linux-kernel - Re: [PATCH 1/2] UNREACHABLE() macro

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Date:	Fri, 11 Sep 2009 14:55:25 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
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

> That's a bit of a mouthful.  Did you consider a runtime probe with
> scripts/Kbuild.include's try-run, cc-option, etc?  

I did not see any precedent in the sources for using those to test for
features by compiling particular test sources (i.e. in autoconf style).
I just followed the model I saw.  Those methods seem sufficiently costly
to make it a little questionable to pile on too many more that get
repeated all the time by make, so I just was not opening that can of worms.

As has been mentioned:

	#if __GNUC_MINOR__ > 4

is a sufficient test for the long run.  People using Fedora gcc-4.4 will
not mind applying a trivial kernel patch to get the benefits sooner.

Thanks,
Roland
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