[Python-Dev] Patch review [ 723201 ] PyArg_ParseTuple problem with 'L' format (original) (raw)

Michiel Jan Laurens de Hoon mdehoon at ims.u-tokyo.ac.jp
Thu Jan 20 14🔞52 CET 2005

Patch review [ 723201 ] PyArg_ParseTuple problem with 'L' format

The PyArg_ParseTuple function (PyObject *args, char *format, ...) parses the arguments args and stores them in the variables specified following the format argument. If format=="i", indicating an integer, but the corresponding Python object in args is not a Python int or long, a TypeError is thrown:

TypeError: an integer is required

For the "L" format, indicating a long long, instead a SystemError is thrown:

SystemError: Objects/longobject.c:788: bad argument to internal function

The submitted patch fixes this, however I think it is not the best way to do it. The original code (part of the convertsimple function in Python/getargs.c) is

case 'L': {/* PY_LONG_LONG */
    PY_LONG_LONG *p = va_arg( *p_va, PY_LONG_LONG * );
    PY_LONG_LONG ival = PyLong_AsLongLong( arg );
    if( ival == (PY_LONG_LONG)-1 && PyErr_Occurred() ) {
        return converterr("long<L>", arg, msgbuf, bufsize);
    } else {
        *p = ival;
    }
    break;
}

In the patch, a PyLong_Check and a PyInt_Check are added:

     case 'L': {/* PY_LONG_LONG */
             PY_LONG_LONG *p = va_arg(*p_va, PY_LONG_LONG *);
             PY_LONG_LONG ival;
    /* ********** patch starts here ********** */
             if (!PyLong_Check(arg) && !PyInt_Check(arg))
                     return converterr("long<L>", arg, msgbuf, bufsize);
    /* ********** patch ends here ********** */
             ival = PyLong_AsLongLong(arg);
             if (ival == (PY_LONG_LONG)-1 && PyErr_Occurred()) {
                     return converterr("long<L>", arg, msgbuf, bufsize);
             } else {
                     *p = ival;
             }
             break;
     }

However, the PyLong_AsLongLong function (in Objects/longobject.c) also contains a call to PyLong_Check and PyInt_Check, so there should be no need for another such check here:

PY_LONG_LONG PyLong_AsLongLong(PyObject *vv) { PY_LONG_LONG bytes; int one = 1; int res;

     if (vv == NULL) {
             PyErr_BadInternalCall();
             return -1;
     }
     if (!PyLong_Check(vv)) {
             if (PyInt_Check(vv))
                     return (PY_LONG_LONG)PyInt_AsLong(vv);
             PyErr_BadInternalCall();
             return -1;
     }

A better solution would be to replace the PyErr_BadInternalCall() in the PyLong_AsLongLong function by PyErr_SetString(PyExc_TypeError, "an integer is required"); This would make it consistent with PyInt_AsLong in Objects/intobject.c:

long PyInt_AsLong(register PyObject *op) { PyNumberMethods *nb; PyIntObject *io; long val;

     if (op && PyInt_Check(op))
             return PyInt_AS_LONG((PyIntObject*) op);

     if (op == NULL || (nb = op->ob_type->tp_as_number) == NULL ||
         nb->nb_int == NULL) {
             PyErr_SetString(PyExc_TypeError, "an integer is required");
             return -1;
     }

By the way, I noticed that a Python float is converted to an int (with a deprecation warning), while trying to convert a Python float into a long long int results in a TypeError. Also, I'm not sure about the function of the calls to converterr (in various places in the convertsimple function); none of the argument type errors seem to lead to the warning messages created by converterr.

--Michiel.

-- Michiel de Hoon, Assistant Professor University of Tokyo, Institute of Medical Science Human Genome Center 4-6-1 Shirokane-dai, Minato-ku Tokyo 108-8639 Japan http://bonsai.ims.u-tokyo.ac.jp/~mdehoon

More information about the Python-Dev mailing list