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Message-Id: <20090911134528.cd1782d9.akpm@linux-foundation.org>
Date: Fri, 11 Sep 2009 13:45:28 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Roland McGrath <roland@...hat.com>
Cc: torvalds@...ux-foundation.org, jakub@...hat.com,
linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
x86@...nel.org
Subject: Re: [PATCH 1/2] UNREACHABLE() macro
On Wed, 9 Sep 2009 19:00:31 -0700 (PDT)
Roland McGrath <roland@...hat.com> wrote:
> +/*
> + * __builtin_unreachable is available in GCC 4.5+ and
> + * also in Fedora/Red Hat GCC 4.4.1-10+.
> + */
> +#if (__GNUC_MINOR__ > 4 \
> + || (__GNUC_MINOR__ == 4 \
> + && defined __GNUC_RH_RELEASE__ \
> + && (__GNUC_PATCHLEVEL__ > 1 \
> + || (__GNUC_PATCHLEVEL__ == 1 \
> + && __GNUC_RH_RELEASE__ >= 10))))
> +#define UNREACHABLE() __builtin_unreachable()
> +#endif
That's a bit of a mouthful. Did you consider a runtime probe with
scripts/Kbuild.include's try-run, cc-option, etc?
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