[issue12340] Access violation when using the C version of the io module

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


--
resolution:  -> out of date
stage:  -> resolved
status: pending -> closed

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[issue12340] Access violation when using the C version of the io module

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Looks as the crash was fixed in one of previous bugfixes. As for memoryview 
related issue, this is a duplicate of issue20699.

--
nosy: +serhiy.storchaka
status: languishing - pending
superseder:  - Behavior of ZipFile with file-like object and BufferedWriter.

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[issue12340] Access violation when using the C version of the io module

[Christian Heimes]

Christian Heimes added the comment:

The issue hasn't seen an update for over two years. Were you able to solve the 
issue?

--
nosy: +christian.heimes
status: open - languishing

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[issue12340] Access violation when using the C version of the io module

[OscarL]

OscarL added the comment:

I can't reproduce the access violation on Windows, using Python 2.7.3.

Using the test_bufio.py script by santa4nt, I can see that the fail still 
happens.

As Santoso Wijaya (santa4nt) said in a previous comment:

The `write(data)` method is getting a `memoryview` object, thus the test code 
should be using `data.tobytes()` instead of using `bytes(data)`. If we 
introduce that logic on the test_bufio.py script it passes.

The thing is that if we, instead of doing `import io` (the C version of the 
module) we do `import _pyio as io` (the pure Python version) the FAIL does not 
appears at all in the original script!

That difference (`write` might receive a `memoryview` object if using the C 
version of this module) is not documented anywhere.

It should, if that's the expected behavior [*], and the code using the io 
module is responsible for using .tobytes() instead of bytes().

[*] Why _pyio.py behaves differently?

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[issue12340] Access violation when using the C version of the io module

[Santoso Wijaya]

Santoso Wijaya santoso.wij...@gmail.com added the comment:

As for the memory at %p string, when _io.BufferedWriter prepares the byte 
buffer into a PyMemoryView wrapper and passes it into the raw IO object:

res = PyObject_CallMethodObjArgs(self-raw, _PyIO_str_write, memobj, NULL);

For some reason, memobj.__repr__ is called before being passed to the raw IO's 
write method.

I can't reproduce this odd behavior using a dumb raw IO that extends 
_io.RawIOBase. Mimicking what pyserial does, however, reproduces both issues 
(see attached).

--
Added file: http://bugs.python.org/file22379/test_bufio.py

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[issue12340] Access violation when using the C version of the io module

[Santoso Wijaya]

Santoso Wijaya santoso.wij...@gmail.com added the comment:

Note: Removing threading call (lock acquire, release) would remove the crash, 
but still triggers the memory at %p conversion of PyMemoryView.

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[issue12340] Access violation when using the C version of the io module

[Santoso Wijaya]

Changes by Santoso Wijaya santoso.wij...@gmail.com:


Added file: http://bugs.python.org/file22380/test_bufio_nothreading.py

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[issue12340] Access violation when using the C version of the io module

[Santoso Wijaya]

Santoso Wijaya santoso.wij...@gmail.com added the comment:

If `write(self, data)` is expected to receive `data` as a memoryview object, 
then it's up to pyserial to use `data.tobytes()` instead of `bytes(data)`, 
though this does not seem to be documented in the io module doc.

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[issue12340] Access violation when using the C version of the io module

[OscarL]

New submission from OscarL oscar.le...@gmail.com:

This is on Windows XP SP2. Using Python 2.7.1 and 2.7.2.

While executing the unit tests of the PySerial package, version 2.5 
(http://pypi.python.org/pypi/pyserial) one of the tests fails when using the C 
version of the io module (io), but pass if the pure Python version is used 
(_pyio.py).

The specific test case in question is: test_iolib.py. When executed like:

 python test_iolib.py loop://

the test fails with the following traceback:


Traceback (most recent call last):
  File C:\pyserial-2.5\test\test_iolib.py, line 68, in test_hello_raw

self.failUnlessEqual(hello, unicode(hello\n))
AssertionError: u'memory at 0x00C5D940' != u'hello\n'


And Windows shows a crash report dialog, with the following information:


AppName: python.exe  AppVer: 0.0.0.0 ModName: python27.dll
ModVer: 2.7.2150.1013Offset: 00089f57

Exception Information
Code: 0xc005Flags: 0x
Record: 0x  Address: 0x1e089f57


As said above, if in the said test case, instead of import io one does 
import _pyio as io, the crash does not happens, and the test succeeds.

--
components: IO
messages: 138382
nosy: OscarL
priority: normal
severity: normal
status: open
title: Access violation when using the C version of the io module
type: crash
versions: Python 2.7

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[issue12340] Access violation when using the C version of the io module

[R. David Murray]

Changes by R. David Murray rdmur...@bitdance.com:


--
nosy: +pitrou

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[issue12340] Access violation when using the C version of the io module

[Santoso Wijaya]

Santoso Wijaya santoso.wij...@gmail.com added the comment:

Regarding the crash,

From what I can see, the `tp_clear` method of bufferedrwpair is called during 
Py_Finalize() that leads to garbage collection. This NULLs `self-writer` for 
the rwpair object.

Later, in the same garbage collection routine, the `tp_clear` of textio (the 
wrapper) is called. This attempts to finalize its wrapped object by first 
calling the `closed` property of the wrapped object. This property read is 
propagated down to the wrapped bufferedrwpair, `bufferedrwpair_closed_get()`.

At this point, `self-writer` for the bufferedrwpair object is already NULL 
from the previous clear. Hence, the crash happens because a NULL pointer 
dereferencing is attempted.

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[issue12340] Access violation when using the C version of the io module

[Benjamin Peterson]

Benjamin Peterson benja...@python.org added the comment:

Can you produce a self-contained test case?

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nosy: +benjamin.peterson

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