[New-bugs-announce] [issue27764] [Patch] Complete bits necessary for making fcntl's file locking optional

[Ed Schouten]

New submission from Ed Schouten:

Python's fcntl module already provides some support for making support for file locking optional. For example, constants like F_SETFL are only defined if present. Unfortunately, the accompanying functions 'flock()' and 'lockf()' are present unconditionally.

CloudABI, a sandboxed runtime environment for UNIX (https://mail.python.org/pipermail/python-dev/2016-July/145708.html), doesn't implement these ways of doing file locking, for the reason that these operations do not fit nicely within its process model. These locks are per-process; not per-descriptor. This means that processes cannot safely be composed or decomposed.

Attached is a relatively small patch to make flock() and lockf() optional, only compiling them when the necessary APIs are present. The LOCK_* constants are now also defined optionally.

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components: Extension Modules
files: patch-no-flock.txt
messages: 272692
nosy: EdSchouten
priority: normal
severity: normal
status: open
title: [Patch] Complete bits necessary for making fcntl's file locking optional
versions: Python 3.6
Added file: http://bugs.python.org/file44105/patch-no-flock.txt

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27764>
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