linux-kernel - Re: [PATCH] selftests/net: fix unused return value warnings in ksft.h

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Message-ID: <270488a6-ec6b-4b38-aa30-b5c9e08cdd18@gmail.com>
Date: Wed, 10 Sep 2025 19:16:13 +0800
From: "Nai-Chen(Simone) Cheng" <bleach1827@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
 netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH] selftests/net: fix unused return value warnings in ksft.h

Hi Jakub,

On 2025-09-10 07:25, Jakub Kicinski wrote:
> Sounds good!

I tried the direct void casting approach, but it still generates 
warnings with GCC 14.2.0:
     (void)write(fd, msg, sizeof(msg));
     still shows: warning: ignoring return value of 'write'...

After further researching, I found this appears to be a known GCC/glibc 
issue dating back to 2015 where direct void casting doesn't work for 
functions with __warn_unused_result__. [1] Since this is a long-standing 
toolchain issue and direct void casting won't suppress warning, I think 
you can skip this patch. Thank you!

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425

Best Regards,
Nai-Chen Cheng