From: Masahiro Yamada <masahiroy@kernel.org> To: Nathan Chancellor <nathan@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org>, kernel test robot <lkp@intel.com>, chongjiapeng <jiapeng.chong@linux.alibaba.com>, llvm@lists.linux.dev, kbuild-all@lists.01.org, Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Subject: Re: kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' Date: Tue, 15 Feb 2022 01:28:53 +0900 [thread overview] Message-ID: <CAK7LNAQmztEn7nN_R05zhXWc-5S44Y5nGQQjzdByTPxgDH13wA@mail.gmail.com> (raw) In-Reply-To: <Ygp64CsyyKyRykqE@dev-arch.archlinux-ax161> On Tue, Feb 15, 2022 at 12:53 AM Nathan Chancellor <nathan@kernel.org> wrote: > > Hi Steve, > > On Mon, Feb 14, 2022 at 10:20:00AM -0500, Steven Rostedt wrote: > > On Sun, 13 Feb 2022 21:03:29 +0800 > > kernel test robot <lkp@intel.com> wrote: > > > > > All errors (new ones prefixed by >>): > > > > > > >> kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' [-Werror,-Wunused-function] > > > static inline void ftrace_startup_enable(int command) { } > > > ^ > > > 1 error generated. > > > > Strange. I always thought that static inline functions do not cause > > warnings when not used? Especially, since they are often in headers when > > things are turned off. Or is it because this is in a C file? > > With -Wunused-function, clang will warn about unused static inline > functions within a .c file (but not .h), whereas GCC will not warn for > either. The unused attribute was added to the definition of inline to > make clang's behavior match GCC's. > > > Is this a new warning caused by a commit, or is it a new warning because > > the compiler now complains about it? > > However, in commit 6863f5643dd7 ("kbuild: allow Clang to find unused > static inline functions for W=1 build"), Masahiro made it so that the > unused attribute does not get added at W=1 so that instances of unused > static inline functions can be caught and eliminated (or put into use, > if the function should have been used), hence this report. BTW, my hope was to move this warning to W=0 someday. (that is, remove __inline_maybe_unused entirely). I do not know how many warnings are still remaining, though. Is it now more difficult due to CONFIG_WERROR? > I will be honest, I don't know why the robot flagged 172f7ba9772c as the > commit that introduced this warning but it seems legitimate if > CONFIG_DYNAMIC_FTRACE is not enabled, since ftrace_startup_enable() is > only ever used within an '#ifdef CONFIG_DYNAMIC_FTRACE' block so I guess > the stub is unnecessary? > > Cheers, > Nathan -- Best Regards Masahiro Yamada
WARNING: multiple messages have this Message-ID (diff)
From: Masahiro Yamada <masahiroy@kernel.org> To: kbuild-all@lists.01.org Subject: Re: kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' Date: Tue, 15 Feb 2022 01:28:53 +0900 [thread overview] Message-ID: <CAK7LNAQmztEn7nN_R05zhXWc-5S44Y5nGQQjzdByTPxgDH13wA@mail.gmail.com> (raw) In-Reply-To: <Ygp64CsyyKyRykqE@dev-arch.archlinux-ax161> [-- Attachment #1: Type: text/plain, Size: 2123 bytes --] On Tue, Feb 15, 2022 at 12:53 AM Nathan Chancellor <nathan@kernel.org> wrote: > > Hi Steve, > > On Mon, Feb 14, 2022 at 10:20:00AM -0500, Steven Rostedt wrote: > > On Sun, 13 Feb 2022 21:03:29 +0800 > > kernel test robot <lkp@intel.com> wrote: > > > > > All errors (new ones prefixed by >>): > > > > > > >> kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' [-Werror,-Wunused-function] > > > static inline void ftrace_startup_enable(int command) { } > > > ^ > > > 1 error generated. > > > > Strange. I always thought that static inline functions do not cause > > warnings when not used? Especially, since they are often in headers when > > things are turned off. Or is it because this is in a C file? > > With -Wunused-function, clang will warn about unused static inline > functions within a .c file (but not .h), whereas GCC will not warn for > either. The unused attribute was added to the definition of inline to > make clang's behavior match GCC's. > > > Is this a new warning caused by a commit, or is it a new warning because > > the compiler now complains about it? > > However, in commit 6863f5643dd7 ("kbuild: allow Clang to find unused > static inline functions for W=1 build"), Masahiro made it so that the > unused attribute does not get added at W=1 so that instances of unused > static inline functions can be caught and eliminated (or put into use, > if the function should have been used), hence this report. BTW, my hope was to move this warning to W=0 someday. (that is, remove __inline_maybe_unused entirely). I do not know how many warnings are still remaining, though. Is it now more difficult due to CONFIG_WERROR? > I will be honest, I don't know why the robot flagged 172f7ba9772c as the > commit that introduced this warning but it seems legitimate if > CONFIG_DYNAMIC_FTRACE is not enabled, since ftrace_startup_enable() is > only ever used within an '#ifdef CONFIG_DYNAMIC_FTRACE' block so I guess > the stub is unnecessary? > > Cheers, > Nathan -- Best Regards Masahiro Yamada
next prev parent reply other threads:[~2022-02-14 16:38 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-13 13:03 kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' kernel test robot 2022-02-13 13:03 ` kernel test robot 2022-02-14 15:20 ` Steven Rostedt 2022-02-14 15:20 ` Steven Rostedt 2022-02-14 15:53 ` Nathan Chancellor 2022-02-14 15:53 ` Nathan Chancellor 2022-02-14 16:28 ` Masahiro Yamada [this message] 2022-02-14 16:28 ` Masahiro Yamada 2022-02-14 17:00 ` Nathan Chancellor 2022-02-14 17:00 ` Nathan Chancellor 2022-02-14 18:57 ` Steven Rostedt 2022-02-14 18:57 ` Steven Rostedt
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