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bh=QOafkmI4WwW6vHAc2vij2yjllG5wUGAf6FA3kgdg+mg=; b=aSrZKHjSpQvWspcgzUltaJaQE99halbS2OoIFVdlIge1Bht0eyZo3Cj7FrkXyzciA4yo5k W+22uBYrSlxXXxJgy61mDhool5IFAGCV7j6MNK4rq0g527oPVF2o5Hj92pFZ98rKpKNhiA DMWeAuFxlOxTMaPdo1TM/q/FuTbVnpM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-496-20v6a3FzNP6jvaIp8L8jwQ-1; Mon, 15 Mar 2021 11:58:09 -0400 X-MC-Unique: 20v6a3FzNP6jvaIp8L8jwQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7C49419200C0; Mon, 15 Mar 2021 15:58:08 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-72.ams2.redhat.com [10.36.112.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id 39DBE5D745; Mon, 15 Mar 2021 15:58:06 +0000 (UTC) Subject: Re: compile warning in i8259.c To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Christian Borntraeger , qemu-devel@nongnu.org, qemu-s390x References: <75aed565-c9a6-6ee1-ab92-d2771df83ff0@redhat.com> From: Thomas Huth Message-ID: Date: Mon, 15 Mar 2021 16:58:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.25, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 15/03/2021 16.50, Philippe Mathieu-Daudé wrote: > On 3/15/21 4:42 PM, Thomas Huth wrote: >> On 15/03/2021 16.14, Christian Borntraeger wrote: >>> For some time now I do see the following, when I compile x86-softmmu >>> on s390: >>> >>> FAILED: libcommon.fa.p/hw_intc_i8259.c.o >>> cc -Ilibcommon.fa.p -I. -I.. -Iqapi -Itrace -Iui -Iui/shader >>> -I/usr/include/capstone -I/usr/include/glib-2.0 >>> -I/usr/lib64/glib-2.0/include -I/usr/include/libmount >>> -I/usr/include/blkid -I/usr/include/gio-unix-2.0 >>> -I/usr/include/libusb-1.0 -I/usr/include/vte-2.91 >>> -I/usr/include/pango-1.0 -I/usr/include/harfbuzz >>> -I/usr/include/freetype2 -I/usr/include/libpng16 >>> -I/usr/include/fribidi -I/usr/include/libxml2 -I/usr/include/cairo >>> -I/usr/include/pixman-1 -I/usr/include/gtk-3.0 >>> -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/atk-1.0 >>> -I/usr/include/at-spi2-atk/2.0 -I/usr/include/dbus-1.0 >>> -I/usr/lib64/dbus-1.0/include -I/usr/include/at-spi-2.0 >>> -I/usr/include/virgl -I/usr/include/p11-kit-1 -I/usr/include/SDL2 >>> -I/usr/include/cacard -I/usr/include/nss3 -I/usr/include/nspr4 >>> -I/usr/include/slirp -fdiagnostics-color=auto -pipe -Wall >>> -Winvalid-pch -Werror -std=gnu99 -O2 -g -isystem >>> /home/cborntra/REPOS/qemu/linux-headers -isystem linux-headers -iquote >>> . -iquote /home/cborntra/REPOS/qemu -iquote >>> /home/cborntra/REPOS/qemu/include -iquote >>> /home/cborntra/REPOS/qemu/disas/libvixl -iquote >>> /home/cborntra/REPOS/qemu/tcg/s390 -iquote >>> /home/cborntra/REPOS/qemu/accel/tcg -pthread -U_FORTIFY_SOURCE >>> -D_FORTIFY_SOURCE=2 -m64 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 >>> -D_LARGEFILE_SOURCE -Wstrict-prototypes -Wredundant-decls -Wundef >>> -Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing -fno-common >>> -fwrapv -Wold-style-declaration -Wold-style-definition -Wtype-limits >>> -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers >>> -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined >>> -Wimplicit-fallthrough=2 -Wno-missing-include-dirs >>> -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIC >>> -DSTRUCT_IOVEC_DEFINED -D_REENTRANT -Wno-undef -D_DEFAULT_SOURCE >>> -D_XOPEN_SOURCE=600 -DNCURSES_WIDECHAR -MD -MQ >>> libcommon.fa.p/hw_intc_i8259.c.o -MF >>> libcommon.fa.p/hw_intc_i8259.c.o.d -o libcommon.fa.p/hw_intc_i8259.c.o >>> -c ../hw/intc/i8259.c >>> ../hw/intc/i8259.c: In function ‘pic_read_irq’: >>> ../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in >>> this function [-Werror=maybe-uninitialized] >>>    203 |         irq = irq2 + 8; >>>        |         ~~~~^~~~~~~~~~ >>> cc1: all warnings being treated as errors >>> >>> Due to other compile warnings I find this hard to bisect. Has anyone >>> seen this as well? >> >> I've never seen this warnings so far... which compiler version is this? >> Looking at the code, it seems to be a false positive to me. > > https://www.mail-archive.com/qemu-devel@nongnu.org/msg599522.html Oh, well, I completely forgot about that one ... but that was with -O3 ... interesting that it now occurs with -O2, too! But even after staring at the code for a while, I cannot see how irq2 may not be initialized here ... so this really rather sounds like a compiler bug to me... anyway, we could simply silence it by pre-initializing the variable to -1 or so? Thomas