#!/bin/sh
#| -*- C -*-
exec racket "$0" > `echo "$0" | sed 's/rktc$/c/'` "$0"
|#

#lang scribble/text

@(require "rktc-utils.rkt")

@header{foreign.rktc}

#include "schpriv.h"

#ifndef DONT_USE_FOREIGN

#include <errno.h>

@@@IFNDEF{WINDOWS_DYNAMIC_LOAD}{

# include <dlfcn.h>

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

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

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

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

}{

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

}

#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*

/*****************************************************************************/
/* 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
}

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

@cdefstruct[ffi-lib
  [handle  "NON_GCBALE_PTR(void)"]
  [name    "Scheme_Object*"]
  [objects "Scheme_Hash_Table*"]]

THREAD_LOCAL_DECL(static Scheme_Hash_Table *opened_libs);

/* (ffi-lib filename no-error?) -> ffi-lib */
@cdefine[ffi-lib 1 2]{
  char *name;
  Scheme_Object *path, *hashname;
  void *handle;
  int null_ok = 0;
  ffi_lib_struct *lib;
  if (!(SCHEME_PATH_STRINGP(argv[0]) || SCHEME_FALSEP(argv[0])))
    scheme_wrong_type(MYNAME, "string-or-false", 0, argc, argv);
  /* leave the filename as given, the system will look for it */
  /* (`#f' means open the executable) */
  path = SCHEME_FALSEP(argv[0]) ? NULL : TO_PATH(argv[0]);
  name = (path==NULL) ? NULL : SCHEME_PATH_VAL(path);
  hashname = (Scheme_Object*)((name==NULL) ? "" : name);
  lib = (ffi_lib_struct*)scheme_hash_get(opened_libs, hashname);
  if (!lib) {
    Scheme_Hash_Table *ht;
    @@@IFDEF{WINDOWS_DYNAMIC_LOAD}{
      if (name==NULL) {
        /* openning the executable is marked by a NULL handle */
        handle = NULL;
        null_ok = 1;
      } else
        handle = LoadLibraryW(WIDE_PATH(name));
    }{
      handle = dlopen(name, RTLD_NOW | RTLD_GLOBAL);
    }
    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);
        }{
          scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                           MYNAME": couldn't open %V (%s)", argv[0], dlerror());
        }
      }
    }
    ht = scheme_make_hash_table(SCHEME_hash_string);
    @cmake["lib" ffi-lib "handle" "argv[0]" "ht"]
    scheme_hash_set(opened_libs, hashname, (Scheme_Object*)lib);
    /* no dlclose finalizer - since the hash table always keeps a reference */
    /* maybe add some explicit unload at some point */
  }
  return (Scheme_Object*)lib;
}

/* (ffi-lib-name ffi-lib) -> string */
@cdefine[ffi-lib-name 1]{
  if (!SCHEME_FFILIBP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-lib", 0, argc, argv);
  return ((ffi_lib_struct*)argv[0])->name;
}

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

@cdefstruct[ffi-obj
  [obj  "NON_GCBALE_PTR(void)"]
  [name "char*"]
  [lib  "NON_GCBALE_PTR(ffi_lib_struct)"]]

/* (ffi-obj objname ffi-lib-or-libname) -> ffi-obj */
@cdefine[ffi-obj 2]{
  ffi_obj_struct *obj;
  void *dlobj;
  ffi_lib_struct *lib = NULL;
  char *dlname;
  if (SCHEME_FFILIBP(argv[1]))
    lib = (ffi_lib_struct*)argv[1];
  else if (SCHEME_PATH_STRINGP(argv[1]) || SCHEME_FALSEP(argv[1]))
    lib = (ffi_lib_struct*)(foreign_ffi_lib(1,&argv[1]));
  else
    scheme_wrong_type(MYNAME, "ffi-lib", 1, argc, argv);
  if (!SCHEME_BYTE_STRINGP(argv[0]))
    scheme_wrong_type(MYNAME, "bytes", 0, argc, argv);
  dlname = SCHEME_BYTE_STR_VAL(argv[0]);
  obj = (ffi_obj_struct*)scheme_hash_get(lib->objects, (Scheme_Object*)dlname);
  if (!obj) {
    @@@IFDEF{WINDOWS_DYNAMIC_LOAD}{
    if (lib->handle) {
      dlobj = GetProcAddress(lib->handle, dlname);
    } else {
      /* this is for the executable-open case, which was marked by a NULL
       * handle, deal with it by searching all current modules */
      @DEFINE{NUM_QUICK_MODS 16}
      HMODULE *mods, me, quick_mods[NUM_QUICK_MODS];
      DWORD cnt = NUM_QUICK_MODS * sizeof(HMODULE), actual_cnt, i;
      me = GetCurrentProcess();
      mods = quick_mods;
      if (mzEnumProcessModules(me, mods, cnt, &actual_cnt)) {
        if (actual_cnt > cnt) {
          cnt = actual_cnt;
          mods = (HMODULE *)scheme_malloc_atomic(cnt);
          if (!mzEnumProcessModules(me, mods, cnt, &actual_cnt))
            mods = NULL;
        } else
          cnt = actual_cnt;
      } else
        mods = NULL;
      if (mods) {
        cnt /= sizeof(HMODULE);
        for (i = 0; i < cnt; i++) {
          dlobj = GetProcAddress(mods[i], dlname);
          if (dlobj) break;
        }
      } else
        dlobj = NULL;
    }
    if (!dlobj) {
      long err;
      err = GetLastError();
      scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                       MYNAME": couldn't get \"%s\" from %V (%E)",
                       dlname, lib->name, err);
    }
    }{
    dlobj = dlsym(lib->handle, dlname);
    if (!dlobj) {
      const char *err;
      err = dlerror();
      if (err != NULL)
        scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                         MYNAME": couldn't get \"%s\" from %V (%s)",
                         dlname, lib->name, err);
    }
    }
    @cmake["obj" ffi-obj "dlobj" "dlname" "lib"]
    scheme_hash_set(lib->objects, (Scheme_Object*)dlname, (Scheme_Object*)obj);
  }
  return (obj == NULL) ? scheme_false : (Scheme_Object*)obj;
}

/* (ffi-obj-lib ffi-obj) -> ffi-lib */
@cdefine[ffi-obj-lib 1]{
  if (!SCHEME_FFIOBJP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj", 0, argc, argv);
  return (Scheme_Object*)(((ffi_obj_struct*)argv[0])->lib);
}

/* (ffi-obj-name ffi-obj) -> string */
@cdefine[ffi-obj-name 1]{
  if (!SCHEME_FFIOBJP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj", 0, argc, argv);
  return scheme_make_byte_string(((ffi_obj_struct*)argv[0])->name);
}

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

}{

/* 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. */
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;
}
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))

}

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

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

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

static unsigned short *ucs4_string_to_utf16_pointer(Scheme_Object *ucs)
{
  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 */

@(begin
;; Types are defined with the `defctype' function.  This looks like:
;;   (defctype 'type-name
;;     'prop1 val1
;;     'prop2 val2
;;     ...)
;; The current properties are:
;;   stype: scheme binding for this type
;;   cname: like stype but used for C identifiers
;;   ftype: type name used by libffi (as ffi_type_X) (defaults to cname)
;;   ctype: C type, or #f if none (defaults to ftype, with proper massaging)
;;   macro: if specified as "X", use "SCHEME_XP" and "SCHEME_X_VAL" as the
;;          defaults for the next two properties
;;   pred:  name of predicate macro
;;    (or a function of the value and an ForeignAny obj pointer name, which
;;     produces an expression that tests the value and sets the ForeignAny obj
;;     accordingly.)
;;   s->c:  name of value extraction macro
;;    (or #f which means that the predicate already sets the value, or a
;;     function with the same arguments as above)
;;   c->s:  name of value construction macro/function
;;    (or a function of the value that generates the expression)
;;   offset: if specified as "X", use "SCHEME_X_OFFSET" to extract an offset
;;    value for s->c, otherwise leave 0 as the offset

(define types null)

(require (for-syntax scheme/base))

(define (get-prop type prop)
  (cadr (assq prop (cdr (assq type types)))))

(define type-counter
  (let ([c 0])
    (lambda ([flag #f])
      (case flag
        [(#f)   (set! c (add1 c)) c]
        [(last) (begin0 (add1 c) (set! c #f))]
        [else (error "internal error")]))))

(define (describe-type stype cname ftype ctype pred s->c c->s offset)
  @list{
    #define FOREIGN_@cname (@(type-counter))
    /* Type Name:   @|stype|@(and (not (equal? cname stype)) @list{ (@cname)})
     * LibFfi type: ffi_type_@ftype
     * C type:      @(or ctype "-none-")
     * Predicate:   @(cond [(not pred) "-none-"]
                           [(procedure? pred) (pred "<Scheme>" "aux")]
                           [else @list{@|pred|(<Scheme>)}])
     * Scheme->C:   @(cond [(not s->c)
                            (if pred "-none- (set by the predicate)" "-none-")]
                           [(procedure? s->c) (s->c "<Scheme>" "aux")]
                           [else @list{@|s->c|(<Scheme>)}])
     * S->C offset: @(or offset 0)
     * C->Scheme:   @(cond [(not c->s) "-none-"]
                           [(procedure? c->s) (c->s "<C>")]
                           [else @list{@|c->s|(<C>)}])
     */})

(define (make-ctype type args)
  (define (prop p . default)
    (let loop ([args args])
      (cond [(null? args) (and (pair? default) (car default))]
            [(eq? p (car args))
             (if (and (pair? (cadr args)) (eq? (caadr args) 'from))
               (get-prop (cadadr args) p)
               (cadr args))]
            [else (loop (cddr args))])))
  (let* ([stype (symbol->string type)]
         [cname (racket-id->c-name stype)]
         [ftype (prop 'ftype cname)]
         [ctype (prop 'ctype
                      (regexp-replace
                       #rx"^sint"
                       (regexp-replace #rx"^(u?int(?:[0-9]+))$" ftype "\\1_t")
                       "int"))]
         [ftype (regexp-replace #rx"^(int|char|long)" ftype "s\\1")]
         [macro (prop 'macro)]
         [pred  (prop 'pred (and macro @list{SCHEME_@|macro|P}))]
         [s->c  (prop 's->c (and macro @list{SCHEME_@|macro|_VAL}))]
         [c->s  (prop 'c->s)]
         [offset (prop 'offset #f)])
    (output (describe-type stype cname ftype ctype pred s->c c->s offset))
    `(,type (stype ,stype) (cname ,cname) (ftype ,ftype) (ctype ,ctype)
      (macro ,macro) (pred ,pred) (s->c ,s->c) (c->s ,c->s) (offset ,offset))))

(define (defctype name . args)
  (set! types (append types (list (make-ctype name args)))))

(define-syntax (map-types stx)
  (syntax-case stx ()
    [(_ body ...)
     (let ()
       (define (id sym) (datum->syntax stx sym stx))
       (define-values (exprs semi?)
          (syntax-case stx ()
            [(_ #:semicolons? s? body ...) (values #'(body ...) #'s?)]
            [(_ body ...) (values #'(body ...) #'#t)]))
       (with-syntax ([(body ...) exprs]
                     [semi? semi?]
                     [stype (id 'stype)]
                     [cname (id 'cname)]
                     [ctype (id 'ctype)]
                     [ftype (id 'ftype)]
                     [macro (id 'macro)]
                     [pred  (id 'pred)]
                     [s->c  (id 's->c)]
                     [c->s  (id 'c->s)]
                     [offset (id 'offset)]
                     [ptr?  (id 'ptr?)])
         #'(maplines #:semicolons? 'semi?
                     (lambda (t)
                       (define data (cdr t))
                       (define (get sym) (cadr (assq sym data)))
                       (let* ([stype (get 'stype)]
                              [cname (get 'cname)]
                              [ftype (get 'ftype)]
                              [ctype (get 'ctype)]
                              [macro (get 'macro)]
                              [pred  (get 'pred)]
                              [s->c  (get 's->c)]
                              [c->s  (get 'c->s)]
                              [offset (get 'offset)]
                              [ptr? (or (equal? "pointer" ftype)
                                        (equal? "gcpointer" ftype))])
                         body ...))
                     types)))]))

(define (defctype* name/+ftype ctype pred s->c c->s)
  (let ([name (if (pair? name/+ftype) (car name/+ftype) name/+ftype)]
        [ftype (and (pair? name/+ftype) (cadr name/+ftype))])
    (apply defctype name
      `(ctype ,ctype
        ,@(if ftype `(ftype ,ftype) `())
        pred ,(if (string? pred) @list{SCHEME_@|pred|P}     pred)
        s->c ,(if (string? s->c) @list{SCHEME_@|s->c|_VAL}  s->c)
        c->s ,(if (string? c->s) @list{scheme_make_@|c->s|} c->s)))))

)

/***********************************************************************
 * 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. */
@(defctype 'void
   'ctype #f 'pred #f 's->c #f 'c->s (lambda (x) "scheme_void"))

@;  libffi primitive types
@;     scheme-name  c-type     SCHEME_?P SCHEME_?_VAL scheme_make_
@(defctype* 'int8   "Tsint8"      "INT"  "INT"        "integer")

@(defctype* 'uint8  "Tuint8"      "INT"  "UINT"       "integer_from_unsigned")

@(defctype* 'int16  "Tsint16"     "INT"  "INT"        "integer")

@(defctype* 'uint16 "Tuint16"     "INT"  "UINT"       "integer_from_unsigned")

/* Treats integers properly: */
@(defctype* 'int32  "Tsint32"
   (lambda (x aux) @list{scheme_get_realint_val(@x,&@aux)}) #f
  "realinteger_value")

/* Treats integers properly: */
@(defctype* 'uint32 "Tuint32"
   (lambda (x aux) @list{scheme_get_unsigned_realint_val(@x,&@aux)}) #f
   "realinteger_value_from_unsigned")

@; mzlonglong is always assumed to be 64 bits, or the above will throw an error
@(defctype* 'int64  "Tsint64"
   (lambda (x aux) @list{scheme_get_long_long_val(@x,&@aux)}) #f
   "integer_value_from_long_long")

@(defctype* 'uint64 "Tuint64"
   (lambda (x aux) @list{scheme_get_unsigned_long_long_val(@x,&@aux)}) #f
   "integer_value_from_unsigned_long_long")

/* This is like int32, but always assumes fixnum: */
@(defctype* '(fixint "int32")   "Tsint32"  "INT" "INT"  "integer")

/* This is like uint32, but always assumes fixnum: */
@(defctype* '(ufixint "uint32") "Tuint32" "INT" "UINT" "integer_from_unsigned")

@@@IFNDEF{SIXTY_FOUR_BIT_LONGS}{
#define ffi_type_smzlong ffi_type_sint32
#define ffi_type_umzlong ffi_type_uint32
}{
#define ffi_type_smzlong ffi_type_sint64
#define ffi_type_umzlong ffi_type_uint64
}

@@@IFNDEF{SIXTY_FOUR_BIT_INTEGERS}{
#define ffi_type_smzintptr ffi_type_sint32
#define ffi_type_umzintptr ffi_type_uint32
}{
#define ffi_type_smzintptr ffi_type_sint64
#define ffi_type_umzintptr ffi_type_uint64
}

/* This is what mzscheme defines as intptr, assuming fixnums: */
@(defctype* '(fixnum "smzintptr")
   "intptr_t"          "INT" "INT"  "integer")

/* This is what mzscheme defines as uintptr, assuming fixnums: */
@(defctype* '(ufixnum "umzintptr")
   "uintptr_t" "INT" "UINT" "integer_from_unsigned")

@(defctype* 'float  "float"        "FLOAT"  "FLOAT"        "double")

@(defctype* 'double "double"       "FLOAT"  "FLOAT"        "double")
@;
@; Not useful?  not implemented in any case.
@; (defctype* 'longdouble "long double" ...???...)

/* A double that will coerce numbers to doubles: */
@(defctype* '(double* "double") "double"
   ;; use a list to avoid automatic "SCHEME_..._VAL" wrapping
   "REAL" '("scheme_real_to_double") "double")

/* Booleans -- implemented as an int which is 1 or 0: */
@(defctype 'bool
   'ftype "int"
   'pred (lambda (x aux) "1")
   's->c "SCHEME_TRUEP"
   'c->s (lambda (x) @list{(@|x|?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. */

@(defctype 'string/ucs-4
   'ftype "gcpointer"
   'ctype "mzchar*"
   'pred  "SCHEME_FALSEP_OR_CHAR_STRINGP"
   's->c  "ucs4_string_or_null_to_ucs4_pointer"
   'c->s  "scheme_make_char_string_without_copying")

@(defctype 'string/utf-16
   'ftype "gcpointer"
   'ctype "unsigned short*"
   'pred  "SCHEME_FALSEP_OR_CHAR_STRINGP"
   's->c  "ucs4_string_or_null_to_utf16_pointer"
   'c->s  "utf16_pointer_to_ucs4_string")

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

@(defctype 'bytes
   'ftype "gcpointer"
   'ctype "char*"
   'pred  (lambda (x aux)
            @list{SCHEME_FALSEP(@x)||SCHEME_BYTE_STRINGP(@x)})
   's->c  (lambda (x aux)
            @list{SCHEME_FALSEP(@x)?NULL:SCHEME_BYTE_STR_VAL(@x)})
   'c->s  (lambda (x)
            @list{(@|x|==NULL)?scheme_false:@;
                  scheme_make_byte_string_without_copying(@x)}))

@(defctype 'path
   'ftype "gcpointer"
   'ctype "char*"
   'pred  (lambda (x aux)
            @list{SCHEME_FALSEP(@x)||SCHEME_PATH_STRINGP(@x)})
   's->c  (lambda (x aux)
            @list{SCHEME_FALSEP(@x)?NULL:SCHEME_PATH_VAL(TO_PATH(@x))})
   'c->s  (lambda (x)
            @list{(@|x|==NULL)?scheme_false:@;
                  scheme_make_path_without_copying(@x)}))

@(defctype 'symbol
   'ftype "pointer"
   'ctype "char*"
   'pred  "SCHEME_SYMBOLP"
   's->c  "SCHEME_SYM_VAL"
   'c->s  "scheme_intern_symbol")

/* 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. */
@(defctype 'pointer
   'ctype "void*"
   'macro "FFIANYPTR"
   'offset "FFIANYPTR"
   'c->s  "scheme_make_foreign_external_cpointer")

@(defctype 'gcpointer
   'ftype "gcpointer"
   'ctype "void*"
   'macro "FFIANYPTR"
   'offset "FFIANYPTR"
   'c->s  "scheme_make_foreign_cpointer")

@; This is probably not needed
@; /* Used for ffi-callback objects: */
@; @(defctype 'callback
@;    'ftype "pointer"
@;    'ctype "void*"
@;    'macro "FFICALLBACK"
@;    's->c  (lambda (x aux) @list{((ffi_callback_struct*)(@x))->callback})
@;    'c->s  (lambda (x) x))
@;
/* This is used for passing and Scheme_Object* value as is.  Useful for
 * functions that know about Scheme_Object*s, like Racket's. */
@(defctype 'scheme
   'ftype "gcpointer"
   'ctype "Scheme_Object*"
   'pred (lambda (x aux) "1")
   's->c (lambda (x aux) x)
   'c->s (lambda (x) x))

/* Special type, not actually used for anything except to mark values
 * that are treated like pointers but not referenced.  Used for
 * creating function types. */
@(defctype 'fpointer 'ftype "pointer" 'ctype "void*")

typedef union _ForeignAny {
  @(map-types (when ctype @list{@ctype x_@cname}))
} ForeignAny;

/* This is a tag that is used to identify user-made struct types. */
@; last makes sure this is the last one value that gets used
#define FOREIGN_struct (@(type-counter))
#define FOREIGN_array (@(type-counter))
#define FOREIGN_union (@(type-counter 'last))

static int is_gcable_pointer(Scheme_Object *o) {
 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.)
 */
@cdefstruct[ctype
  [basetype    "Scheme_Object*"]
  [scheme_to_c "Scheme_Object*"]
  [c_to_scheme "Scheme_Object*"]]

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. */
@cdefine[ctype-basetype 1]{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return CTYPE_BASETYPE(argv[0]);
}

@cdefine[ctype-scheme->c 1]{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return (CTYPE_PRIMP(argv[0])) ? scheme_false :
           ((ctype_struct*)(argv[0]))->scheme_to_c;
}

@cdefine[ctype-c->scheme 1]{
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "ctype", 0, argc, argv);
  return (CTYPE_PRIMP(argv[0])) ? scheme_false :
           ((ctype_struct*)(argv[0]))->c_to_scheme;
}

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

/* Returns the size, 0 for void, -1 if no such type */
static int ctype_sizeof(Scheme_Object *type)
{
  type = get_ctype_base(type);
  if (type == NULL) return -1;
  switch (CTYPE_PRIMLABEL(type)) {
  @(map-types @list{case FOREIGN_@|cname|: @;
                      return @(if ctype @list{sizeof(@ctype)} "0")})
  /* 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. */
@cdefine[make-ctype 3]{
  ctype_struct *type;
  if (!SCHEME_CTYPEP(argv[0]))
    scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  else if (!(SCHEME_FALSEP(argv[1]) || SCHEME_PROCP(argv[1])))
    scheme_wrong_type(MYNAME, "procedure-or-false", 1, argc, argv);
  else if (!(SCHEME_FALSEP(argv[2]) || SCHEME_PROCP(argv[2])))
    scheme_wrong_type(MYNAME, "procedure-or-false", 2, argc, argv);
  else if (SCHEME_FALSEP(argv[1]) && SCHEME_FALSEP(argv[2]))
    return argv[0];
  else {
    @cmake["type" ctype "argv[0]" "argv[1]" "argv[2]"]
    return (Scheme_Object*)type;
  }
  @hush
}

/* 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 */

@defsymbols[default stdcall sysv]

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 */

/* (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. */
@cdefine[make-cstruct-type 1 3]{
  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_type(MYNAME, "proper 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_type(MYNAME, "1, 2, 4, 8, 16, or #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_type(MYNAME, "list-of-C-types", 0, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 0, argc, argv);
    elements[i] = CTYPE_PRIMTYPE(base);
    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");
  @cmake["type" ctype "argv[0]"
         "(Scheme_Object*)libffi_type"
         "(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;
}

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

/* (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. */
@cdefine[make-array-type 2 2]{
  Scheme_Object *base, *basetype;
  GC_CAN_IGNORE ffi_type *libffi_type, **elements;
  ctype_struct *type;
  intptr_t len;

  if (NULL == (base = get_ctype_base(argv[0])))
    scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  if (!scheme_get_int_val(argv[1], &len) || (len < 0))
    scheme_wrong_type(MYNAME, "pointer-sized nonnegative exact 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));
  libffi_type->size      = CTYPE_PRIMTYPE(base)->size * len;
  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];

  @cmake["type" ctype "basetype"
         "(Scheme_Object*)libffi_type"
         "(Scheme_Object*)FOREIGN_array"]

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

  return (Scheme_Object*)type;
}

/*****************************************************************************/
/* 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. */
@cdefine[make-union-type 1 -1]{
  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_type(MYNAME, "C-type", 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));

  @cmake["type" ctype "basetype"
         "(Scheme_Object*)libffi_type"
         "(Scheme_Object*)FOREIGN_union"]

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

  return (Scheme_Object*)type;
}

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

@cdefstruct[ffi-callback
  [callback "NON_GCBALE_PTR(void)"]
  [proc     "Scheme_Object*"]
  [itypes   "Scheme_Object*"]
  [otype    "Scheme_Object*"]
  [sync     "Scheme_Object*"]]

/* 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))

@cdefine[cpointer? 1]{
  return SCHEME_FFIANYPTRP(argv[0]) ? scheme_true : scheme_false;
}

@cdefine[cpointer-tag 1]{
  Scheme_Object *tag = NULL;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (SCHEME_CPTRP(argv[0])) tag = SCHEME_CPTR_TYPE(argv[0]);
  return (tag == NULL) ? scheme_false : tag;
}

@cdefine[set-cpointer-tag! 2]{
  if (!SCHEME_CPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "proper-cpointer", 0, argc, argv);
  SCHEME_CPTR_TYPE(argv[0]) = argv[1];
  return scheme_void;
}

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

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

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

static Scheme_Object *C2SCHEME(Scheme_Object *type, void *src,
                               intptr_t delta, int args_loc, int gcsrc)
{
  Scheme_Object *res;
  if (!SCHEME_CTYPEP(type))
    scheme_wrong_type("C->Scheme", "C-type", 0, 1, &type);
  if (CTYPE_USERP(type)) {
    res = C2SCHEME(CTYPE_BASETYPE(type), src, delta, args_loc, 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) {
    return scheme_make_foreign_external_cpointer(*(void **)W_OFFSET(src, delta));
  } else switch (CTYPE_PRIMLABEL(type)) {
    @(map-types
      @list{case FOREIGN_@|cname|: return @;
              @(if ctype
                 (let ([x (list "REF_CTYPE("ctype")")])
                   (if (procedure? c->s) (c->s x) (list c->s"("x")")))
                 "scheme_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);
  }
  @hush
}
#undef REF_CTYPE

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

/* Usually writes the C object to dst and returns NULL.  When basetype_p is not
 * NULL, then any pointer value (any pointer or a struct 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(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_type("Scheme->C", "C-type", 0, 1, &type);
  while (CTYPE_USERP(type)) {
    if (!SCHEME_FALSEP(CTYPE_USER_S2C(type)))
      val = _scheme_apply(CTYPE_USER_S2C(type), 1, (Scheme_Object**)(&val));
    type = CTYPE_BASETYPE(type);
  }
  if (CTYPE_PRIMLABEL(type) == FOREIGN_fpointer) {
    /* No need for the SET_CTYPE trick for pointers. */
    if (SCHEME_FFICALLBACKP(val))
      ((void**)W_OFFSET(dst,delta))[0] = ((ffi_callback_struct*)val)->callback;
    else if (SCHEME_CPTRP(val))
      ((void**)W_OFFSET(dst,delta))[0] = SCHEME_CPTR_VAL(val);
    else if (SCHEME_FFIOBJP(val))
      ((void**)W_OFFSET(dst,delta))[0] = ((ffi_obj_struct*)val)->obj;
    else if (SCHEME_FALSEP(val))
      ((void**)W_OFFSET(dst,delta))[0] = NULL;
    else /* ((void**)W_OFFSET(dst,delta))[0] = val; */
         scheme_wrong_type("Scheme->C", "cpointer", 0, 1, &val);
  } else switch (CTYPE_PRIMLABEL(type)) {
    @(map-types #:semicolons? #f
       (define (wrong-type obj type)
         @list{scheme_wrong_type("Scheme->C","@type",0,1,&(@obj))})
       @list{
         case FOREIGN_@|cname|:
           @(let* ([x (and ctype @list{(((@|ctype|*)W_OFFSET(dst,delta))[0])})]
                   [f (lambda (p)
                        (if (procedure? p) @p["val" x] @list{@|p|(val)}))])
              (cond
                [(not x)
                 @list{if (!ret_loc) @wrong-type["type" "non-void-C-type"];
                       break;
                      }]
                [(not s->c)
                 @list{if (!(@(if ptr? "ret_loc" (pred "val" x)))) @;
                         @wrong-type["val" stype];
                       @(if ptr? "break" "return NULL");}]
                [else
                 @list{
                   @@IFDEF{SCHEME_BIG_ENDIAN}{
                   if (sizeof(@ctype)<sizeof(int) && ret_loc) {
                     ((int*)W_OFFSET(dst,delta))[0] = 0;
                     delta += (sizeof(int)-sizeof(@ctype));
                   }}
                   if (@f[pred]) {
                     @ctype tmp@";"@and[offset]{ intptr_t toff@";"}
                     tmp = (@ctype)(@f[s->c]);
                     @and[offset @list{toff = SCHEME_@|offset|_OFFSET(val);@"\n"}]@;
                     @(if ptr?
                          @list{if (basetype_p == NULL || @;
                                    @(if offset
                                       @list{(tmp == NULL && toff == 0)}
                                       @list{tmp == NULL}) || @;
                                    @(if (equal? ftype "pointer")
                                         @list{!is_gcable_pointer(val)}
                                         @list{0})) {
                                  @and[offset @list{if (_offset) *_offset = 0;@"\n"}]@;
                                  @x = @(if offset
                                         @list{(@ctype)W_OFFSET(tmp, toff);}
                                         "tmp");
                                  return NULL;
                                } else {
                                  *basetype_p = FOREIGN_@cname;
                                  @and[offset @list{
                                      toff = SCHEME_@|offset|_OFFSET(val);
                                      if (_offset) *_offset = toff;@;
                                      @"\n"  }]@;
                                  return @(if offset
                                            @list{_offset ? tmp : @;
                                                    (@ctype)W_OFFSET(tmp, toff)}
                                            "tmp");
                                }}
                          @list{@x = tmp@";" return NULL@";"})
                   } else {
                     @wrong-type["val" stype];
                     @hush
                   }}]))})
    case FOREIGN_struct:
    case FOREIGN_array:
    case FOREIGN_union:
      if (!SCHEME_FFIANYPTRP(val))
        scheme_wrong_type("Scheme->C", "pointer", 0, 1, &val);
      {
        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 */
@cdefine[ctype-sizeof 1]{
  int size;
  size = ctype_sizeof(argv[0]);
  if (size >= 0) return scheme_make_integer(size);
  else scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  return NULL; /* hush the compiler */
}

/* (ctype-alignof type) -> int, returns 0 for void, error if not a C type */
@cdefine[ctype-alignof 1]{
  Scheme_Object *type;
  type = get_ctype_base(argv[0]);
  if (type == NULL) scheme_wrong_type(MYNAME, "C-type", 0, argc, argv);
  else return scheme_make_integer(CTYPE_PRIMTYPE(type)->alignment);
  return NULL; /* hush the compiler */
}

/* (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.) */
@cdefine[compiler-sizeof 1]{
  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_type(MYNAME, "symbol or list of symbols", 0, argc, argv);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"int")) {
      if (basetype==0) basetype=1;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"char")) {
      if (basetype==0) basetype=2;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"void")) {
      if (basetype==0) basetype=3;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"float")) {
      if (basetype==0) basetype=4;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"double")) {
      if (basetype==0 || basetype==4) basetype=5;
      else scheme_signal_error(MYNAME": extraneous type: %V", p);
    } else if (!strcmp(SCHEME_SYM_VAL(p),"short")) {
      if (intsize>0)
        scheme_signal_error(MYNAME": cannot use both 'short and 'long");
      else intsize--;
    } else if (!strcmp(SCHEME_SYM_VAL(p),"long")) {
      if (intsize<0)
        scheme_signal_error(MYNAME": cannot use both 'short and 'long");
      else intsize++;
    } else if (!strcmp(SCHEME_SYM_VAL(p),"*")) {
      stars++;
    } else {
      scheme_wrong_type(MYNAME, "C type symbol or list of C type symbols", 0, argc, argv);
    }
  }
  if (stars > 1)
    scheme_signal_error(MYNAME": cannot handle more than one '*");
  if (intsize < -1)
    scheme_signal_error(MYNAME": cannot handle more than one 'short");
  if (intsize > 2)
    scheme_signal_error(MYNAME": cannot handle more than two 'long");
  if (basetype == 0) basetype = 1; /* int is the default type */
  /* don't assume anything, so it can be used to verify compiler assumptions */
  /* (only forbid stuff that the compiler doesn't allow) */
  @@DEFINE{RETSIZE(t) res=((stars==0)?sizeof(t):sizeof(t *))}
  switch (basetype) {
  case 1: /* int */
    switch (intsize) {
    case 0:  RETSIZE(int); break;
    case 1:  RETSIZE(long int); break;
    @@@IFDEF{INT64_AS_LONG_LONG}{
    case 2:  RETSIZE(_int64); break; /* MSVC doesn't allow long long */
    }{
    case 2:  RETSIZE(long long int); break;
    }
    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);
}

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

@defsymbols[nonatomic atomic stubborn uncollectable eternal
            interior atomic-interior raw fail-ok]

/* (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. */
@cdefine[malloc 1 5]{
  int i, failok=0;
  intptr_t size=0, num=0;
  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];
    if (SCHEME_INTP(a)) {
      if (num != 0)
        scheme_signal_error(MYNAME": specifying a second integer size: %V", a);
      num = SCHEME_INT_VAL(a);
      if (num <= 0)
        scheme_wrong_type(MYNAME, "positive 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_type(MYNAME, "C-type", i, argc, argv);
      size = ctype_sizeof(a);
      if (size <= 0)
        scheme_wrong_type(MYNAME, "non-void-C-type", i, argc, argv);
    } else if (SAME_OBJ(a, fail_ok_sym)) {
      failok = 1;
    } else if (SCHEME_SYMBOLP(a)) {
      if (mode != NULL)
        scheme_signal_error(MYNAME": specifying a second mode symbol: %V", a);
      mode = a;
    } else if (SCHEME_FFIANYPTRP(a) && !SCHEME_FALSEP(a)) {
      if (from != NULL)
        scheme_signal_error(MYNAME": specifying a second source pointer: %V",
                            a);
      from = SCHEME_FFIANYPTR_VAL(a);
      foff = SCHEME_FFIANYPTR_OFFSET(a);
    } else {
      scheme_wrong_type(MYNAME, "malloc-argument", i, argc, argv);
    }
  }
  if ((num == 0) && (size == 0)) scheme_signal_error(MYNAME": no size given");
  size = ((size==0) ? 1 : size) * ((num==0) ? 1 : num);
  if (mode == NULL)
    mf = (base != NULL && CTYPE_PRIMTYPE(base) == &ffi_type_gcpointer)
      ? scheme_malloc : scheme_malloc_atomic;
  else if (SAME_OBJ(mode, nonatomic_sym))     mf = scheme_malloc;
  else if (SAME_OBJ(mode, atomic_sym))        mf = scheme_malloc_atomic;
  else if (SAME_OBJ(mode, stubborn_sym))      mf = scheme_malloc_stubborn;
  else if (SAME_OBJ(mode, eternal_sym))       mf = scheme_malloc_eternal;
  else if (SAME_OBJ(mode, uncollectable_sym)) mf = scheme_malloc_uncollectable;
  else if (SAME_OBJ(mode, interior_sym))      mf = scheme_malloc_atomic_allow_interior;
  else if (SAME_OBJ(mode, atomic_interior_sym)) mf = scheme_malloc_atomic_allow_interior;
  else if (SAME_OBJ(mode, raw_sym))           mf = malloc;
  else {
    scheme_signal_error(MYNAME": bad allocation mode: %V", mode);
    return NULL; /* hush the compiler */
  }
  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);
}

/* (end-stubborn-change ptr) */
@cdefine[end-stubborn-change 1]{
  void *ptr;
  intptr_t poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  scheme_end_stubborn_change(W_OFFSET(ptr, poff));
  return scheme_void;
}

/* (free ptr) */
/* This is useful for raw-malloced objects, including objects from C libraries
 * that the library is mallocing itself. */
@cdefine[free 1]{
  void *ptr;
  intptr_t poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  free(W_OFFSET(ptr, poff));
  return scheme_void;
}

/* (malloc-immobile-cell v) */
@cdefine[malloc-immobile-cell 1]{
  void *p;
  p = scheme_malloc_immobile_box(argv[0]);
  return scheme_make_foreign_external_cpointer(p); /* <- beware: macro duplicates `p' */
}

/* (free-immobile-cell b) */
@cdefine[free-immobile-cell 1]{
  void *ptr;
  intptr_t poff;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  poff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (poff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  scheme_free_immobile_box((void **)W_OFFSET(ptr, poff));
  return scheme_void;
}

#define C_INTPTR_T_TYPE_STR "exact integer that fits a C intptr_t"

/* (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;
  if (is_bang) {
    if (!SCHEME_CPOINTER_W_OFFSET_P(argv[0]))
      scheme_wrong_type(who, "offset-cpointer", 0, argc, argv);
  } else {
    if (!SCHEME_FFIANYPTRP(argv[0]))
      scheme_wrong_type(who, "cpointer", 0, argc, argv);
  }
  if (!scheme_get_int_val(argv[1], &noff))
    scheme_wrong_type(who, C_INTPTR_T_TYPE_STR, 1, argc, argv);
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      intptr_t size;
      size = ctype_sizeof(argv[2]);
      if (size <= 0) scheme_wrong_type(who, "non-void-C-type", 2, argc, argv);
      noff = noff * size;
    } else
      scheme_wrong_type(who, "C-type", 2, argc, argv);
  }
  if (is_bang) {
    ((Scheme_Offset_Cptr*)(argv[0]))->offset += noff;
    return scheme_void;
  } else {
    if (SCHEME_CPTRP(argv[0]) && (SCHEME_CPTR_FLAGS(argv[0]) & 0x1))
      return scheme_make_offset_external_cptr
        (SCHEME_FFIANYPTR_VAL(argv[0]),
         SCHEME_FFIANYPTR_OFFSET(argv[0]) + noff,
         (SCHEME_CPTRP(argv[0])) ? SCHEME_CPTR_TYPE(argv[0]) : NULL);
    else
      return scheme_make_offset_cptr
        (SCHEME_FFIANYPTR_VAL(argv[0]),
         SCHEME_FFIANYPTR_OFFSET(argv[0]) + noff,
         (SCHEME_CPTRP(argv[0])) ? SCHEME_CPTR_TYPE(argv[0]) : NULL);
  }
}

/* (ptr-add cptr offset-k [type]) */
@cdefine[ptr-add 2 3]{return do_ptr_add(MYNAME, 0, argc, argv);}
/* (ptr-add! cptr offset-k [type]) */
@cdefine[ptr-add! 2 3]{return do_ptr_add(MYNAME, 1, argc, argv);}

/* (offset-ptr? x) */
/* Returns #t if the argument is a cpointer with an offset */
@cdefine[offset-ptr? 1 1]{
  return (SCHEME_CPOINTER_W_OFFSET_P(argv[0])) ? scheme_true : scheme_false;
}

/* (ptr-offset ptr) */
/* Returns the offset of a cpointer (0 if it's not an offset pointer) */
@cdefine[ptr-offset 1 1]{
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  return scheme_make_integer_value(SCHEME_FFIANYPTR_OFFSET(argv[0]));
}

/* (set-ptr-offset! ptr offset [type]) */
/* Sets the offset of an offset-cpointer (possibly multiplied by the size of
 * the given ctype) */
@cdefine[set-ptr-offset! 2 3]{
  intptr_t noff;
  if (!SCHEME_CPOINTER_W_OFFSET_P(argv[0]))
    scheme_wrong_type(MYNAME, "offset-cpointer", 0, argc, argv);
  if (!scheme_get_int_val(argv[1], &noff)) {
    scheme_wrong_type(MYNAME, C_INTPTR_T_TYPE_STR, 1, argc, argv);
  }
  if (argc > 2) {
    if (SCHEME_CTYPEP(argv[2])) {
      intptr_t size;
      if (NULL == get_ctype_base(argv[2]))
        scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
      size = ctype_sizeof(argv[2]);
      if (size <= 0)
        scheme_wrong_type(MYNAME, "non-void-C-type", 2, argc, argv);
      noff = noff * size;
    } else
      scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
  }
  ((Scheme_Offset_Cptr*)(argv[0]))->offset = noff;
  return scheme_void;
}

/* (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;

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

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

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

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

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

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

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

  return scheme_void;
}

@cdefine[vector->cpointer 1]{
  if (!SCHEME_VECTORP(argv[0]))
    scheme_wrong_type(MYNAME, "vector", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (intptr_t)SCHEME_VEC_ELS((Scheme_Object *)0x0), NULL);
}

@cdefine[flvector->cpointer 1]{
  if (!SCHEME_FLVECTORP(argv[0]))
    scheme_wrong_type(MYNAME, "flvector", 0, argc, argv);
  return scheme_make_offset_cptr(argv[0], (intptr_t)SCHEME_FLVEC_ELS((Scheme_Object *)0x0), NULL);
}

@cdefine[memset  3 5]{return do_memop(MYNAME, 0, argc, argv);}
@cdefine[memmove 3 6]{return do_memop(MYNAME, 1, argc, argv);}
@cdefine[memcpy  3 6]{return do_memop(MYNAME, 2, argc, argv);}

@defsymbols[abs]

/* (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. */
@cdefine[ptr-ref 2 4]{
  int size=0; void *ptr; Scheme_Object *base;
  intptr_t delta; int gcsrc=1;

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

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

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

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

/* (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. */
@cdefine[ptr-set! 3 5]{
  int size=0; void *ptr;
  intptr_t delta;
  Scheme_Object *val = argv[argc-1], *base;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  ptr = SCHEME_FFIANYPTR_VAL(argv[0]);
  delta = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((ptr == NULL) && (delta == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  if (NULL == (base = get_ctype_base(argv[1])))
    scheme_wrong_type(MYNAME, "C-type", 1, argc, argv);
  size = ctype_sizeof(base);

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

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

/* (ptr-equal? cpointer cpointer) -> boolean */
@cdefine[ptr-equal? 2 2]{
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (!SCHEME_FFIANYPTRP(argv[1]))
    scheme_wrong_type(MYNAME, "cpointer", 1, argc, argv);
  return (SAME_OBJ(argv[0],argv[1]) ||
          (SCHEME_FFIANYPTR_OFFSETVAL(argv[0])
           == SCHEME_FFIANYPTR_OFFSETVAL(argv[1])))
         ? scheme_true : scheme_false;
}

/* (make-sized-byte-string cpointer len) */
@cdefine[make-sized-byte-string 2 2]{
  /* 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;
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "cpointer", 0, argc, argv);
  if (!scheme_get_int_val(argv[1],&len))
    scheme_wrong_type(MYNAME, "integer in a C intptr_t range", 1, argc, argv);
  if (SCHEME_FALSEP(argv[0])) return scheme_false;
  else return
         scheme_make_sized_byte_string(SCHEME_FFIANYPTR_OFFSETVAL(argv[0]),
                                       len, 0);
}

/* *** 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;
}

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

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

#define MAX_QUICK_ARGS 16

typedef void(*VoidFun)();

#ifdef MZ_USE_PLACES

typedef struct FFI_Orig_Place_Call {
  ffi_cif *cif;
  VoidFun proc;
  void *p;
  void **avalues;
  mzrt_sema *sema;
  struct FFI_Orig_Place_Call *next;
} FFI_Orig_Place_Call;

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

void ffi_call_in_orig_place(ffi_cif *cif, VoidFun proc, void *p, void **avalues)
  XFORM_SKIP_PROC
{
  if (scheme_current_place_id == 0) {
    ffi_call(cif, proc, p, avalues);
  } else {
    FFI_Orig_Place_Call *todo;

    todo = (FFI_Orig_Place_Call *)malloc(sizeof(FFI_Orig_Place_Call));
    todo->cif = cif;
    todo->proc = proc;
    todo->p = p;
    todo->avalues = avalues;
    mzrt_sema_create(&todo->sema, 0);

    mzrt_mutex_lock(orig_place_mutex);
    todo->next = orig_place_calls;
    orig_place_calls = todo;
    mzrt_mutex_unlock(orig_place_mutex);    

    scheme_signal_received_at(orig_place_signal_handle);

    mzrt_sema_wait(todo->sema);
    
    mzrt_sema_destroy(todo->sema);
    free(todo);
  }
}
#endif

Scheme_Object *ffi_do_call(void *data, int argc, Scheme_Object *argv[])
/* data := {name, c-function, itypes, otype, cif} */
{
  /* The name is not currently used */
  /* char *name = SCHEME_BYTE_STR_VAL(SCHEME_VEC_ELS(data)[0]); */
  void          *c_func = (void*)(SCHEME_VEC_ELS(data)[1]);
  Scheme_Object *itypes = SCHEME_VEC_ELS(data)[2];
  Scheme_Object *otype  = SCHEME_VEC_ELS(data)[3];
  Scheme_Object *base;
  ffi_cif       *cif    = (ffi_cif*)(SCHEME_VEC_ELS(data)[4]);
  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;
  /* 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.)
   */
  GC_CAN_IGNORE ForeignAny *ivals, oval;
  void **avalues, *p, *newp;
  GC_CAN_IGNORE ForeignAny stack_ivals[MAX_QUICK_ARGS];
  void *stack_avalues[MAX_QUICK_ARGS];
  intptr_t stack_offsets[MAX_QUICK_ARGS];
  int i;
  intptr_t basetype, offset, *offsets;
  if (nargs <= MAX_QUICK_ARGS) {
    ivals   = stack_ivals;
    avalues = stack_avalues;
    offsets = stack_offsets;
  } else {
    ivals   = malloc(nargs * sizeof(ForeignAny));
    avalues = scheme_malloc(nargs * sizeof(void*));
    offsets = scheme_malloc_atomic(nargs * sizeof(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(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;
  }
  /* We finished with all possible mallocs, clear up the avalues and offsets
   * mess */
  for (i=0; i<nargs; i++) {
    if ((avalues[i] == NULL) && !offsets[i]) /* if this was a non-pointer... */
      avalues[i] = &(ivals[i]); /* ... set the avalues pointer */
    else if ((ivals[i].x_fixnum != FOREIGN_struct)
             && (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 */
#ifdef MZ_USE_PLACES
  if (orig_place) {
    ffi_call_in_orig_place(cif, (VoidFun)W_OFFSET(c_func, cfoff), p, avalues);
  } else
#endif
    ffi_call(cif, (VoidFun)W_OFFSET(c_func, cfoff), p, avalues);
  if (save_errno != 0) save_errno_values(save_errno);
  if (ivals != stack_ivals) free(ivals);
  ivals = NULL; /* no need now to hold on to this */
  for (i=0; i<nargs; i++) { avalues[i] = NULL; } /* no need for these refs */
  avalues = NULL;
  switch (CTYPE_PRIMLABEL(base)) {
  case FOREIGN_struct:
  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(otype, p, 0, 1, 1);
}

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

static Scheme_Object *ffi_name_prefix = 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 */
@cdefine[ffi-call 3 6]{
  Scheme_Object *itypes = argv[1];
  Scheme_Object *otype  = argv[2];
  Scheme_Object *obj, *data, *p, *base;
  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
# define FFI_CALL_VEC_SIZE 7
#endif
  if (!SCHEME_FFIANYPTRP(argv[0]))
    scheme_wrong_type(MYNAME, "ffi-obj-or-cpointer", 0, argc, argv);
  obj = SCHEME_FFIANYPTR_VAL(argv[0]);
  ooff = SCHEME_FFIANYPTR_OFFSET(argv[0]);
  if ((obj == NULL) && (ooff == 0))
    scheme_wrong_type(MYNAME, "non-null-cpointer", 0, argc, argv);
  nargs = scheme_proper_list_length(itypes);
  if (nargs < 0)
    scheme_wrong_type(MYNAME, "proper list", 1, argc, argv);
  if (NULL == (base = get_ctype_base(otype)))
    scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
  rtype = CTYPE_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_type(MYNAME, "'posix, 'windows, or #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
  atypes = malloc(nargs * sizeof(ffi_type*));
  for (i=0, p=itypes; i<nargs; i++, p=SCHEME_CDR(p)) {
    if (NULL == (base = get_ctype_base(SCHEME_CAR(p))))
      scheme_wrong_type(MYNAME, "list-of-C-types", 1, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 1, argc, argv);
    atypes[i] = CTYPE_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);
  p = scheme_append_byte_string
        (ffi_name_prefix,
         scheme_make_byte_string_without_copying
           (SCHEME_FFIOBJP(argv[0]) ?
             ((ffi_obj_struct*)(argv[0]))->name : "proc"));
  SCHEME_VEC_ELS(data)[0] = p;
  SCHEME_VEC_ELS(data)[1] = obj;
  SCHEME_VEC_ELS(data)[2] = itypes;
  SCHEME_VEC_ELS(data)[3] = otype;
  SCHEME_VEC_ELS(data)[4] = (Scheme_Object*)cif;
  SCHEME_VEC_ELS(data)[5] = scheme_make_integer(ooff);
  SCHEME_VEC_ELS(data)[6] = scheme_make_integer(save_errno);
#ifdef MZ_USE_PLACES
  SCHEME_VEC_ELS(data)[7] = (orig_place ? scheme_true : scheme_false);
#endif
  scheme_register_finalizer(data, free_fficall_data, cif, NULL, NULL);
  return scheme_make_closed_prim_w_arity
           (ffi_do_call, (void*)data, SCHEME_BYTE_STR_VAL(p),
            nargs, nargs);
}

/*****************************************************************************/
/* 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(t, *(void **)(args[i]), 0, 0, 0);
    } else
      v = C2SCHEME(t, args[i], 0, 0, 0);
    argv[i] = v;
  }
  p = _scheme_apply(data->proc, argc, argv);
  SCHEME2C(data->otype, resultp, 0, p, NULL, NULL, 1);
  if (data->sync && !SCHEME_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;
}

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

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

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

        data = extract_ffi_callback(qc->userdata);

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

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

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

    } while (qc);
  }

#ifdef MZ_USE_PLACES
  if ((scheme_current_place_id == 0) && orig_place_mutex) {
    FFI_Orig_Place_Call *todo, *next;

    mzrt_mutex_lock(orig_place_mutex);
    todo = orig_place_calls;
    orig_place_calls = NULL;
    mzrt_mutex_unlock(orig_place_mutex);

    while (todo) {
      ffi_call(todo->cif, todo->proc, todo->p, todo->avalues);      
      next = todo->next;
      mzrt_sema_post(todo->sema);
      todo = next;
    }
  }
#endif
}

#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 */
@cdefine[ffi-callback 3 6]{
  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

  if (!SCHEME_PROCP(argv[0]))
    scheme_wrong_type(MYNAME, "procedure", 0, argc, argv);
  nargs = scheme_proper_list_length(itypes);
  if (nargs < 0)
    scheme_wrong_type(MYNAME, "proper list", 1, argc, argv);
  if (NULL == (base = get_ctype_base(otype)))
    scheme_wrong_type(MYNAME, "C-type", 2, argc, argv);
  rtype = CTYPE_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
    do_callback = ffi_queue_callback;
  } else
    do_callback = ffi_do_callback;
  /* malloc space for everything needed, so a single free gets rid of this */
  cl_cif_args = scheme_malloc_code(sizeof(closure_and_cif) + nargs*sizeof(ffi_cif*));
  cl = &(cl_cif_args->closure); /* cl is the same as cl_cif_args */
  cif = &(cl_cif_args->cif);
  atypes = (ffi_type **)(((char*)cl_cif_args) + sizeof(closure_and_cif));
  for (i=0, p=itypes; i<nargs; i++, p=SCHEME_CDR(p)) {
    if (NULL == (base = get_ctype_base(SCHEME_CAR(p))))
      scheme_wrong_type(MYNAME, "list-of-C-types", 1, argc, argv);
    if (CTYPE_PRIMLABEL(base) == FOREIGN_void)
      scheme_wrong_type(MYNAME, "list-of-non-void-C-types", 1, argc, argv);
    atypes[i] = CTYPE_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");
  @cmake["data" ffi-callback
         "cl_cif_args" "argv[0]" "argv[1]" "argv[2]"
         "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;
  }
  }{
  callback_data = (void*)data;
  }
#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
  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
    scheme_register_finalizer(data, free_cl_cif_args, cl_cif_args, NULL, NULL);
  return (Scheme_Object*)data;
}

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

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();
    }
    p->saved_errno = v;
    return;
  }

  p->saved_errno = errno;
}

@cdefine[saved-errno 0]{
  Scheme_Thread *p = scheme_current_thread;
  return scheme_make_integer_value(p->saved_errno);
}

@cdefine[lookup-errno 1]{
  Scheme_Object *v = argv[0];
  @(let* ([errnos '(EINTR EEXIST EAGAIN)]
          [syms (let loop ([errnos errnos])
                  (if (null? (cdr errnos))   
                      (format "or '~a" (car errnos))
                      (format "'~a, ~a" (car errnos) (loop (cdr errnos)))))])
    @list{
      if (SCHEME_SYMBOLP(v) && !SCHEME_SYM_WEIRDP(v)) {
        @(add-newlines
          (for/list ([e errnos])
            @string-append{
              if (!strcmp("@symbol->string[e]", SCHEME_SYM_VAL(v)))
                return scheme_make_integer(@symbol->string[e]);
            }))
      }
      scheme_wrong_type(MYNAME, "@syms",0, argc, argv);
      return NULL;
    })
}

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

/* (make-stubborn-will-executor) -> #<will-executor> */
@cdefine[make-stubborn-will-executor 0]{
  return scheme_make_stubborn_will_executor();
}

/* (make-late-weak-box val) -> #<weak-box> */
@cdefine[make-late-weak-box 1]{
  return scheme_make_late_weak_box(argv[0]);
}

/* (make-late-weak-hasheq) -> #<hash> */
@cdefine[make-late-weak-hasheq 0]{
  return (Scheme_Object *)scheme_make_bucket_table(20, SCHEME_hash_late_weak_ptr);
}

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

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

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

/* types need to be initialized before places can spawn
 * types become entries in the GC mark and fixup tables
 * this function should initialize read-only globals that can be 
 * shared without locking */
void scheme_init_foreign_globals()
{
  @(maplines (lambda (x)
               @list{@(cadr x)_tag = scheme_make_type("<@(car x)>")})
             (reverse (cstructs)))
  @@IFDEF{MZ_PRECISE_GC}{
    @(maplines (lambda (x)
                 @list{GC_register_traversers(@(cadr x)_tag, @(cadr x)_SIZE, @;
                         @(cadr x)_MARK, @(cadr x)_FIXUP, 1, 0)})
                 (reverse (cstructs)))
  }
  scheme_set_type_printer(ctype_tag, ctype_printer);
  @(maplines (lambda (sym)
               @list{MZ_REGISTER_STATIC(@(cadr sym));
                     @(cadr sym) = scheme_intern_symbol("@(car sym)")})
             (reverse (symbols)))

  MZ_REGISTER_STATIC(ffi_name_prefix);
  ffi_name_prefix = scheme_make_byte_string_without_copying("ffi:");
}

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);
  @(maplines
     (lambda (x)
       (define-values (sname cfun min max) (apply values x))
       @list{scheme_add_global("@sname",
               scheme_make_prim_w_arity(@cfun, "@sname", @min, @max), menv)})
      (reverse (cfunctions)))
  @(map-types
     ;; no need for these, at least for now:
     ;;   MZ_REGISTER_STATIC(@|cname|_sym);
     ;;   @|cname|_sym = scheme_intern_symbol("@stype");
     @list{s = scheme_intern_symbol("@stype");
           @cmake["t" ctype "s"
                  @list{(Scheme_Object*)(void*)(&ffi_type_@ftype)}
                  @list{(Scheme_Object*)FOREIGN_@cname}]
           scheme_add_global("_@stype", (Scheme_Object*)t, menv)})
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

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

#else /* DONT_USE_FOREIGN */

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

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

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

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

@(define (lookup name)
  (if (member (cadr name) '("compiler_sizeof"
                            "make_ctype" 
                            "make_stubborn_will_executor"))
      name
      'unimplemented))

void scheme_init_foreign(Scheme_Env *env)
{
  /* Create a dummy module. */
  Scheme_Env *menv;
  menv = scheme_primitive_module(scheme_intern_symbol("#%foreign"), env);
  @(maplines
     (lambda (x)
       (define-values (sname cfun min max) (apply values x))
       @list{scheme_add_global("@sname",
              scheme_make_prim_w_arity((Scheme_Prim *)@(lookup cfun), "@sname", @min, @max), menv)})
      (reverse (cfunctions)))
  @(map-types
     @list{scheme_add_global("_@stype", scheme_false, menv)})
  scheme_finish_primitive_module(menv);
  scheme_protect_primitive_provide(menv, NULL);
}

#endif
