From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fencepost.gnu.org (fencepost.gnu.org [IPv6:2001:470:142:3::e]) by sourceware.org (Postfix) with ESMTPS id AE0B03850419 for ; Wed, 18 May 2022 18:32:32 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org AE0B03850419 Received: from eggs.gnu.org ([2001:470:142:3::10]:42984) by fencepost.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nrOTE-00041r-SS for gcc-help@gnu.org; Wed, 18 May 2022 14:32:28 -0400 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]:38699) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nrOTD-0000Bb-Bt for gcc-help@gnu.org; Wed, 18 May 2022 14:32:28 -0400 Received: by mail-wm1-x32a.google.com with SMTP id 1-20020a05600c248100b00393fbf11a05so3666545wms.3 for ; Wed, 18 May 2022 11:32:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=uZGxGe/u4p7A+/mwK9vb7dYLjdwASyfuSlSxG3TxMMw=; b=fRWfsfGoeSLQkatUQtwx6JvHo2JNDA0nosB+jAQ+PO0I3sQTvPhTdMty9iolGmdPto Yaj0xq8G7cq/CLJ9IN/d5AFV6/oLyHCbSELLQX2lmUsQP4ZKLMCA6MXPSShuVobm9dxM hm3GkMMyfmD3G4LyQp8KZXKL/ok8oTKbiHaBBovbGWFSDAVFGp48NYefjgBDCefHZD2a FMRkkThAeuEIvZAveiKE82V+TSbq8fagkeLRvwD6Bm5stACLWSsH+xyxjC00hnPSNakP Ck4odUXQgWx5B+hJD0AenAHHKYMop3zBsH8WhwX2n8eUIccRZwxOziFnlTmIII1VDvXD ApJg== X-Gm-Message-State: AOAM532zM4bnaRB2nUnVLS9WxSO27EG9WJfaD6RXi/ZnZEfZT9z658E/ QEsLfTfoeGYAF3wvI7wkEkrFd0NBhfQgCi+10hQ= X-Google-Smtp-Source: ABdhPJyMcI/1J5cEfKkc5BOy78NiNhcc8ZrlQBLoSz28aaFcEGOTF7qjAMJQVA0l3jMs19ld0m1xhIpVXLoGUNjF+/0= X-Received: by 2002:a05:600c:4e4d:b0:396:37ef:b17e with SMTP id e13-20020a05600c4e4d00b0039637efb17emr624407wmq.30.1652898744991; Wed, 18 May 2022 11:32:24 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Jonathan Wakely Date: Wed, 18 May 2022 19:32:13 +0100 Message-ID: Subject: Re: GCC 12.1, -isystem, -Wsystem-headers, and -Wmaybe-uninitialized To: Tom Kacvinsky Cc: gcc-help@gnu.org Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=jwakely.gcc@gmail.com; helo=mail-wm1-x32a.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, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-Spam-Status: No, score=-0.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, HTML_MESSAGE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: gcc-help@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-help mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 May 2022 18:32:33 -0000 On Wed, 18 May 2022, 17:57 Tom Kacvinsky via Gcc-help, wrote: > We were happily using -Wall -Wextra -Werror with GCC 8.3.0 and -isystem > for Boost header files to squelch any warnings that would come out of > Boost. > > I recently switched to GCC 12.1 and now we are getting > -Wmaybe-uninitialized errors out of Boost. So I am not sure if > -Wsystem-headers was not part of -Wall -Wextra in GCC 8.3.0 but is now > part of GCC 12.1.0. > No it isn't, it's just that some warnings are now given even if they occur in system headers. > Optimization level plays a role in this. With -O0 (GCC 12.1), the > warning does not happen, but with -O3, it does. > The uninitialised warnings depend on data flow analysis, which only happens with optimization. > So I am not sure of the interaction between optimization, -Wall -Wextra, > -Wsystem-headers, and GCC 8.3.0 and GCC 12.1.0. > > Any ideas? > > Thanks, Tom >