Fix invalid function cast warnings with gcc 8
for method conventions different from METH_NOARGS, METH_O and
METH_VARARGS excluding Argument Clinic generated code.
METH_NOARGS functions need only a single argument but they are cast
into a PyCFunction, which takes two arguments. This triggers an
invalid function cast warning in gcc8 due to the argument mismatch.
Fix this by adding a dummy unused argument.
Issue #29300: Rename struct.unpack() second parameter from "inputstr" to
"buffer", and use the Py_buffer type.
Fix also unit tests on struct.unpack() which passed a Unicode string instead of
a bytes string as struct.unpack() second parameter. The purpose of
test_trailing_counter() is to test invalid format strings, not to test the
buffer parameter.
* The struct module now requires contiguous buffers.
* Convert most functions and methods of the _struct module to Argument Clinic
* Use "Py_buffer" type for the "buffer" argument. Argument Clinic is
responsible to create and release the Py_buffer object.
* Use "PyStructObject *" type for self to avoid explicit conversions.
* Add an unit test on the _struct.Struct.unpack_from() method to test passing
arguments as keywords.
* Rephrase docstrings.
* Rename "fmt" argument to "format" in docstrings and the documentation.
As a side effect, functions and methods which used METH_VARARGS calling
convention like struct.pack() now use the METH_FASTCALL calling convention
which avoids the creation of temporary tuple to pass positional arguments and
so is faster. For example, struct.pack("i", 1) becomes 1.56x faster (-36%)::
$ ./python -m perf timeit \
-s 'import struct; pack=struct.pack' 'pack("i", 1)' \
--compare-to=../default-ref/python
Median +- std dev: 119 ns +- 1 ns -> 76.8 ns +- 0.4 ns: 1.56x faster (-36%)
Significant (t=295.91)
Patch co-written with Serhiy Storchaka.
Issue #28858: The change b9c9691c72c5 introduced a regression. It seems like
_PyObject_CallArg1() uses more stack memory than
PyObject_CallFunctionObjArgs().
* PyObject_CallFunctionObjArgs(func, NULL) => _PyObject_CallNoArg(func)
* PyObject_CallFunctionObjArgs(func, arg, NULL) => _PyObject_CallArg1(func, arg)
PyObject_CallFunctionObjArgs() allocates 40 bytes on the C stack and requires
extra work to "parse" C arguments to build a C array of PyObject*.
_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.
This change is part of the fastcall project. The change on listsort() is
related to the issue #23507.
