From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by sourceware.org (Postfix) with ESMTPS id A1F153858D3C for ; Tue, 21 Mar 2023 19:51:23 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org A1F153858D3C Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pl1-x62f.google.com with SMTP id u5so17199320plq.7 for ; Tue, 21 Mar 2023 12:51:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679428282; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=Gkigm04r8l5wjgbLYOT6W9bYlFRiiUNt8XbpNPI3Lcs=; b=QSMKM9oet53PoWvz7UzOXd8qUBKulgCllwIuXiA16VJKZG7qRTs4u7I5jo5KHcW4Fp mlaxx3AYjSkslFqYl0nCNdYPIexhtuotiEFSvgOgfBwEc8bIp0xuJ6NsH6t39GaFJ09e zS6vRN5+afmhsUIJsFwYAd7NbUzALEXs8CVbyOhPOAC0pbqk/lFwxKtbKWVQTwnk6vxu dnCk36PeP15j7qaml48MXvnHqYUQ6I/BXAzChLkK38r2IDzvmMHaAAwp2hwV0gFCu1AH PHZKFwhvy4gj4oLpZupINewWPROyBC+/pC8dF4RcGlTO0RpdN4BJSGwHArtm3IzlxyTD uYHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679428282; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Gkigm04r8l5wjgbLYOT6W9bYlFRiiUNt8XbpNPI3Lcs=; b=rADMxWuCuMmLtGmRLHgyXb/MLtR1M7sFIg9hG3HscZk2N+RRgObrzxr+C8lL0tf08x J1u7LQP418FJ2QhwceoCuRwnyVGsro4PBi2c3/vA7SmniE7RncKM5jWgO5FrepWLPT9V gTm/sQ0/h3JxUjdlDbehPGVlelipIp4tmgrmzqNjmS8sb2UZGvZBazXgXEJTg4SHllyg hRuil9iV07MTtQVB/FUIt38Anxo9j+44MXOljkqYWse9kVPAKlcH6N2ss+bTZmXot5ao K3cdGMxg0iheXEHdeVwlt1u398e6Q4w8rd9c1ztCZEglVgfrA19qj+GkMmgvnqgC3Aj9 CANw== X-Gm-Message-State: AO0yUKVnYbSjKrvy9Kh+3YZh1UUiYJ8JyQClP7TkmHVPiAxeT17OdI7L vNn3AEoZBrxzoqOBXSvX/KY= X-Google-Smtp-Source: AK7set8ys7FTZqWbnmpg/+wEP1jvAVvukm9uJ1HuDHrRvZZfiSD32RDEBm6M2ie8etVEi67myIYqSw== X-Received: by 2002:a17:90b:1b0c:b0:234:ba34:71bf with SMTP id nu12-20020a17090b1b0c00b00234ba3471bfmr1069719pjb.1.1679428282465; Tue, 21 Mar 2023 12:51:22 -0700 (PDT) Received: from ?IPV6:2601:681:8600:13d0::f0a? ([2601:681:8600:13d0::f0a]) by smtp.gmail.com with ESMTPSA id v20-20020a17090ac91400b002349608e80csm8361225pjt.47.2023.03.21.12.51.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Mar 2023 12:51:21 -0700 (PDT) Message-ID: <8df774e4-0711-23ba-786e-4c9ccfb3d450@gmail.com> Date: Tue, 21 Mar 2023 13:51:20 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: Should -ffp-contract=off the default on GCC? Content-Language: en-US To: Qing Zhao Cc: "gcc-patches@gcc.gnu.org" References: <6659A77B-DA2F-40A6-BDBD-E8B29B9E901D@oracle.com> <87384938-FDB1-487B-8B03-7787996435B2@comcast.net> <7C6B7ED7-7AA4-47EF-8E44-E3AD81BF3E29@oracle.com> <4a670847-9728-e0cb-46f3-d476839f7cd4@gmail.com> <9787B47E-9800-47B1-B98D-60430257C4E5@oracle.com> From: Jeff Law In-Reply-To: <9787B47E-9800-47B1-B98D-60430257C4E5@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 3/21/23 13:01, Qing Zhao wrote: > > The code previously worked now has some issue since we added some new stuff into standard, and the compiler added some new transformation based on this new stuff. Should the compiler issue some warnings to warn the users about such change? Then the user will go to the new standard to get more info? It is not at all uncommon to have old code no longer work due to a compiler update. This can happen if the compiler changes the default version of the language it's supporting (say c99 to c11) or fixes a missed-error bug (more common in C++) or the optimizers just get smarter and code which was always buggy, but worked by accident no longer works. When we can reasonably give diagnostics, we try to. Improvements in this space are appreciated :-) Jeff