/********************************************
 ** 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>
#else /* WINDOWS_DYNAMIC_LOAD defined */
# include <windows.h>
#endif /* WINDOWS_DYNAMIC_LOAD */

#if !defined(WINDOWS_DYNAMIC_LOAD) || defined(__MINGW32__)
# 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 /* !defined(WINDOWS_DYNAMIC_LOAD) || defined(__MINGW32__)  */

# 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 /* !defined(WINDOWS_DYNAMIC_LOAD) || defined(__MINGW32__) */

#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);

/* This make hides pointerness from cdefstruct so that it
   doesn't generate a mark/fixup action: */
#define NON_GCBALE_PTR(t) t*

static void overflow_error(const char *who, const char *op, intptr_t a, intptr_t b)
{
  scheme_contract_error(who, "arithmetic overflow",
                        "operation", 0, op,
                        "first argument", 1, scheme_make_integer(a),
                        "first argument", 1, scheme_make_integer(b),
                        NULL);
}

intptr_t mult_check_overflow(const char *who, intptr_t a, intptr_t b)
{
  Scheme_Object *c;
  c = scheme_bin_mult(scheme_make_integer(a), scheme_make_integer(b));
  if (!SCHEME_INTP(c))
    overflow_error(who, "multiply", a, b);
  return SCHEME_INT_VAL(c);
}

intptr_t add_check_overflow(const char *who, intptr_t a, intptr_t b)
{
  Scheme_Object *c;
  c = scheme_bin_plus(scheme_make_integer(a), scheme_make_integer(b));
  if (!SCHEME_INTP(c))
    overflow_error(who, "add", a, b);
  return SCHEME_INT_VAL(c);
}

/*****************************************************************************/
/* 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;
  NON_GCBALE_PTR(void) handle;
  Scheme_Object* name;
  Scheme_Hash_Table* objects;
  int is_global;
} 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->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->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? global?) -> 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, as_global = 0;
  ffi_lib_struct *lib;
  if (!(SCHEME_PATH_STRINGP(argv[0]) || SCHEME_FALSEP(argv[0])))
    scheme_wrong_contract(MYNAME, "(or/c string? #f)", 0, argc, argv);
  as_global = ((argc > 2) && SCHEME_TRUEP(argv[2]));
  /* 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 = LoadLibraryW(WIDE_PATH(name));
#   else /* WINDOWS_DYNAMIC_LOAD undefined */
    handle = dlopen(name, RTLD_NOW | (as_global ? RTLD_GLOBAL : RTLD_LOCAL));
#   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);
    lib->is_global = (!name);
    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_contract(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;
  NON_GCBALE_PTR(void) obj;
  char* name;
  NON_GCBALE_PTR(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->name);
  return gcBYTES_TO_WORDS(sizeof(ffi_obj_struct));
}
int ffi_obj_FIXUP(void *p) {
  ffi_obj_struct *s = (ffi_obj_struct *)p;
  gcFIXUP(s->name);
  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, *lib2;
  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_contract(MYNAME, "ffi-lib?", 1, argc, argv);
  if (!SCHEME_BYTE_STRINGP(argv[0]))
    scheme_wrong_contract(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 && lib->is_global) {
      /* Try every handle in the table of opened libraries. */
      int i;
      for (i = opened_libs->size; i--; ) {
        if (opened_libs->vals[i]) {
          lib2 = (ffi_lib_struct *)opened_libs->vals[i];
          dlobj = dlsym(lib2->handle, dlname);
          if (dlobj) break;
        }
      }
    }
    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_contract(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_contract(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 *)((((uintptr_t)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,(intptr_t*)(y))
#define scheme_get_unsigned_realint_val(x,y) \
  scheme_get_unsigned_int_val(x,(uintptr_t*)(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. */
XFORM_NONGCING MZ_INLINE int scheme_get_realint_val(Scheme_Object *o, int *v)
{
  if (SCHEME_INTP(o)) {
    uintptr_t lv = SCHEME_INT_VAL(o);
    int i = (int)lv;
    if (i != lv)
      return 0;
    *v = i;
    return 1;
  } else return 0;
}
XFORM_NONGCING MZ_INLINE int scheme_get_unsigned_realint_val(Scheme_Object *o, unsigned int *v)
{
  if (SCHEME_INTP(o)) {
    uintptr_t 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((intptr_t)(ri))
#define scheme_make_realinteger_value_from_unsigned(ri) \
  scheme_make_integer((uintptr_t)(ri))

#endif /* SIXTY_FOUR_BIT_INTEGERS */

XFORM_NONGCING MZ_INLINE static int get_byte_val(Scheme_Object *o, Tsint8 *_v)
{
  if (SCHEME_INTP(o)) {
    intptr_t v = SCHEME_INT_VAL(o);
    if ((v >= -128) && (v <= 127)) {
      *_v = v;
      return 1;
    }
  }
  return 0;
}

XFORM_NONGCING MZ_INLINE static int get_ubyte_val(Scheme_Object *o, Tuint8 *_v)
{
  if (SCHEME_INTP(o)) {
    intptr_t v = SCHEME_INT_VAL(o);
    if ((v >= 0) && (v <= 255)) {
      *_v = v;
      return 1;
    }
  }
  return 0;
}

XFORM_NONGCING MZ_INLINE static int get_short_val(Scheme_Object *o, Tsint16 *_v)
{
  if (SCHEME_INTP(o)) {
    intptr_t v = SCHEME_INT_VAL(o);
    if ((v >= -32768) && (v <= 32767)) {
      *_v = v;
      return 1;
    }
  }
  return 0;
}

XFORM_NONGCING MZ_INLINE static int get_ushort_val(Scheme_Object *o, Tuint16 *_v)
{
  if (SCHEME_INTP(o)) {
    intptr_t v = SCHEME_INT_VAL(o);
    if ((v >= 0) && (v <= 65536)) {
      *_v = v;
      return 1;
    }
  }
  return 0;
}

/* 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))

XFORM_NONGCING 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)
{
  intptr_t ulen;
  unsigned short *res;
  res = scheme_ucs4_to_utf16
          (SCHEME_CHAR_STR_VAL(ucs), 0, SCHEME_CHAR_STRLEN_VAL(ucs),
           NULL, -1, &ulen, 1);
  res[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)
{
  intptr_t ulen, end;
  mzchar *res;
  if (!utf) return scheme_false;
  for (end=0; utf[end] != 0; end++) { /**/ }
  res = scheme_utf16_to_ucs4(utf, 0, end, NULL, -1, &ulen, 1);
  res[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(intptr_t) == 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' and `intptr_t' 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-
 * Racket->C:   -none-
 * S->C offset: 0
 * C->Racket:   scheme_void
 */

#define FOREIGN_int8 (2)
/* Type Name:   int8
 * LibFfi type: ffi_type_sint8
 * C type:      Tsint8
 * Predicate:   get_byte_val(<Scheme>,&aux)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   scheme_make_integer(<C>)
 */

#define FOREIGN_uint8 (3)
/* Type Name:   uint8
 * LibFfi type: ffi_type_uint8
 * C type:      Tuint8
 * Predicate:   get_ubyte_val(<Scheme>,&aux)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   scheme_make_integer(<C>)
 */

#define FOREIGN_int16 (4)
/* Type Name:   int16
 * LibFfi type: ffi_type_sint16
 * C type:      Tsint16
 * Predicate:   get_short_val(<Scheme>,&aux)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   scheme_make_integer(<C>)
 */

#define FOREIGN_uint16 (5)
/* Type Name:   uint16
 * LibFfi type: ffi_type_uint16
 * C type:      Tuint16
 * Predicate:   get_ushort_val(<Scheme>,&aux)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   scheme_make_integer(<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)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   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)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   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)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   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)
 * Racket->C:   -none- (set by the predicate)
 * S->C offset: 0
 * C->Racket:   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>)
 * Racket->C:   SCHEME_INT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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>)
 * Racket->C:   SCHEME_UINT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   scheme_make_integer_from_unsigned(<C>)
 */

#ifndef SIXTY_FOUR_BIT_LONGS
#define ffi_type_smzlong ffi_type_sint32
#define ffi_type_umzlong ffi_type_uint32
#else /* SIXTY_FOUR_BIT_LONGS defined */
#define ffi_type_smzlong ffi_type_sint64
#define ffi_type_umzlong ffi_type_uint64
#endif /* SIXTY_FOUR_BIT_LONGS */

#ifndef SIXTY_FOUR_BIT_INTEGERS
#define ffi_type_smzintptr ffi_type_sint32
#define ffi_type_umzintptr ffi_type_uint32
#else /* SIXTY_FOUR_BIT_INTEGERS defined */
#define ffi_type_smzintptr ffi_type_sint64
#define ffi_type_umzintptr ffi_type_uint64
#endif /* SIXTY_FOUR_BIT_INTEGERS */

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

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

#define FOREIGN_float (14)
/* Type Name:   float
 * LibFfi type: ffi_type_float
 * C type:      float
 * Predicate:   SCHEME_FLOATP(<Scheme>)
 * Racket->C:   SCHEME_FLOAT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   scheme_make_double(<C>)
 */

#define FOREIGN_double (15)
/* Type Name:   double
 * LibFfi type: ffi_type_double
 * C type:      double
 * Predicate:   SCHEME_FLOATP(<Scheme>)
 * Racket->C:   SCHEME_FLOAT_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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>)
 * Racket->C:   scheme_real_to_double(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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
 * Racket->C:   SCHEME_TRUEP(<Scheme>)
 * S->C offset: 0
 * C->Racket:   (<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_gcpointer
 * C type:      mzchar*
 * Predicate:   SCHEME_FALSEP_OR_CHAR_STRINGP(<Scheme>)
 * Racket->C:   ucs4_string_or_null_to_ucs4_pointer(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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_gcpointer
 * C type:      unsigned short*
 * Predicate:   SCHEME_FALSEP_OR_CHAR_STRINGP(<Scheme>)
 * Racket->C:   ucs4_string_or_null_to_utf16_pointer(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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_gcpointer
 * C type:      char*
 * Predicate:   SCHEME_FALSEP(<Scheme>)||SCHEME_BYTE_STRINGP(<Scheme>)
 * Racket->C:   SCHEME_FALSEP(<Scheme>)?NULL:SCHEME_BYTE_STR_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   (<C>==NULL)?scheme_false:scheme_make_byte_string_without_copying(<C>)
 */

#define FOREIGN_path (21)
/* Type Name:   path
 * LibFfi type: ffi_type_gcpointer
 * C type:      char*
 * Predicate:   SCHEME_FALSEP(<Scheme>)||SCHEME_PATH_STRINGP(<Scheme>)
 * Racket->C:   SCHEME_FALSEP(<Scheme>)?NULL:SCHEME_PATH_VAL(TO_PATH(<Scheme>))
 * S->C offset: 0
 * C->Racket:   (<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>)
 * Racket->C:   SCHEME_SYM_VAL(<Scheme>)
 * S->C offset: 0
 * C->Racket:   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>)
 * Racket->C:   SCHEME_FFIANYPTR_VAL(<Scheme>)
 * S->C offset: FFIANYPTR
 * C->Racket:   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>)
 * Racket->C:   SCHEME_FFIANYPTR_VAL(<Scheme>)
 * S->C offset: FFIANYPTR
 * C->Racket:   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
 * Racket->C:   <Scheme>
 * S->C offset: 0
 * C->Racket:   <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-
 * Racket->C:   -none-
 * S->C offset: 0
 * C->Racket:   -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;
  intptr_t x_fixnum;
  uintptr_t 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)
#define FOREIGN_array (28)
#define FOREIGN_union (29)

XFORM_NONGCING static int is_gcable_pointer(Scheme_Object *o) {
  if (SCHEME_FFIOBJP(o)) return 0;
  return (!SCHEME_CPTRP(o)
          || !(SCHEME_CPTR_FLAGS(o) & 0x1));
}

/*****************************************************************************/
/* 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) ((intptr_t)(((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)

#define CTYPE_ARG_PRIMTYPE(x) ((CTYPE_PRIMLABEL(x) == FOREIGN_array) ? &ffi_type_pointer : CTYPE_PRIMTYPE(x))

/* 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_contract(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_contract(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_contract(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 */
XFORM_NONGCING 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 */
XFORM_NONGCING static intptr_t 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(intptr_t);
  case FOREIGN_ufixnum: return sizeof(uintptr_t);
  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 and arrays */
  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_contract(MYNAME, "ctype?", 0, argc, argv);
  else if (!(SCHEME_FALSEP(argv[1]) || SCHEME_PROCP(argv[1])))
    scheme_wrong_contract(MYNAME, "(or/c procedure? #f)", 1, argc, argv);
  else if (!(SCHEME_FALSEP(argv[2]) || SCHEME_PROCP(argv[2])))
    scheme_wrong_contract(MYNAME, "(or/c procedure? #f)", 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);
}

void free_libffi_type_with_alignment(void *ignored, void *p)
{
  int i;

  for (i = 0; ((ffi_type*)p)->elements[i]; i++) {
    free(((ffi_type*)p)->elements[i]);
  }
  free_libffi_type(ignored, 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)) {
#if defined(WINDOWS_DYNAMIC_LOAD) && !defined(_WIN64)
    return FFI_SYSV;
#else
    scheme_signal_error("%s: ABI not implemented: %V", who, sym);
#endif
  } else if (SAME_OBJ(sym, stdcall_sym)) {
#if defined(WINDOWS_DYNAMIC_LOAD) && !defined(_WIN64)
    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 */

static void wrong_void(const char *who, Scheme_Object *list_element, int specifically_void,
                       int which, int argc, Scheme_Object **argv)
{
  intptr_t len;
  char *s;

  if (argc > 1)
    s = scheme_make_arg_lines_string("  ", which, argc, argv, &len);
  else
    s = NULL;

  if (list_element) {
    scheme_contract_error(who,
                          (specifically_void
                           ? "C type within list is based on _void"
                           : "C type within list has a zero size"),
                          "C type", 1, list_element,
                          "list", 1, argv[which],
                          s ? "other arguments" : NULL, 0, s,
                          NULL);
  } else
    scheme_contract_error(who,
                          (specifically_void
                           ? "given C type is based on _void"
                           : "given C type has a zero size"),
                          "given C type", 1, argv[which],
                          s ? "other arguments" : NULL, 0, s,
                          NULL);
}

/* (make-cstruct-type types [abi alignment]) -> 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 Racket. */
#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, with_alignment;
  ffi_abi abi;
  nargs = scheme_proper_list_length(argv[0]);
  if (nargs < 0) scheme_wrong_contract(MYNAME, "list?", 0, argc, argv);
  abi = GET_ABI(MYNAME,1);
  if (argc > 2) {
    if (!SCHEME_FALSEP(argv[2])) {
      if (!SAME_OBJ(argv[2], scheme_make_integer(1))
          && !SAME_OBJ(argv[2], scheme_make_integer(2))
          && !SAME_OBJ(argv[2], scheme_make_integer(4))
          && !SAME_OBJ(argv[2], scheme_make_integer(8))
          && !SAME_OBJ(argv[2], scheme_make_integer(16)))
        scheme_wrong_contract(MYNAME, "(or/c 1 2 4 8 16 #f)", 2, argc, argv);
      with_alignment = SCHEME_INT_VAL(argv[2]);
    } else
      with_alignment = 0;
  } else
    with_alignment = 0;
  /* 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_contract(MYNAME, "(listof ctype?)", 0, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      wrong_void(MYNAME, SCHEME_CAR(p), 1, 0, argc, argv);
    elements[i] = CTYPE_PRIMTYPE(base);
    if (with_alignment) {
      /* copy the type to set an alignment: */
      libffi_type = malloc(sizeof(ffi_type));
      memcpy(libffi_type, elements[i], sizeof(ffi_type));
      elements[i] = libffi_type;
      if (with_alignment < elements[i]->alignment)
        elements[i]->alignment = with_alignment;
    }
  }
  /* 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);
  if (with_alignment)
    scheme_register_finalizer(type, free_libffi_type_with_alignment, libffi_type, NULL, NULL);
  else
    scheme_register_finalizer(type, free_libffi_type, libffi_type, NULL, NULL);
  return (Scheme_Object*)type;
}
#undef MYNAME

/*****************************************************************************/
/* array types */

static void wrong_intptr(const char *who, int which, int argc, Scheme_Object **argv)
{
  if (!SCHEME_INTP(argv[which]) && !SCHEME_BIGNUMP(argv[which])) {
    scheme_wrong_contract(who, "exact-integer?", which, argc, argv);
  } else {
    intptr_t len;
    char *s;

    if (argc > 1)
      s = scheme_make_arg_lines_string("  ", which, argc, argv, &len);
    else
      s = NULL;

    scheme_contract_error(who,
                          "given integer does not fit into the _intptr type",
                          "given integer", 1, argv[which],
                          s ? "other arguments" : NULL, 0, s,
                          NULL);
  }
}

/* (make-array-type type len) -> ctype */
/* This creates a new primitive type that is an array. An array is the
 * same as a cpointer as an argument, but it behave differently within
 * a struct or for allocation. Marshaling to lists or whatever should
 * be done in Racket. */
#define MYNAME "make-array-type"
static Scheme_Object *foreign_make_array_type(int argc, Scheme_Object *argv[])
{
  Scheme_Object *base, *basetype;
  GC_CAN_IGNORE ffi_type *libffi_type, **elements;
  ctype_struct *type;
  intptr_t len, size;

  if (NULL == (base = get_ctype_base(argv[0])))
    scheme_wrong_contract(MYNAME, "ctype?", 0, argc, argv);
  if (!scheme_get_int_val(argv[1], &len) || (len < 0)) {
    if ((SCHEME_INTP(argv[1]) && SCHEME_INT_VAL(argv[1]) > 0)
        || (SCHEME_BIGNUMP(argv[1]) && SCHEME_BIGPOS(argv[1])))
      wrong_intptr(MYNAME, 1, argc, argv);
    else
      scheme_wrong_contract(MYNAME, "exact-nonnegative-integer?", 1, argc, argv);
  }

  /* libffi doesn't seem to support array types, but we try to make
     libffi work anyway by making a structure type that is used when
     an array appears as a struct field. If the array size is 4 or
     less, or if the total size is 32 bytes or less, then we make a
     full `elements' array, because the x86_64 ABI always shifts
     to memory mode after 32 bytes. */

  /* Allocate the new libffi type object, which is only provided to
     libffi as a type for a structure field.  When a FOREIGN_array
     type is used for a function argument or result, it is replaced
     with FOREIGN_pointer.  We put FFI_TYPE_STRUCT in
     libffi_type->type and make an elements array that contains
     a single instance of the element type... which seems to work
     ok so far.  */
  libffi_type = malloc(sizeof(ffi_type));
  size = mult_check_overflow(MYNAME, CTYPE_PRIMTYPE(base)->size, len);
  libffi_type->size      = size;
  libffi_type->alignment = CTYPE_PRIMTYPE(base)->alignment;
  libffi_type->type      = FFI_TYPE_STRUCT;

  if ((libffi_type->size <= 32) || (len <= 4)) {
    int i;
    elements = malloc((len + 1) * sizeof(ffi_type*));
    for (i = 0; i < len; i++) {
      elements[i] = CTYPE_PRIMTYPE(base);
    }
    elements[len] = NULL;
  } else {
    elements = malloc(2 * sizeof(ffi_type*));
    elements[0] = CTYPE_PRIMTYPE(base);
    elements[1] = NULL;
  }
  libffi_type->elements  = elements;

  basetype = scheme_make_vector(2, argv[0]);
  SCHEME_VEC_ELS(basetype)[1] = argv[1];

  type = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  type->so.type = ctype_tag;
  type->basetype = (basetype);
  type->scheme_to_c = ((Scheme_Object*)libffi_type);
  type->c_to_scheme = ((Scheme_Object*)FOREIGN_array);

  scheme_register_finalizer(type, free_libffi_type, libffi_type, NULL, NULL);

  return (Scheme_Object*)type;
}
#undef MYNAME

/*****************************************************************************/
/* union types */

/* (make-union-type type ...+) -> ctype */
/* This creates a new primitive type that is a union. All unions
 * behave like structs. Marshaling to lists or whatever should
 * be done in Racket. */
#define MYNAME "make-union-type"
static Scheme_Object *foreign_make_union_type(int argc, Scheme_Object *argv[])
{
  Scheme_Object *base, *basetype;
  GC_CAN_IGNORE ffi_type *libffi_type, **elements;
  ctype_struct *type;
  int i, align = 1, a, sz = 0;

  elements = malloc((argc + 1) * sizeof(ffi_type*));

  /* find max required alignment and size: */
  for (i = 0; i < argc; i++) {
    if (NULL == (base = get_ctype_base(argv[i]))) {
      free(elements);
      scheme_wrong_contract(MYNAME, "ctype?", i, argc, argv);
    }
    a = CTYPE_PRIMTYPE(base)->alignment;
    if (a > align) align = a;
    a = CTYPE_PRIMTYPE(base)->size;
    if (sz < a) sz = a;
    elements[i] = CTYPE_PRIMTYPE(base);
  }

  elements[argc] = NULL;

  /* round size up to alignment: */
  if ((sz % align) != 0) {
    sz += (align - (sz % align));
  }

  /* libffi doesn't seem to support union types, but we try to make
     libffi work anyway by making a structure type. We put all the
     element types in the `elements' array, because their shapes may
     affect argument passing. */

  /* Allocate the new libffi type object. */
  libffi_type = malloc(sizeof(ffi_type));
  libffi_type->size      = sz;
  libffi_type->alignment = align;
  libffi_type->type      = FFI_TYPE_STRUCT;
  libffi_type->elements  = elements;

  basetype = scheme_box(scheme_build_list(argc, argv));

  type = (ctype_struct*)scheme_malloc_tagged(sizeof(ctype_struct));
  type->so.type = ctype_tag;
  type->basetype = (basetype);
  type->scheme_to_c = ((Scheme_Object*)libffi_type);
  type->c_to_scheme = ((Scheme_Object*)FOREIGN_union);

  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;
  NON_GCBALE_PTR(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->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->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
 *   #t => atomic mode, no sync proc
 *   proc => non-atomic mode, sync proc
 *   (box 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) \
  (SCHEME_CPTRP(x) && SCHEME_CPTR_HAS_OFFSET(x))

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

#define scheme_make_foreign_offset_cpointer(x, delta) \
  ((delta == 0) ? scheme_make_foreign_cpointer(x) : scheme_make_offset_cptr(x,delta,NULL))

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

#define scheme_make_foreign_offset_external_cpointer(x, delta) \
  ((delta == 0) ? scheme_make_foreign_external_cpointer(x) : scheme_make_offset_external_cptr(x,delta,NULL))

static int check_cpointer_property(Scheme_Object *v)
{
  if (SCHEME_CHAPERONE_STRUCTP(v)
      && scheme_struct_type_property_ref(scheme_cpointer_property, v))
    return 1;
  else
    return 0;
}

static Scheme_Object *unwrap_cpointer_property(Scheme_Object *orig_v)
{
  Scheme_Object *v = orig_v, *val;
  int must = 0;

  while (1) {
    if (SCHEME_CHAPERONE_STRUCTP(v)) {
      val = scheme_struct_type_property_ref(scheme_cpointer_property, v);
      if (val) {
        if (SCHEME_INTP(val))
          v = scheme_struct_ref(v, SCHEME_INT_VAL(val));
        else if (SCHEME_PROCP(val)) {
          Scheme_Object *a[1];
          a[0] = v;
          v = _scheme_apply(val, 1, a);
        } else
          v = val;
        must = 1;
      } else
        break;
    } else
      break;
  }

  if (must && !SCHEME_FFIANYPTRP(v)) {
    scheme_wrong_contract("prop:cpointer accessor", "cpointer?", 0, -1, &v);
    return NULL;
  }

  return v;
}

int scheme_is_cpointer(Scheme_Object *cp) {
  return (SCHEME_FFIANYPTRP(cp) || check_cpointer_property(cp));
}

#define MYNAME "cpointer?"
static Scheme_Object *foreign_cpointer_p(int argc, Scheme_Object *argv[])
{
  return (scheme_is_cpointer(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;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  if (SCHEME_CPTRP(cp)) tag = SCHEME_CPTR_TYPE(cp);
  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[])
{
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_CPTRP(cp))
    scheme_wrong_contract(MYNAME, "proper-cpointer?", 0, argc, argv);
  SCHEME_CPTR_TYPE(cp) = argv[1];
  return scheme_void;
}
#undef MYNAME

#define MYNAME "cpointer-gcable?"
static Scheme_Object *foreign_cpointer_gcable_p(int argc, Scheme_Object *argv[])
{
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (SCHEME_CPTRP(cp)) {
    return ((SCHEME_CPTR_FLAGS(cp) & 0x1)
            ? scheme_false
            : scheme_true);
  } else if (SCHEME_FALSEP(cp)
             || SCHEME_FFIOBJP(cp)
             || SCHEME_FFICALLBACKP(cp))
    return scheme_false;
  else if (SCHEME_BYTE_STRINGP(cp))
    return scheme_true;
  else {
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
    return NULL;
  }
}
#undef MYNAME

void *scheme_extract_pointer(Scheme_Object *v) {
  return SCHEME_FFIANYPTR_VAL(v);
}

/*****************************************************************************/
/* Racket<-->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(ap,typ,src,delta,argsloc,gcsrc) c_to_scheme(ap,typ,src,delta,argsloc,gcsrc)
#define REF_CTYPE(ctype) (((sizeof(ctype)<sizeof(intptr_t)) && args_loc) \
  ? ((ctype)(((intptr_t*)W_OFFSET(src,delta))[0])) \
  : (((ctype *)W_OFFSET(src,delta))[0]))
#else
#define C2SCHEME(ap,typ,src,delta,argsloc,gcsrc) c_to_scheme(ap,typ,src,delta,gcsrc)
#define REF_CTYPE(ctype) (((ctype *)W_OFFSET(src,delta))[0])
#endif

static Scheme_Object *C2SCHEME(Scheme_Object *already_ptr, Scheme_Object *type, void *src,
                               intptr_t delta, int args_loc, int gcsrc)
{
  Scheme_Object *res;
  if (!SCHEME_CTYPEP(type))
    scheme_wrong_contract("C->Racket", "ctype?", 0, 1, &type);
  if (CTYPE_USERP(type)) {
    res = C2SCHEME(already_ptr, CTYPE_BASETYPE(type), src, delta, args_loc, gcsrc);
    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) {
    if (already_ptr) return already_ptr;
    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(REF_CTYPE(Tuint8));
    case FOREIGN_int16: return scheme_make_integer(REF_CTYPE(Tsint16));
    case FOREIGN_uint16: return scheme_make_integer(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(intptr_t));
    case FOREIGN_ufixnum: return scheme_make_integer_from_unsigned(REF_CTYPE(uintptr_t));
    case FOREIGN_float: return scheme_make_double(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:
    case FOREIGN_array:
    case FOREIGN_union:
      if (gcsrc)
        return scheme_make_foreign_offset_cpointer(src, delta);
      else
        return scheme_make_foreign_offset_external_cpointer(src, delta);
    default: scheme_signal_error("corrupt foreign type: %V", type);
  }
  return NULL; /* hush the compiler */
}
#undef REF_CTYPE

static void wrong_value(const char *who, const char *type, Scheme_Object *val)
{
  scheme_contract_error(who,
                        "given value does not fit primitive C type",
                        "C type", 0, type,
                        "given value", 1, val,
                        NULL);
}

/* 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 or array) is returned, and the
 * basetype_p is set to the corrsponding number tag.  If basetype_p is NULL,
 * then a struct or array value will be *copied* into dst. */
static void* SCHEME2C(const char *who,
                      Scheme_Object *type, void *dst, intptr_t delta,
                      Scheme_Object *val, intptr_t *basetype_p, intptr_t *_offset,
                      int ret_loc)
{
  if (!SCHEME_CTYPEP(type))
    scheme_wrong_contract(who, "ctype?", 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);
  }
  val = unwrap_cpointer_property(val);
  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; */
      wrong_value(who, "_fpointer", val);
  } else switch (CTYPE_PRIMLABEL(type)) {
    case FOREIGN_void:
      if (!ret_loc) wrong_value(who, "_void", val);;
      break;
    case FOREIGN_int8:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint8)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tsint8));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(get_byte_val(val,&(((Tsint8*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_int8", val);;
      return NULL;
    case FOREIGN_uint8:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint8)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tuint8));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(get_ubyte_val(val,&(((Tuint8*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_uint8", val);;
      return NULL;
    case FOREIGN_int16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint16)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tsint16));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(get_short_val(val,&(((Tsint16*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_int16", val);;
      return NULL;
    case FOREIGN_uint16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint16)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tuint16));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(get_ushort_val(val,&(((Tuint16*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_uint16", val);;
      return NULL;
    case FOREIGN_int32:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint32)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tsint32));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(scheme_get_realint_val(val,&(((Tsint32*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_int32", val);;
      return NULL;
    case FOREIGN_uint32:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint32)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tuint32));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(scheme_get_unsigned_realint_val(val,&(((Tuint32*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_uint32", val);;
      return NULL;
    case FOREIGN_int64:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint64)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tsint64));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(scheme_get_long_long_val(val,&(((Tsint64*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_int64", val);;
      return NULL;
    case FOREIGN_uint64:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint64)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Tuint64));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(scheme_get_unsigned_long_long_val(val,&(((Tuint64*)W_OFFSET(dst,delta))[0])))) wrong_value(who, "_uint64", val);;
      return NULL;
    case FOREIGN_fixint:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tsint32)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 {
        wrong_value(who, "_fixint", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_ufixint:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Tuint32)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 {
        wrong_value(who, "_ufixint", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_fixnum:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(intptr_t)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(intptr_t));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        intptr_t tmp;
        tmp = (intptr_t)(SCHEME_INT_VAL(val));
        (((intptr_t*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        wrong_value(who, "_fixnum", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_ufixnum:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(uintptr_t)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(uintptr_t));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_INTP(val)) {
        uintptr_t tmp;
        tmp = (uintptr_t)(SCHEME_UINT_VAL(val));
        (((uintptr_t*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        wrong_value(who, "_ufixnum", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_float:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(float)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(float));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FLOATP(val)) {
        float tmp;
        tmp = (float)(SCHEME_FLOAT_VAL(val));
        (((float*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        wrong_value(who, "_float", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_double:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(double)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(double));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FLOATP(val)) {
        double tmp;
        tmp = (double)(SCHEME_FLOAT_VAL(val));
        (((double*)W_OFFSET(dst,delta))[0]) = tmp; return NULL;
      } else {
        wrong_value(who, "_double", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_doubleS:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(double)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 {
        wrong_value(who, "_double*", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_bool:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(int)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 {
        wrong_value(who, "_bool", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_string_ucs_4:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(mzchar*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 || 0) {
          (((mzchar**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_string_ucs_4;
          return tmp;
        }
      } else {
        wrong_value(who, "_string/ucs-4", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_string_utf_16:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(unsigned short*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 || 0) {
          (((unsigned short**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_string_utf_16;
          return tmp;
        }
      } else {
        wrong_value(who, "_string/utf-16", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_bytes:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 || 0) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_bytes;
          return tmp;
        }
      } else {
        wrong_value(who, "_bytes", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_path:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-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 || 0) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_path;
          return tmp;
        }
      } else {
        wrong_value(who, "_path", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_symbol:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(char*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(char*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_SYMBOLP(val)) {
        char* tmp;
        tmp = (char*)(SCHEME_SYM_VAL(val));
        if (basetype_p == NULL || tmp == NULL || !is_gcable_pointer(val)) {
          (((char**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_symbol;
          return tmp;
        }
      } else {
        wrong_value(who, "_symbol", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_pointer:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(void*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(void*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FFIANYPTRP(val)) {
        void* tmp; intptr_t toff;
        tmp = (void*)(SCHEME_FFIANYPTR_VAL(val));
        toff = SCHEME_FFIANYPTR_OFFSET(val);
        if (basetype_p == NULL || (tmp == NULL && toff == 0) || !is_gcable_pointer(val)) {
          if (_offset) *_offset = 0;
          (((void**)W_OFFSET(dst,delta))[0]) = (void*)W_OFFSET(tmp, toff);;
          return NULL;
        } else {
          *basetype_p = FOREIGN_pointer;
          toff = SCHEME_FFIANYPTR_OFFSET(val);
          if (_offset) *_offset = toff;
          return _offset ? tmp : (void*)W_OFFSET(tmp, toff);
        }
      } else {
        wrong_value(who, "_pointer", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_gcpointer:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(void*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(void*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (SCHEME_FFIANYPTRP(val)) {
        void* tmp; intptr_t toff;
        tmp = (void*)(SCHEME_FFIANYPTR_VAL(val));
        toff = SCHEME_FFIANYPTR_OFFSET(val);
        if (basetype_p == NULL || (tmp == NULL && toff == 0) || 0) {
          if (_offset) *_offset = 0;
          (((void**)W_OFFSET(dst,delta))[0]) = (void*)W_OFFSET(tmp, toff);;
          return NULL;
        } else {
          *basetype_p = FOREIGN_gcpointer;
          toff = SCHEME_FFIANYPTR_OFFSET(val);
          if (_offset) *_offset = toff;
          return _offset ? tmp : (void*)W_OFFSET(tmp, toff);
        }
      } else {
        wrong_value(who, "_gcpointer", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_scheme:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(Scheme_Object*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(Scheme_Object*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (1) {
        Scheme_Object* tmp;
        tmp = (Scheme_Object*)(val);
        if (basetype_p == NULL || tmp == NULL || 0) {
          (((Scheme_Object**)W_OFFSET(dst,delta))[0]) = tmp;
          return NULL;
        } else {
          *basetype_p = FOREIGN_scheme;
          return tmp;
        }
      } else {
        wrong_value(who, "_scheme", val);;
        return NULL; /* hush the compiler */
      }
    case FOREIGN_fpointer:
#     ifdef SCHEME_BIG_ENDIAN
      if (sizeof(void*)<sizeof(intptr_t) && ret_loc) {
        ((int*)W_OFFSET(dst,delta))[0] = 0;
        delta += (sizeof(intptr_t)-sizeof(void*));
      }
#     endif /* SCHEME_BIG_ENDIAN */
      if (!(ret_loc)) wrong_value(who, "_fpointer", val);;
      break;
    case FOREIGN_struct:
    case FOREIGN_array:
    case FOREIGN_union:
      if (!SCHEME_FFIANYPTRP(val)) {
        switch (CTYPE_PRIMLABEL(type)) {
        case FOREIGN_struct:
          wrong_value(who, "(_struct ....)", val);
          break;
        case FOREIGN_array:
          wrong_value(who, "(_array ....)", val);
          break;
        default:
        case FOREIGN_union:
          wrong_value(who, "(_union ....)", val);
          break;
        }
      }
      {
        void* p = SCHEME_FFIANYPTR_VAL(val);
        intptr_t 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 = CTYPE_PRIMLABEL(type);
          if (_offset && is_gcable_pointer(val)) {
            *_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[])
{
  intptr_t size;
  size = ctype_sizeof(argv[0]);
  if (size >= 0) return scheme_make_integer(size);
  else scheme_wrong_contract(MYNAME, "ctype?", 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_contract(MYNAME, "ctype?", 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 */
  int must_list = 0;
  Scheme_Object *l = argv[0], *p;
  while (!SAME_OBJ(l, scheme_null)) {
    if (SCHEME_PAIRP(l)) { p = SCHEME_CAR(l); l = SCHEME_CDR(l); must_list = 1;}
    else if (must_list) { p = scheme_false; l = scheme_null; }
    else { p = l; l = scheme_null; }
    if (!SCHEME_SYMBOLP(p)) {
      scheme_wrong_contract(MYNAME, "(or/c symbol? (listof symbol?))", 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_contract(MYNAME, "(or/c ctype-symbol? (listof ctype-symbol?))", 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, failok=0;
  intptr_t size=0, num=-1;
  void *from = NULL, *res = NULL;
  intptr_t foff = 0;
  Scheme_Object *mode = NULL, *a, *base = NULL;
  void *(*mf)(size_t);
  for (i=0; i<argc; i++) {
    a = argv[i];
    a = unwrap_cpointer_property(argv[i]);
    if (SCHEME_INTP(a)) {
      if (num != -1)
        scheme_signal_error(MYNAME": specifying a second integer size: %V", a);
      num = SCHEME_INT_VAL(a);
      if (num < 0)
        scheme_wrong_contract(MYNAME, "(and/c exact-nonnegative-integer? fixnum?)", 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_contract(MYNAME, "ctype?", i, argc, argv);
      size = ctype_sizeof(a);
      if (size <= 0)
        wrong_void(MYNAME, NULL, 0, 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_contract(MYNAME,
                            "(or/c (and/c exact-nonnegative-integer? fixnum?)\n"
                            "      ctype?\n"
                            "      (or/c 'nonatomic 'stubborn 'uncollectable\n"
                            "             'eternal 'interior 'atomic-interior 'raw)\n"
                            "      'fail-on\n"
                            "      (and/c cpointer? (not/c #f)))",
                            i, argc, argv);
    }
  }
  if (!num) return scheme_false;
  if ((num == -1) && (size == 0)) scheme_signal_error(MYNAME": no size given");
  size = mult_check_overflow(MYNAME, ((size==0) ? 1 : size), ((num==-1) ? 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 */
  }
  res = scheme_malloc_fail_ok(mf,size);
  if (failok && (res == NULL)) scheme_signal_error("malloc: out of memory");
  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

#define NON_NULL_CPOINTER "(and/c cpointer? (not/c (lambda (p) (pointer-equal? p #f))))"

/* (end-stubborn-change ptr) */
#define MYNAME "end-stubborn-change"
static Scheme_Object *foreign_end_stubborn_change(int argc, Scheme_Object *argv[])
{
  void *ptr;
  intptr_t poff;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(cp);
  poff = SCHEME_FFIANYPTR_OFFSET(cp);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_contract(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;
  intptr_t poff;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(cp);
  poff = SCHEME_FFIANYPTR_OFFSET(cp);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_contract(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[])
{
  void *p;
  p = scheme_malloc_immobile_box(argv[0]);
  return scheme_make_foreign_external_cpointer(p); /* <- beware: macro duplicates `p' */
}
#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;
  intptr_t poff;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(cp);
  poff = SCHEME_FFIANYPTR_OFFSET(cp);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_contract(MYNAME, NON_NULL_CPOINTER, 0, argc, argv);
  scheme_free_immobile_box((void **)W_OFFSET(ptr, poff));
  return scheme_void;
}
#undef MYNAME

/* (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)
{
  intptr_t noff;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (is_bang) {
    if (!SCHEME_CPOINTER_W_OFFSET_P(cp))
      scheme_wrong_contract(who, "offset-ptr?", 0, argc, argv);
  } else {
    if (!SCHEME_FFIANYPTRP(cp))
      scheme_wrong_contract(who, "cpointer?", 0, argc, argv);
  }
  if (!scheme_get_int_val(argv[1], &noff))
    wrong_intptr(who, 1, argc, argv);
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      intptr_t size;
      size = ctype_sizeof(argv[2]);
      if (size < 0)
        scheme_wrong_contract(who, "ctype?", 2, argc, argv);
      if (size <= 0) wrong_void(who, NULL, 0, 2, argc, argv);
      noff = mult_check_overflow(who, noff, size);
    } else
      scheme_wrong_contract(who, "ctype?", 2, argc, argv);
  }
  if (is_bang) {
    intptr_t delta;
    delta = add_check_overflow(who, ((Scheme_Offset_Cptr*)(cp))->offset, noff);
    ((Scheme_Offset_Cptr*)(cp))->offset = delta;
    return scheme_void;
  } else {
    intptr_t delta;
    delta = add_check_overflow(who, SCHEME_FFIANYPTR_OFFSET(cp), noff);
    if (SCHEME_CPTRP(cp) && (SCHEME_CPTR_FLAGS(cp) & 0x1))
      return scheme_make_offset_external_cptr
        (SCHEME_FFIANYPTR_VAL(cp),
         delta,
         (SCHEME_CPTRP(cp)) ? SCHEME_CPTR_TYPE(cp) : NULL);
    else
      return scheme_make_offset_cptr
        (SCHEME_FFIANYPTR_VAL(cp),
         delta,
         (SCHEME_CPTRP(cp)) ? SCHEME_CPTR_TYPE(cp) : 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[])
{
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  return (SCHEME_CPOINTER_W_OFFSET_P(cp)) ? 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[])
{
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  return scheme_make_integer_value(SCHEME_FFIANYPTR_OFFSET(cp));
}
#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[])
{
  intptr_t noff;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_CPOINTER_W_OFFSET_P(cp))
    scheme_wrong_contract(MYNAME, "offset-ptr?", 0, argc, argv);
  if (!scheme_get_int_val(argv[1], &noff))
    wrong_intptr(MYNAME, 1, argc, argv);
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      intptr_t size;
      if (NULL == get_ctype_base(argv[2]))
        scheme_wrong_contract(MYNAME, "ctype?", 2, argc, argv);
      size = ctype_sizeof(argv[2]);
      if (size <= 0)
        wrong_void(MYNAME, NULL, 0, 2, argc, argv);
      noff = mult_check_overflow(MYNAME, noff, size);
    } else
      scheme_wrong_contract(MYNAME, "ctype?", 2, argc, argv);
  }
  ((Scheme_Offset_Cptr*)(cp))->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;
  intptr_t soff = 0, doff = 0, count, v, mult = 0;
  int i, j, ch = 0, argc1 = argc;
  Scheme_Object *cp;

  /* 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_contract(who, "ctype?", argc1, argc, argv);
    if (mult <= 0)
      wrong_void(who, NULL, 0, argc1, argc, argv);
  }

  /* get the count argument */
  argc1--;
  if ((!scheme_get_int_val(argv[argc1], &count)) || (count < 0))
    wrong_intptr(who, 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_contract(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"));
    cp = unwrap_cpointer_property(argv[i]);
    if (!SCHEME_FFIANYPTRP(cp))
      scheme_wrong_contract(who, "cpointer?", i, argc, argv);
    switch (j) {
    case 0: dest = SCHEME_FFIANYPTR_VAL(cp);
            doff = SCHEME_FFIANYPTR_OFFSET(cp);
            break;
    case 1: src  = SCHEME_FFIANYPTR_VAL(cp);
            soff = SCHEME_FFIANYPTR_OFFSET(cp);
            break;
    }
    i++;
    if ((i<argc1) && SCHEME_EXACT_INTEGERP(argv[i])) {
      if (!scheme_get_int_val(argv[i], &v))
        wrong_intptr(who, 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_contract(MYNAME, "vector?", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (intptr_t)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_contract(MYNAME, "flvector?", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (intptr_t)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[])
{
  intptr_t size=0; void *ptr; Scheme_Object *base;
  intptr_t delta; int gcsrc=1;
  Scheme_Object *cp, *already_ptr = NULL;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(cp);
  delta = SCHEME_FFIANYPTR_OFFSET(cp);
  if (!is_gcable_pointer(cp))
    gcsrc = 0;
  if ((ptr == NULL) && (delta == 0))
    scheme_wrong_contract(MYNAME, NON_NULL_CPOINTER, 0, argc, argv);
  if (NULL == (base = get_ctype_base(argv[1])))
    scheme_wrong_contract(MYNAME, "ctype?", 1, argc, argv);
  size = ctype_sizeof(base);

  if (CTYPE_PRIMLABEL(base) == FOREIGN_fpointer) {
    if (SCHEME_FFIOBJP(cp)) {
      /* The ffiobj pointer is the function pointer. */
      ptr = cp;
      delta = (intptr_t)&(((ffi_obj_struct*)0x0)->obj);
      /* Helps propagate a function name from `ffi-obj' to `ffi-call': */
      already_ptr = cp;
    }
  }

  if (size < 0) {
    /* should not happen */
    scheme_wrong_contract(MYNAME, "ctype?", 1, argc, argv);
  } else if (size == 0) {
    wrong_void(MYNAME, NULL, 0, 1, argc, argv);
  }

  if (argc > 3) {
    if (!SAME_OBJ(argv[2],abs_sym))
      scheme_wrong_contract(MYNAME, "'abs", 2, argc, argv);
    if (!SCHEME_INTP(argv[3]))
      scheme_wrong_contract(MYNAME, "fixnum?", 3, argc, argv);
    if (SCHEME_INT_VAL(argv[3])) {
      delta = add_check_overflow(MYNAME, delta, SCHEME_INT_VAL(argv[3]));
      already_ptr = NULL;
    }
  } else if (argc > 2) {
    if (!SCHEME_INTP(argv[2]))
      scheme_wrong_contract(MYNAME, "fixnum?", 2, argc, argv);
    if (!size)
      scheme_signal_error(MYNAME": cannot multiply fpointer type by offset");
    if (SCHEME_INT_VAL(argv[2])) {
      delta = add_check_overflow(MYNAME, delta, mult_check_overflow(MYNAME, size, SCHEME_INT_VAL(argv[2])));
      already_ptr = NULL;
    }
  }
  return C2SCHEME(already_ptr, argv[1], ptr, delta, 0, gcsrc);
}
#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[])
{
  intptr_t size=0; void *ptr;
  intptr_t delta;
  Scheme_Object *val = argv[argc-1], *base;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(cp);
  delta = SCHEME_FFIANYPTR_OFFSET(cp);
  if ((ptr == NULL) && (delta == 0))
    scheme_wrong_contract(MYNAME, NON_NULL_CPOINTER, 0, argc, argv);
  if (NULL == (base = get_ctype_base(argv[1])))
    scheme_wrong_contract(MYNAME, "ctype?", 1, argc, argv);
  size = ctype_sizeof(base);

  if (size < 0) {
    /* should not happen */
    scheme_wrong_contract(MYNAME, "ctype?", 1, argc, argv);
  } else if (size == 0) {
    wrong_void(MYNAME, NULL, 0, 1, argc, argv);
  }

  if (argc > 4) {
    if (!SAME_OBJ(argv[2],abs_sym))
      scheme_wrong_contract(MYNAME, "'abs", 2, argc, argv);
    if (!SCHEME_INTP(argv[3]))
      scheme_wrong_contract(MYNAME, "fixnum?", 3, argc, argv);
    delta = add_check_overflow(MYNAME, delta, SCHEME_INT_VAL(argv[3]));
  } else if (argc > 3) {
    if (!SCHEME_INTP(argv[2]))
      scheme_wrong_contract(MYNAME, "fixnum?", 2, argc, argv);
    if (!size)
      scheme_signal_error(MYNAME": cannot multiply fpointer type by offset");
    delta = add_check_overflow(MYNAME, delta, mult_check_overflow(MYNAME, size, SCHEME_INT_VAL(argv[2])));
  }
  SCHEME2C(MYNAME, 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[])
{
  Scheme_Object *cp1, *cp2;
  cp1 = unwrap_cpointer_property(argv[0]);
  cp2 = unwrap_cpointer_property(argv[1]);
  if (!SCHEME_FFIANYPTRP(cp1))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  if (!SCHEME_FFIANYPTRP(cp2))
    scheme_wrong_contract(MYNAME, "cpointer?", 1, argc, argv);
  return (SAME_OBJ(cp1, cp2) ||
          (SCHEME_FFIANYPTR_OFFSETVAL(cp1)
           == SCHEME_FFIANYPTR_OFFSETVAL(cp2)))
         ? 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.) */
  intptr_t len;
  Scheme_Object *cp;
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "cpointer?", 0, argc, argv);
  if (!scheme_get_int_val(argv[1],&len))
    wrong_intptr(MYNAME, 1, argc, argv);
  if (SCHEME_FALSEP(cp)) return scheme_false;
  else return
         scheme_make_sized_byte_string(SCHEME_FFIANYPTR_OFFSETVAL(cp),
                                       len, 0);
}
#undef MYNAME

/* *** Calling Racket code while the GC is working leads to subtle bugs, so
   *** this is implemented now in Racket 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;
}

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

#define MAX_QUICK_ARGS 16

typedef void(*VoidFun)();

#ifdef MZ_USE_PLACES

typedef struct FFI_Orig_Place_Call {
  int needs_queue;
  ffi_cif *cif;
  void *c_func;
  intptr_t cfoff;
  int nargs;
  ForeignAny *ivals;
  void **avalues;
  intptr_t *offsets;
  void *p;
  void **signal_handle;
  struct FFI_Orig_Place_Call *next, *prev;
} FFI_Orig_Place_Call;

static mzrt_mutex *orig_place_mutex;
static FFI_Orig_Place_Call *orig_place_calls, *orig_place_calls_tail;
static void *orig_place_signal_handle;

static void check_foreign_work(int check_for_in_original);

static void ffi_call_in_orig_place(ffi_cif *cif, void *c_func, intptr_t cfoff,
                                   int nargs, GC_CAN_IGNORE ForeignAny *ivals, void **avalues,
                                   intptr_t *offsets, void *p)
/* This function can trigger a GC, but it won't escape --- unless
   the called function goes back to Racket and raises an exception,
   and raising an exception in a callback creates all sorts of
   other problems, anyway. No other Racket threads will run in the
   place, so it's ok for the arguments to have stack addresses. */
{
  FFI_Orig_Place_Call *todo;
  void *sh;
  int ready;

  todo = (FFI_Orig_Place_Call *)malloc(sizeof(FFI_Orig_Place_Call));
  sh = scheme_get_signal_handle();
  todo->signal_handle = sh;
  todo->needs_queue = 1;

  /* It would be simplest to just block the current place while the
     original place handles the call. Unfortunately, something like a
     master GC might be required between now and when the call is
     handled. So, we have to block in an atomic-like way to minimize
     GCs while we wait, but still wake up on an external signal. */

  GC_check_master_gc_request();
  /* If a GC is needed from here on, a signal will be posted
     to the current place */

  while (1) {
    todo->cif = cif;
    todo->c_func = c_func;
    todo->cfoff = cfoff;
    todo->nargs = nargs;
    todo->ivals = ivals;
    todo->avalues = avalues;
    todo->offsets = offsets;
    todo->p = p;

    mzrt_mutex_lock(orig_place_mutex);
    if (todo->needs_queue) {
      todo->next = orig_place_calls;
      todo->prev = NULL;
      if (orig_place_calls)
        orig_place_calls->prev = todo;
      else
        orig_place_calls_tail = todo;
      orig_place_calls = todo;
      ready = 0;
    } else {
      ready = !todo->signal_handle;
    }
    mzrt_mutex_unlock(orig_place_mutex);

    if (!ready) {
      /* Tell original-place thread that there's work: */
      scheme_signal_received_at(orig_place_signal_handle);
      /* Wait for notificiation or a master-GC request: */
      scheme_wait_until_signal_received();
    }

    mzrt_mutex_lock(orig_place_mutex);
    if (!todo->signal_handle) {
      /* Done */
      mzrt_mutex_unlock(orig_place_mutex);
      free(todo);
      break;
    } else {
      /* Pause to allow actions such as a master GC.... */
      if (todo->needs_queue) {
        /* Remove from queue while we might GC: */
        if (todo->prev)
          todo->prev->next = todo->next;
        else
          orig_place_calls = todo->next;
        if (todo->next)
          todo->next->prev = todo->prev;
        else
          orig_place_calls_tail = todo->prev;
      } else {
        /* The call is being handled, so it's too late
           to remove it from the queue! */
      }
      mzrt_mutex_unlock(orig_place_mutex);

      /* Here's the atomic pause: */
      GC_check_master_gc_request();
      scheme_start_atomic();
      scheme_thread_block(0.0);
      scheme_end_atomic_no_swap();

      /* Since we called scheme_thread_block() in atomic mode,
         it doesn't check for foreign callbacks. We'd like
         to handle those anyway, since the call in the original
         place may lead to a callback that should run in
         this place. */
      check_foreign_work(0);
    }
  }
}
#endif

static void finish_ffi_call(ffi_cif *cif, void *c_func, intptr_t cfoff,
                            int nargs, GC_CAN_IGNORE ForeignAny *ivals, void **avalues,
                            intptr_t *offsets, void *p)
/* Complete an FFI call in non-GC mode, so that arguments won't move around: */
  XFORM_SKIP_PROC
{
  int i;
  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)
             && (ivals[i].x_fixnum != FOREIGN_union)) { /* 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]);
    } else if (offsets[i]) {
      /* struct argument has an offset */
      avalues[i] = (char *)avalues[i] + offsets[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);
}

Scheme_Object *ffi_do_call(int argc, Scheme_Object *argv[], Scheme_Object *self)
/* data := {name, c-function, itypes, otype, cif} */
{
  Scheme_Object *data = SCHEME_PRIM_CLOSURE_ELS(self)[0];
  const 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]);
  intptr_t      cfoff   = SCHEME_INT_VAL(SCHEME_VEC_ELS(data)[5]);
  int           save_errno = SCHEME_INT_VAL(SCHEME_VEC_ELS(data)[6]);
#ifdef MZ_USE_PLACES
  int           orig_place = SCHEME_TRUEP(SCHEME_VEC_ELS(data)[7]);
#endif
  int           nargs /* = cif->nargs, after checking cif */;
  /* 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
   * Racket 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.)
   */
  ForeignAny *ivals;
  void **avalues, *p, *newp;
  GC_CAN_IGNORE ForeignAny stack_ivals[MAX_QUICK_ARGS], oval;
  void *stack_avalues[MAX_QUICK_ARGS];
  intptr_t stack_offsets[MAX_QUICK_ARGS];
  int i;
  intptr_t basetype, offset, *offsets;
#ifdef MZ_USE_PLACES
  if (orig_place && (scheme_current_place_id == 0))
    orig_place = 0;
#endif
  if (!cif) {
    scheme_signal_error("ffi-call: foreign-function reference was already finalized%s%s",
                        name ? "\n  name: " : "",
                        name ? name : "");
    return NULL;
  }
  nargs =  cif->nargs;
  if ((nargs <= MAX_QUICK_ARGS)) {
    ivals   = stack_ivals;
    avalues = stack_avalues;
    offsets = stack_offsets;
  } else {
    ivals   = scheme_malloc_atomic_allow_interior(nargs * sizeof(ForeignAny));
    avalues = scheme_malloc(nargs * sizeof(void*));
    offsets = scheme_malloc_atomic(nargs * sizeof(intptr_t));
  }
  /* 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(name, 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)
      || (CTYPE_PRIMLABEL(base) == FOREIGN_union)) {
    /* 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;
  }

#ifdef MZ_USE_PLACES
  if (orig_place)
    ffi_call_in_orig_place(cif, c_func, cfoff,
                           nargs, ivals, avalues,
                           offsets, p);
  else
#endif
    finish_ffi_call(cif, c_func, cfoff,
                    nargs, ivals, avalues,
                    offsets, p);

  if (save_errno != 0) save_errno_values(save_errno);
  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:
  case FOREIGN_union:
    memcpy(newp, p, CTYPE_PRIMTYPE(base)->size);
    free(p);
    p = newp;
    break;
  case FOREIGN_array:
    /* array as result is treated as a pointer, so
       adjust `p' to make C2SCHEME work right */
    p = *(void **)p;
    break;
  }
  return C2SCHEME(NULL, otype, p, 0, 1, 1);
}

/* see below */
void free_fficall_data(void *data, void *p)
{
  SCHEME_VEC_ELS(data)[4] = NULL;
  free(((ffi_cif*)p)->arg_types);
  free(p);
}

static Scheme_Object *ffi_name = NULL;

/* (ffi-call ffi-obj in-types out-type [abi save-errno? orig-place?]) -> (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[])
{
  Scheme_Object *itypes = argv[1];
  Scheme_Object *otype  = argv[2];
  Scheme_Object *obj, *data, *p, *base, *cp, *name, *a[1];
  ffi_abi abi;
  intptr_t ooff;
  GC_CAN_IGNORE ffi_type *rtype, **atypes;
  GC_CAN_IGNORE ffi_cif *cif;
  int i, nargs, save_errno;
# ifdef MZ_USE_PLACES
  int orig_place;
# define FFI_CALL_VEC_SIZE 8
# else /* MZ_USE_PLACES undefined */
# define FFI_CALL_VEC_SIZE 7
# endif /* MZ_USE_PLACES */
  cp = unwrap_cpointer_property(argv[0]);
  if (!SCHEME_FFIANYPTRP(cp))
    scheme_wrong_contract(MYNAME, "(or/c ffi-obj? cpointer?)", 0, argc, argv);
  obj = SCHEME_FFIANYPTR_VAL(cp);
  ooff = SCHEME_FFIANYPTR_OFFSET(cp);
  if ((obj == NULL) && (ooff == 0))
    scheme_wrong_contract(MYNAME, NON_NULL_CPOINTER, 0, argc, argv);
  nargs = scheme_proper_list_length(itypes);
  if (nargs < 0)
    scheme_wrong_contract(MYNAME, "list?", 1, argc, argv);
  if (NULL == (base = get_ctype_base(otype)))
    scheme_wrong_contract(MYNAME, "ctype?", 2, argc, argv);
  rtype = CTYPE_ARG_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_contract(MYNAME, "(or/c 'posix 'windows #f)", 4, argc, argv);
    }
  } else
    save_errno = 0;
# ifdef MZ_USE_PLACES
  if (argc > 5) orig_place = SCHEME_TRUEP(argv[5]);
  else orig_place = 0;
# endif /* MZ_USE_PLACES */
  if (SCHEME_FFIOBJP(cp))
    name = scheme_make_byte_string(((ffi_obj_struct*)(cp))->name);
  else
    name = ffi_name;
  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_contract(MYNAME, "(listof ctype?)", 1, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      wrong_void(MYNAME, SCHEME_CAR(p), 1, 1, argc, argv);
    atypes[i] = CTYPE_ARG_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(FFI_CALL_VEC_SIZE, NULL);
  SCHEME_VEC_ELS(data)[0] = name;
  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);
# ifdef MZ_USE_PLACES
  SCHEME_VEC_ELS(data)[7] = (orig_place ? scheme_true : scheme_false);
# endif /* MZ_USE_PLACES */
  scheme_register_finalizer(data, free_fficall_data, cif, NULL, NULL);
  a[0] = data;
  return scheme_make_prim_closure_w_arity(ffi_do_call,
                                          1, a,
                                          SCHEME_BYTE_STR_VAL(name),
                                          nargs, nargs);
}
#undef MYNAME

/*****************************************************************************/
/* Racket 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, *t;

  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_PROCP(data->sync))
    scheme_start_in_scheduler();
  for (i=0, p=data->itypes; i<argc; i++, p=SCHEME_CDR(p)) {
    t = SCHEME_CAR(p);
    if (CTYPE_PRIMLABEL(get_ctype_base(t)) == FOREIGN_array) {
      /* array as argument is treated as a pointer */
      v = C2SCHEME(NULL, t, *(void **)(args[i]), 0, 0, 0);
    } else
      v = C2SCHEME(NULL, t, args[i], 0, 0, 0);
    argv[i] = v;
  }
  p = _scheme_apply(data->proc, argc, argv);
  SCHEME2C("callback result", data->otype, resultp, 0, p, NULL, NULL, 1);
  if (data->sync && !SCHEME_PROCP(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 Racket 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;
}

static void check_foreign_work(int check_for_in_original)
{
  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);

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

    } while (qc);
  }

#ifdef MZ_USE_PLACES
  if (check_for_in_original && (scheme_current_place_id == 0) && orig_place_mutex) {
    FFI_Orig_Place_Call *todo;
    void *sh;

    while (1) {
      mzrt_mutex_lock(orig_place_mutex);
      todo = orig_place_calls_tail;
      if (todo) {
        orig_place_calls_tail = todo->prev;
        if (todo->prev)
          todo->prev->next = NULL;
        else
          orig_place_calls = NULL;
        todo->needs_queue = 0;
      }
      mzrt_mutex_unlock(orig_place_mutex);

      if (todo) {
        finish_ffi_call(todo->cif, todo->c_func, todo->cfoff,
                        todo->nargs, todo->ivals, todo->avalues,
                        todo->offsets, todo->p);
        mzrt_mutex_lock(orig_place_mutex);
        sh = todo->signal_handle;
        todo->signal_handle = NULL; /* indicates "done" */
        scheme_signal_received_at(sh);
        mzrt_mutex_unlock(orig_place_mutex);
      } else
        break;
    }
  }
#endif
}

void scheme_check_foreign_work(void)
{
  check_foreign_work(1);
}

#endif

void ffi_queue_callback(ffi_cif* cif, void* resultp, void** args, void *userdata)
  XFORM_SKIP_PROC
{
#ifdef MZ_USE_MZRT
  /* This function must not refer to any GCable address, not even
     temporarily, because a GC may occur concurrent to this
     function if it's in another thread. */
  FFI_Sync_Queue *queue;

  queue = (FFI_Sync_Queue *)((void **)userdata)[1];
  userdata = ((void **)userdata)[0];

  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);
}

#ifdef MZ_USE_MZRT
void free_cl_cif_queue_args(void *ignored, void *p)
{
  void *data = ((closure_and_cif*)p)->data;
  void **q = (void **)data;
  data = q[0];
  free(q);
#ifdef MZ_PRECISE_GC
  GC_free_immobile_box((void**)data);
#endif
  scheme_free_code(p);
}
#endif

/* (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 Racket 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                 :               |  \-----> Racket 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;
  GC_CAN_IGNORE void *callback_data;
# ifdef MZ_USE_MZRT
  int keep_queue = 0;
# endif /* MZ_USE_MZRT */

  if (!SCHEME_PROCP(argv[0]))
    scheme_wrong_contract(MYNAME, "procedure?", 0, argc, argv);
  nargs = scheme_proper_list_length(itypes);
  if (nargs < 0)
    scheme_wrong_contract(MYNAME, "list?", 1, argc, argv);
  if (NULL == (base = get_ctype_base(otype)))
    scheme_wrong_contract(MYNAME, "ctype?", 2, argc, argv);
  rtype = CTYPE_ARG_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 = argv[5];
    if (is_atomic) sync = scheme_box(sync);
    keep_queue = 1;
#   endif /* MZ_USE_MZRT */
    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_contract(MYNAME, "(listof ctype?)", 1, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      wrong_void(MYNAME, SCHEME_CAR(p), 1, 1, argc, argv);
    atypes[i] = CTYPE_ARG_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 */
    GC_CAN_IGNORE void **tmp;
    tmp = GC_malloc_immobile_box(GC_malloc_weak_box(data, NULL, 0, 1));
    callback_data = (struct immobile_box*)tmp;
  }
# else /* MZ_PRECISE_GC undefined */
  callback_data = (void*)data;
# endif /* MZ_PRECISE_GC */
# ifdef MZ_USE_MZRT
  if (keep_queue) {
    /* For ffi_queue_callback(), add a level of indirection in `data' to
       hold the place-specific `ffi_sync_queue'.  Use
       `free_cl_cif_data_args' to clean up this extra level. */
    GC_CAN_IGNORE void **tmp;
    tmp = (void **)malloc(sizeof(void*) * 2);
    tmp[0] = callback_data;
    tmp[1] = ffi_sync_queue;
    callback_data = (void *)tmp;
  }
# endif /* MZ_USE_MZRT */
  cl_cif_args->data = callback_data;
  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");
# ifdef MZ_USE_MZRT
  if (keep_queue)
    scheme_register_finalizer(data, free_cl_cif_queue_args, cl_cif_args,
                              NULL, NULL);
  else
# endif /* MZ_USE_MZRT */
  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) {
    intptr_t 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_contract(MYNAME, "(or/c 'EINTR 'EEXIST 'EAGAIN)",0, argc, argv);
  return NULL;
}
#undef MYNAME

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

/* (make-stubborn-will-executor) -> #<will-executor> */
#define MYNAME "make-stubborn-will-executor"
static Scheme_Object *foreign_make_stubborn_will_executor(int argc, Scheme_Object *argv[])
{
  return scheme_make_stubborn_will_executor();
}
#undef MYNAME

/* (make-late-weak-box val) -> #<weak-box> */
#define MYNAME "make-late-weak-box"
static Scheme_Object *foreign_make_late_weak_box(int argc, Scheme_Object *argv[])
{
  return scheme_make_late_weak_box(argv[0]);
}
#undef MYNAME

/* (make-late-weak-hasheq) -> #<hash> */
#define MYNAME "make-late-weak-hasheq"
static Scheme_Object *foreign_make_late_weak_hasheq(int argc, Scheme_Object *argv[])
{
  return (Scheme_Object *)scheme_make_bucket_table(20, SCHEME_hash_late_weak_ptr);
}
#undef MYNAME

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

void ctype_printer(Scheme_Object *ctype, int dis, Scheme_Print_Params *pp)
{
  char *str;
  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");

  MZ_REGISTER_STATIC(ffi_name);
  ffi_name = scheme_make_byte_string("ffi:proc");
}

void scheme_init_foreign_places() {
  MZ_REGISTER_STATIC(opened_libs);
  opened_libs = scheme_make_hash_table(SCHEME_hash_string);
#ifdef MZ_USE_PLACES
  if (!orig_place_mutex) {
    mzrt_mutex_create(&orig_place_mutex);
    orig_place_signal_handle = scheme_get_signal_handle();
  }
#endif
}

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, 3), 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, 3), menv);
  scheme_add_global("make-array-type",
    scheme_make_prim_w_arity(foreign_make_array_type, "make-array-type", 2, 2), menv);
  scheme_add_global("make-union-type",
    scheme_make_prim_w_arity(foreign_make_union_type, "make-union-type", 1, -1), 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("cpointer-gcable?",
    scheme_make_prim_w_arity(foreign_cpointer_gcable_p, "cpointer-gcable?", 1, 1), 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, 6), 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);
  scheme_add_global("make-stubborn-will-executor",
    scheme_make_prim_w_arity(foreign_make_stubborn_will_executor, "make-stubborn-will-executor", 0, 0), menv);
  scheme_add_global("make-late-weak-box",
    scheme_make_prim_w_arity(foreign_make_late_weak_box, "make-late-weak-box", 1, 1), menv);
  scheme_add_global("make-late-weak-hasheq",
    scheme_make_prim_w_arity(foreign_make_late_weak_hasheq, "make-late-weak-hasheq", 0, 0), 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_smzintptr));
  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_umzintptr));
  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_gcpointer));
  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_gcpointer));
  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_gcpointer));
  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_gcpointer));
  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_add_global_constant("prop:cpointer", scheme_cpointer_property, menv);
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

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

#else /* DONT_USE_FOREIGN */

int scheme_is_cpointer(Scheme_Object *cp)
{
  return (SCHEME_FALSEP(cp)
          || SCHEME_CPTRP(x)
          || SCHEME_BYTE_STRINGP(x)
          || (SCHEME_CHAPERONE_STRUCTP(cp)
              && scheme_struct_type_property_ref(scheme_cpointer_property, cp)));
}

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;
}

static Scheme_Object *foreign_make_stubborn_will_executor(int argc, Scheme_Object *argv[])
{
  return scheme_make_stubborn_will_executor();
}

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, 3), 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, 3), menv);
  scheme_add_global("make-array-type",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-array-type", 2, 2), menv);
  scheme_add_global("make-union-type",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-union-type", 1, -1), 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("cpointer-gcable?",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "cpointer-gcable?", 1, 1), 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, 6), 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("make-stubborn-will-executor",
   scheme_make_prim_w_arity((Scheme_Prim *)foreign_make_stubborn_will_executor, "make-stubborn-will-executor", 0, 0), menv);
  scheme_add_global("make-late-weak-box",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-late-weak-box", 1, 1), menv);
  scheme_add_global("make-late-weak-hasheq",
   scheme_make_prim_w_arity((Scheme_Prim *)unimplemented, "make-late-weak-hasheq", 0, 0), 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_add_global_constant("prop:cpointer", scheme_cpointer_property, menv);
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

#endif
