New submission from Anthony Zhang:
Summary
---
This shows up as two closely-related issues:
* ``aifc.open`` leaks file object when invalid AIFF file encountered. This is
probably a bug.
* ``aifc.close`` closes file object even when it didn't open the file object to
begin with. While this is technically documented behaviour [1], it's
inconsistent with how similar modules like ``wave`` work [2].
I have confirmed the issue is present in all the selected Python versions.
Steps to reproduce
--
For the first issue, run this code:
#!/usr/bin/env python3
# to simplify this example, use this script itself as a random non-AIFF
file (though any non-AIFF file will work fine)
FILE = __file__
# print warnings on stderr
import warnings
warnings.resetwarnings()
# try to open the non-AIFF file as an AIFF file, which should fail, but
shouldn't give any ResourceWarnings
import aifc
try: aifc.open(FILE, "rb")
except: pass
For the second issue, run this code:
#!/usr/bin/env python3
from os import path
FILE = path.expanduser("~/cpython/Lib/test/audiodata/pluck-pcm8.aiff")
# open the file as a file-like object, then open it again with ``aifc.open``
import aifc
with open(FILE, "rb") as f:
assert not f.closed, "Before opening with AIFC"
with aifc.open(f, "rb"):
pass
assert not f.closed, "After opening with AIFC"
Expected result
---
For the first code sample, code should give no output - ``aifc.open`` should
throw an exception due to the passed filename being an invalid AIFF file, but
that exception should be caught and suppressed. by the ``try``/``except``
statements.
For the second code sample, all assertions should pass - the file should be
opened with ``open``, "opened" again with ``aifc.open``, and should not be
closed when the inner context manager exits.
Actual result
-
For the first code sample:
$ python3 test.py
/home/anthony/Desktop/test.py:13: ResourceWarning: unclosed file
<_io.BufferedReader name='/home/anthony/Desktop/test.py'>
except: pass
In other words, code executes as described in "Expected result", but also
prints a warning to stderr about the file object not being closed.
For the second code sample:
$ python3 "/home/anthony/Desktop/test.py"
Traceback (most recent call last):
File "/home/anthony/Desktop/test.py", line 11, in
assert not f.closed, "After opening with AIFC"
AssertionError: After opening with AIFC
In other words, code runs normally until the inner context manager exits, and
the file object gets closed, even though the file object wasn't opened by
``aifc``.
Solution
Attached are patches that fix each issue separately - the first patch fixes the
first mentioned issue, while the second patch fixes both at once.
Backwards compatibility:
* The first patch, "fix_aifc_leak.patch", makes no functionality changes, so
there shouldn't be any backwards compatibility concerns.
* The second patch, "fix_aifc_leak_and_file_object_close.patch", slightly
changes the behaviour of `aifc_instance.close()` so that it closes in only a
subset of cases it would originally. While it is possible for this to lead to
leaks in certain cases (example below), the impact shoul be low, as existing
codebases seem to use context managers and similar constructs that clean
everything up properly.
#!/usr/bin/env python3
from os import path
FILE = path.expanduser("~/cpython/Lib/test/audiodata/pluck-pcm8.aiff")
import aifc
f = open(FILE, "rb")
with aifc.open(f, "rb"):
pass
# with the patch applied, `f` is not closed at this point anymore
[1]: https://docs.python.org/3/library/aifc.html#aifc.aifc.close
[2]: https://docs.python.org/3/library/wave.html#wave.Wave_read.close
--
components: Library (Lib)
files: fix_aifc_leak.patch
keywords: patch
messages: 284299
nosy: azhang
priority: normal
severity: normal
status: open
title: [patch] Fix file object leak in `aifc.open` when given invalid AIFF file.
type: behavior
versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7
Added file: http://bugs.python.org/file46087/fix_aifc_leak.patch
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<http://bugs.python.org/issue29110>
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