linux-kernel - Re: [PATCH] kbuild: fix make V=1

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Date:	Tue, 12 Feb 2008 11:18:10 -0500
From:	Mike Frysinger <vapier@...too.org>
To:	"Oleg Verych" <olecom@...il.com>
Cc:	"Oleg Verych" <olecom@...wer.upol.cz>,
	"Sam Ravnborg" <sam@...nborg.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] kbuild: fix make V=1

On Tuesday 12 February 2008, Oleg Verych wrote:
> On Feb 12, 2008 4:07 PM, Mike Frysinger <vapier@...too.org> wrote:
> []
>
> > > - quiet_chk_filechk = echo '  CHK     $@'
> > > -silent_chk_filechk = :
> > > - quiet_upd_filechk = echo '  UPD     $@'
> > > -silent_upd_filechk = :
> > > +quiet_chk_filechk = '  CHK     $@'
> > > +quiet_upd_filechk = '  UPD     $@'
> > > +
> > >  define filechk
> > >       $(Q)set -e;                             \
> > > -     $($(quiet)chk_filechk);                 \
> > > +     echo $($(quiet)chk_filechk);            \
> > >       mkdir -p $(dir $@);                     \
> > >       $(filechk_$(1)) < $< > $@...p;          \
> > >       if [ -r $@ ] && cmp -s $@ $@...p; then  \
> > >               rm -f $@...p;                   \
> > >       else                                    \
> > > -             $($(quiet)upd_filechk);         \
> > > +             echo $($(quiet)upd_filechk);    \
> > >               mv -f $@...p $@;                \
> > >       fi
> > >  endef
> >
> > i dont see how yours is more efficient when it always runs echo.
>
> Oh, this? It's like doing syscall for every write to "/dev/null".

how is that relevant ?  there is no /dev/null redirection anywhere here

> > nor does it give the same behavior ... your propposed change will echo
> > blank lines in the silent mode which is incorrect.
>
> At least this will not crash, if you don't have some variable set.
>
> Efficiency there is lesser number of variables(-2 vs +2), that are copied
> for every make job, and are textually parsed and searched.

which is most likely less than executing `echo` everytime instead of ":"

> > it also does not seem to follow the standard convention of other
> > kconfig commands that have quiet/silent prefixes ... such commands do
> > not define arguments to an unknown program/function, nor do they add
> > arbitrary redirection which gets leads to confusion as to final
> > expansion, they define the entire command.
>
> Right. Seems like you are talking about "[quite_]cmd_*", which are
> commands. Here you've invented such rules for ordinary utility in
> `filechk`.

just like every other place in the tree.

> And by try they've failed due to mixing functionality 
> dependency on having arbitrary variable being set.

and by "arbitrary" you mean "like every other kconfig consumer".  sounds 
pretty arbitrary to me.

> Shell syntax tried to avoid this, but `make` syntax and ``convention''
> did a boom. Boom, where hacker's V=1 mode failed itself and failed to
> give a clue about problem (at least, when i saw Sam's message in
> linux-kbuild). Yea, `make` is not needed.

shell syntax is irrelevant.  a bug was introduced and it was fixed.  saying a 
bug existed is poor reasoning to introduce worse code.
-mike

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