Integrate patch from Neal Norwitz. He writes:

Thomas Heller · Thomas Heller · commit fe8f862cda0e · 2006-03-14T19:53:09.000Z
"""
The attached patch fixes all the ctypes tests so they pass on amd64.
It also fixes several warnings.  I'm not sure what else to do with the
patch.  Let me know how you want to handle these in the future.

I'm not sure the patch is 100% correct.  You will need to decide what
can be 64 bits and what can't.  I believe
sq_{item,slice,ass_item,ass_slice} all need to use Py_ssize_t.  The
types in ctypes.h may not require all the changes I made.  I don't
know how you want to support older version, so I unconditionally
changed the types to Py_ssize_t.
"""

The patch is also in the ctypes SVN repository now, after small
changes to add compatibility with older Python versions.
diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
@@ -335,7 +335,7 @@ static PyMethodDef CDataType_methods[] = {
 };
 
 static PyObject *
-CDataType_repeat(PyObject *self, int length)
+CDataType_repeat(PyObject *self, Py_ssize_t length)
 {
 	return CreateArrayType(self, length);
 }
@@ -695,7 +695,7 @@ static int
 CharArray_set_raw(CDataObject *self, PyObject *value)
 {
 	char *ptr;
-	int size;
+	Py_ssize_t size;
 	if (PyBuffer_Check(value)) {
 		size = value->ob_type->tp_as_buffer->bf_getreadbuffer(value, 0, (void *)&ptr);
 		if (size < 0)
@@ -1789,13 +1789,11 @@ unique_key(CDataObject *target, int index)
 {
 	char string[256]; /* XXX is that enough? */
 	char *cp = string;
-	int len;
 	*cp++ = index + '0';
 	while (target->b_base) {
 		*cp++ = target->b_index + '0';
 		target = target->b_base;
 	}
-	len = cp - string;
 	return PyString_FromStringAndSize(string, cp-string);
 }
 /* Keep a reference to 'keep' in the 'target', at index 'index' */
@@ -1806,7 +1804,7 @@ unique_key(CDataObject *target, int index)
  * key int the root object's _objects dict.
  */
 static int
-KeepRef(CDataObject *target, int index, PyObject *keep)
+KeepRef(CDataObject *target, Py_ssize_t index, PyObject *keep)
 {
 	int result;
 	CDataObject *ob;
@@ -1875,7 +1873,7 @@ static PyMemberDef CData_members[] = {
 	{ NULL },
 };
 
-static int CData_GetBuffer(CDataObject *self, int seg, void **pptr)
+static Py_ssize_t CData_GetBuffer(CDataObject *self, Py_ssize_t seg, void **pptr)
 {
 	if (seg != 0) {
 		/* Hm. Must this set an exception? */
@@ -1885,18 +1883,18 @@ static int CData_GetBuffer(CDataObject *self, int seg, void **pptr)
 	return self->b_size;
 }
 
-static int CData_GetSegcount(CDataObject *self, int *lenp)
+static Py_ssize_t CData_GetSegcount(CDataObject *self, Py_ssize_t *lenp)
 {
 	if (lenp)
 		*lenp = 1;
 	return 1;
 }
 
 static PyBufferProcs CData_as_buffer = {
-	(getreadbufferproc)CData_GetBuffer,
-	(getwritebufferproc)CData_GetBuffer,
-	(getsegcountproc)CData_GetSegcount,
-	(getcharbufferproc)NULL,
+	(readbufferproc)CData_GetBuffer,
+	(writebufferproc)CData_GetBuffer,
+	(segcountproc)CData_GetSegcount,
+	(charbufferproc)NULL,
 };
 
 /*
@@ -1985,7 +1983,7 @@ static void CData_MallocBuffer(CDataObject *obj, StgDictObject *dict)
 }
 
 PyObject *
-CData_FromBaseObj(PyObject *type, PyObject *base, int index, char *adr)
+CData_FromBaseObj(PyObject *type, PyObject *base, Py_ssize_t index, char *adr)
 {
 	CDataObject *cmem;
 	StgDictObject *dict;
@@ -2064,7 +2062,7 @@ int IsSimpleSubType(PyObject *obj)
 
 PyObject *
 CData_get(PyObject *type, GETFUNC getfunc, PyObject *src,
-	  int index, int size, char *adr)
+	  Py_ssize_t index, Py_ssize_t size, char *adr)
 {
 	StgDictObject *dict;
 	if (getfunc)
@@ -2081,7 +2079,7 @@ CData_get(PyObject *type, GETFUNC getfunc, PyObject *src,
 */
 static PyObject *
 _CData_set(CDataObject *dst, PyObject *type, SETFUNC setfunc, PyObject *value,
-	   int size, char *ptr)
+	   Py_ssize_t size, char *ptr)
 {
 	CDataObject *src;
 
@@ -2177,7 +2175,7 @@ _CData_set(CDataObject *dst, PyObject *type, SETFUNC setfunc, PyObject *value,
  */
 int
 CData_set(PyObject *dst, PyObject *type, SETFUNC setfunc, PyObject *value,
-	  int index, int size, char *ptr)
+	  Py_ssize_t index, Py_ssize_t size, char *ptr)
 {
 	CDataObject *mem = (CDataObject *)dst;
 	PyObject *result;
@@ -3318,7 +3316,7 @@ Struct_init(PyObject *self, PyObject *args, PyObject *kwds)
 
 	if (kwds) {
 		PyObject *key, *value;
-		int pos = 0;
+		Py_ssize_t pos = 0;
 		while(PyDict_Next(kwds, &pos, &key, &value)) {
 			if (-1 == PyObject_SetAttr(self, key, value))
 				return -1;
@@ -3471,12 +3469,12 @@ Array_item(CDataObject *self, int index)
 }
 
 static PyObject *
-Array_slice(CDataObject *self, int ilow, int ihigh)
+Array_slice(CDataObject *self, Py_ssize_t ilow, Py_ssize_t ihigh)
 {
 	StgDictObject *stgdict, *itemdict;
 	PyObject *proto;
 	PyListObject *np;
-	int i, len;
+	Py_ssize_t i, len;
 
 	if (ilow < 0)
 		ilow = 0;
@@ -3587,13 +3585,13 @@ Array_length(CDataObject *self)
 }
 
 static PySequenceMethods Array_as_sequence = {
-	(inquiry)Array_length,			/* sq_length; */
+	(lenfunc)Array_length,			/* sq_length; */
 	0,					/* sq_concat; */
 	0,					/* sq_repeat; */
-	(intargfunc)Array_item,			/* sq_item; */
-	(intintargfunc)Array_slice,		/* sq_slice; */
-	(intobjargproc)Array_ass_item,		/* sq_ass_item; */
-	(intintobjargproc)Array_ass_slice,	/* sq_ass_slice; */
+	(ssizeargfunc)Array_item,		/* sq_item; */
+	(ssizessizeargfunc)Array_slice,		/* sq_slice; */
+	(ssizeobjargproc)Array_ass_item,	/* sq_ass_item; */
+	(ssizessizeobjargproc)Array_ass_slice,	/* sq_ass_slice; */
 	0,					/* sq_contains; */
 	
 	0,					/* sq_inplace_concat; */
@@ -3664,7 +3662,7 @@ PyTypeObject Array_Type = {
 };
 
 PyObject *
-CreateArrayType(PyObject *itemtype, int length)
+CreateArrayType(PyObject *itemtype, Py_ssize_t length)
 {
 	static PyObject *cache;
 	PyObject *key;
@@ -3676,7 +3674,7 @@ CreateArrayType(PyObject *itemtype, int length)
 		if (cache == NULL)
 			return NULL;
 	}
-	key = Py_BuildValue("(Oi)", itemtype, length);
+	key = Py_BuildValue("(On)", itemtype, length);
 	if (!key)
 		return NULL;
 	result = PyDict_GetItem(cache, key);
@@ -3691,11 +3689,16 @@ CreateArrayType(PyObject *itemtype, int length)
 				"Expected a type object");
 		return NULL;
 	}
-	sprintf(name, "%.200s_Array_%d",
+#ifdef MS_WIN64
+	sprintf(name, "%.200s_Array_%Id",
 		((PyTypeObject *)itemtype)->tp_name, length);
+#else
+	sprintf(name, "%.200s_Array_%ld",
+		((PyTypeObject *)itemtype)->tp_name, (long)length);
+#endif
 
 	result = PyObject_CallFunction((PyObject *)&ArrayType_Type,
-				       "s(O){s:i,s:O}",
+				       "s(O){s:n,s:O}",
 				       name,
 				       &Array_Type,
 				       "_length_",
@@ -3869,7 +3872,7 @@ Simple_repr(CDataObject *self)
 
 	name = PyString_FromString(self->ob_type->tp_name);
 	if (name == NULL) {
-		Py_DECREF(name);
+		Py_DECREF(val);
 		return NULL;
 	}
 
@@ -4101,12 +4104,12 @@ Pointer_new(PyTypeObject *type, PyObject *args, PyObject *kw)
 }
 
 static PyObject *
-Pointer_slice(CDataObject *self, int ilow, int ihigh)
+Pointer_slice(CDataObject *self, Py_ssize_t ilow, Py_ssize_t ihigh)
 {
 	PyListObject *np;
 	StgDictObject *stgdict, *itemdict;
 	PyObject *proto;
-	int i, len;
+	Py_ssize_t i, len;
 
 	if (ilow < 0)
 		ilow = 0;
@@ -4142,9 +4145,9 @@ static PySequenceMethods Pointer_as_sequence = {
 	0,					/* inquiry sq_length; */
 	0,					/* binaryfunc sq_concat; */
 	0,					/* intargfunc sq_repeat; */
-	(intargfunc)Pointer_item,		/* intargfunc sq_item; */
-	(intintargfunc)Pointer_slice,		/* intintargfunc sq_slice; */
-	(intobjargproc)Pointer_ass_item,	/* intobjargproc sq_ass_item; */
+	(ssizeargfunc)Pointer_item,		/* intargfunc sq_item; */
+	(ssizessizeargfunc)Pointer_slice,	/* intintargfunc sq_slice; */
+	(ssizeobjargproc)Pointer_ass_item,	/* intobjargproc sq_ass_item; */
 	0,					/* intintobjargproc sq_ass_slice; */
 	0,					/* objobjproc sq_contains; */
 	/* Added in release 2.0 */
@@ -4318,7 +4321,7 @@ create_comerror(void)
 #endif
 
 static PyObject *
-string_at(const char *ptr, int size)
+string_at(const char *ptr, Py_ssize_t size)
 {
 	if (size == 0)
 		return PyString_FromString(ptr);
@@ -4336,7 +4339,7 @@ wstring_at(const wchar_t *ptr, int size)
 }
 #endif
 
-DL_EXPORT(void)
+PyMODINIT_FUNC
 init_ctypes(void)
 {
 	PyObject *m;
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
@@ -721,8 +721,9 @@ static PyObject *GetResult(PyObject *restype, void *result, PyObject *checker)
 		   O_get), we have to call Py_DECREF because O_get has already
 		   called Py_INCREF.
 		*/
-		if (dict->getfunc == getentry("O")->getfunc)
+		if (dict->getfunc == getentry("O")->getfunc) {
 			Py_DECREF(retval);
+		}
 	} else
 		retval = CData_FromBaseObj(restype, NULL, 0, result);
 
diff --git a/Modules/_ctypes/ctypes.h b/Modules/_ctypes/ctypes.h
@@ -50,9 +50,9 @@ struct tagCDataObject {
 	char *b_ptr;		/* pointer to memory block */
 	int  b_needsfree;	/* need _we_ free the memory? */
 	CDataObject *b_base;	/* pointer to base object or NULL */
-	int b_size;		/* size of memory block in bytes */
-	int b_length;		/* number of references we need */
-	int b_index;		/* index of this object into base's
+	Py_ssize_t b_size;	/* size of memory block in bytes */
+	Py_ssize_t b_length;	/* number of references we need */
+	Py_ssize_t b_index;	/* index of this object into base's
 				   b_object list */
 	PyObject *b_objects;	/* list of references we need to keep */
 	union value b_value;
@@ -64,9 +64,9 @@ typedef struct {
 	char *b_ptr;		/* pointer to memory block */
 	int  b_needsfree;	/* need _we_ free the memory? */
 	CDataObject *b_base;	/* pointer to base object or NULL */
-	int b_size;		/* size of memory block in bytes */
-	int b_length;		/* number of references we need */
-	int b_index;		/* index of this object into base's
+	Py_ssize_t b_size;	/* size of memory block in bytes */
+	Py_ssize_t b_length;	/* number of references we need */
+	Py_ssize_t b_index;	/* index of this object into base's
 				   b_object list */
 	PyObject *b_objects;	/* list of references we need to keep */
 	union value b_value;
@@ -94,8 +94,8 @@ extern PyTypeObject StgDict_Type;
 #define StgDict_Check(v)	    PyObject_TypeCheck(v, &StgDict_Type)
 
 extern int StructUnionType_update_stgdict(PyObject *fields, PyObject *type, int isStruct);
-extern int PyType_stginfo(PyTypeObject *self, int *psize, int *palign, int *plength);
-extern int PyObject_stginfo(PyObject *self, int *psize, int *palign, int *plength);
+extern int PyType_stginfo(PyTypeObject *self, Py_ssize_t *psize, Py_ssize_t *palign, Py_ssize_t *plength);
+extern int PyObject_stginfo(PyObject *self, Py_ssize_t *psize, Py_ssize_t *palign, Py_ssize_t *plength);
 
 
 
@@ -118,7 +118,7 @@ CField_FromDesc(PyObject *desc, int index,
 		int pack, int is_big_endian);
 
 extern PyObject *CData_AtAddress(PyObject *type, void *buf);
-extern PyObject *CData_FromBytes(PyObject *type, char *data, int length);
+extern PyObject *CData_FromBytes(PyObject *type, char *data, Py_ssize_t length);
 
 extern PyTypeObject ArrayType_Type;
 extern PyTypeObject Array_Type;
@@ -137,7 +137,7 @@ extern PyTypeObject StructType_Type;
 #define StructTypeObject_Check(v)	PyObject_TypeCheck(v, &StructType_Type)
 
 extern PyObject *
-CreateArrayType(PyObject *itemtype, int length);
+CreateArrayType(PyObject *itemtype, Py_ssize_t length);
 
 extern void init_callbacks_in_module(PyObject *m);
 
@@ -164,9 +164,9 @@ struct fielddesc {
 
 typedef struct {
 	PyObject_HEAD
-	int offset;
-	int size;
-	int index;			/* Index into CDataObject's
+	Py_ssize_t offset;
+	Py_ssize_t size;
+	Py_ssize_t index;		/* Index into CDataObject's
 					   object array */
 	PyObject *proto;		/* a type or NULL */
 	GETFUNC getfunc;		/* getter function if proto is NULL */
@@ -185,9 +185,9 @@ typedef struct {
    too much risk to change that now, and there are other fields which doen't
    belong into this structure anyway.  Maybe in ctypes 2.0... (ctypes 2000?)
 */
-	int size;		/* number of bytes */
-	int align;		/* alignment requirements */
-	int length;		/* number of fields */
+	Py_ssize_t size;	/* number of bytes */
+	Py_ssize_t align;	/* alignment requirements */
+	Py_ssize_t length;	/* number of fields */
 	ffi_type ffi_type;
 	PyObject *proto;	/* Only for Pointer/ArrayObject */
 	SETFUNC setfunc;	/* Only for simple objects */
@@ -298,17 +298,17 @@ extern PyCArgObject *new_CArgObject(void);
 
 extern PyObject *
 CData_get(PyObject *type, GETFUNC getfunc, PyObject *src,
-	  int index, int size, char *ptr);
+	  Py_ssize_t index, Py_ssize_t size, char *ptr);
 
 extern int
 CData_set(PyObject *dst, PyObject *type, SETFUNC setfunc, PyObject *value,
-	  int index, int size, char *ptr);
+	  Py_ssize_t index, Py_ssize_t size, char *ptr);
 
 extern void Extend_Error_Info(PyObject *exc_class, char *fmt, ...);
 
 struct basespec {
 	CDataObject *base;
-	int index;
+	Py_ssize_t index;
 	char *adr;
 };
 
@@ -374,7 +374,7 @@ extern void *MallocClosure(void);
 
 extern void _AddTraceback(char *, char *, int);
 
-extern PyObject *CData_FromBaseObj(PyObject *type, PyObject *base, int index, char *adr);
+extern PyObject *CData_FromBaseObj(PyObject *type, PyObject *base, Py_ssize_t index, char *adr);
 
 /* XXX better name needed! */
 extern int IsSimpleSubType(PyObject *obj);
