[New-bugs-announce] [issue33773] test.support.fd_count(): off-by-one error when listing /proc/self/fd/

[STINNER Victor]

New submission from STINNER Victor <vstinner at redhat.com>:

test.support.fd_count() has two implementation: list /proc/self/fd/ on Linux and FreeBSD, or check all file descriptors from 0 and MAXFD. The problem is that the two implementation don't give the same result...

List /proc/self/fd/ (used by default on Linux):

vstinner at apu$ ./python -c 'from test.support import fd_count; print(fd_count())'
4

Check all FD (I modified fd_count() to force using this implementation):

vstinner at apu$ ./python -c 'from test.support import fd_count; print(fd_count())'
3

On Linux and FreeBSD, listdir() opens internally a file descriptor to list the content of the /proc/self/fd/ directory. So the function should substract one to the result.

Attached PR fixes the issue.

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components: Tests
messages: 318734
nosy: pitrou, vstinner
priority: normal
severity: normal
status: open
versions: Python 2.7, Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33773>
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