linux-kernel - Re: [PATCH next] minmax.h: Use auto for variables in __minmax

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Message-Id: <20260207182559.2223b2ab166877e80714449f@linux-foundation.org>
Date: Sat, 7 Feb 2026 18:25:59 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Laight <david.laight.linux@...il.com>
Cc: Peter Anvin <hpa@...or.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, Arnd Bergmann <arnd@...nel.org>,
 Christoph Hellwig <hch@...radead.org>, "Jason A . Donenfeld"
 <Jason@...c4.com>, Herve Codina <herve.codina@...tlin.com>, Linus Torvalds
 <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] minmax.h: Use auto for variables in
 __minmax_array()

On Sat, 7 Feb 2026 10:25:51 +0000 David Laight <david.laight.linux@...il.com> wrote:

> On Fri, 6 Feb 2026 14:41:35 -0800
> Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > On Fri,  6 Feb 2026 22:25:54 +0000 david.laight.linux@...il.com wrote:
> > 
> > > From: David Laight <david.laight.linux@...il.com>
> > > 
> > > While 'auto __element = _array[--__len]' should remove 'const',
> > > gcc prior to version 11 are buggy and retain it.  
> > 
> > With what effect?
> 
> If you have:
> int f(const int x)
> {
> 	auto y = x;
> 	y++;
> 	return y;
> }
> gcc prior to 11.0 error that y is const.
> So in this case the loop can't change __element.

Still not undersanding, sorry.  Does this patch fix a build issue with
any compiler/kernel combination?

> > I'm not understanding the motivation for this change.  Is there some
> > compilation issue to be addressed?
> 
> Mainly unqual_scalar_typeof() being horrid.
> There is an ongoing long thread about its use in the arm64 LTO READ_ONCE().
> Newer compilers do have a builtin, and there are some shorter alternatives
> that work in some places.
> But here is just isn't needed.
> So one less place to check.

OK, so it's a cleanup.

> I did mean to copy the main contributers to that thread, but forgot.

I think a v2 would be good please, to clarify the effects of and
motivation for the change.