Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: Build failures since 5.4-rc3
To:     Joe Perches <joe@perches.com>, LKML <linux-kernel@vger.kernel.org>
References: <2da85bba-ab2a-b993-be1a-c98222819b37@lwfinger.net>
 <44f9a9bde7cf7885a8e55a52260b59240cb9a157.camel@perches.com>
From:   Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <bf0fbe49-65ec-e110-e937-b3b18df126c0@lwfinger.net>
Date:   Tue, 15 Oct 2019 15:27:23 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.1.1
MIME-Version: 1.0
In-Reply-To: <44f9a9bde7cf7885a8e55a52260b59240cb9a157.camel@perches.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/15/19 2:32 PM, Joe Perches wrote:
> 
> Hey Larry.
> 
> 
> Looks like this should be:
> 
> #define FALL_THROUGH __attribute__((__fallthrough__))
> 
> and there appear to be many of these #defines that
> use __attribute__((foo)) where foo does not use the
> double underscored prefix and suffix form
> 
> I also downloaded and trivially attempted to build vbox
> without success, but I don't find this #define anywhere
> in the sources.  Clues?
> 
> $ git clone git://github.com/mirror/vbox.git
> $ cd vbox
> 
> $ git grep FALL_THROUGH
> $
> 
> $ ./configure
> Checking for environment: Determined build machine: linux.amd64, target machine: linux.amd64, OK.
> Checking for kBuild:
>    ** kmk (variable KBUILDDIR) not found!
> Check /home/joe/vbox/configure.log for details
> 
> 
> $ cat configure.log
> # Log file generated by
> #
> #   './configure '
> #
> 
> ***** Checking environment *****
> Determined build machine: linux.amd64, target machine: linux.amd64
> 
> 
> ***** Checking kBuild *****
> ** kmk (variable KBUILDDIR) not found!
> 
> $

I am the maintainer of VirtualBox for openSUSE, and it is their version that has 
the problem.

The original code had the following macro definitions:

# define RT_FALL_THROUGH()      __attribute__((fallthrough))
#define RT_FALL_THRU()          RT_FALL_THROUGH()

The code uses both forms interchangeably. That failed - I think the () fooled 
the compiler.

I replaced those with

#define FALL_THROUGH          __attribute__((__fallthrough__))
#define RT_FALL_THRU()          FALL_THROUGH
#define RT_FALL_THROUGH()       FALL_THROUGH

My initial try was without the underscores around fallthrough, which caused a 
conflict with the one in your changes. Putting them back resulted in code that 
builds fine. Thanks for the help.

Larry