Compilation Warning for memoryview.tobytes and _collections._tuplegetter.__reduce__

[matrixise]

BPO	36197
Nosy	@vstinner, @serhiy-storchaka, @matrixise
PRs	bpo-33012: Fix compilation warnings for memoryview.tobytes and _collections._tuplegetter.__reduce__ #12179 Fix the C function signature for _collections._tuplegetter.__reduce__. #12180
Superseder	bpo-33012: Invalid function cast warnings with gcc 8 for METH_NOARGS

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/matrixise'
closed_at = <Date 2019-03-05.14:57:52.535>
created_at = <Date 2019-03-05.14:31:54.058>
labels = ['easy', '3.8']
title = 'Compilation Warning for memoryview.tobytes and _collections._tuplegetter.__reduce__'
updated_at = <Date 2019-03-05.16:41:13.004>
user = 'https://github.com/matrixise'

bugs.python.org fields:

activity = <Date 2019-03-05.16:41:13.004>
actor = 'serhiy.storchaka'
assignee = 'matrixise'
closed = True
closed_date = <Date 2019-03-05.14:57:52.535>
closer = 'vstinner'
components = []
creation = <Date 2019-03-05.14:31:54.058>
creator = 'matrixise'
dependencies = []
files = []
hgrepos = []
issue_num = 36197
keywords = ['patch', 'easy (C)']
message_count = 7.0
messages = ['337191', '337195', '337196', '337208', '337211', '337212', '337226']
nosy_count = 3.0
nosy_names = ['vstinner', 'serhiy.storchaka', 'matrixise']
pr_nums = ['12179', '12180']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = '33012'
type = None
url = 'https://bugs.python.org/issue36197'
versions = ['Python 3.8']

[matrixise]

gcc -pthread -c -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -g -Og -Wall -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -I./Include/internal -I. -I./Include -DPy_BUILD_CORE -o Objects/memoryobject.o Objects/memoryobject.c
Objects/memoryobject.c:3112:21: warning: cast between incompatible function types from 'PyObject * ()(PyMemoryViewObject *, PyObject *, PyObject *)' {aka 'struct _object * ()(struct <anonymous> *, struct _object *, struct _object *)'} to 'PyObject * ()(PyObject *, PyObject *)' {aka 'struct _object * ()(struct _object *, struct _object *)'} [-Wcast-function-type]
{"tobytes", (PyCFunction)memory_tobytes, METH_VARARGS|METH_KEYWORDS, memory_tobytes_doc},

I am preparing a small PR for this issue.

[matrixise]

Fix an other warning in the same PR

_collections._tuplegetter.__reduce__

[vstinner]

I prefer to reuse bpo-33012.

[serhiy-storchaka]

This is not correct fix for tuplegetter_reduce. tuplegetter_reduce should have two parameters, just the second is unused.

[matrixise]

Hi @serhiy,

Thank you for your PR, I prefer your patch, just because you have just added the PyObject *Py_UNUSED(ignored) to the tuplegetter_reduce function. And in this case, you don't need to cast to (void(*)(void)).

I will use this tip for the next time.

Thank

[serhiy-storchaka]

This is only for methods with METH_NOARGS. The code that calls such method, calls it with two arguments, passing NULL as the second argument. So the signature of the C function should have two parameters. Functions for methods with METH_KEYWORDS or METH_FASTCALL should have different corresponding signatures.

[serhiy-storchaka]

New changeset adfffc7 by Serhiy Storchaka in branch 'master':
Fix the C function signature for _collections._tuplegetter.__reduce__. (GH-12180)
adfffc7