test_regrtest leaves a test_python_* directory in TEMPDIR

[xdegaye]

BPO	32252
Nosy	@vstinner, @xdegaye
PRs	bpo-32252: Fix faulthandler_suppress_crash_report() #4794 [3.6] bpo-32252: Fix faulthandler_suppress_crash_report() (GH-4794) #4795

^{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 2019-06-21.09:38:28.575>
created_at = <Date 2017-12-08.08:49:13.334>
labels = ['3.7', 'type-bug', 'tests']
title = 'test_regrtest  leaves a test_python_* directory in TEMPDIR'
updated_at = <Date 2019-06-21.09:38:28.570>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2019-06-21.09:38:28.570>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-06-21.09:38:28.575>
closer = 'vstinner'
components = ['Tests']
creation = <Date 2017-12-08.08:49:13.334>
creator = 'xdegaye'
dependencies = []
files = []
hgrepos = []
issue_num = 32252
keywords = ['patch']
message_count = 14.0
messages = ['307837', '307855', '307885', '307886', '308032', '308033', '308034', '308035', '308036', '308037', '308038', '308039', '308041', '346197']
nosy_count = 2.0
nosy_names = ['vstinner', 'xdegaye']
pr_nums = ['4794', '4795']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32252'
versions = ['Python 3.7']

[xdegaye]

After running test_regrtest in the source tree on linux, the build/ subdirectory (i.e. test.libregrtest.main.TEMPDIR) contains a new test_python_* directory that contains a core file when the core file size is unlimited.

I did not test on 3.6.

[vstinner]

After running test_regrtest in the source tree on linux, the build/ subdirectory (i.e. test.libregrtest.main.TEMPDIR) contains a new test_python_* directory that contains a core file when the core file size is unlimited.

Can you please explain how to reproduce the bug? (Which commands should I type?)

What is your /proc/sys/kernel/core_pattern?

On my Fedora 27, /proc/sys/kernel/core_pattern is "|/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %e".

[xdegaye]

Can you please explain how to reproduce the bug? (Which commands should I type?)

./python -m test test_regrtest

What is your /proc/sys/kernel/core_pattern?

$ cat /proc/sys/kernel/core_pattern
core-%e.%s
$ ulimit -c
unlimited

FWIW on archlinux (my platform) coredumps are handled by systemd and to enable coredumps the file /etc/sysctl.d/50-coredump.conf has to be updated to contain:

kernel.core_pattern=core-%e.%s

[xdegaye]

Oh it seems your Fedora 27 also uses systemd and uses the same configuration as archlinux, see https://wiki.archlinux.org/index.php/Core_dump. In that case according to this wiki your core dumps go to /var/lib/systemd/coredump and this may explain the different behaviors between your system and mine.

My setup (updating the file /etc/sysctl.d/50-coredump.conf) was the documented archlinux practice 4 years ago when systemd used to store the coredumps in log files (very annoying). This setup is still working although it is not documented in this wiki (maybe somewhere else).

FWIW I have kept the notes made when configuring archlinux at that time, they are:

disable core dumps managed by systemd-coredumpctl(1) - see also man pages for sysctl.d and sysctl
/etc/sysctl.d/50-coredump.conf # same file name as in /usr/lib/sysctl.d/
kernel.core_pattern=core-%e.%s
echo "core-%e.%s" > /proc/sys/kernel/core_pattern # or reboot

# per user
ulimit -c unlimited

[vstinner]

I'm unable to reproduce the issue on Fedora 27:

vstinner@apu$ cat /proc/sys/kernel/core_pattern
core-%e.%s
vstinner@apu$ ulimit -c
unlimited
vstinner@apu$ ./python -m test test_regrtest
Run tests sequentially
0:00:00 load avg: 0.70 [1/1] test_regrtest
1 test OK.

Total duration: 14 sec
Tests result: SUCCESS

While core dump works as expected:

vstinner@apu$ ./python
>>> import faulthandler
>>> faulthandler._sigsegv()
Segmentation fault (core dumped)
vstinner@apu$ ls core*
core-python.11.32456

[vstinner]

Ah! I misunderstood the bug report. I was looking for a ENV_FAILED failure, but no, regrtest fails to remove its temporary directory but no warning is emitted in this case.

vstinner@apu$ ls -d build/test_python_; ./python -m test test_regrtest -m test.test_regrtest.ArgsTestCase.test_crashed; ls -d build/test_python_
ls: impossible d'accéder à 'build/test_python_*': No such file or directory

Run tests sequentially
0:00:00 load avg: 0.42 [1/1] test_regrtest
1 test OK.

Total duration: 537 ms
Tests result: SUCCESS

build/test_python_816

So running test_regrtest creates build/test_python_816/ but fails to remove it because it contains a core dump: core-python.11.816.

• No core dump must be written, Python is supposed to disable that
• regrtest must emit a warning if it fails to remove the temporary directory, maybe also fail with an error? (non-zero exit code)

[xdegaye]

What is now the content of the 'build/' subdirectory of the source tree ?

[xdegaye]

Ah! I misunderstood the bug report. I was looking for a ENV_FAILED failure, but no, regrtest fails to remove its temporary directory but no warning is emitted in this case.

Yes :-)

[xdegaye]

So running test_regrtest creates build/test_python_816/ but fails to remove it because it contains a core dump: core-python.11.816.

Not sure that it is because it contains a core file. Maybe it just does not remove it because the test crashed ?

[vstinner]

Maybe it just does not remove it because the test crashed ?

Ah, you're right :-)

[vstinner]

• No core dump must be written, Python is supposed to disable that

My bad. It's an obvious bug that was missed before because regrtest creates a temporary directory to run tests and then remove it.

I wrote the PR 4794 to fix faulthandler.

[vstinner]

New changeset 48d4dd9 by Victor Stinner in branch 'master':
bpo-32252: Fix faulthandler_suppress_crash_report() (bpo-4794)
48d4dd9