linux-kernel - Re: Build failures since 5.4-rc3

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Message-ID: <bf0fbe49-65ec-e110-e937-b3b18df126c0@lwfinger.net>
Date:   Tue, 15 Oct 2019 15:27:23 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Joe Perches <joe@...ches.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Build failures since 5.4-rc3

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