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Date:   Thu, 30 May 2019 08:54:04 -0600
From:   Jonathan Corbet <corbet@lwn.net>
To:     Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc:     Linux Doc Mailing List <linux-doc@vger.kernel.org>,
        Mauro Carvalho Chehab <mchehab@infradead.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] docs: by default, build docs a lot faster with
 Sphinx >= 1.7
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On Wed, 29 May 2019 22:53:05 -0300
Mauro Carvalho Chehab <mchehab+samsung@kernel.org> wrote:

> > Yup.  The point is that I see the sphinx-build output *in the docs-build
> > output", not when I run it standalone (where it does the expected thing).  
> 
> Weird... could some versions of Sphinx be redirecting the output of
> --version to stderr instead of stdout?
> 
> If so, something like:
> 
> 	perl -e 'open IN,"sphinx-build --version 2>&1 |"; while (<IN>) { if (m/([\d\.]+)/) { print "-jauto\n" if ($1 >= "1.7") } ;} close IN'
> 
> would make it print "-jauto" with those other versions you're trying.

That does improve the behavior from the command line; it seems that
sphinx-build is indeed writing to stderr.  BUT that still doesn't fix the
docs build!  To get the option to take effect, I also have to explicitly
export SPHINXOPTS.  So the winning combination is:

  export SPHINXOPTS = $(shell perl -e 'open IN,"sphinx-build --version
  2>&1 |"; while (<IN>) { if (m/([\d\.]+)/) { print "-jauto" if ($$1 >= "1.7") } ;} close IN')

I don't have any weird version of make, so I'm not sure why you see
different results than I do here.

I can apply those tweaks to your patch if it's OK with you.

> I didn't try the python2 versions, though.

Interestingly, I would appear to have both versions installed, with
python2 winning in $PATH.

jon