Class PyObjectPtr

Tools/gdb/libpython.py:160–406

Class wrapping a gdb.Value that's either a (PyObject*) within the inferior process, or some subclass pointer e.g. (PyBytesObject*) There will be a subclass for every refined PyObject type that we care about. Note that at every stage the underlying pointer could be NULL, point

class PyObjectPtr(object):
    """
    Class wrapping a gdb.Value that's either a (PyObject*) within the
    inferior process, or some subclass pointer e.g. (PyBytesObject*)

    There will be a subclass for every refined PyObject type that we care
    about.

    Note that at every stage the underlying pointer could be NULL, point
    to corrupt data, etc; this is the debugger, after all.
    """
    _typename = 'PyObject'

    def __init__(self, gdbval, cast_to=None):
        # Clear the tagged pointer
        if gdbval.type.name == '_PyStackRef':
            if cast_to is None:
                cast_to = gdb.lookup_type('PyObject').pointer()
            self._gdbval = _PyStackRef_AsPyObjectBorrow(gdbval).cast(cast_to)
        elif cast_to:
            self._gdbval = gdbval.cast(cast_to)
        else:
            self._gdbval = gdbval

    def field(self, name):
        '''
        Get the gdb.Value for the given field within the PyObject.

        Various libpython types are defined using the "PyObject_HEAD" and
        "PyObject_VAR_HEAD" macros.

        In Python, this is defined as an embedded PyVarObject type thus:
           PyVarObject ob_base;
        so that the "ob_size" field is located insize the "ob_base" field, and
        the "ob_type" is most easily accessed by casting back to a (PyObject*).
        '''
        if self.is_null():
            raise NullPyObjectPtr(self)

        if name == 'ob_type':
            pyo_ptr = self._gdbval.cast(PyObjectPtr.get_gdb_type())
            return pyo_ptr.dereference()[name]

        if name == 'ob_size':
            pyo_ptr = self._gdbval.cast(PyVarObjectPtr.get_gdb_type())
            return pyo_ptr.dereference()[name]

        # General case: look it up inside the object:
        return self._gdbval.dereference()[name]

    def pyop_field(self, name):
        '''
        Get a PyObjectPtr for the given PyObject* field within this PyObject.
        '''
        return PyObjectPtr.from_pyobject_ptr(self.field(name))

    def write_field_repr(self, name, out, visited):
        '''