bpo-30579: Allow TracebackType creation and tb_next mutation from Python (GH-4793)
Third party projects may wish to hide their own internal machinery in order to present more comprehensible tracebacks to end users (e.g. Jinja2 and Trio both do this). Previously such projects have had to rely on ctypes to do so:fe3dadacdf/jinja2/debug.py (L345)
1e86b1aee8/trio/_core/_multierror.py (L296)
This provides a Python level API for creating and modifying real Traceback objects, allowing tracebacks to be edited at runtime. Patch by Nathaniel Smith.
This commit is contained in:
parent
d327ae6ba1
commit
e46a8af450
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@ -228,6 +228,72 @@ class TestTraceback(unittest.TestCase):
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self.fail("No exception raised")
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class TestTracebackType(unittest.TestCase):
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def raiser(self):
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raise ValueError
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def test_attrs(self):
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try:
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self.raiser()
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except Exception as exc:
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tb = exc.__traceback__
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self.assertIsInstance(tb.tb_next, types.TracebackType)
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self.assertIs(tb.tb_frame, sys._getframe())
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self.assertIsInstance(tb.tb_lasti, int)
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self.assertIsInstance(tb.tb_lineno, int)
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self.assertIs(tb.tb_next.tb_next, None)
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# Invalid assignments
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with self.assertRaises(TypeError):
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del tb.tb_next
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with self.assertRaises(TypeError):
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tb.tb_next = "asdf"
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# Loops
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with self.assertRaises(ValueError):
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tb.tb_next = tb
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with self.assertRaises(ValueError):
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tb.tb_next.tb_next = tb
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# Valid assignments
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tb.tb_next = None
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self.assertIs(tb.tb_next, None)
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new_tb = get_tb()
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tb.tb_next = new_tb
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self.assertIs(tb.tb_next, new_tb)
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def test_constructor(self):
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other_tb = get_tb()
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frame = sys._getframe()
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tb = types.TracebackType(other_tb, frame, 1, 2)
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self.assertEqual(tb.tb_next, other_tb)
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self.assertEqual(tb.tb_frame, frame)
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self.assertEqual(tb.tb_lasti, 1)
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self.assertEqual(tb.tb_lineno, 2)
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tb = types.TracebackType(None, frame, 1, 2)
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self.assertEqual(tb.tb_next, None)
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with self.assertRaises(TypeError):
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types.TracebackType("no", frame, 1, 2)
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with self.assertRaises(TypeError):
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types.TracebackType(other_tb, "no", 1, 2)
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with self.assertRaises(TypeError):
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types.TracebackType(other_tb, frame, "no", 2)
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with self.assertRaises(TypeError):
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types.TracebackType(other_tb, frame, 1, "nuh-uh")
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class TestContext(unittest.TestCase):
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def test_instance_context_instance_raise(self):
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context = IndexError()
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@ -0,0 +1,2 @@
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Implement TracebackType.__new__ to allow Python-level creation of
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traceback objects, and make TracebackType.tb_next mutable.
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@ -0,0 +1,35 @@
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/*[clinic input]
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preserve
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[clinic start generated code]*/
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PyDoc_STRVAR(tb_new__doc__,
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"TracebackType(tb_next, tb_frame, tb_lasti, tb_lineno)\n"
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"--\n"
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"\n"
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"Create a new traceback object.");
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static PyObject *
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tb_new_impl(PyTypeObject *type, PyObject *tb_next, PyFrameObject *tb_frame,
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int tb_lasti, int tb_lineno);
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static PyObject *
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tb_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
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{
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PyObject *return_value = NULL;
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static const char * const _keywords[] = {"tb_next", "tb_frame", "tb_lasti", "tb_lineno", NULL};
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static _PyArg_Parser _parser = {"OO!ii:TracebackType", _keywords, 0};
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PyObject *tb_next;
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PyFrameObject *tb_frame;
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int tb_lasti;
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int tb_lineno;
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if (!_PyArg_ParseTupleAndKeywordsFast(args, kwargs, &_parser,
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&tb_next, &PyFrame_Type, &tb_frame, &tb_lasti, &tb_lineno)) {
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goto exit;
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}
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return_value = tb_new_impl(type, tb_next, tb_frame, tb_lasti, tb_lineno);
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exit:
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return return_value;
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}
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/*[clinic end generated code: output=0133130d7d19556f input=a9049054013a1b77]*/
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@ -27,6 +27,65 @@ _Py_IDENTIFIER(close);
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_Py_IDENTIFIER(open);
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_Py_IDENTIFIER(path);
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/*[clinic input]
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class TracebackType "PyTracebackObject *" "&PyTraceback_Type"
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[clinic start generated code]*/
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/*[clinic end generated code: output=da39a3ee5e6b4b0d input=928fa06c10151120]*/
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#include "clinic/traceback.c.h"
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static PyObject *
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tb_create_raw(PyTracebackObject *next, PyFrameObject *frame, int lasti,
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int lineno)
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{
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PyTracebackObject *tb;
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if ((next != NULL && !PyTraceBack_Check(next)) ||
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frame == NULL || !PyFrame_Check(frame)) {
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PyErr_BadInternalCall();
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return NULL;
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}
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tb = PyObject_GC_New(PyTracebackObject, &PyTraceBack_Type);
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if (tb != NULL) {
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Py_XINCREF(next);
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tb->tb_next = next;
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Py_XINCREF(frame);
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tb->tb_frame = frame;
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tb->tb_lasti = lasti;
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tb->tb_lineno = lineno;
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PyObject_GC_Track(tb);
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}
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return (PyObject *)tb;
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}
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/*[clinic input]
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@classmethod
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TracebackType.__new__ as tb_new
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tb_next: object
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tb_frame: object(type='PyFrameObject *', subclass_of='&PyFrame_Type')
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tb_lasti: int
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tb_lineno: int
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Create a new traceback object.
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[clinic start generated code]*/
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static PyObject *
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tb_new_impl(PyTypeObject *type, PyObject *tb_next, PyFrameObject *tb_frame,
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int tb_lasti, int tb_lineno)
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/*[clinic end generated code: output=fa077debd72d861a input=01cbe8ec8783fca7]*/
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{
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if (tb_next == Py_None) {
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tb_next = NULL;
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} else if (!PyTraceBack_Check(tb_next)) {
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return PyErr_Format(PyExc_TypeError,
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"expected traceback object or None, got '%s'",
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Py_TYPE(tb_next)->tp_name);
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}
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return tb_create_raw((PyTracebackObject *)tb_next, tb_frame, tb_lasti,
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tb_lineno);
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}
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static PyObject *
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tb_dir(PyTracebackObject *self)
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{
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@ -34,19 +93,72 @@ tb_dir(PyTracebackObject *self)
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"tb_lasti", "tb_lineno");
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}
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static PyObject *
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tb_next_get(PyTracebackObject *self, void *Py_UNUSED(_))
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{
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PyObject* ret = (PyObject*)self->tb_next;
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if (!ret) {
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ret = Py_None;
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}
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Py_INCREF(ret);
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return ret;
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}
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static int
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tb_next_set(PyTracebackObject *self, PyObject *new_next, void *Py_UNUSED(_))
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{
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if (!new_next) {
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PyErr_Format(PyExc_TypeError, "can't delete tb_next attribute");
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return -1;
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}
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/* We accept None or a traceback object, and map None -> NULL (inverse of
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tb_next_get) */
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if (new_next == Py_None) {
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new_next = NULL;
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} else if (!PyTraceBack_Check(new_next)) {
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PyErr_Format(PyExc_TypeError,
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"expected traceback object, got '%s'",
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Py_TYPE(new_next)->tp_name);
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return -1;
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}
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/* Check for loops */
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PyTracebackObject *cursor = (PyTracebackObject *)new_next;
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while (cursor) {
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if (cursor == self) {
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PyErr_Format(PyExc_ValueError, "traceback loop detected");
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return -1;
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}
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cursor = cursor->tb_next;
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}
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PyObject *old_next = (PyObject*)self->tb_next;
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Py_XINCREF(new_next);
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self->tb_next = (PyTracebackObject *)new_next;
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Py_XDECREF(old_next);
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return 0;
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}
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static PyMethodDef tb_methods[] = {
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{"__dir__", (PyCFunction)tb_dir, METH_NOARGS},
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{NULL, NULL, 0, NULL},
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};
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static PyMemberDef tb_memberlist[] = {
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{"tb_next", T_OBJECT, OFF(tb_next), READONLY},
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{"tb_frame", T_OBJECT, OFF(tb_frame), READONLY},
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{"tb_lasti", T_INT, OFF(tb_lasti), READONLY},
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{"tb_lineno", T_INT, OFF(tb_lineno), READONLY},
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{NULL} /* Sentinel */
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};
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static PyGetSetDef tb_getsetters[] = {
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{"tb_next", (getter)tb_next_get, (setter)tb_next_set, NULL, NULL},
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{NULL} /* Sentinel */
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};
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static void
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tb_dealloc(PyTracebackObject *tb)
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{
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@ -94,7 +206,7 @@ PyTypeObject PyTraceBack_Type = {
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
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0, /* tp_doc */
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tb_new__doc__, /* tp_doc */
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(traverseproc)tb_traverse, /* tp_traverse */
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(inquiry)tb_clear, /* tp_clear */
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0, /* tp_richcompare */
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@ -103,39 +215,24 @@ PyTypeObject PyTraceBack_Type = {
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0, /* tp_iternext */
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tb_methods, /* tp_methods */
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tb_memberlist, /* tp_members */
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0, /* tp_getset */
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tb_getsetters, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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0, /* tp_init */
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0, /* tp_alloc */
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tb_new, /* tp_new */
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};
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static PyTracebackObject *
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newtracebackobject(PyTracebackObject *next, PyFrameObject *frame)
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{
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PyTracebackObject *tb;
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if ((next != NULL && !PyTraceBack_Check(next)) ||
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frame == NULL || !PyFrame_Check(frame)) {
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PyErr_BadInternalCall();
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return NULL;
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}
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tb = PyObject_GC_New(PyTracebackObject, &PyTraceBack_Type);
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if (tb != NULL) {
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Py_XINCREF(next);
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tb->tb_next = next;
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Py_XINCREF(frame);
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tb->tb_frame = frame;
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tb->tb_lasti = frame->f_lasti;
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tb->tb_lineno = PyFrame_GetLineNumber(frame);
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PyObject_GC_Track(tb);
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}
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return tb;
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}
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int
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PyTraceBack_Here(PyFrameObject *frame)
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{
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PyObject *exc, *val, *tb, *newtb;
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PyErr_Fetch(&exc, &val, &tb);
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newtb = (PyObject *)newtracebackobject((PyTracebackObject *)tb, frame);
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newtb = tb_create_raw((PyTracebackObject *)tb, frame, frame->f_lasti,
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PyFrame_GetLineNumber(frame));
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if (newtb == NULL) {
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_PyErr_ChainExceptions(exc, val, tb);
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return -1;
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