linux-kernel - RE: [PATCH] fixdep: use fflush() and ferror() to ensure successful write to files

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Message-ID: <1b44951e776b4f4d9a5b786f2ba896d4@AcuMS.aculab.com>
Date:   Tue, 22 Feb 2022 09:09:38 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Masahiro Yamada' <masahiroy@...nel.org>
CC:     "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: RE: [PATCH] fixdep: use fflush() and ferror() to ensure successful
 write to files

From: Masahiro Yamada <masahiroy@...nel.org>
> Sent: 22 February 2022 03:44
> 
> On Tue, Feb 22, 2022 at 7:33 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > From: Masahiro Yamada
> > > Sent: 21 February 2022 16:43
> > > To: linux-kbuild@...r.kernel.org
> > >
> > > Checking the return value of (v)printf does not ensure the successful
> > > write to the .cmd file.
> > >
> > > Call fflush() and ferror() to make sure that everything has been
> > > written to the file.
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> >
> > Reviewed-by: David Laight <dvid.laight@...lab.com>
> >
> > I'll note that you've lost the perror("fixdep").
> > But I suspect that isn't very meaningful.
> > If the disk is full it'd probably get lost anyway.
> 
> 
> perror() will go to stderr, i.e. tty here.
> So, that is not the issue.
> 
> ferror() itself does not set errno here; "man ferror" says,
> "These  functions  should  not  fail  and  do  not set the external
> variable errno"
> 
> So, I dropped perror() because I am not sure if any related error
> message is printed here.
> 
> Perhaps, errno was set by some of preceding printf() calls,
> but I am not quite sure if it is carried all the way to the end
> of this program.

I was thinking or a slightly more descriptive error message :-)

	David

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