Python 3.5.2 strange-behavior issues (from PyPy)

[arigo]

BPO	28885
Nosy	@brettcannon, @arigo, @rhettinger, @gpshead, @vstinner, @larryhastings, @serhiy-storchaka, @1st1
Dependencies	bpo-18018: SystemError: Parent module '' not loaded, cannot perform relative import bpo-28893: Make sure exceptions raised in aiter are properly chained in ceval
Files	os-chmod-EINTR-retry.gps01.diff

^{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 = None
closed_at = None
created_at = <Date 2016-12-06.12:02:48.508>
labels = ['type-bug']
title = 'Python 3.5.2 strange-behavior issues (from PyPy)'
updated_at = <Date 2017-01-10.18:47:42.441>
user = 'https://github.com/arigo'

bugs.python.org fields:

activity = <Date 2017-01-10.18:47:42.441>
actor = 'brett.cannon'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2016-12-06.12:02:48.508>
creator = 'arigo'
dependencies = ['18018', '28893']
files = ['45781']
hgrepos = []
issue_num = 28885
keywords = ['patch']
message_count = 20.0
messages = ['282537', '282538', '282539', '282540', '282541', '282542', '282546', '282547', '282562', '282566', '282579', '282584', '282589', '282596', '282601', '283561', '285101', '285102', '285132', '285143']
nosy_count = 8.0
nosy_names = ['brett.cannon', 'arigo', 'rhettinger', 'gregory.p.smith', 'vstinner', 'larry', 'serhiy.storchaka', 'yselivanov']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue28885'
versions = ['Python 3.5']

[arigo]

As discussed on python-dev, I am creating omnibus issues from the lists of crashers, of wrong-according-to-the-docs, and of strange-behavior-only issues that I found while developing Python 3.5.2 support for PyPy. These occur with CPython 3.5.2 but most of them are likely still here in trunk.

This is the issue containing the "strange behaviors" and some of them, or possibly most, will turn out to be my own feelings only and not python-dev's, which is fine by me.

[arigo]

(S1) ceval.c: GET_AITER: calls _PyCoro_GetAwaitableIter(), which might
get an exception from calling the user-defined __await__() or checking
what it returns; such an exception is completely eaten.

[arigo]

(S2) argument clinic turns the "bool" specifier into
PyObject_IsTrue(), accepting any argument whatsoever. This can easily
get very confusing for the user, e.g. after messing up the number of
arguments. For example: os.symlink("/path1", "/path2", "/path3")
doesn't fail, it just considers the 3rd argument as some true value.

[arigo]

(S3) hash({}.values()) works (but hash({}.keys()) correctly gives
TypeError). That's a bit confusing and, as far as I can tell, always
pointless. Also, related: d.keys()==d.keys() but
d.values()!=d.values().

[arigo]

(S4) if you write from .a import b inside the Python prompt, or in
a module not in any package, then you get a SystemError(!) with an
error message that is unlikely to help newcomers.

[arigo]

(S5) PEP-475: unclear why 'os.fchmod(fd)' retries automatically when
it gets EINTR but the otherwise-equivalent 'os.chmod(fd)' does not.
(The documentation says they are fully equivalent, so someone is
wrong.)

[serhiy-storchaka]

(S4) was fixed in 3.6 (bpo-18018). But the fix was not applied to 3.5.

[serhiy-storchaka]

(S2) is related not to Argument Clinic itself, but to the 'p' format unit added in 3.3 (bpo-14705).

[brettcannon]

Victor & Yury for S1.

[1st1]

I'll take a look at s1 later tonight

[gpshead]

+larry for (S2) regarding argument clinic's treatment of bool.

[gpshead]

attaching a proposed fix for (S5). os.chmod should have the same EINTR retry treatment as everything else. That it does not appears to have been an oversight.

[larryhastings]

I assert that Argument Clinic's / PyArg_ParseTuple's handling of bool is correct.

• Python has a well-established concept of "truth":

  https://docs.python.org/3/library/stdtypes.html#truth-value-testing

  The C equivalent is, indeed, PyObject_IsTrue().

• When we added the 'p' format unit to PyArg_ParseTuple, I originally had a second format unit 'P' that would only accept boolean literal values. But nobody could come up with a use case for it. So we removed it. See bpo-14705 for the discussion.

• Existing code often does something half-assed here. eg. stat_float_times uses the PyArg_ParseTuple "i" format unit for its boolean parameter, which accepts booleans and integers but not strings. This is strange and inconsistent. (Of course, you can do this with Argument Clinic, just specify the parameter as an int. But, yuck.)

If you have a counter-proposal for how it should behave, I'd be interested to hear it. But as far as I'm concerned, the two legitimate answers for "how to handle integers" are either a) accept literally only True and False--an approach which nobody has a use case for--or b) PyObject_IsTrue(), which behaves exactly like Python.

[1st1]

I created an issue to track S1: http://bugs.python.org/issue28893