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[187.189.51.144]) by smtp.gmail.com with ESMTPSA id 17sm12234168qky.7.2021.03.15.06.18.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Mar 2021 06:18:45 -0700 (PDT) Subject: Re: [PATCH] utils: Reduce chance of rounding inaccuracy in qemu_strtosz. To: Eric Blake , qemu-devel@nongnu.org References: <20210311200702.1302855-1-eblake@redhat.com> From: Richard Henderson Message-ID: <8dd4a71a-7fe9-a6c3-290d-81adf5c53a4d@linaro.org> Date: Mon, 15 Mar 2021 07:18:43 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::72c; envelope-from=richard.henderson@linaro.org; helo=mail-qk1-x72c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, 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_NONE=-0.0001, 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: , Cc: Peter Maydell , berrange@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/15/21 5:33 AM, Eric Blake wrote: > On 3/13/21 3:48 PM, Richard Henderson wrote: >> On 3/11/21 2:07 PM, Eric Blake wrote: >>> +        /* >>> +         * Add in a fudge-factor (2^53 when double is IEEE format) for >>> +         * all scales less than P (2^50), so that things like >>> +         * 12.345M with unit 1000 produce 12345000 instead of >>> +         * 12344999. >>> +         */ >>> +        if (mul > 1e49) { >> >> The comment says less than, the code says greater than. > > Shoot. A demonstration that I did not have an environment that actually > reproduced the bug Any i686 vm will do. I had a debian 10 vm hanging around in which I could reproduce it. r~