr-ref", 2, 4), menv);
  scheme_add_global("ptr-set!",
    scheme_make_prim_w_arity(foreign_ptr_set_bang, "ptr-set!", 3, 5), menv);
  scheme_add_global("ptr-equal?",
    scheme_make_prim_w_arity(foreign_ptr_equal_p, "ptr-equal?", 2, 2), menv);
  scheme_add_global("make-sized-byte-string",
    scheme_make_prim_w_arity(foreign_make_sized_byte_string, "make-sized-byte-string", 2, 2), menv);
  scheme_add_global("ffi-call",
    scheme_make_prim_w_arity(foreign_ffi_call, "ffi-call", 3, 5), menv);
  scheme_add_global("ffi-callback",
    scheme_make_prim_w_arity(foreign_ffi_callback, "ffi-callback", 3, 6), menv);
  scheme_add_global("saved-errno",
    scheme_make_prim_w_arity(foreign_saved_errno, "saved-errno", 0, 0), menv);
  scheme_add_global("lookup-errno",
    scheme_make_prim_w_arity(foreign_lookup_errno, "lookup-errno", 1, 1), menv);
  s = scheme_intern_symbol("void");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_void));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_void);
  scheme_add_global("_void", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("int8");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint8));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_int8);
  scheme_add_global("_int8", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("uint8");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_uint8));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_uint8);
  scheme_add_global("_uint8", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("int16");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint16));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_int16);
  scheme_add_global("_int16", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("uint16");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_uint16));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_uint16);
  scheme_add_global("_uint16", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("int32");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint32));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_int32);
  scheme_add_global("_int32", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("uint32");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_uint32));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_uint32);
  scheme_add_global("_uint32", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("int64");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint64));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_int64);
  scheme_add_global("_int64", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("uint64");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_uint64));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_uint64);
  scheme_add_global("_uint64", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("fixint");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint32));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_fixint);
  scheme_add_global("_fixint", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("ufixint");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_uint32));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_ufixint);
  scheme_add_global("_ufixint", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("fixnum");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_smzlong));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_fixnum);
  scheme_add_global("_fixnum", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("ufixnum");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_umzlong));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_ufixnum);
  scheme_add_global("_ufixnum", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("float");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_float));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_float);
  scheme_add_global("_float", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("double");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_double));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_double);
  scheme_add_global("_double", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("double*");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_double));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_doubleS);
  scheme_add_global("_double*", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("bool");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_sint));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_bool);
  scheme_add_global("_bool", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("string/ucs-4");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_string_ucs_4);
  scheme_add_global("_string/ucs-4", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("string/utf-16");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_string_utf_16);
  scheme_add_global("_string/utf-16", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("bytes");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_bytes);
  scheme_add_global("_bytes", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("path");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_path);
  scheme_add_global("_path", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("symbol");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_symbol);
  scheme_add_global("_symbol", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("pointer");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_pointer);
  scheme_add_global("_pointer", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("gcpointer");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_gcpointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_gcpointer);
  scheme_add_global("_gcpointer", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("scheme");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_gcpointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_scheme);
  scheme_add_global("_scheme", (Scheme_Object*)t, menv);
  s = scheme_intern_symbol("fpointer");
  t = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  t->so.type = ctype_tag;
  t->basetype = (s);
  t->scheme_to_c = ((Scheme_Object*)(void*)(&ffi_type_pointer));
  t->c_to_scheme = ((Scheme_Object*)FOREIGN_fpointer);
  scheme_add_global("_fpointer", (Scheme_Object*)t, menv);
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

/*****************************************************************************/

#else /* DONT_USE_FOREIGN */

static Scheme_Object *unimplemented(int argc, Scheme_Object **argv, Scheme_Object *who)
{
  scheme_signal_error("%s: foreign interface not supported for this platform",
                      ((Scheme_Primitive_Proc *)who)->name);
  return NULL;
}

static Scheme_Object *foreign_compiler_sizeof(int argc, Scheme_Object **argv)
{
  return scheme_make_integer(4);
}

static Scheme_Object *foreign_make_ctype(int argc, Scheme_Object **argv)
{
  return scheme_false;
}

void scheme_init_foreign(Scheme_Env *env)
{
  /* Create a dummy module. */
  Scheme_Env *menv;
  menv = scheme_primitive_module(scheme_intern_symbol("#%foreign"), env);
  scheme_add_global("ffi-lib?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-lib?", 1, 1), menv);
  scheme_add_global("ffi-lib",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-lib", 1, 2), menv);
  scheme_add_global("ffi-lib-name",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-lib-name", 1, 1), menv);
  scheme_add_global("ffi-obj?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-obj?", 1, 1), menv);
  scheme_add_global("ffi-obj",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-obj", 2, 2), menv);
  scheme_add_global("ffi-obj-lib",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-obj-lib", 1, 1), menv);
  scheme_add_global("ffi-obj-name",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-obj-name", 1, 1), menv);
  scheme_add_global("ctype?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype?", 1, 1), menv);
  scheme_add_global("ctype-basetype",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype-basetype", 1, 1), menv);
  scheme_add_global("ctype-scheme->c",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype-scheme->c", 1, 1), menv);
  scheme_add_global("ctype-c->scheme",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype-c->scheme", 1, 1), menv);
  scheme_add_global("make-ctype",
   scheme_make_prim_w_arity((Scheme_Prim *)foreign_make_ctype, "make-ctype", 3, 3), menv);
  scheme_add_global("make-cstruct-type",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-cstruct-type", 1, 2), menv);
  scheme_add_global("ffi-callback?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-callback?", 1, 1), menv);
  scheme_add_global("cpointer?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "cpointer?", 1, 1), menv);
  scheme_add_global("cpointer-tag",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "cpointer-tag", 1, 1), menv);
  scheme_add_global("set-cpointer-tag!",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "set-cpointer-tag!", 2, 2), menv);
  scheme_add_global("ctype-sizeof",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype-sizeof", 1, 1), menv);
  scheme_add_global("ctype-alignof",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ctype-alignof", 1, 1), menv);
  scheme_add_global("compiler-sizeof",
   scheme_make_prim_w_arity((Scheme_Prim *)foreign_compiler_sizeof, "compiler-sizeof", 1, 1), menv);
  scheme_add_global("malloc",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "malloc", 1, 5), menv);
  scheme_add_global("end-stubborn-change",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "end-stubborn-change", 1, 1), menv);
  scheme_add_global("free",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "free", 1, 1), menv);
  scheme_add_global("malloc-immobile-cell",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "malloc-immobile-cell", 1, 1), menv);
  scheme_add_global("free-immobile-cell",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "free-immobile-cell", 1, 1), menv);
  scheme_add_global("ptr-add",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-add", 2, 3), menv);
  scheme_add_global("ptr-add!",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-add!", 2, 3), menv);
  scheme_add_global("offset-ptr?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "offset-ptr?", 1, 1), menv);
  scheme_add_global("ptr-offset",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-offset", 1, 1), menv);
  scheme_add_global("set-ptr-offset!",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "set-ptr-offset!", 2, 3), menv);
  scheme_add_global("vector->cpointer",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "vector->cpointer", 1, 1), menv);
  scheme_add_global("flvector->cpointer",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "flvector->cpointer", 1, 1), menv);
  scheme_add_global("memset",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "memset", 3, 5), menv);
  scheme_add_global("memmove",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "memmove", 3, 6), menv);
  scheme_add_global("memcpy",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "memcpy", 3, 6), menv);
  scheme_add_global("ptr-ref",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-ref", 2, 4), menv);
  scheme_add_global("ptr-set!",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-set!", 3, 5), menv);
  scheme_add_global("ptr-equal?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ptr-equal?", 2, 2), menv);
  scheme_add_global("make-sized-byte-string",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-sized-byte-string", 2, 2), menv);
  scheme_add_global("ffi-call",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-call", 3, 5), menv);
  scheme_add_global("ffi-callback",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "ffi-callback", 3, 6), menv);
  scheme_add_global("saved-errno",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "saved-errno", 0, 0), menv);
  scheme_add_global("lookup-errno",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "lookup-errno", 1, 1), menv);
  scheme_add_global("_void", scheme_false, menv);
  scheme_add_global("_int8", scheme_false, menv);
  scheme_add_global("_uint8", scheme_false, menv);
  scheme_add_global("_int16", scheme_false, menv);
  scheme_add_global("_uint16", scheme_false, menv);
  scheme_add_global("_int32", scheme_false, menv);
  scheme_add_global("_uint32", scheme_false, menv);
  scheme_add_global("_int64", scheme_false, menv);
  scheme_add_global("_uint64", scheme_false, menv);
  scheme_add_global("_fixint", scheme_false, menv);
  scheme_add_global("_ufixint", scheme_false, menv);
  scheme_add_global("_fixnum", scheme_false, menv);
  scheme_add_global("_ufixnum", scheme_false, menv);
  scheme_add_global("_float", scheme_false, menv);
  scheme_add_global("_double", scheme_false, menv);
  scheme_add_global("_double*", scheme_false, menv);
  scheme_add_global("_bool", scheme_false, menv);
  scheme_add_global("_string/ucs-4", scheme_false, menv);
  scheme_add_global("_string/utf-16", scheme_false, menv);
  scheme_add_global("_bytes", scheme_false, menv);
  scheme_add_global("_path", scheme_false, menv);
  scheme_add_global("_symbol", scheme_false, menv);
  scheme_add_global("_pointer", scheme_false, menv);
  scheme_add_global("_gcpointer", scheme_false, menv);
  scheme_add_global("_scheme", scheme_false, menv);
  scheme_add_global("_fpointer", scheme_false, menv);
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

#endif
