linux-kernel - Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

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Date:   Fri, 19 Nov 2021 17:27:17 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ajit Khaparde <ajit.khaparde@...adcom.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
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        Borislav Petkov <bp@...e.de>,
        Corey Minyard <cminyard@...sta.com>, Chris Mason <clm@...com>,
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        David Sterba <dsterba@...e.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Jason Wang <jasowang@...hat.com>,
        Jitendra Bhivare <jitendra.bhivare@...adcom.com>,
        John Hubbard <jhubbard@...dia.com>,
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Subject: Re: [PATCH 00/17] Add memberof(), split some headers, and slightly
 simplify code

On Fri, Nov 19, 2021 at 5:22 PM Alejandro Colomar (man-pages)
<alx.manpages@...il.com> wrote:
> On 11/19/21 17:18, Arnd Bergmann wrote:
> > On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> >> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:
> >
> >>> The main problem with this approach is that as soon as you start
> >>> actually reducing the unneeded indirect includes, you end up with
> >>> countless .c files that no longer build because they are missing a
> >>> direct include for something that was always included somewhere
> >>> deep underneath, so I needed a second set of scripts to add
> >>> direct includes to every .c file.
> >>
> >> Can't it be done with cocci support?
> >
> > There are many ways of doing it, but they all tend to suffer from the
> > problem of identifying which headers are actually needed based on
> > the contents of a file, and also figuring out where to put the extra
> > #include if there are complex #ifdefs.
> >
> > For reference, see below for the naive pattern matching I tried.
> > This is obviously incomplete and partially wrong.
>
> FYI, if you may not know the tool,
> theres include-what-you-use(1) (a.k.a. iwyu(1))[1],
> although it is still not mature,
> and I'm helping improve it a bit.

Yes, I know that one, I tried using it as well, but it did not really
scale to the size of the kernel as it requires having all files to use
the correct set of #include, and to know about all the definitions.

       Arnd