Re: [PATCH v2 4/6] gdb: new setters and getters for __dict__, and attributes

[Tom Tromey <tom@tromey.com>]

>>>>> "Matthieu" == Matthieu Longo <matthieu.longo@arm.com> writes:

Matthieu> GDB is currently using the Python unlimited API. Migrating the codebase
Matthieu> to the Python limited API would have for benefit to make a GDB build
Matthieu> artifacts compatible with older and newer versions of Python that they
Matthieu> were built with.

Thanks again.

Matthieu> +  value = PyDict_GetItemWithError (dict.get (), attr);
Matthieu> +  if (value != nullptr)
Matthieu> +    return Py_NewRef (value);
Matthieu> +
Matthieu> +  /* PyDict_GetItemWithError() has a misleading name that lets one believe that
Matthieu> +     the function sets PyExc_AttributeError when the key is not found, whereas
Matthieu> +     it actually does not and only returns NULL.
Matthieu> +     Not setting the exception for an unfound key causes the raising of another
Matthieu> +     exception:
Matthieu> +       <class 'SystemError'>: error return without exception set
Matthieu> +     Hence this surprising manual setting of an exception to makes everything
Matthieu> +     fit into place.  */
Matthieu> +  PyErr_Format (PyExc_AttributeError,
Matthieu> +		"'%s' object has no attribute '%s'",
Matthieu> +		Py_TYPE (self)->tp_name,
Matthieu> +		PyUnicode_AsUTF8AndSize (attr, nullptr));


It seems to me that there should be an additional check between the call
to PyDict_GetItemWithError and PyErr_Format, like:

    if (PyErr_Occurred () != nullptr)
      return nullptr;

Since according to the PyDict_GetItemWithError docs, this function can
return null with the error set.

With that change the comment could probably be shortened a bit since
it's no longer surprising to have to set the exception.

Tom