linux-kernel - Re: [PATCH v3] kconfig.h: Include compiler types to avoid missed struct attributes

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Message-ID: <66556bf7-3e67-5793-081e-76a01f598374@prevas.dk>
Date:   Thu, 22 Feb 2018 22:07:35 +0100
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Patrick McLean <chutzpah@...too.org>,
        "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] kconfig.h: Include compiler types to avoid missed
 struct attributes

On 2018-02-22 19:04, Linus Torvalds wrote:
> 
> Lookie here (in a fully built tree):
> 
>     find . -name '*.o.cmd' |
>         xargs grep -L linux/compiler_types.h |
>         xargs grep -l linux/kconfig.h |
>         while read i; do
>             j=$(echo $i | sed 's/\.o.cmd$/\.c/' | sed 's:/\.:/:');
>             test -f $j && echo $j;
>         done
> 
> shows that a number of files don't end up depending on that header
> file, even though it's included (that "grep -l linux/kconfig,h"
> triggers on the command itself having that "-include linux/kconfig.h"
> line).
> 
> It looks like "gcc -M" just doesn't list any files that get included
> on the command line with "-include".

It does, both per the documentation and testing it. But fixdep
explicitly removes include/linux/kconfig.h along with
include/generated/autoconf.h and a few others. So when you rebuilt after
adding the #include to kconfig.h, I think nothing actually got built,
and no new .o.cmd files got generated.

Doing a clean build does make include/linux/compiler_{types,gcc}.h and
the various fake include/config/.... they "depend" on appear in e.g.
lib/.clz_tab.o.cmd.

The whole point of fixdep and the include/config hierarchy is to be able
to remove the dependency on autoconf.h, but I'm not sure I understand
why kconfig.h itself is also forcibly removed.

Rasmus