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Thu, 8 May 2025 19:21:09 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 019422004B; Thu, 8 May 2025 19:21:09 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 40DA220040; Thu, 8 May 2025 19:21:08 +0000 (GMT) Received: from [127.0.0.1] (unknown [9.152.108.100]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 8 May 2025 19:21:08 +0000 (GMT) Message-ID: <15bf9a71b8185006c8d19a3aefb331a2765629c5.camel@linux.ibm.com> Subject: Re: [PATCH bpf-next] selftests/bpf: Fix "expression result unused" warnings From: Ilya Leoshkevich To: Alexei Starovoitov Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Date: Thu, 08 May 2025 21:21:07 +0200 In-Reply-To: References: <20250508113804.304665-1-iii@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.4 (3.52.4-2.fc40) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=NLnV+16g c=1 sm=1 tr=0 ts=681d042a cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=xKKioOc97a1CM_68BB0A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: _RooUDHxsLioQV17eB3A9zycnEGQ3IWB X-Proofpoint-GUID: NUD7uCAeocPrSy9qYcP7hgktgJ6CHz85 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA4MDE3MCBTYWx0ZWRfX6XonOwNZY0d8 M9GiE4/7r/Vbjqabavn9edb/TZxg34KiQL2UGJybt6AVoTL8JwrcLp61YG40ljZL03Pv7vrEMa4 Cq4HJMQEOTvgdnEfmXJw5r2hdmj7ZZsmq6HzshYtceBRaIaPb2ScTxKFs0E7OwSzUSJo8ioEyq2 OYNxRLrl8802kgv5PcD4cWz6eOY2r6+CBwinZpjC9tMLg6t5pEe68GjsQ8Tj9Z0RyxoUavPt4ny CvPAfbME7g2Embj/Dl2NMKZVBb1MpyIsoy4ma9o1vffEcm3t6ns/oFCrY79DBtHUhkqT3fHnL2G z6XoqlP6ARz0/NFOCslx9ZYMikO0YY2+ZJUyW82EMxPG9/IjyNmcR6clMQto0VeH5gcxkoea2YJ l3dd4AfUOSUQroQpzzbY5856054GB0M0OyHAfwT5U2V+Q7tZ5wUt7Q60JFYXVYN78lceGnlG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-08_06,2025-05-08_02,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 suspectscore=0 mlxlogscore=856 phishscore=0 mlxscore=0 impostorscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 malwarescore=0 priorityscore=1501 adultscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505080170 On Thu, 2025-05-08 at 11:38 -0700, Alexei Starovoitov wrote: > On Thu, May 8, 2025 at 4:38=E2=80=AFAM Ilya Leoshkevich > wrote: > >=20 > > clang-21 complains about unused expressions in a few progs. > > Fix by explicitly casting the respective expressions to void. >=20 > ... > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (val & _Q_LOCKED_MASK) > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 smp_cond_load_acquire_label(&lock->locked, !VAL, > > release_err); > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 (void)smp_cond_load_acquire_label(&lock->locked, > > !VAL, release_err); >=20 > Hmm. I'm on clang-21 too and I don't see them. > What warnings do you see ? In file included from progs/arena_spin_lock.c:7: progs/bpf_arena_spin_lock.h:305:1756: error: expression result unused [-Werror,-Wunused-value] 305 | ({ typeof(_Generic((*&lock->locked), char: (char)0, unsigned char : (unsigned char)0, signed char : (signed char)0, unsigned short : (unsigned short)0, signed short : (signed short)0, unsigned int : (unsigned int)0, signed int : (signed int)0, unsigned long : (unsigned long)0, signed long : (signed long)0, unsigned long long : (unsigned long long)0, signed long long : (signed long long)0, default: (typeof(*&lock->locked))0)) __val =3D ({ typeof(&lock->locked) __ptr =3D (&lock->locked); typeof(_Generic((*(&lock->locked)), char: (char)0, unsigned char : (unsigned char)0, signed char : (signed char)0, unsigned short : (unsigned short)0, signed short : (signed short)0, unsigned int : (unsigned int)0, signed int : (signed int)0, unsigned long : (unsigned long)0, signed long : (signed long)0, unsigned long long : (unsigned long long)0, signed long long : (signed long long)0, default: (typeof(*(&lock->locked)))0)) VAL; for (;;) { VAL =3D (typeof(_Generic((*(&lock->locked)), char: (char)0, unsigned char : (unsigned char)0, signed char : (signed char)0, unsigned short : (unsigned short)0, signed short : (signed short)0, unsigned int : (unsigned int)0, signed int : (signed int)0, unsigned long : (unsigned long)0, signed long : (signed long)0, unsigned long long : (unsigned long long)0, signed long long : (signed long long)0, default: (typeof(*(&lock->locked)))0)))(*(volatile typeof(*__ptr) *)&(*__ptr)); if (!VAL) break; ({ __label__ l_break, l_continue; asm volatile goto("may_goto %l[l_break]" :::: l_break); goto l_continue; l_break: goto release_err; l_continue:; }); ({}); } (typeof(*(&lock- >locked)))VAL; }); ({ ({ if (!CONFIG_X86_64) ({ unsigned long __val; __sync_fetch_and_add(&__val, 0); }); else asm volatile("" ::: "memory"); }); }); (typeof(*(&lock->locked)))__val; }); | =20 ^ ~~~~~ 1 error generated. It started today. Here is the full compiler version: $ clang-21 --version Debian clang version 21.0.0 (++20250501112544+75d1cceb9486- 1~exp1~20250501112558.1422) Target: s390x-unknown-linux-gnu Thread model: posix InstalledDir: /usr/lib/llvm-21/bin Best regards, Ilya