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

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Message-ID: <6e07949b-d86f-46d8-a68c-9717cfb26084@kernel.org>
Date: Fri, 7 Nov 2025 10:27:27 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
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 06.11.25 13:02, Ankit Khushwaha wrote:
> 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, and thanks to Lorenzo for the details.

Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

-- 
Cheers

David