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[209.132.180.67]) by mx.google.com with ESMTP id y34-v6si518976plb.317.2018.06.19.13.17.37; Tue, 19 Jun 2018 13:17:37 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757227AbeFSURf (ORCPT + 30 others); Tue, 19 Jun 2018 16:17:35 -0400 Received: from 9pmail.ess.barracuda.com ([64.235.150.224]:47398 "EHLO 9pmail.ess.barracuda.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755072AbeFSURd (ORCPT ); Tue, 19 Jun 2018 16:17:33 -0400 Received: from mipsdag02.mipstec.com (mail2.mips.com [12.201.5.32]) by mx4.ess.sfj.cudaops.com (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA256 bits=128 verify=NO); Tue, 19 Jun 2018 20:15:57 +0000 Received: from mipsdag02.mipstec.com (10.20.40.47) by mipsdag02.mipstec.com (10.20.40.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1415.2; Tue, 19 Jun 2018 13:15:22 -0700 Received: from pburton-laptop.mipstec.com (10.20.2.29) by mipsdag02.mipstec.com (10.20.40.47) with Microsoft SMTP Server id 15.1.1415.2 via Frontend Transport; Tue, 19 Jun 2018 13:15:22 -0700 From: Paul Burton To: CC: Mauro Carvalho Chehab , , Arnd Bergmann , Ingo Molnar , Matthew Wilcox , Thomas Gleixner , Douglas Anderson , Josh Poimboeuf , Andrew Morton , Matthias Kaehlcke , He Zhe , Benjamin Herrenschmidt , Michal Marek , Khem Raj , Christophe Leroy , Al Viro , Stafford Horne , Gideon Israel Dsouza , Masahiro Yamada , Kees Cook , Michael Ellerman , Heiko Carstens , , Paul Mackerras , , Paul Burton Subject: [PATCH v2 1/3] kbuild: add macro for controlling warnings to linux/compiler.h Date: Tue, 19 Jun 2018 13:14:56 -0700 Message-ID: <20180619201458.4559-2-paul.burton@mips.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180619201458.4559-1-paul.burton@mips.com> References: <20180619190225.7eguhiw3ixaiwpgl@pburton-laptop> <20180619201458.4559-1-paul.burton@mips.com> MIME-Version: 1.0 X-BESS-ID: 1529439356-298555-14291-6912-1 X-BESS-VER: 2018.7-r1806151722 X-BESS-Apparent-Source-IP: 12.201.5.32 X-BESS-Envelope-From: Paul.Burton@mips.com X-BESS-Outbound-Spam-Score: 0.00 X-BESS-Outbound-Spam-Report: Code version 3.2, rules version 3.2.2.194199 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------- 0.00 BSF_BESS_OUTBOUND META: BESS Outbound X-BESS-Outbound-Spam-Status: SCORE=0.00 using account:ESS59374 scores of KILL_LEVEL=7.0 tests=BSF_BESS_OUTBOUND X-BESS-Orig-Rcpt: linux-kbuild@vger.kernel.org, paulus@samba.org, linux-kernel@vger.kernel.org, heiko.carstens@de.ibm.com, mpe@ellerman.id.au, keescook@chromium.org, yamada.masahiro@socionext.com, gidisrael@gmail.com, shorne@gmail.com, viro@zeniv.linux.org.uk, christophe.leroy@c-s.fr, raj.khem@gmail.com, linuxppc-dev@lists.ozlabs.org, michal.lkml@markovi.net, zhe.he@windriver.com, mka@chromium.org, akpm@linux-foundation.org, jpoimboe@redhat.com, dianders@chromium.org, tglx@linutronix.de, matthew@wil.cx, mingo@kernel.org, arnd@arndb.de, linux-mips@linux-mips.org, mchehab@kernel.org, benh@kernel.crashing.org X-BESS-BRTS-Status: 1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann I have occasionally run into a situation where it would make sense to control a compiler warning from a source file rather than doing so from a Makefile using the $(cc-disable-warning, ...) or $(cc-option, ...) helpers. The approach here is similar to what glibc uses, using __diag() and related macros to encapsulate a _Pragma("GCC diagnostic ...") statement that gets turned into the respective "#pragma GCC diagnostic ..." by the preprocessor when the macro gets expanded. Like glibc, I also have an argument to pass the affected compiler version, but decided to actually evaluate that one. For now, this supports GCC_4_6, GCC_4_7, GCC_4_8, GCC_4_9, GCC_5, GCC_6, GCC_7, GCC_8 and GCC_9. Adding support for CLANG_5 and other interesting versions is straightforward here. GNU compilers starting with gcc-4.2 could support it in principle, but "#pragma GCC diagnostic push" was only added in gcc-4.6, so it seems simpler to not deal with those at all. The same versions show a large number of warnings already, so it seems easier to just leave it at that and not do a more fine-grained control for them. The use cases I found so far include: - turning off the gcc-8 -Wattribute-alias warning inside of the SYSCALL_DEFINEx() macro without having to do it globally. - Reducing the build time for a simple re-make after a change, once we move the warnings from ./Makefile and ./scripts/Makefile.extrawarn into linux/compiler.h - More control over the warnings based on other configurations, using preprocessor syntax instead of Makefile syntax. This should make it easier for the average developer to understand and change things. - Adding an easy way to turn the W=1 option on unconditionally for a subdirectory or a specific file. This has been requested by several developers in the past that want to have their subsystems W=1 clean. - Integrating clang better into the build systems. Clang supports more warnings than GCC, and we probably want to classify them as default, W=1, W=2 etc, but there are cases in which the warnings should be classified differently due to excessive false positives from one or the other compiler. - Adding a way to turn the default warnings into errors (e.g. using a new "make E=0" tag) while not also turning the W=1 warnings into errors. This patch for now just adds the minimal infrastructure in order to do the first of the list above. As the #pragma GCC diagnostic takes precedence over command line options, the next step would be to convert a lot of the individual Makefiles that set nonstandard options to use __diag() instead. [paul.burton@mips.com: - Rebase atop current master. - Add __diag_GCC, or more generally __diag_, abstraction to avoid code outside of linux/compiler-gcc.h needing to duplicate knowledge about different GCC versions. - Add a comment argument to __diag_{ignore,warn,error} which isn't used in the expansion of the macros but serves to push people to document the reason for using them - per feedback from Kees Cook. - Translate severity to GCC-specific pragmas in linux/compiler-gcc.h rather than using GCC-specific in linux/compiler_types.h. - Drop all but GCC 8 macros, since we only need to define macros for versions that we need to introduce pragmas for, and as of this series that's just GCC 8. - Capitalize comments in linux/compiler-gcc.h to match the style of the rest of the file. - Line up macro definitions with tabs in linux/compiler-gcc.h.] Signed-off-by: Arnd Bergmann Signed-off-by: Paul Burton Tested-by: Christophe Leroy Tested-by: Stafford Horne Cc: Michal Marek Cc: Masahiro Yamada Cc: Douglas Anderson Cc: Al Viro Cc: Heiko Carstens Cc: Mauro Carvalho Chehab Cc: Matthew Wilcox Cc: Matthias Kaehlcke Cc: Arnd Bergmann Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Kees Cook Cc: Andrew Morton Cc: Thomas Gleixner Cc: Gideon Israel Dsouza Cc: Christophe Leroy Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Stafford Horne Cc: Khem Raj Cc: He Zhe Cc: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: linuxppc-dev@lists.ozlabs.org --- Changes in v2: - Add version argument to fallback __diag_GCC definition. - Translate severity from generic ignore,warn,error to GCC-specific pragma content ignored,warning,error in linux/compiler-gcc.h in order to keep linux/compiler_types.h generic per feedback from Masahiro Yamada. - Drop all but GCC 8 macros, since we only need to define macros for versions that we need to introduce pragmas for, and as of this series that's just GCC 8. - Capitalize comments in linux/compiler-gcc.h to match the style of the rest of the file. - Line up macro definitions with tabs in linux/compiler-gcc.h. include/linux/compiler-gcc.h | 27 +++++++++++++++++++++++++++ include/linux/compiler_types.h | 18 ++++++++++++++++++ 2 files changed, 45 insertions(+) -- 2.17.1 diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index f1a7492a5cc8..5067a90af9c3 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -347,3 +347,30 @@ #if GCC_VERSION >= 50100 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 #endif + +/* + * Turn individual warnings and errors on and off locally, depending + * on version. + */ +#define __diag_GCC(version, severity, s) \ + __diag_GCC_ ## version(__diag_GCC_ ## severity s) + +/* Severity used in pragma directives */ +#define __diag_GCC_ignore ignored +#define __diag_GCC_warn warning +#define __diag_GCC_error error + +/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */ +#if GCC_VERSION >= 40600 +#define __diag_str1(s) #s +#define __diag_str(s) __diag_str1(s) +#define __diag(s) _Pragma(__diag_str(GCC diagnostic s)) +#else +#define __diag(s) +#endif + +#if GCC_VERSION >= 80000 +#define __diag_GCC_8(s) __diag(s) +#else +#define __diag_GCC_8(s) +#endif diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 6b79a9bba9a7..a8ba6b04152c 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -271,4 +271,22 @@ struct ftrace_likely_data { # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) #endif +#ifndef __diag +#define __diag(string) +#endif + +#ifndef __diag_GCC +#define __diag_GCC(version, severity, string) +#endif + +#define __diag_push() __diag(push) +#define __diag_pop() __diag(pop) + +#define __diag_ignore(compiler, version, option, comment) \ + __diag_ ## compiler(version, ignore, option) +#define __diag_warn(compiler, version, option, comment) \ + __diag_ ## compiler(version, warn, option) +#define __diag_error(compiler, version, option, comment) \ + __diag_ ## compiler(version, error, option) + #endif /* __LINUX_COMPILER_TYPES_H */