netdev - Re: [PATCH 1/3] treewide: Lift switch variables out of switches

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Date:   Wed, 23 Jan 2019 12:58:29 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Laura Abbott <labbott@...hat.com>,
        Alexander Popov <alex.popov@...ux.com>,
        xen-devel@...ts.xenproject.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        dev@...nvswitch.org, linux-kbuild@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 1/3] treewide: Lift switch variables out of switches

On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> Variables declared in a switch statement before any case statements
> cannot be initialized, so move all instances out of the switches.
> After this, future always-initialized stack variables will work
> and not throw warnings like this:
> 
> fs/fcntl.c: In function ‘send_sigio_to_task’:
> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>    siginfo_t si;
>              ^~

That's a pain, so this means we can't have any new variables in { }
scope except for at the top of a function?

That's going to be a hard thing to keep from happening over time, as
this is valid C :(

greg k-h