linux-kernel - RE: [PATCH 20/20] tools lib: Fix builds when glibc contains strlcpy()

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Message-ID: <bd755ddc840a485098f9e51d2692f39d@AcuMS.aculab.com>
Date:   Mon, 6 Jan 2020 17:03:26 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnaldo Carvalho de Melo' <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
CC:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        "Clark Williams" <williams@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        Vitaly Chikunov <vt@...linux.org>,
        Dmitry Levin <ldv@...linux.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        kbuild test robot <lkp@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: RE: [PATCH 20/20] tools lib: Fix builds when glibc contains strlcpy()

From: Arnaldo Carvalho de Melo
> Sent: 06 January 2020 16:07
> 
> From: Vitaly Chikunov <vt@...linux.org>
> 
> Disable a couple of compilation warnings (which are treated as errors)
> on strlcpy() definition and declaration, allowing users to compile perf
> and kernel (objtool) when:
> 
> 1. glibc have strlcpy() (such as in ALT Linux since 2004) objtool and
>    perf build fails with this (in gcc):
> 
>   In file included from exec-cmd.c:3:
>   tools/include/linux/string.h:20:15: error: redundant redeclaration of ‘strlcpy’ [-Werror=redundant-decls]
>      20 | extern size_t strlcpy(char *dest, const char *src, size_t size);
> 
> 2. clang ignores `-Wredundant-decls', but produces another warning when
>    building perf:
> 
>     CC       util/string.o
>   ../lib/string.c:99:8: error: attribute declaration must precede definition [-Werror,-Wignored-attributes]
>   size_t __weak strlcpy(char *dest, const char *src, size_t size)
>   ../../tools/include/linux/compiler.h:66:34: note: expanded from macro '__weak'
>   # define __weak                 __attribute__((weak))
>   /usr/include/bits/string_fortified.h:151:8: note: previous definition is here
>   __NTH (strlcpy (char *__restrict __dest, const char *__restrict __src,

Why not just always use the local version by renaming it?

	David

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