From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 990FEC7618F for ; Fri, 19 Jul 2019 20:04:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D4762186A for ; Fri, 19 Jul 2019 20:04:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="P0+v4hJr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730366AbfGSUEp (ORCPT ); Fri, 19 Jul 2019 16:04:45 -0400 Received: from mail-qk1-f194.google.com ([209.85.222.194]:38664 "EHLO mail-qk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727497AbfGSUEo (ORCPT ); Fri, 19 Jul 2019 16:04:44 -0400 Received: by mail-qk1-f194.google.com with SMTP id a27so24161378qkk.5; Fri, 19 Jul 2019 13:04:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=KgzbnyihRsw5YwTm7SdiFF/zXhcaOpif95Kf3MqJxBY=; b=P0+v4hJrU8jqZSNngmeP7/FXPteQB0Dx84Z0ggbNG42+cxT84wlm6NRuIGK3mkqLxG ofS9GFmbUExt7b5uNYvs+83qh/XXFlQz/1MA9VQQ3Ocu9tNpZ5r4pWlX5WnLHlQV7toQ jNW1KaP0GQ4azRxarWFymz2vu+mldivdMuouHnGRq8xsuQGNxtI6GBQWmeN/9JMZ+nkc JG2W8Nd3qj4ew5YX1rakVmCuZKjOxl/+keUVxgwPIMo7VTjPcJvfYH3wwigx00M/F0PL mWwjKfUPHhLSC44oLDrlRqBx8b9SCIntDdqbyt7YBPzNHiMbw2oZ9Tnm0+6UQGXZM7BG BvFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=KgzbnyihRsw5YwTm7SdiFF/zXhcaOpif95Kf3MqJxBY=; b=sefcYwPVvg0KI/rt5qL61h3yLlU9QH5HD7EDcYLA65RR6r9I4ZTg593veZGcixiMnw 7AfV1ZSox+3dazqFFCGxVDYrCzkRnMKZcM4TSVPs1JD21gr4RDernfr5us6w/onz4a5Z 3WQM9XaQU/7at8md+5L08QXn6hjfk1D8gZqMpvdR6Z0yWK9dMB6BIODkKvbhDhXP5+0N ZzIbpx1AIBxTxOIGuXUrOrtfucc5L1bkCPFoNpcRvclPWF1N/55HUnhumPKitGX6MMTJ xjZdQG0HyPYIyzw9iyHAisNK1pmChE+X36nN8wfPBt9/yYpZQq9uOrea5J9m+qcLogbq Rx3w== X-Gm-Message-State: APjAAAW3T+qIwcyya0wIc9OdFm1l6Qz5skOxJIBMn9o+XqScwFhVFHWV wNSO3CxtGwthCEkgs6jn9PpsTYF3BOKXIiaFSdQucO3S X-Google-Smtp-Source: APXvYqzeRSpz2YxRkp57icEpaASDSR1b/c8uGpQ5DxBVTEvjIKmj+n5EoFQT33OMXuUkApGXQEmNTekrxUxC3fPkLec= X-Received: by 2002:a37:9b48:: with SMTP id d69mr38532135qke.449.1563566683627; Fri, 19 Jul 2019 13:04:43 -0700 (PDT) MIME-Version: 1.0 References: <20190718172513.2394157-1-andriin@fb.com> <20190718175533.GG2093@redhat.com> <20190718185619.GL3624@kernel.org> <20190718191452.GM3624@kernel.org> <20190719011644.GN3624@kernel.org> <20190719181423.GO3624@kernel.org> <20190719183417.GQ3624@kernel.org> In-Reply-To: <20190719183417.GQ3624@kernel.org> From: Andrii Nakryiko Date: Fri, 19 Jul 2019 13:04:32 -0700 Message-ID: Subject: Re: [PATCH bpf] libbpf: fix missing __WORDSIZE definition To: Arnaldo Carvalho de Melo Cc: Andrii Nakryiko , bpf , Networking , Daniel Borkmann , Alexei Starovoitov , Kernel Team , Jiri Olsa , Namhyung Kim Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jul 19, 2019 at 11:34 AM Arnaldo Carvalho de Melo wrote: > > Em Fri, Jul 19, 2019 at 11:26:50AM -0700, Andrii Nakryiko escreveu: > > On Fri, Jul 19, 2019 at 11:14 AM Arnaldo Carvalho de Melo wrote: > > > Em Fri, Jul 19, 2019 at 10:54:44AM -0700, Andrii Nakryiko escreveu: > > > > Ok, did some more googling. This warning (turned error in your setup) > > > > is emitted when -Wshadow option is enabled for GCC/clang. It appears > > > > to be disabled by default, so it must be enabled somewhere for perf > > > > build or something. > > > > Right, I came to the exact same conclusion, doing tests here: > > > > [perfbuilder@3a58896a648d tmp]$ gcc -Wshadow shadow_global_decl.c -o shadow_global_decl > > > shadow_global_decl.c: In function 'main': > > > shadow_global_decl.c:9: warning: declaration of 'link' shadows a global declaration > > > shadow_global_decl.c:4: warning: shadowed declaration is here > > > [perfbuilder@3a58896a648d tmp]$ gcc --version |& head -1 > > > gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23) > > > [perfbuilder@3a58896a648d tmp]$ gcc shadow_global_decl.c -o shadow_global_decl > > > [perfbuilder@3a58896a648d tmp]$ > > > > So I'm going to remove this warning from the places where it causes > > > problems. > > > > > Would it be possible to disable it at least for libbpf when building > > > > from perf either everywhere or for those systems where you see this > > > > warning? I don't think this warning is useful, to be honest, just > > > > random name conflict between any local and global variables will cause > > > > this. > > > > Yeah, I might end up having this applied. > > > Thanks! > > So, I'm ending up with the patch below, there is some value after all in > Wshadow, that is, from gcc 4.8 onwards :-) I agree with the intent, but see below. > > - Arnaldo > > diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include > index 495066bafbe3..ded7a950dc40 100644 > --- a/tools/scripts/Makefile.include > +++ b/tools/scripts/Makefile.include > @@ -32,7 +32,6 @@ EXTRA_WARNINGS += -Wno-system-headers > EXTRA_WARNINGS += -Wold-style-definition > EXTRA_WARNINGS += -Wpacked > EXTRA_WARNINGS += -Wredundant-decls > -EXTRA_WARNINGS += -Wshadow > EXTRA_WARNINGS += -Wstrict-prototypes > EXTRA_WARNINGS += -Wswitch-default > EXTRA_WARNINGS += -Wswitch-enum > @@ -69,8 +68,16 @@ endif > # will do for now and keep the above -Wstrict-aliasing=3 in place > # in newer systems. > # Needed for the __raw_cmpxchg in tools/arch/x86/include/asm/cmpxchg.h > +# > +# See https://lkml.org/lkml/2006/11/28/253 and https://gcc.gnu.org/gcc-4.8/changes.html, > +# that takes into account Linus's comments (search for Wshadow) for the reasoning about > +# -Wshadow not being interesting before gcc 4.8. > + > ifneq ($(filter 3.%,$(MAKE_VERSION)),) # make-3 This is checking make version, not GCC version. So code comment and configurations are not in sync? > EXTRA_WARNINGS += -fno-strict-aliasing > +EXTRA_WARNINGS += -Wno-shadow > +else > +EXTRA_WARNINGS += -Wshadow > endif > > ifneq ($(findstring $(MAKEFLAGS), w),w)