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Message-ID: <20090911205915.GA19494@bombadil.infradead.org>
Date: Fri, 11 Sep 2009 16:59:15 -0400
From: Kyle McMartin <kyle@...artin.ca>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Roland McGrath <roland@...hat.com>, 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 Fri, Sep 11, 2009 at 01:45:28PM -0700, Andrew Morton wrote:
> 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?
If the crap for determining if it's a RH gcc is removed, then it becomes
really straightforward... Should probably just do that and then apply a
patch to Fedora if it's so damned important it can't just wait for the
next GCC release.
regards, Kyle
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