[New-bugs-announce] [issue26814] Add a new _PyObject_CallStack() function which avoids the creation of a tuple or dict for arguments
report at bugs.python.org
Thu Apr 21 04:57:21 EDT 2016
New submission from STINNER Victor:
Attached patch adds the following new function:
PyObject* _PyObject_CallStack(PyObject *func,
int na, int nk);
where na is the number of positional arguments and nk is the number of (key, pair) arguments stored in the stack.
Example of C code to call a function with one positional argument:
stack = arg;
return _PyObject_CallStack(func, stack, 1, 0);
Simple, isn't it?
The difference with PyObject_Call() is that its API avoids the creation of a tuple and a dictionary to pass parameters to functions when possible. Currently, the temporary tuple and dict can be avoided to call Python functions (nice, isn't it?) and C function declared with METH_O (not the most common API, but many functions are declared like that).
The patch only modifies property_descr_set() to test the feature, but I'm sure that *a lot* of C code can be modified to use this new function to beneift from its optimization.
Should we make this new _PyObject_CallStack() function official: call it PyObject_CallStack() (without the understand prefix) or experiment it in CPython 3.6 and decide later to make it public? If it's made private, it will require a large replacement patch later to replace all calls to _PyObject_CallStack() with PyObject_CallStack() (strip the underscore prefix).
The next step is to add a new METH_STACK flag to pass parameters to C functions using a similar API (PyObject **stack, int na, int nk) and modify the argument clinic to use this new API.
Thanks to Larry Hasting who gave me the idea in a previous edition of Pycon US ;-)
This issue was created after the discussion on issue #26811 which is an issue in a micro-optimization in property_descr_set() to avoid the creation of a tuple: it caches a private tuple inside property_descr_set().
nosy: haypo, larry, rhettinger, serhiy.storchaka
title: Add a new _PyObject_CallStack() function which avoids the creation of a tuple or dict for arguments
versions: Python 3.6
Added file: http://bugs.python.org/file42549/call_stack.patch
Python tracker <report at bugs.python.org>
More information about the New-bugs-announce