linux-kernel - Re: [PATCH 5/7] kbuild: get rid of duplication in *.mod files

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Date:   Fri, 8 Apr 2022 13:42:50 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>
Subject: Re: [PATCH 5/7] kbuild: get rid of duplication in *.mod files

On Thu, Apr 7, 2022 at 5:08 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Fri, Apr 8, 2022 at 2:55 AM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
> >
> > On Wed, Apr 6, 2022 at 8:31 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> > >
> > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > index 6ae92d119dfa..f7a30f378e20 100644
> > > --- a/scripts/Makefile.build
> > > +++ b/scripts/Makefile.build
> > > @@ -303,7 +303,8 @@ $(obj)/%.prelink.o: $(obj)/%.o FORCE
> > >         $(call if_changed,cc_prelink_modules)
> > >  endif
> > >
> > > -cmd_mod = echo $(addprefix $(obj)/, $(call real-search, $*.o, .o, -objs -y -m)) > $@
> > > +cmd_mod = echo $(addprefix $(obj)/, $(call real-search, $*.o, .o, -objs -y -m)) | \
> > > +       $(AWK) -v RS='( |\n)' '!x[$$0]++' > $@
> >
> > God AWK is unreadable. Any reason we can't use GNU make's sort builtin?
> > https://www.gnu.org/software/make/manual/html_node/Text-Functions.html
>
>
> I did that in the previous submission.
> https://lore.kernel.org/lkml/20220405113359.2880241-8-masahiroy@kernel.org/
>
>
> After some thoughts, I decided to drop duplicates without sorting.
>
> If I alphabetically sorted the object list,
> 7/7 of this series would be impossible.
>
>
> I am not a big fan of AWK, but I do not know a cleaner way.
> If you know a better idea, please tell me.

```
# stable_dedup.py
from sys import argv

wordset = set()
argv.pop(0)
for word in argv: wordset.add(word)
for word in wordset: print(word)
```
If that ever shows up in a profile of a kernel build, <set> in C++
looks pretty similar.  Then that script can be reused in a couple of
other places, and has a more descriptive name that hints at what it
does.

Compare that with `$(AWK) -v RS='( |\n)' '!x[$$0]++'`.
-- 
Thanks,
~Nick Desaulniers