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Mon, 24 Oct 2022 08:42:47 -0700 (PDT) X-Google-Smtp-Source: AMsMyM6pokXIVH/8hXZWOWq2dTPuG8dUrLYq3lwfosVDmQAKHhUyxguz9D1idm2xsIJ0Z1hZ7epE2A== X-Received: by 2002:a05:620a:4005:b0:6ee:d836:9ed4 with SMTP id h5-20020a05620a400500b006eed8369ed4mr23377209qko.352.1666626167652; Mon, 24 Oct 2022 08:42:47 -0700 (PDT) Received: from localhost ([31.111.84.238]) by smtp.gmail.com with ESMTPSA id y19-20020a05620a25d300b006ec62032d3dsm184354qko.30.2022.10.24.08.42.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Oct 2022 08:42:47 -0700 (PDT) To: Mike Frysinger Subject: Re: [PATCH 4/5] sim/erc32: avoid dereferencing type-punned pointer warnings In-Reply-To: References: Date: Mon, 24 Oct 2022 16:42:45 +0100 Message-ID: <87tu3t8byi.fsf@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Andrew Burgess via Gdb-patches Reply-To: Andrew Burgess Cc: gdb-patches@sourceware.org Errors-To: gdb-patches-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb-patches" Mike Frysinger writes: > On 12 Oct 2022 13:38, Andrew Burgess via Gdb-patches wrote: >> When building the erc32 simulator I get a few warnings like this: >> >> /tmp/build/sim/../../src/sim/erc32/exec.c:1377:21: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing] >> 1377 | sregs->fs[rd] = *((float32 *) & ddata[0]); >> | ~^~~~~~~~~~~~~~~~~~~~~~~ >> >> The type of '& ddata[0]' will be 'uint32_t *', which is what triggers >> the warning. >> >> This commit uses an intermediate pointer of type 'char *' when >> performing the type-punning, which is well-defined behaviour, and will >> silence the above warning. > > this is kind of a poor fix. if we can't arrange for the pointers to be > the right type, at least a memcpy would be better. This was already discussed in this thread: https://sourceware.org/pipermail/gdb-patches/2022-October/192604.html The version that got pushed: https://sourceware.org/pipermail/gdb-patches/2022-October/192647.html does make use of memcpy. Thanks, Andrew