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	Wed, 01 Apr 2026 20:22:31 +0000
Date: Wed, 1 Apr 2026 21:22:30 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: chriscli@google.com, linux-sparse@vger.kernel.org,
	dan.carpenter@linaro.org, ben.dooks@codethink.co.uk,
	rf@opensource.cirrus.com, Eric Zhang <zxh@xh-zhang.com>
Subject: Re: [RFC PATCH] pre-process: add __VA_OPT__ support
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Wed, Apr 01, 2026 at 08:52:52PM +0100, Al Viro wrote:

> Something like delta below ought to take care of __builtin_strcmp(); figuring
> out the things like "ab"[1] being equal to 'b' is something I'd rather
> leave for later - at the very least after I resurrect and repost the
> busy-wait in shrink_dcache_parent() patchset.  I've really spent way
> too much of the last couple of months on digging in sparse ;-/

BTW, gcc doesn't accept a trick allowed by clang (as well as by sparse with
this patch):

#define splat() ({	\
	_Static_assert(__builtin_strcmp(__func__, "foo") == 0, \
		       "use only in foo()");	\
	something();	\
})

gcc does not realize that __func__ is a constant array with known contents.
Oh, well...