namedtuple's exec() throws segmentation fault

[turicas]

BPO	34539
Nosy	@rhettinger, @tirkarthi
Files	namedtuple_bug.py

^{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 2018-09-24.15:50:48.324>
created_at = <Date 2018-08-29.04:20:50.366>
labels = ['3.7', 'library', 'type-crash']
title = "namedtuple's exec() throws segmentation fault"
updated_at = <Date 2018-09-24.15:50:48.322>
user = 'https://bugs.python.org/turicas'

bugs.python.org fields:

activity = <Date 2018-09-24.15:50:48.322>
actor = 'xtreak'
assignee = 'none'
closed = True
closed_date = <Date 2018-09-24.15:50:48.324>
closer = 'xtreak'
components = ['Library (Lib)']
creation = <Date 2018-08-29.04:20:50.366>
creator = 'turicas'
dependencies = []
files = ['47772']
hgrepos = []
issue_num = 34539
keywords = []
message_count = 6.0
messages = ['324300', '324314', '324325', '324357', '324387', '326256']
nosy_count = 3.0
nosy_names = ['rhettinger', 'turicas', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue34539'
versions = ['Python 3.7']

[turicas]

I was working on a library called rows[https://github.com/turicas/rows] when a segmentation fault was thrown in the moment I've tried to read a CSV file. Since this part of the code is implemented completely in Python, I thought it could be a bug in Python itself.
Investigating the code I found it was faulting at exec()'s line inside namedtuple code (Lib/collections/init.py). After some time testing, I've came up with this piece of code to reproduce it:

try:
    float('áxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx')
except:
    from collections import namedtuple
    namedtuple('T', 'f')

The code works if I:

• Run passing PYTHONMALLOC=debug
• Place 'from collections import namedtuple' into the first line
• Remove any char from the string in the 'float(...)' line
• Remove the 'á' from the string in the 'float(...)' line

I've tested the code on Python 3.6.6, 3.7.0, 3.7-dev and 3.8-dev (versions installed using pyenv on a Debian GNU/Linux machine) and the problem happened only in 3.7.0.
This issue seems to be related to https://bugs.python.org/issue34087 but I preferred to create a new one since I don't know if there are automated tests for this specific case.

[rhettinger]

The works for me. Can you try it on a fresh build or install of Python 3.7?

[turicas]

I've cloned the cpython git repository and made fresh builds here:

On v.3.6.6 (4cf1f54) it works:

    $ git checkout v3.6.6 && ./configure && make && ./python --version && ./python namedtuple_bug.py
    [...compilation lines supressed...]
    Python 3.6.6

On the v.3.7.0 (1bf9cc5) it segfaults:

    $ git checkout v3.7.0 && make clean && ./configure && make && ./python --version && ./python namedtuple_bug.py
    [...compilation lines supressed...]
    Python 3.7.0
    Segmentation fault

On the most recent 3.7 branch (65ef742) it works:

    $ git checkout 3.7 && make clean && ./configure && make && ./python --version && ./python namedtuple_bug.py
    [...compilation lines supressed...]
    Python 3.7.0+

On master branch (2c8ddcf) it also works:

    $ git checkout master && make clean && ./configure && make && ./python --version && ./python namedtuple_bug.py
    [...compilation lines supressed...]
    Python 3.8.0a0

Note: I've tried to add a print('works!') at the end of the script, so we can see the result when it does not segfault, but adding this actually make it works on all versions; removing this line has the behaviour reported above.

[rhettinger]

If this is only present in 3.7.0 and not in the current branches, it implies there was an exec() or ceval-loop bug in that release and it has been already fixed.

This bug report may be out-of-date.

[turicas]

Yes, I think it was fixed in https://bugs.python.org/issue34087 (didn't see the commits), I just wanted to report it because I don't know if a test for this specific case is needed (the other bug is not related to namedtuples).

[tirkarthi]

Thanks Álvaro for the report and script. As part of triaging I am closing this as out of date since this bug seemed to have been fixed with bpo-34087 and is not reproducible on latest master and 3.7 branch. Feel free to reopen this if needed.

Thanks again!