linux-kernel - Re: [PATCH] selftest/mm: fix pointer comparison in mremap

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Message-ID: <aQyOZ6eYng-IjxS_@fedora>
Date: Thu, 6 Nov 2025 17:32:47 +0530
From: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Shuah Khan <shuah@...nel.org>,
	linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftest/mm: fix pointer comparison in mremap_test

On Thu, Nov 06, 2025 at 12:18:57PM +0100, David Hildenbrand (Red Hat) wrote:
> On 06.11.25 11:49, Ankit Khushwaha wrote:
> > Pointer arthemitic with 'void * addr' and 'unsigned long long dest_alignment'
> > triggers following warning:
> > 
> > mremap_test.c:1035:31: warning: pointer comparison always evaluates to
> > false [-Wtautological-compare]
> >   1035 |                 if (addr + c.dest_alignment < addr) {
> >        |                                             ^
> > 
> > typecasting 'addr' to 'unsigned long long' to fix pointer comparison.
> 
> With which compiler are you seeing this?

Hi David,

clang version 20.1.8 (Fedora 20.1.8-4.fc42) raised this warning.

To reproduce:
	make -C tools/testing/selftests/mm CC=clang

Thanks,
-- 
Ankit