infinite loop in PyRun_InteractiveLoopFlags()

[xdegaye]

BPO	30696
Nosy	@vstinner, @xdegaye
PRs	bpo-30696: Fix the REPL looping endlessly when no memory #4160 [3.6] bpo-30696: Fix the REPL looping endlessly when no memory (GH-41… #4379
Files	infinite_loop.patch

^{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 = <Date 2017-11-12.16:33:59.948>
created_at = <Date 2017-06-18.10:33:04.834>
labels = ['interpreter-core', 'type-bug', '3.7']
title = 'infinite loop in PyRun_InteractiveLoopFlags()'
updated_at = <Date 2017-11-13.12:40:12.021>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2017-11-13.12:40:12.021>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-12.16:33:59.948>
closer = 'xdegaye'
components = ['Interpreter Core']
creation = <Date 2017-06-18.10:33:04.834>
creator = 'xdegaye'
dependencies = []
files = ['46959']
hgrepos = []
issue_num = 30696
keywords = ['patch']
message_count = 9.0
messages = ['296267', '296322', '296324', '306118', '306120', '306151', '306152', '306153', '306155']
nosy_count = 2.0
nosy_names = ['vstinner', 'xdegaye']
pr_nums = ['4160', '4379']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue30696'
versions = ['Python 3.6', 'Python 3.7']

[xdegaye]

To reproduce the problem, apply the nomemory_allocator.patch from issue 30695 and run the following two statements that must be interrupted with ^C:
$  ./python -q
>>> import _testcapi
>>> _testcapi.set_nomemory_allocator()
sys.excepthook is missing
^Cpython: Objects/call.c:785: PyEval_CallObjectWithKeywords: Assertion `!PyErr_Occurred()' failed.
Aborted (core dumped)

The attached patch fixes this problem.
No PR for the moment: this patch and nomemory_allocator.patch are needed to demonstrate other issues.

[xdegaye]

The patch is far too simplistic. With this patch an exception kills the interactive loop, for example:

$ ./python -q
>>> x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'x' is not defined
$

[vstinner]

See also my old issue bpo-8070 opened 7 years ago :-)

[xdegaye]

New changeset e0582a3 by xdegaye in branch 'master':
bpo-30696: Fix the REPL looping endlessly when no memory (GH-4160)
e0582a3

[xdegaye]

New changeset ea5b545 by xdegaye in branch '3.6':
[3.6] bpo-30696: Fix the REPL looping endlessly when no memory (GH-4160). (bpo-4379)
ea5b545

[vstinner]

Thanks for fixing this very old bug!

What about Python 2.7?

[xdegaye]

What about Python 2.7?

_testcapi.set_nomemory() does not exist on Pyhton 2.7 so the changes cannot be tested. Applying the changes to PyRun_InteractiveLoopFlags() in 2.7 looks rather straightforward but there are too many differences in PyRun_InteractiveOneFlags() between 2.7 and 3.7.

[xdegaye]

Also the existing test coverage of these functions in all the Python versions is very weak.

[vstinner]

Ok, I understand, thanks for the explanation.