linux-kernel - -Wimplicit-fallthrough not working with ccache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 16 Feb 2019 13:21:06 +0200
From:   Kalle Valo <kvalo@...eaurora.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, ath10k@...ts.infradead.org,
        "David S. Miller" <davem@...emloft.net>,
        linux-kbuild@...r.kernel.org
Subject: -Wimplicit-fallthrough not working with ccache

(replying to an old thread but renaming it)

Kalle Valo <kvalo@...eaurora.org> writes:

> "Gustavo A. R. Silva" <gustavo@...eddedor.com> wrote:
>
>> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
>> where we are expecting to fall through.
>> 
>> Notice that in this particular case, I replaced "pass through" with
>> a proper "fall through" comment, which is what GCC is expecting
>> to find.
>> 
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
>
> Patch applied to ath-next branch of ath.git, thanks.
>
> f1d270ae10ff ath10k: htt_tx: mark expected switch fall-throughs

Gustavo, I enabled W=1 on my ath10k build checks and it took me a while
to figure out why GCC was warning about fall through annotations missing
even I knew you had fixed them. Finally I figured out that the reason
was ccache, which I need because I work with different branches and need
to recompile the kernel quite often.

If the plan is to enable -Wimplicit-fallthrough by default in the kernel
IMHO this might become an issue, as otherwise people using ccache start
seeing lots of invalid warnings. Apparently CCACHE_COMMENTS=1 will fix
that but my version of ccache doesn't support it, and how would everyone
learn that trick anyway? Or maybe CCACHE_COMMENTS can enabled through
kernel Makefile?

-- 
Kalle Valo