From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v2 5/5] bug: Make BUG() call unreachable()
Date: Wed, 26 Feb 2014 14:29:06 +0100
Message-ID: <201402261429.06553.arnd@arndb.de>
References: <469b5dc113cb468232291527642f8dc47663e945.1393385236.git.josh@joshtriplett.org> <d97712e037ea4c90e9cb30c56229383d257831de.1393385236.git.josh@joshtriplett.org>
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Sender: linux-kernel-owner@vger.kernel.org
To: Josh Triplett <josh@joshtriplett.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
List-Id: linux-arch.vger.kernel.org

On Wednesday 26 February 2014, Josh Triplett wrote:
> @@ -134,7 +134,7 @@ extern void warn_slowpath_null(const char *file, const int line);
>  
>  #else /* !CONFIG_BUG */
>  #ifndef HAVE_ARCH_BUG
> -#define BUG() do {} while (0)
> +#define BUG() do { unreachable(); } while (0)
>  #endif

I disagree with this one. As Alan said, we really want to use an
arch specific BUG() even in the !CONFIG_BUG case.

For the cases where this is not yet possible, I'd suggest using

#define BUG() do { } while (1)


For older gcc versions, this is actually the same as unreachable(), but
it is not the same as __builtin_unreachable, because it causes undefined
behavior.

	Arnd