exceptions.c

/*
 * New exceptions.c written in Iceland by Richard Jones and Georg Brandl.
 *
 * Thanks go to Tim Peters and Michael Hudson for debugging.
 */

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "structmember.h"
#include "osdefs.h"


/* NOTE: If the exception class hierarchy changes, don't forget to update
 * Lib/test/exception_hierarchy.txt
 */

/*
 *    BaseException
 */
static PyObject *
BaseException_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    PyBaseExceptionObject *self;

    self = (PyBaseExceptionObject *)type->tp_alloc(type, 0);
    if (!self)
        return NULL;
    /* the dict is created on the fly in PyObject_GenericSetAttr */
    self->dict = NULL;
    self->traceback = self->cause = self->context = NULL;

    if (args) {
        self->args = args;
        Py_INCREF(args);
        return (PyObject *)self;
    }

    self->args = PyTuple_New(0);
    if (!self->args) {
        Py_DECREF(self);
        return NULL;
    }

    return (PyObject *)self;
}

static int
BaseException_init(PyBaseExceptionObject *self, PyObject *args, PyObject *kwds)
{
    PyObject *tmp;

    if (!_PyArg_NoKeywords(Py_TYPE(self)->tp_name, kwds))
        return -1;

    tmp = self->args;
    self->args = args;
    Py_INCREF(self->args);
    Py_XDECREF(tmp);

    return 0;
}

static int
BaseException_clear(PyBaseExceptionObject *self)
{
    Py_CLEAR(self->dict);
    Py_CLEAR(self->args);
    Py_CLEAR(self->traceback);
    Py_CLEAR(self->cause);
    Py_CLEAR(self->context);
    return 0;
}

static void
BaseException_dealloc(PyBaseExceptionObject *self)
{
    _PyObject_GC_UNTRACK(self);
    BaseException_clear(self);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static int
BaseException_traverse(PyBaseExceptionObject *self, visitproc visit, void *arg)
{
    Py_VISIT(self->dict);
    Py_VISIT(self->args);
    Py_VISIT(self->traceback);
    Py_VISIT(self->cause);
    Py_VISIT(self->context);
    return 0;
}

static PyObject *
BaseException_str(PyBaseExceptionObject *self)
{
    switch (PyTuple_GET_SIZE(self->args)) {
    case 0:
        return PyUnicode_FromString("");
    case 1:
        return PyObject_Str(PyTuple_GET_ITEM(self->args, 0));
    default:
        return PyObject_Str(self->args);
    }
}

static PyObject *
BaseException_repr(PyBaseExceptionObject *self)
{
    char *name;
    char *dot;

    name = (char *)Py_TYPE(self)->tp_name;
    dot = strrchr(name, '.');
    if (dot != NULL) name = dot+1;

    return PyUnicode_FromFormat("%s%R", name, self->args);
}

/* Pickling support */
static PyObject *
BaseException_reduce(PyBaseExceptionObject *self)
{
    if (self->args && self->dict)
        return PyTuple_Pack(3, Py_TYPE(self), self->args, self->dict);
    else
        return PyTuple_Pack(2, Py_TYPE(self), self->args);
}

/*
 * Needed for backward compatibility, since exceptions used to store
 * all their attributes in the __dict__. Code is taken from cPickle's
 * load_build function.
 */
static PyObject *
BaseException_setstate(PyObject *self, PyObject *state)
{
    PyObject *d_key, *d_value;
    Py_ssize_t i = 0;

    if (state != Py_None) {
        if (!PyDict_Check(state)) {
            PyErr_SetString(PyExc_TypeError, "state is not a dictionary");
            return NULL;
        }
        while (PyDict_Next(state, &i, &d_key, &d_value)) {
            if (PyObject_SetAttr(self, d_key, d_value) < 0)
                return NULL;
        }
    }
    Py_RETURN_NONE;
}

static PyObject *
BaseException_with_traceback(PyObject *self, PyObject *tb) {
    if (PyException_SetTraceback(self, tb))
        return NULL;

    Py_INCREF(self);
    return self;
}

PyDoc_STRVAR(with_traceback_doc,
"Exception.with_traceback(tb) --\n\
    set self.__traceback__ to tb and return self.");


static PyMethodDef BaseException_methods[] = {
   {"__reduce__", (PyCFunction)BaseException_reduce, METH_NOARGS },
   {"__setstate__", (PyCFunction)BaseException_setstate, METH_O },
   {"with_traceback", (PyCFunction)BaseException_with_traceback, METH_O,
    with_traceback_doc},
   {NULL, NULL, 0, NULL},
};


static PyObject *
BaseException_get_dict(PyBaseExceptionObject *self)
{
    if (self->dict == NULL) {
        self->dict = PyDict_New();
        if (!self->dict)
            return NULL;
    }
    Py_INCREF(self->dict);
    return self->dict;
}

static int
BaseException_set_dict(PyBaseExceptionObject *self, PyObject *val)
{
    if (val == NULL) {
        PyErr_SetString(PyExc_TypeError, "__dict__ may not be deleted");
        return -1;
    }
    if (!PyDict_Check(val)) {
        PyErr_SetString(PyExc_TypeError, "__dict__ must be a dictionary");
        return -1;
    }
    Py_CLEAR(self->dict);
    Py_INCREF(val);
    self->dict = val;
    return 0;
}

static PyObject *
BaseException_get_args(PyBaseExceptionObject *self)
{
    if (self->args == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    Py_INCREF(self->args);
    return self->args;
}

static int
BaseException_set_args(PyBaseExceptionObject *self, PyObject *val)
{
    PyObject *seq;
    if (val == NULL) {
        PyErr_SetString(PyExc_TypeError, "args may not be deleted");
        return -1;
    }
    seq = PySequence_Tuple(val);
    if (!seq)
        return -1;
    Py_CLEAR(self->args);
    self->args = seq;
    return 0;
}

static PyObject *
BaseException_get_tb(PyBaseExceptionObject *self)
{
    if (self->traceback == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    Py_INCREF(self->traceback);
    return self->traceback;
}

static int
BaseException_set_tb(PyBaseExceptionObject *self, PyObject *tb)
{
    if (tb == NULL) {
        PyErr_SetString(PyExc_TypeError, "__traceback__ may not be deleted");
        return -1;
    }
    else if (!(tb == Py_None || PyTraceBack_Check(tb))) {
        PyErr_SetString(PyExc_TypeError,
                        "__traceback__ must be a traceback or None");
        return -1;
    }

    Py_XINCREF(tb);
    Py_XDECREF(self->traceback);
    self->traceback = tb;
    return 0;
}

static PyObject *
BaseException_get_context(PyObject *self) {
    PyObject *res = PyException_GetContext(self);
    if (res)
        return res;  /* new reference already returned above */
    Py_RETURN_NONE;
}

static int
BaseException_set_context(PyObject *self, PyObject *arg) {
    if (arg == NULL) {
        PyErr_SetString(PyExc_TypeError, "__context__ may not be deleted");
        return -1;
    } else if (arg == Py_None) {
        arg = NULL;
    } else if (!PyExceptionInstance_Check(arg)) {
        PyErr_SetString(PyExc_TypeError, "exception context must be None "
                        "or derive from BaseException");
        return -1;
    } else {
        /* PyException_SetContext steals this reference */
        Py_INCREF(arg);
    }
    PyException_SetContext(self, arg);
    return 0;
}

static PyObject *
BaseException_get_cause(PyObject *self) {
    PyObject *res = PyException_GetCause(self);
    if (res)
        return res;  /* new reference already returned above */
    Py_RETURN_NONE;
}

static int
BaseException_set_cause(PyObject *self, PyObject *arg) {
    if (arg == NULL) {
        PyErr_SetString(PyExc_TypeError, "__cause__ may not be deleted");
        return -1;
    } else if (arg == Py_None) {
        arg = NULL;
    } else if (!PyExceptionInstance_Check(arg)) {
        PyErr_SetString(PyExc_TypeError, "exception cause must be None "
                        "or derive from BaseException");
        return -1;
    } else {
        /* PyException_SetCause steals this reference */
        Py_INCREF(arg);
    }
    PyException_SetCause(self, arg);
    return 0;
}


static PyGetSetDef BaseException_getset[] = {
    {"__dict__", (getter)BaseException_get_dict, (setter)BaseException_set_dict},
    {"args", (getter)BaseException_get_args, (setter)BaseException_set_args},
    {"__traceback__", (getter)BaseException_get_tb, (setter)BaseException_set_tb},
    {"__context__", (getter)BaseException_get_context,
     (setter)BaseException_set_context, PyDoc_STR("exception context")},
    {"__cause__", (getter)BaseException_get_cause,
     (setter)BaseException_set_cause, PyDoc_STR("exception cause")},
    {NULL},
};


PyObject *
PyException_GetTraceback(PyObject *self) {
    PyBaseExceptionObject *base_self = (PyBaseExceptionObject *)self;
    Py_XINCREF(base_self->traceback);
    return base_self->traceback;
}


int
PyException_SetTraceback(PyObject *self, PyObject *tb) {
    return BaseException_set_tb((PyBaseExceptionObject *)self, tb);
}

PyObject *
PyException_GetCause(PyObject *self) {
    PyObject *cause = ((PyBaseExceptionObject *)self)->cause;
    Py_XINCREF(cause);
    return cause;
}

/* Steals a reference to cause */
void
PyException_SetCause(PyObject *self, PyObject *cause) {
    PyObject *old_cause = ((PyBaseExceptionObject *)self)->cause;
    ((PyBaseExceptionObject *)self)->cause = cause;
    Py_XDECREF(old_cause);
}

PyObject *
PyException_GetContext(PyObject *self) {
    PyObject *context = ((PyBaseExceptionObject *)self)->context;
    Py_XINCREF(context);
    return context;
}

/* Steals a reference to context */
void
PyException_SetContext(PyObject *self, PyObject *context) {
    PyObject *old_context = ((PyBaseExceptionObject *)self)->context;
    ((PyBaseExceptionObject *)self)->context = context;
    Py_XDECREF(old_context);
}


static PyTypeObject _PyExc_BaseException = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "BaseException", /*tp_name*/
    sizeof(PyBaseExceptionObject), /*tp_basicsize*/
    0,                          /*tp_itemsize*/
    (destructor)BaseException_dealloc, /*tp_dealloc*/
    0,                          /*tp_print*/
    0,                          /*tp_getattr*/
    0,                          /*tp_setattr*/
    0,                          /* tp_reserved; */
    (reprfunc)BaseException_repr, /*tp_repr*/
    0,                          /*tp_as_number*/
    0,                          /*tp_as_sequence*/
    0,                          /*tp_as_mapping*/
    0,                          /*tp_hash */
    0,                          /*tp_call*/
    (reprfunc)BaseException_str,  /*tp_str*/
    PyObject_GenericGetAttr,    /*tp_getattro*/
    PyObject_GenericSetAttr,    /*tp_setattro*/
    0,                          /*tp_as_buffer*/
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
        Py_TPFLAGS_BASE_EXC_SUBCLASS,  /*tp_flags*/
    PyDoc_STR("Common base class for all exceptions"), /* tp_doc */
    (traverseproc)BaseException_traverse, /* tp_traverse */
    (inquiry)BaseException_clear, /* tp_clear */
    0,                          /* tp_richcompare */
    0,                          /* tp_weaklistoffset */
    0,                          /* tp_iter */
    0,                          /* tp_iternext */
    BaseException_methods,      /* tp_methods */
    0,                          /* tp_members */
    BaseException_getset,       /* tp_getset */
    0,                          /* tp_base */
    0,                          /* tp_dict */
    0,                          /* tp_descr_get */
    0,                          /* tp_descr_set */
    offsetof(PyBaseExceptionObject, dict), /* tp_dictoffset */
    (initproc)BaseException_init, /* tp_init */
    0,                          /* tp_alloc */
    BaseException_new,          /* tp_new */
};
/* the CPython API expects exceptions to be (PyObject *) - both a hold-over
from the previous implmentation and also allowing Python objects to be used
in the API */
PyObject *PyExc_BaseException = (PyObject *)&_PyExc_BaseException;

/* note these macros omit the last semicolon so the macro invocation may
 * include it and not look strange.
 */
#define SimpleExtendsException(EXCBASE, EXCNAME, EXCDOC) \
static PyTypeObject _PyExc_ ## EXCNAME = { \
    PyVarObject_HEAD_INIT(NULL, 0) \
    # EXCNAME, \
    sizeof(PyBaseExceptionObject), \
    0, (destructor)BaseException_dealloc, 0, 0, 0, 0, 0, 0, 0, \
    0, 0, 0, 0, 0, 0, 0, \
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC, \
    PyDoc_STR(EXCDOC), (traverseproc)BaseException_traverse, \
    (inquiry)BaseException_clear, 0, 0, 0, 0, 0, 0, 0, &_ ## EXCBASE, \
    0, 0, 0, offsetof(PyBaseExceptionObject, dict), \
    (initproc)BaseException_init, 0, BaseException_new,\
}; \
PyObject *PyExc_ ## EXCNAME = (PyObject *)&_PyExc_ ## EXCNAME

#define MiddlingExtendsException(EXCBASE, EXCNAME, EXCSTORE, EXCDOC) \
static PyTypeObject _PyExc_ ## EXCNAME = { \
    PyVarObject_HEAD_INIT(NULL, 0) \
    # EXCNAME, \
    sizeof(Py ## EXCSTORE ## Object), \
    0, (destructor)EXCSTORE ## _dealloc, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
    0, 0, 0, 0, 0, \
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC, \
    PyDoc_STR(EXCDOC), (traverseproc)EXCSTORE ## _traverse, \
    (inquiry)EXCSTORE ## _clear, 0, 0, 0, 0, 0, 0, 0, &_ ## EXCBASE, \
    0, 0, 0, offsetof(Py ## EXCSTORE ## Object, dict), \
    (initproc)EXCSTORE ## _init, 0, BaseException_new,\
}; \
PyObject *PyExc_ ## EXCNAME = (PyObject *)&_PyExc_ ## EXCNAME

#define ComplexExtendsException(EXCBASE, EXCNAME, EXCSTORE, EXCDEALLOC, EXCMETHODS, EXCMEMBERS, EXCSTR, EXCDOC) \
static PyTypeObject _PyExc_ ## EXCNAME = { \
    PyVarObject_HEAD_INIT(NULL, 0) \
    # EXCNAME, \
    sizeof(Py ## EXCSTORE ## Object), 0, \
    (destructor)EXCSTORE ## _dealloc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
    (reprfunc)EXCSTR, 0, 0, 0, \
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC, \
    PyDoc_STR(EXCDOC), (traverseproc)EXCSTORE ## _traverse, \
    (inquiry)EXCSTORE ## _clear, 0, 0, 0, 0, EXCMETHODS, \
    EXCMEMBERS, 0, &_ ## EXCBASE, \
    0, 0, 0, offsetof(Py ## EXCSTORE ## Object, dict), \
    (initproc)EXCSTORE ## _init, 0, BaseException_new,\
}; \
PyObject *PyExc_ ## EXCNAME = (PyObject *)&_PyExc_ ## EXCNAME


/*
 *    Exception extends BaseException
 */
SimpleExtendsException(PyExc_BaseException, Exception,
                       "Common base class for all non-exit exceptions.");


/*
 *    TypeError extends Exception
 */
SimpleExtendsException(PyExc_Exception, TypeError,
                       "Inappropriate argument type.");


/*
 *    StopIteration extends Exception
 */
SimpleExtendsException(PyExc_Exception, StopIteration,
                       "Signal the end from iterator.__next__().");


/*
 *    GeneratorExit extends BaseException
 */
SimpleExtendsException(PyExc_BaseException, GeneratorExit,
                       "Request that a generator exit.");


/*
 *    SystemExit extends BaseException
 */

static int
SystemExit_init(PySystemExitObject *self, PyObject *args, PyObject *kwds)
{
    Py_ssize_t size = PyTuple_GET_SIZE(args);

    if (BaseException_init((PyBaseExceptionObject *)self, args, kwds) == -1)
        return -1;

    if (size == 0)
        return 0;
    Py_CLEAR(self->code);
    if (size == 1)
        self->code = PyTuple_GET_ITEM(args, 0);
    else if (size > 1)
        self->code = args;
    Py_INCREF(self->code);
    return 0;
}

static int
SystemExit_clear(PySystemExitObject *self)
{
    Py_CLEAR(self->code);
    return BaseException_clear((PyBaseExceptionObject *)self);
}

static void
SystemExit_dealloc(PySystemExitObject *self)
{
    _PyObject_GC_UNTRACK(self);
    SystemExit_clear(self);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static int
SystemExit_traverse(PySystemExitObject *self, visitproc visit, void *arg)
{
    Py_VISIT(self->code);
    return BaseException_traverse((PyBaseExceptionObject *)self, visit, arg);
}

static PyMemberDef SystemExit_members[] = {
    {"code", T_OBJECT, offsetof(PySystemExitObject, code), 0,
        PyDoc_STR("exception code")},
    {NULL}  /* Sentinel */
};

ComplexExtendsException(PyExc_BaseException, SystemExit, SystemExit,
                        SystemExit_dealloc, 0, SystemExit_members, 0,
                        "Request to exit from the interpreter.");

/*
 *    KeyboardInterrupt extends BaseException
 */
SimpleExtendsException(PyExc_BaseException, KeyboardInterrupt,
                       "Program interrupted by user.");


/*
 *    ImportError extends Exception
 */
SimpleExtendsException(PyExc_Exception, ImportError,
          "Import can't find module, or can't find name in module.");


/*
 *    EnvironmentError extends Exception
 */

/* Where a function has a single filename, such as open() or some
 * of the os module functions, PyErr_SetFromErrnoWithFilename() is
 * called, giving a third argument which is the filename.  But, so
 * that old code using in-place unpacking doesn't break, e.g.:
 *
 * except IOError, (errno, strerror):
 *
 * we hack args so that it only contains two items.  This also
 * means we need our own __str__() which prints out the filename
 * when it was supplied.
 */
static int
EnvironmentError_init(PyEnvironmentErrorObject *self, PyObject *args,
    PyObject *kwds)
{
    PyObject *myerrno = NULL, *strerror = NULL, *filename = NULL;
    PyObject *subslice = NULL;

    if (BaseException_init((PyBaseExceptionObject *)self, args, kwds) == -1)
        return -1;

    if (PyTuple_GET_SIZE(args) <= 1 || PyTuple_GET_SIZE(args) > 3) {
        return 0;
    }

    if (!PyArg_UnpackTuple(args, "EnvironmentError", 2, 3,
                           &myerrno, &strerror, &filename)) {
        return -1;
    }
    Py_CLEAR(self->myerrno);       /* replacing */
    self->myerrno = myerrno;
    Py_INCREF(self->myerrno);

    Py_CLEAR(self->strerror);      /* replacing */
    self->strerror = strerror;
    Py_INCREF(self->strerror);

    /* self->filename will remain Py_None otherwise */
    if (filename != NULL) {
        Py_CLEAR(self->filename);      /* replacing */
        self->filename = filename;
        Py_INCREF(self->filename);

        subslice = PyTuple_GetSlice(args, 0, 2);
        if (!subslice)
            return -1;

        Py_DECREF(self->args);  /* replacing args */
        self->args = subslice;
    }
    return 0;
}

static int
EnvironmentError_clear(PyEnvironmentErrorObject *self)
{
    Py_CLEAR(self->myerrno);
    Py_CLEAR(self->strerror);
    Py_CLEAR(self->filename);
    return BaseException_clear((PyBaseExceptionObject *)self);
}

static void
EnvironmentError_dealloc(PyEnvironmentErrorObject *self)
{
    _PyObject_GC_UNTRACK(self);
    EnvironmentError_clear(self);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static int
EnvironmentError_traverse(PyEnvironmentErrorObject *self, visitproc visit,
        void *arg)
{
    Py_VISIT(self->myerrno);
    Py_VISIT(self->strerror);
    Py_VISIT(self->filename);
    return BaseException_traverse((PyBaseExceptionObject *)self, visit, arg);
}

static PyObject *
EnvironmentError_str(PyEnvironmentErrorObject *self)
{
    if (self->filename)
        return PyUnicode_FromFormat("[Errno %S] %S: %R",
                                    self->myerrno ? self->myerrno: Py_None,
                                    self->strerror ? self->strerror: Py_None,
                                    self->filename);
    else if (self->myerrno && self->strerror)
        return PyUnicode_FromFormat("[Errno %S] %S",
                                    self->myerrno ? self->myerrno: Py_None,
                                    self->strerror ? self->strerror: Py_None);
    else
        return BaseException_str((PyBaseExceptionObject *)self);
}

static PyMemberDef EnvironmentError_members[] = {
    {"errno", T_OBJECT, offsetof(PyEnvironmentErrorObject, myerrno), 0,
        PyDoc_STR("exception errno")},
    {"strerror", T_OBJECT, offsetof(PyEnvironmentErrorObject, strerror), 0,
        PyDoc_STR("exception strerror")},
    {"filename", T_OBJECT, offsetof(PyEnvironmentErrorObject, filename), 0,
        PyDoc_STR("exception filename")},
    {NULL}  /* Sentinel */
};


static PyObject *
EnvironmentError_reduce(PyEnvironmentErrorObject *self)
{
    PyObject *args = self->args;
    PyObject *res = NULL, *tmp;

    /* self->args is only the first two real arguments if there was a
     * file name given to EnvironmentError. */
    if (PyTuple_GET_SIZE(args) == 2 && self->filename) {
        args = PyTuple_New(3);
        if (!args)
            return NULL;

        tmp = PyTuple_GET_ITEM(self->args, 0);
        Py_INCREF(tmp);
        PyTuple_SET_ITEM(args, 0, tmp);

        tmp = PyTuple_GET_ITEM(self->args, 1);
        Py_INCREF(tmp);
        PyTuple_SET_ITEM(args, 1, tmp);

        Py_INCREF(self->filename);
        PyTuple_SET_ITEM(args, 2, self->filename);
    } else
        Py_INCREF(args);

    if (self->dict)
        res = PyTuple_Pack(3, Py_TYPE(self), args, self->dict);
    else
        res = PyTuple_Pack(2, Py_TYPE(self), args);
    Py_DECREF(args);
    return res;
}


static PyMethodDef EnvironmentError_methods[] = {
    {"__reduce__", (PyCFunction)EnvironmentError_reduce, METH_NOARGS},
    {NULL}
};

ComplexExtendsException(PyExc_Exception, EnvironmentError,
                        EnvironmentError, EnvironmentError_dealloc,
                        EnvironmentError_methods, EnvironmentError_members,
                        EnvironmentError_str,
                        "Base class for I/O related errors.");


/*
 *    IOError extends EnvironmentError
 */
MiddlingExtendsException(PyExc_EnvironmentError, IOError,
                         EnvironmentError, "I/O operation failed.");


/*
 *    OSError extends EnvironmentError
 */
MiddlingExtendsException(PyExc_EnvironmentError, OSError,
                         EnvironmentError, "OS system call failed.");


/*
 *    WindowsError extends OSError
 */
#ifdef MS_WINDOWS
#include "errmap.h"

static int
WindowsError_clear(PyWindowsErrorObject *self)
{
    Py_CLEAR(self->myerrno);
    Py_CLEAR(self->strerror);
    Py_CLEAR(self->filename);
    Py_CLEAR(self->winerror);
    return BaseException_clear((PyBaseExceptionObject *)self);
}

static void
WindowsError_dealloc(PyWindowsErrorObject *self)
{
    _PyObject_GC_UNTRACK(self);
    WindowsError_clear(self);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static int
WindowsError_traverse(PyWindowsErrorObject *self, visitproc visit, void *arg)
{
    Py_VISIT(self->myerrno);
    Py_VISIT(self->strerror);
    Py_VISIT(self->filename);
    Py_VISIT(self->winerror);
    return BaseException_traverse((PyBaseExceptionObject *)self, visit, arg);
}

static int
WindowsError_init(PyWindowsErrorObject *self, PyObject *args, PyObject *kwds)
{
    PyObject *o_errcode = NULL;
    long errcode;
    long posix_errno;

    if (EnvironmentError_init((PyEnvironmentErrorObject *)self, args, kwds)
            == -1)
        return -1;

    if (self->myerrno == NULL)
        return 0;

    /* Set errno to the POSIX errno, and winerror to the Win32
       error code. */
    errcode = PyLong_AsLong(self->myerrno);
    if (errcode == -1 && PyErr_Occurred())
        return -1;
    posix_errno = winerror_to_errno(errcode);

    Py_CLEAR(self->winerror);
    self->winerror = self->myerrno;

    o_errcode = PyLong_FromLong(posix_errno);
    if (!o_errcode)
        return -1;

    self->myerrno = o_errcode;

    return 0;
}


static PyObject *
WindowsError_str(PyWindowsErrorObject *self)
{
    if (self->filename)
        return PyUnicode_FromFormat("[Error %S] %S: %R",
                                    self->winerror ? self->winerror: Py_None,
                                    self->strerror ? self->strerror: Py_None,
                                    self->filename);
    else if (self->winerror && self->strerror)
        return PyUnicode_FromFormat("[Error %S] %S",
                                    self->winerror ? self->winerror: Py_None,
                                    self->strerror ? self->strerror: Py_None);
    else
        return EnvironmentError_str((PyEnvironmentErrorObject *)self);
}

static PyMemberDef WindowsError_members[] = {
    {"errno", T_OBJECT, offsetof(PyWindowsErrorObject, myerrno), 0,
        PyDoc_STR("POSIX exception code")},
    {"strerror", T_OBJECT, offsetof(PyWindowsErrorObject, strerror), 0,
        PyDoc_STR("exception strerror")},
    {"filename", T_OBJECT, offsetof(PyWindowsErrorObject, filename), 0,
        PyDoc_STR("exception filename")},
    {"winerror", T_OBJECT, offsetof(PyWindowsErrorObject, winerror), 0,
        PyDoc_STR("Win32 exception code")},
    {NULL}  /* Sentinel */
};

ComplexExtendsException(PyExc_OSError, WindowsError, WindowsError,
                        WindowsError_dealloc, 0, WindowsError_members,
                        WindowsError_str, "MS-Windows OS system call failed.");

#endif /* MS_WINDOWS */


/*
 *    VMSError extends OSError (I think)
 */
#ifdef __VMS
MiddlingExtendsException(PyExc_OSError, VMSError, EnvironmentError,
                         "OpenVMS OS system call failed.");
#endif


/*
 *    EOFError extends Exception
 */
SimpleExtendsException(PyExc_Exception, EOFError,
                       "Read beyond end of file.");


/*
 *    RuntimeError extends Exception
 */
SimpleExtendsException(PyExc_Exception, RuntimeError,
                       "Unspecified run-time error.");


/*
 *    NotImplementedError extends RuntimeError
 */
SimpleExtendsException(PyExc_RuntimeError, NotImplementedError,
                       "Method or function hasn't been implemented yet.");

/*
 *    NameError extends Exception
 */
SimpleExtendsException(PyExc_Exception, NameError,
                       "Name not found globally.");

/*
 *    UnboundLocalError extends NameError
 */
SimpleExtendsException(PyExc_NameError, UnboundLocalError,
                       "Local name referenced but not bound to a value.");

/*
 *    AttributeError extends Exception
 */
SimpleExtendsException(PyExc_Exception, AttributeError,
                       "Attribute not found.");


/*
 *    SyntaxError extends Exception
 */

static int
SyntaxError_init(PySyntaxErrorObject *self, PyObject *args, PyObject *kwds)
{
    PyObject *info = NULL;
    Py_ssize_t lenargs = PyTuple_GET_SIZE(args);

    if (BaseException_init((PyBaseExceptionObject *)self, args, kwds) == -1)
        return -1;

    if (lenargs >= 1) {
        Py_CLEAR(self->msg);
        self->msg = PyTuple_GET_ITEM(args, 0);
        Py_INCREF(self->msg);
    }
    if (lenargs == 2) {
        info = PyTuple_GET_ITEM(args, 1);
        info = PySequence_Tuple(info);
        if (!info)
            return -1;

        if (PyTuple_GET_SIZE(info) != 4) {
            /* not a very good error message, but it's what Python 2.4 gives */
            PyErr_SetString(PyExc_IndexError, "tuple index out of range");
            Py_DECREF(info);
            return -1;
        }

        Py_CLEAR(self->filename);
        self->filename = PyTuple_GET_ITEM(info, 0);
        Py_INCREF(self->filename);

        Py_CLEAR(self->lineno);
        self->lineno = PyTuple_GET_ITEM(info, 1);
        Py_INCREF(self->lineno);

        Py_CLEAR(self->offset);
        self->offset = PyTuple_GET_ITEM(info, 2);
        Py_INCREF(self->offset);

        Py_CLEAR(self->text);
        self->text = PyTuple_GET_ITEM(info, 3);
        Py_INCREF(self->text);

        Py_DECREF(info);
    }
    return 0;
}

static int
SyntaxError_clear(PySyntaxErrorObject *self)
{
    Py_CLEAR(self->msg);
    Py_CLEAR(self->filename);
    Py_CLEAR(self->lineno);
    Py_CLEAR(self->offset);
    Py_CLEAR(self->text);
    Py_CLEAR(self->print_file_and_line);
    return BaseException_clear((PyBaseExceptionObject *)self);
}

static void
SyntaxError_dealloc(PySyntaxErrorObject *self)
{
    _PyObject_GC_UNTRACK(self);
    SyntaxError_clear(self);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static int
SyntaxError_traverse(PySyntaxErrorObject *self, visitproc visit, void *arg)
{
    Py_VISIT(self->msg);
    Py_VISIT(self->filename);
    Py_VISIT(self->lineno);
    Py_VISIT(self->offset);
    Py_VISIT(self->text);
    Py_VISIT(self->print_file_and_line);
    return BaseException_traverse((PyBaseExceptionObject *)self, visit, arg);
}

/* This is called "my_basename" instead of just "basename" to avoid name
   conflicts with glibc; basename is already prototyped if _GNU_SOURCE is
   defined, and Python does define that. */
static PyObject*
my_basename(PyObject *name)
{
    Py_UNICODE *unicode;
    Py_ssize_t i, size, offset;

    unicode = PyUnicode_AS_UNICODE(name);
    size = PyUnicode_GET_SIZE(name);
    offset = 0;
    for(i=0; i < size; i++) {
        if (unicode[i] == SEP)
            offset = i + 1;
    }
    if (offset != 0) {
        return PyUnicode_FromUnicode(
            PyUnicode_AS_UNICODE(name) + offset,
            size - offset);
    } else {
        Py_INCREF(name);
        return name;
    }
}


static PyObject *