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Thu, 15 Aug 2024 07:05:31 -0400 X-MC-Unique: e2hN7Z13Pu-XyTKFdIjgMA-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BA7311956048; Thu, 15 Aug 2024 11:05:29 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.137]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 723D71955DC6; Thu, 15 Aug 2024 11:05:22 +0000 (UTC) Date: Thu, 15 Aug 2024 12:05:18 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Maydell Cc: Pierrick Bouvier , qemu-devel@nongnu.org, Beraldo Leal , David Hildenbrand , Thomas Huth , Marcelo Tosatti , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini , kvm@vger.kernel.org, Wainer dos Santos Moschetta , qemu-s390x@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Richard Henderson , Alex =?utf-8?Q?Benn=C3=A9e?= , Ilya Leoshkevich Subject: Re: [PATCH v2 1/4] meson: hide tsan related warnings Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20240814224132.897098-1-pierrick.bouvier@linaro.org> <20240814224132.897098-2-pierrick.bouvier@linaro.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On Thu, Aug 15, 2024 at 11:12:39AM +0100, Peter Maydell wrote: > On Wed, 14 Aug 2024 at 23:42, Pierrick Bouvier > wrote: > > > > When building with gcc-12 -fsanitize=thread, gcc reports some > > constructions not supported with tsan. > > Found on debian stable. > > > > qemu/include/qemu/atomic.h:36:52: error: ‘atomic_thread_fence’ is not supported with ‘-fsanitize=thread’ [-Werror=tsan] > > 36 | #define smp_mb() ({ barrier(); __atomic_thread_fence(__ATOMIC_SEQ_CST); }) > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > Signed-off-by: Pierrick Bouvier > > --- > > meson.build | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/meson.build b/meson.build > > index 81ecd4bae7c..52e5aa95cc0 100644 > > --- a/meson.build > > +++ b/meson.build > > @@ -499,7 +499,15 @@ if get_option('tsan') > > prefix: '#include ') > > error('Cannot enable TSAN due to missing fiber annotation interface') > > endif > > - qemu_cflags = ['-fsanitize=thread'] + qemu_cflags > > + tsan_warn_suppress = [] > > + # gcc (>=11) will report constructions not supported by tsan: > > + # "error: ‘atomic_thread_fence’ is not supported with ‘-fsanitize=thread’" > > + # https://gcc.gnu.org/gcc-11/changes.html > > + # However, clang does not support this warning and this triggers an error. > > + if cc.has_argument('-Wno-tsan') > > + tsan_warn_suppress = ['-Wno-tsan'] > > + endif > > That last part sounds like a clang bug -- -Wno-foo is supposed > to not be an error on compilers that don't implement -Wfoo for > any value of foo (unless some other warning/error would also > be emitted). -Wno-foo isn't an error, but it is a warning... which we then turn into an error due to -Werror, unless we pass -Wno-unknown-warning-option to clang. > At any rate, that's how gcc does it > (see the paragraph "When an unrecognized warning option ..." > in https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html ) > and I thought clang did too... > > thanks > -- PMM > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|