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Message-ID: <1465307382.13979.78.camel@linuxfoundation.org>
From: Richard Purdie <richard.purdie@linuxfoundation.org>
To: Mike Looijmans <mike.looijmans@topic.nl>,
	openembedded-devel@lists.openembedded.org
Date: Tue, 07 Jun 2016 14:49:42 +0100
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Subject: Re: [PATCH 1/3] gitkpkgv: Ensure files are closed
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On Tue, 2016-06-07 at 11:02 +0200, Mike Looijmans wrote:
> Looks like regression in Python itself?
> 
> In both Python 2 and 3, the file is closed properly if the file
> object is not 
> being stored:
> 
>  >>> import os
>  >>> os.listdir('/proc/self/fd')
> ['0', '1', '2', '3']
>  >>> l=open('/proc/self/stat').readline()
>  >>> os.listdir('/proc/self/fd')
> ['0', '1', '2', '3']
>  >>> f=open('/proc/self/stat')
>  >>> os.listdir('/proc/self/fd')
> ['0', '1', '2', '3', '4']
>  >>>
> 
> 
> (file descriptor "3" is the one being used to read the /proc/self/fd 
> directory, "4" is the one used for reading the stat file)
> 
> The "with" construction should not be needed here. Something else is
> causing 
> this (e.g. nested function definition or exception handler?).

$ python2 -Wdefault -c "open('/bin/bash')"
$ python3 -Wdefault -c "open('/bin/bash')"
-c:1: ResourceWarning: unclosed file <_io.TextIOWrapper name='/bin/bash' mode='r' encoding='UTF-8'>

Admittedly its not an out the box warning but it is one that seems to
be enabled under bitbake. Details in:

https://bugs.python.org/issue10093

but the gist of the issue is that relying on the garbage collector to
close files is a cpython'ism and other implementations of python may
not do this.

So whilst "with" might not be strictly required, it is recommended.

Cheers,

Richard