test_resource fails when file size is limited

[nnorwitz]

BPO	678264
Nosy	@loewis, @giampaolo, @devdanzin, @bitdancer, @wiggin15

^{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 2003-01-31.18:06:24.000>
labels = ['type-bug', 'tests', '3.9', '3.10', '3.11']
title = 'test_resource fails when file size is limited'
updated_at = <Date 2021-12-17.00:35:56.774>
user = 'https://bugs.python.org/nnorwitz'

bugs.python.org fields:

activity = <Date 2021-12-17.00:35:56.774>
actor = 'ajaksu2'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Tests']
creation = <Date 2003-01-31.18:06:24.000>
creator = 'nnorwitz'
dependencies = []
files = []
hgrepos = []
issue_num = 678264
keywords = []
message_count = 18.0
messages = ['14342', '14343', '14344', '14345', '14346', '14347', '81850', '114216', '116449', '116479', '116520', '117049', '117051', '117122', '117130', '221696', '227778', '251772']
nosy_count = 8.0
nosy_names = ['loewis', 'nnorwitz', 'mdr0', 'sable', 'giampaolo.rodola', 'ajaksu2', 'r.david.murray', 'wiggin15']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue678264'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Linked PRs

• gh-37883: Fix test_resource failures with file size limits #140872
• gh-37883: Fix test_resource.test_fsize_ismax for systems with limited… #141704
• gh-37883: Safely skip test_resource file size tests when limits are strict #145579

[nnorwitz]

test_resource does:

print resource.RLIM_INFINITY == max

I'm not sure of the benefit of this line. For machines
which have limited file sizes, it causes the test to fail.
Otherwise the test seems to work properly.

[nnorwitz]

Logged In: YES
user_id=33168

Martin, welcome back! Now I get to assign some bugs to you
to see if you have any input. :-)

[loewis]

Logged In: YES
user_id=21627

The rationale of the line is explained in the comment: The
code tests whether the limit is a really large number, i.e.
whether represenation of large limits works.

Unfortunately, it doesn't (which is a separate issue): On
Linux, RLIM_INFINITY is reported as -1. This comes from
RLIM_INFINITY being the larges unsigned long long number,
i.e. 0xffffffffffffffffuLL. The resource module represents
this incorrectly.

I think there is no way to verify that Python computes the
real limit correctly (unless we invoke the shell's ulimit
for comparison). So you could weaken the test to verify that
the limit is non-negative (and, as a side effect, verify
that it doesn't raise an exception).

If you do so, you'll also have to fix the implementation, so
that the weakened-strengthened test passes on Linux.

[nnorwitz]

Logged In: YES
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Hmmm, sounds like a lot of work. How about something like this:

    expected_max = resource.RLIM_INFINITY
    if expected_max != max:
        # read the file resource limit
        fsize_ulimit = os.popen('ulimit -f').read()
        try:
            # convert the file size to bytes (from 512 byte
blocks)
            expected_max = int(fsize_ulimit.strip()) * 512
        except ValueError:
            raise TestSkipped, "unable to determine expected
resource value"
    print expected_max == max

This works, but I'm pretty sure this is not portable. On
Linux blocks are 1k. This only works when the block size is
512 bytes. Shall we close this bug as a test environment
problem and won't fix?

[loewis]

Logged In: YES
user_id=21627

I'm really not that much concerned about fixing the test,
but more about fixing the code itself.

[mdr0]

Logged In: YES
user_id=994239

I'm running into this problem under AIX 4.3.3 and 5.1. Is
this going to cause a problem if I put python into
production, or is it "safe" to ignore it?

[devdanzin]

Is this still a problem?