[Python-Dev] Using argument clinic to replace timemodule.c:parse_time_t_args()

[Nikolaus Rath]

Serhiy Storchaka <storchaka at gmail.com> writes:
> 20.01.14 06:19, Nikolaus Rath написав(ла):
>> This works if the user calls time.gmtime(None), but it fails for
>> time.gmtime(). It seems that in that case my C converter function is
>> never called.
>>
>> What's the trick that I'm missing?
>
> /*[clinic input]
> time.gmtime
>
>     [
>     seconds: time_t
>     ]
>     /
>

Ahh, interesting. So this works, but now the C default is evaluated even
if the user passed an argument (so that answers my question about
decreased performance in the other subthread). The generated code is:

time_gmtime(PyModuleDef *module, PyObject *args)
{
    PyObject *return_value = NULL;
    int group_right_1 = 0;
    time_t seconds = time(NULL);

    switch (PyTuple_GET_SIZE(args)) {
        case 0:
            break;
        case 1:
            if (!PyArg_ParseTuple(args, "O&:gmtime", PyObject_to_time_t, &seconds))
                return NULL;
            group_right_1 = 1;
            break;
        default:
            PyErr_SetString(PyExc_TypeError, "time.gmtime requires 0 to 1 arguments");
            return NULL;
    }
    return_value = time_gmtime_impl(module, group_right_1, seconds);


All in all, I'm still not sure how I'm supposed to proceed. I see the
following options (and I'm fine with all of them):

1. Use the option group with a custom converter. This means a time(NULL)
   call even if the caller passed a parameter.

2. Declare the _impl parameter as PyObject* instead of time_t, and
   explicitly call a C conversion function.
   
3. Patch clinic.py to only evaluate the C default if the caller does not
   pass a parameter. This seemest cleanest, but I don't know if the
   design of clinic.py actually allows that.


   
Best,
Nikolaus

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