From nobody Mon Apr 6 21:33:51 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88509ECAAD1 for ; Thu, 1 Sep 2022 17:59:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233875AbiIAR7a (ORCPT ); Thu, 1 Sep 2022 13:59:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232332AbiIAR71 (ORCPT ); Thu, 1 Sep 2022 13:59:27 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D383A78236 for ; Thu, 1 Sep 2022 10:59:25 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id i6-20020a259786000000b0069648392979so4954211ybo.11 for ; Thu, 01 Sep 2022 10:59:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc; bh=Eznf++i6Hiz/WgIi82JzYKRSk0zp5tPqXtS/6z0a6sk=; b=h9YGObLHX574s+ltrn3qvuINtF7Mwp9izXYVcU/MiCMtbC+bh3egxPZtvsTwVTeAgG 6b6GeDMbE4/+glo+q8cl6aUxaA+++6QSpSkAdZMgFF6EIZpx1z5hW02V/L8/QIz3FpLO oqexKNlYmrdBv5ZelOAxDTWCzejmPXDdexwdovsenVp34C20CiuugavdpmX7tvxTJ1Om 9G0v9guIwUOxCTW2b+k3/6QZxkIy9lyrDQpyqXxFpLCup5veGSRnxx+oqVUk4S6to6SR 0se0Vmp+9gjWe0RXXJSRyDvTMdL3SlJW071KmqmdpuMRVqg5s10e1OA7yogkADN2GxN9 4Wmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc; bh=Eznf++i6Hiz/WgIi82JzYKRSk0zp5tPqXtS/6z0a6sk=; b=g78qm9SUlJ2bDU4aPXfoPoStYjf2Je7RenyaYIpJiY5mOqHxemS0qFx1PK1gWnuzPy 9imNTFyRsj7AFQIfHbf6pX+F4TaAwW0bdZnLkddjZxOzRfJJMDLVlLQtxQEep14cQi5s zpyt3sqiMYnqoFrbIKf07kpJMIFF1k76wIurzgNwigR2dvjuYbCQqtfXzxk8fcw1S/N4 teoVYiYC3kXDvYMH1OZB0/wAPtkWiO15/M8YKULKlOdaaOdCVIbfZCH2peijBh9Axe3o f6w5BZ9RdH1PEMhCCCy1BRl+hps8j5tNIfO/m2/fDT4zyWvAa3OcMoUfDlS/Boduy29G OcOA== X-Gm-Message-State: ACgBeo2BMTbq+8mZ0hYg8OH0xaC+Vm8SbogHH/9QiklkHi7n4XySZ9dk pnvF9lGVxuW6g/sSDm1CAiZhXib97FQQB19wPII= X-Google-Smtp-Source: AA6agR6RJOq/gy/EH6yiM3DkBfPhDnWdLGHnc6wAPOgfY+13FEVuqxmoAP2HSwm1jTlTOzhNNaAj/fpOCZD6V1SfPis= X-Received: from ndesaulniers1.mtv.corp.google.com ([2620:0:100e:712:99db:dcd4:6e34:2651]) (user=ndesaulniers job=sendgmr) by 2002:a81:149:0:b0:33d:b55e:7e7a with SMTP id 70-20020a810149000000b0033db55e7e7amr24083872ywb.413.1662055165101; Thu, 01 Sep 2022 10:59:25 -0700 (PDT) Date: Thu, 1 Sep 2022 10:59:13 -0700 In-Reply-To: Mime-Version: 1.0 References: X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=lvO/pmg+aaCb6dPhyGC1GyOCvPueDrrc8Zeso5CaGKE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1662055153; l=3012; i=ndesaulniers@google.com; s=20211004; h=from:subject; bh=9aydxQMib3Wu+j+JM/2pa56zYSBHnbBYkj5Ry7clV1E=; b=V5pYURGX/bQh0MwFkI4b7b7jGl3OPcO1iK4p/wUDPggm9TysXodSu4OtOQNYCGxI1z+nJKDhCRmX 6yxh8RG3BC4kr39mCeEaGf9u65MRqo6o2+OYMNjIzi3V7kaX4jzw X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220901175913.2183047-1-ndesaulniers@google.com> Subject: [PATCH] Makefile.extrawarn: re-enable -Wformat for clang; take 2 From: Nick Desaulniers To: Linus Torvalds Cc: Joe Perches , Nathan Chancellor , "Sudip Mukherjee (Codethink)" , Masahiro Yamada , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux , Nick Desaulniers , Justin Stitt , Youngmin Nam Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" -Wformat was recently re-enabled for builds with clang, then quickly re-disabled, due to concerns stemming from the frequency of default argument promotion related warning instances. commit 258fafcd0683 ("Makefile.extrawarn: re-enable -Wformat for clang") commit 21f9c8a13bb2 ("Revert "Makefile.extrawarn: re-enable -Wformat for cl= ang"") ISO WG14 has ratified N2562 to address default argument promotion explicitly for printf, as part of the upcoming ISO C2X standard. The behavior of clang was changed in clang-16 to not warn for the cited cases in all language modes. Add a version check, so that users of clang-16 now get the full effect of -Wformat. For older clang versions, re-enable flags under the -Wformat group that way users still get some useful checks related to format strings, without noisy default argument promotion warnings. I intentionally omitted -Wformat-y2k and -Wformat-security from being re-enabled, which are also part of -Wformat in clang-16. Link: https://github.com/ClangBuiltLinux/linux/issues/378 Link: https://github.com/llvm/llvm-project/issues/57102 Link: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2562.pdf Suggested-by: Justin Stitt Suggested-by: Nathan Chancellor Suggested-by: Youngmin Nam Signed-off-by: Nick Desaulniers Reviewed-by: Masahiro Yamada Reviewed-by: Nathan Chancellor --- Linus, I figured I'd send this to you to see whether you'd prefer to apply it, or let it "ride the trains" up through the kbuild tree? I do have another series I'm working on to improve the compiler version checks where I can/will improve the checks used here, but I'm also interested in having something that might backport cleanly to stable. scripts/Makefile.extrawarn | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index 0621c39a3955..6ae482158bc4 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -47,7 +47,19 @@ else =20 ifdef CONFIG_CC_IS_CLANG KBUILD_CFLAGS +=3D -Wno-initializer-overrides +# Clang before clang-16 would warn on default argument promotions. +ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -lt 160000 ] && echo y),y) +# Disable -Wformat KBUILD_CFLAGS +=3D -Wno-format +# Then re-enable flags that were part of the -Wformat group that aren't +# problematic. +KBUILD_CFLAGS +=3D -Wformat-extra-args -Wformat-invalid-specifier +KBUILD_CFLAGS +=3D -Wformat-zero-length -Wnonnull +# Requires clang-12+. +ifeq ($(shell [ $(CONFIG_CLANG_VERSION) -ge 120000 ] && echo y),y) +KBUILD_CFLAGS +=3D -Wformat-insufficient-args +endif +endif KBUILD_CFLAGS +=3D -Wno-sign-compare KBUILD_CFLAGS +=3D $(call cc-disable-warning, pointer-to-enum-cast) KBUILD_CFLAGS +=3D -Wno-tautological-constant-out-of-range-compare base-commit: 2880e1a175b9f31798f9d9482ee49187f61b5539 --=20 2.37.2.789.g6183377224-goog