checks whether PyArg_ParseTuple returned a negative int

[orenmn]

BPO	31243
Nosy	@benjaminp, @serhiy-storchaka, @orenmn
PRs	bpo-31243: fix PyArg_ParseTuple failure checks #3171 [3.6] bpo-31243: Fixed PyArg_ParseTuple failure checks. (GH-3171) #3233 [2.7] bpo-31243: Fixed PyArg_ParseTuple failure checks. (GH-3171) #3235

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

Show more details

GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2017-08-29.16:18:10.107>
created_at = <Date 2017-08-21.08:33:08.944>
labels = ['extension-modules', 'easy', '3.7', 'expert-IO', 'type-crash']
title = 'checks whether PyArg_ParseTuple returned a negative int'
updated_at = <Date 2017-08-29.16:18:10.106>
user = 'https://github.com/orenmn'

bugs.python.org fields:

activity = <Date 2017-08-29.16:18:10.106>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2017-08-29.16:18:10.107>
closer = 'serhiy.storchaka'
components = ['Extension Modules', 'IO']
creation = <Date 2017-08-21.08:33:08.944>
creator = 'Oren Milman'
dependencies = []
files = []
hgrepos = []
issue_num = 31243
keywords = ['easy (C)']
message_count = 7.0
messages = ['300613', '300616', '300618', '300977', '300982', '300993', '300994']
nosy_count = 4.0
nosy_names = ['benjamin.peterson', 'stutzbach', 'serhiy.storchaka', 'Oren Milman']
pr_nums = ['3171', '3233', '3235']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue31243'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7']

[orenmn]

according to the docs (https://docs.python.org/3.7/c-api/arg.html?highlight=pyarg_parsetuple#c.PyArg_ParseTuple), PyArg_ParseTuple
returns true for success or false for failure. I also looked at the
implementation in Python/getargs.c, and it seems that indeed PyArg_ParseTuple
can return only 0 or 1.

however, in some places in the codebase, there are checks whether
PyArg_ParseTuple returned a negative int.
I found a bunch in Modules/_testcapimodule.c, and one in Modules/_io/textio.c
in textiowrapper_read_chunk. (hopefully i haven't missed other places.)

this code crashes because of the check in textiowrapper_read_chunk:
import codecs
import _io
class MyDec():
def getstate(self):
return 420
class MyDecWrapper():
def __call__(self, blabla):
return MyDec()
quopri = codecs.lookup("quopri")
quopri._is_text_encoding = True
quopri.incrementaldecoder = MyDecWrapper()
t = _io.TextIOWrapper(_io.BytesIO(b'aaaaaa'),
newline='\n', encoding="quopri")
t.read(42)

I guess all of these checks should be changed to check whether PyArg_ParseTuple
returned 0.

also, before this specific call to PyArg_ParseTuple in textiowrapper_read_chunk,
we should check whether 'state' is a tuple.
Moreover, this call shouldn't produce a wrong error message, as explained in
bpo-28261.

[serhiy-storchaka]

Do you want to provide a PR Oren?

[orenmn]

yes, soon.
(just wanted to hear your opinion before doing that.)

[serhiy-storchaka]

New changeset ba7d736 by Serhiy Storchaka (Oren Milman) in branch 'master':
bpo-31243: Fixed PyArg_ParseTuple failure checks. (bpo-3171)
ba7d736

[serhiy-storchaka]

New changeset c7750c2 by Serhiy Storchaka (Oren Milman) in branch '3.6':
[3.6] bpo-31243: Fixed PyArg_ParseTuple failure checks. (GH-3171) (bpo-3233)
c7750c2

[serhiy-storchaka]

New changeset 20958e6 by Serhiy Storchaka (Oren Milman) in branch '2.7':
[2.7] bpo-31243: Fixed PyArg_ParseTuple failure checks. (GH-3171) (bpo-3235)
20958e6

[serhiy-storchaka]

Thank you for your contribution Oren!