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

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Message-ID: <8499950a0802120749r33323a15k7cde80862ae26c3d@mail.gmail.com>
Date:	Tue, 12 Feb 2008 16:49:16 +0100
From:	"Oleg Verych" <olecom@...il.com>
To:	"Mike Frysinger" <vapier@...too.org>
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 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".

> 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.

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

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.

> what Sam posted (and what was merged) makes sense to me.
> -mike
> 
-- 
-o--=O`C
 #oo'L O
<___=E M
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