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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Mon, 14 Sep 2020 23:29:32 +0900
Message-ID: <CAK7LNASDLZ_=b5vM48mBT1SsLY-m5bXWBVBf7FbqJMGtc5XaMw@mail.gmail.com>
Subject: Re: [PATCH] kbuild: Run syncconfig with -s
To:     Alexey Dobriyan <adobriyan@gmail.com>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
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On Mon, Sep 14, 2020 at 10:36 PM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > BTW., there's another, rather spurious bug I recently triggered in kbuild.
> >
> > Occasionally when I Ctrl-C a kernel build on a system with a lot of CPUs,
> > the .o.cmd file gets corrupted:
>
> Those are temporary files, truncated at page boundary.
>
>         $ stat -c %s XXX.pata_sil680.mod.o.cmd
>         12288
>
> I tried to fix this by inserting shell 'trap' directive but it failed
> somewhere else.
>
>         cmd_and_fixdep =                                                     \
>         $(cmd);                                                              \
>         scripts/basic/fixdep $(depfile) $@ '$(make-cmd)' > $(dot-target).cmd;\
>         rm -f $(depfile)


No. It is *OK* to have broken .o.cmd files
as long as .o files are deleted on error or interruption
(and this should be automatically handled by GNU Make).


.o.cmd is included only when the corresponding .o exists.


This is explained in the case [2] of commit
392885ee82d35d515ba2af7b72c5e357c3002113


-- 
Best Regards
Masahiro Yamada