[pypy-dev] fdopen(fd, 'w') whe fd is opened 'r'

[Matti Picus]

I tested with win32 2.7.8
The issue addressed in 21191 was that posix.fdopen was not closing fd on 
error. On windows there is no posix module so test_posix.py is skipped 
entirely. While the skipped test was modified in issue 21191 to test 
mode compatibility, posixmodule.c does not actually compare the input fd 
mode (perhaps via a call to fstat(fd, stat)? ) to the requested mode, 
rahter it only verifies that the requested mode itself is a valid mode 
for a call to fdopen.
On windows posix.fdopen is exposed through os.fdopen, which AFAICT is 
only minimally tested outside of test_posix.py.


On 22/02/2015 12:44 AM, Brian Kearns wrote:
> What version of CPython did you compare with? This behavior was 
> added/changed in 2.7.8. CPython has the exact same test and it doesn't 
> seem to be skipped on Windows. Comparing directly with C fdopen does 
> not make sense because os.fdopen isn't just a direct call to fdopen 
> (includes verification of mode, fd, etc).
>
> http://bugs.python.org/issue21191
>
> On Sat, Feb 21, 2015 at 1:58 PM, Matti Picus <matti.picus at gmail.com 
> <mailto:matti.picus at gmail.com>> wrote:
>
>     Looking at this test test_fdopen_keeps_fd_open_on_errors which
>     fails on win32
>     http://buildbot.pypy.org/summary/longrepr?testname=AppTestPosix.%28%29.test_fdopen_keeps_fd_open_on_errors&builder=own-win-x86-32&build=442&mod=module.posix.test.test_posix2
>
>     It also fails when run with python -A, on cpython. It even fails
>     in C when running the code from the MSDN example of fdopen,
>     https://msdn.microsoft.com/en-us/library/dye30d82.aspx
>     if you replace the mode flag "r" with "w", windows will happily
>     repopen a read-only file in write mode.
>
>     The MSDN documentation is quiet on the issue of mode conflict
>     between fd and a call to fdopen, where posix explicitly will
>     return an error
>     http://linux.die.net/man/3/fdopen "The mode of the stream (one of
>     the values "r", "r+", "w", "w+", "a", "a+") must be compatible
>     with the mode of the file descriptor." I could find any google
>     results for complaints about win32's reckless behaviour.
>
>     Two courses of action are possible:
>     - fix the test to reflect current cpython and pypy behaviour on win32
>     - file a bug with cpython and fix our win32 implementation to pass
>     the current test
>
>     Any thoughts?
>     Matti
>
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