commit 6c4798d3f08b81c2c52936b10e0fa872590c96ae upstream.

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,

Committer notes:

The

 #pragma GCC diagnostic

directive was introduced in gcc 4.6, so check for that as well.

Fixes: ce99091 ("perf tools: Move strlcpy() from perf to tools/lib/string.c")
Fixes: 0215d59 ("tools lib: Reinstate strlcpy() header guard with __UCLIBC__")
Resolves: https://bugzilla.kernel.org/show_bug.cgi?id=118481
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Reviewed-by: Dmitry Levin <ldv@altlinux.org>
Cc: Dmitry Levin <ldv@altlinux.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: kbuild test robot <lkp@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Cc: Vineet Gupta <vineet.gupta1@synopsys.com>
Link: http://lore.kernel.org/lkml/20191224172029.19690-1-vt@altlinux.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

strlcpy() will be needed by the subcmd library.  Move it to the shared
tools/lib/string.c file which can be used by other tools.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/71e2804b973bf39ad3d3b9be10f99f2ea630be46.1450193761.git.jpoimboe@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Copying it to tools/lib/string.c, the counterpart to the kernel's
lib/string.c.

This is preparation for enhancing BPF program configuration, which will
allow config string like 'inlines=yes'.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1447675815-166222-6-git-send-email-wangnan0@huawei.com
[ Copied it to tools/lib/string.c instead, to make it usable by other tools/ ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

That will contain more string functions with counterparts, sometimes
verbatim copies, in the kernel.

Acked-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-rah6g97kn21vfgmlramorz6o@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>