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Tue, 16 Nov 2021 12:00:07 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.159]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BF98960C81; Tue, 16 Nov 2021 12:00:06 +0000 (UTC) Date: Tue, 16 Nov 2021 12:00:04 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Maydell Subject: Re: [PATCH] meson: fix botched compile check conversions Message-ID: References: <20211116093834.76615-1-pbonzini@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.697, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Paolo Bonzini , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Nov 16, 2021 at 11:51:16AM +0000, Peter Maydell wrote: > On Tue, 16 Nov 2021 at 09:38, Paolo Bonzini wrote: > > > > Fix a bunch of incorrect conversions from configure to Meson, which result > > in different outcomes with --extra-cflags=-Werror. > > FWIW this still won't give the right answer for the 'struct iovec' > test if you include -Werror via --extra-cflags, because the > generated code trips over an "expression result unused" warning: > > > Running compile: > Working directory: > /mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/arm-clang/meson-private/tmpeiz36t2n > Command line: clang-7 -m64 -mcx16 > /mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/arm-clang/meson-private/tmpeiz36t2n/testfile.c > -o /mnt/nvmedis > k/linaro/qemu-from-laptop/qemu/build/arm-clang/meson-private/tmpeiz36t2n/output.obj > -c -fsanitize=undefined -fno-sanitize=shift-base -Werror -D_FI > LE_OFFSET_BITS=64 -O0 -Werror=implicit-function-declaration > -Werror=unknown-warning-option -Werror=unused-command-line-argument > -Werror=ignored-op > timization-argument -std=gnu11 > > Code: > #include > void bar(void) { > sizeof(struct iovec); > }; > Compiler stdout: > > Compiler stderr: > /mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/arm-clang/meson-private/tmpeiz36t2n/testfile.c:3:13: > error: expression result unused [-Werror,-Wunused-value] > sizeof(struct iovec); > ^~~~~~~~~~~~~~~~~~~~ > 1 error generated. > > Checking for type "struct iovec" : NO > > > But maybe we should just explicitly reject -Werror in --extra-cflags... I wonder if the problem is more fundamental than that. Passing stuff in --extra-cflags is done to influence the flags used to compile the QEMU end user binaries. Unfortunately --extra-cflags is also getting applied to all the meson.build feature checks. IMHO we would get a more reliable result if the meson.build checks were fully isolated from the cflags we used for building everything else, so the checks get a well understood, predictable environment. IIUC, this current behaviour is a result of us adding cflags using add_global_arguments / add_project_arguments. I wonder if we need to exclusively use the 'c_args' parameter to library()/executable() and friends ? The downside is of course would be extra work to make sure we pass c_args in all the right places. 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 :|