linux-kernel - Re: [PATCH v2 4/8] selftests/mm: Add -Wunused family of flags

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8e9d7c59-46b4-4e1b-8a55-1898302f5080@collabora.com>
Date: Thu, 21 Aug 2025 11:28:59 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Kevin Brodsky <kevin.brodsky@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 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>,
 Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
 Peter Xu <peterx@...hat.com>, Leon Romanovsky <leon@...nel.org>,
 Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
 Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-riscv@...ts.infradead.org, Shuah Khan <shuah@...nel.org>
Cc: usama.anjum@...labora.com, kernel@...labora.com
Subject: Re: [PATCH v2 4/8] selftests/mm: Add -Wunused family of flags

On 8/18/25 1:16 PM, Kevin Brodsky wrote:
> On 31/07/2025 18:01, Muhammad Usama Anjum wrote:
>> [...]
>>
>> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
>> index 23d4bf6215465..d75f1effcb791 100644
>> --- a/tools/testing/selftests/mm/Makefile
>> +++ b/tools/testing/selftests/mm/Makefile
>> @@ -20,7 +20,6 @@ endif
>>  # thus tricking Make (and you!) into believing that All Is Well, in subsequent
>>  # make invocations:
>>  .DELETE_ON_ERROR:
>> -
>>  # Avoid accidental wrong builds, due to built-in rules working just a little
>>  # bit too well--but not quite as well as required for our situation here.
>>  #
>> @@ -35,6 +34,7 @@ MAKEFLAGS += --no-builtin-rules
>>  
>>  CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
>>  CFLAGS += -Wunreachable-code
>> +CFLAGS += -Wunused  -Wunused-parameter -Wunused-function -Wunused-label -Wunused-variable -Wunused-value
> 
> -Wall implies all of these except -Wunused-parameter (at least according
> to gcc(1)).
I'll remove others in separate patch.

> 
> As to -Wunused-parameter I am frankly not convinced it's worth the
> hassle. We're getting 90 lines changed in patch 6-8 just to mark
> parameters as unused, in other words noise to keep the compiler happy.
> It is not enabled by default in the kernel proper precisely because it
> is so noisy when callbacks are involved.
> 
> Patch 5 is clearly an improvement, but I'd rather take it without
> actually enabling -Wunused-parameter. The rest of this patch isn't that
> useful either IMHO.
Patch 5 removes genuinely unused parameters flagged by the compiler. If we
drop the -Wunused-parameter option, however, new unused parameters will
continue to creep in with future patches. The goal of enabling this warning
is to surface such issues early so developers can address them during
development, rather than later during review or debugging.

Long term, I’d like us to rely more on compiler and static analysis just like
kernel to catch these kinds of problems proactively, instead of waiting until
they’re reported or someone fixes them later. While it may feel like noise
initially, this is largely a one-time cleanup—once done, developers will
simply fix warnings as they arise, keeping the codebase cleaner going forward.

> 
> - Kevin

-- 
---
Thanks,
Usama