Author methane
Recipients lemburg, methane
Date 2017-02-14.03:00:30
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <1487041232.48.0.941964119334.issue29548@psf.upfronthosting.co.za>
In-reply-to
Content
Thanks, Lemburg to pointing it out.
Here is detail of the difference.

## PyEval_CallFunction(), PyEval_CallMethod()

They are very similar to PyObject_CallFunction() and PyObject_CallMethod().  difference are:

* PyEval_Call...() doesn't respect Py_SSIZE_T_CLEAN
* PyObject_Call... has following special case.  PyEval_CallFunction(callable, "i", (int)i) will raise TypeError("keyword list must be a tuple") and PyObject_CallFunction(callable, "i", (int)i) calls `callable(i)`

    if (nargs == 1 && PyTuple_Check(stack[0])) {
        /* Special cases for backward compatibility:
           - PyObject_CallFunction(func, "O", tuple) calls func(*tuple)
           - PyObject_CallFunction(func, "(OOO)", arg1, arg2, arg3) calls
             func(*(arg1, arg2, arg3)): func(arg1, arg2, arg3) */
        PyObject *args = stack[0];
        result = _PyObject_FastCall(callable,
                                    &PyTuple_GET_ITEM(args, 0),
                                    PyTuple_GET_SIZE(args));
    }

PyEval_CallFunction is not called from Python source tree.
PyEval_CallMethod has only one caller in tree and format string is "(Oi)".  It can be replaced with PyObject_CallMethod safely.


## PyEval_CallObject(), PyEval_CallObjectWithKeywords()

PyEval_CallObject() is a just macro calling PyEval_CallObjectWithKeywords() (call it COWK later).
PyEval_CallObject() is identical to PyObject_CallObject().  Only difference is it's a macro or function.

COWK is similar to PyObject_Call(), but COWK raise TypeError when args is not a tuple or kwds is not a dictionary and PyObject_Call() uses assert.

There are only two caller of PyEval_CallObjectWithKeywords() other than PyEval_CallObject and PyObject_CallObject.
One is tp_call of weakcallableproxy.  Type of kwargs is checked before calling tp_call.
Another is in threading (boot->keyw).  The threading module checks it's a dict.
So replacing them to PyObject_CallObject() is safe.

----

While they are complex API, there are few (or no) callers in Python tree.
It's too hard to maintain.  Actually, I found regression of COWK in Python 3.6.

https://github.com/python/cpython/commit/155ea65e5c88d250a752ee5321860ef11ede4085

It calls _PyObject_FastCallDict() when args is NULL.  If kwargs is not dict, it can crash instead of raising TypeError.
History
Date User Action Args
2017-02-14 03:00:32methanesetrecipients: + methane, lemburg
2017-02-14 03:00:32methanesetmessageid: <1487041232.48.0.941964119334.issue29548@psf.upfronthosting.co.za>
2017-02-14 03:00:32methanelinkissue29548 messages
2017-02-14 03:00:30methanecreate