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SubjectRe: [PATCH] tools lib: Disable redundant-delcs error for strlcpy
Em Tue, Dec 17, 2019 at 03:23:32PM +0300, Vitaly Chikunov escreveu:
> Arnaldo,
>
> Ping. Can you accept or comment on this patch? There is further
> explanations of it:

Will this work when building with clang

- Arnaldo

> 1. It seems that people putting strlcpy() into the tools was already aware of
> the problems it causes and tried to solve them. Probably, that's why they put
> `__weak` attribute on it (so it would be linkable in the presence of another
> strlcpy). Then `#ifndef __UCLIBC__`ed and later `#if defined(__GLIBC__) &&
> !defined(__UCLIBC__)` its declaration. But, solution was incomplete and could
> be improved to make kernel buildable on more systems (where libc contains
> strlcpy).
>
> There is not need to make `redundant redeclaration` warning an error in
> this case.
>
> 2. `#pragma GCC diagnostic ignored` trick is already used multiple times
> in the kernel:
>
> $ git grep '#pragma GCC diagnostic ignored'
> arch/arm/lib/xor-neon.c:#pragma GCC diagnostic ignored "-Wunused-variable"
> tools/build/feature/test-gtk2-infobar.c:#pragma GCC diagnostic ignored "-Wstrict-prototypes"
> tools/build/feature/test-gtk2.c:#pragma GCC diagnostic ignored "-Wstrict-prototypes"
> tools/include/linux/string.h:#pragma GCC diagnostic ignored "-Wredundant-decls"
> tools/lib/bpf/libbpf.c:#pragma GCC diagnostic ignored "-Wformat-nonliteral"
> tools/perf/ui/gtk/gtk.h:#pragma GCC diagnostic ignored "-Wstrict-prototypes"
> tools/testing/selftests/kvm/lib/assert.c:#pragma GCC diagnostic ignored "-Wunused-result"
> tools/usb/ffs-test.c:#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
>
> So the solution does not seem alien in the kernel and should be acceptable.
>
> (I also send this to another of your emails in case I used wrong one before.)
>
> Thanks,
>
>
> On Mon, Dec 09, 2019 at 12:46:07AM +0300, Vitaly Chikunov wrote:
> > Disable `redundant-decls' error for strlcpy declaration and solve build
> > error allowing users to compile vanilla kernels.
> >
> > When glibc have strlcpy (such as in ALT linux since 2004) objtool and
> > perf build fails with something like:
> >
> > 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);
> > | ^~~~~~~
> >
> > It's very hard to produce a perfect fix for that since it is a header
> > file indirectly pulled from many sources from different Makefile builds.
> >
> > Fixes: ce99091 ("perf tools: Move strlcpy() from perf to tools/lib/string.c")
> > Fixes: 0215d59 ("tools lib: Reinstate strlcpy() header guard with __UCLIBC__")
> > Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
> > Cc: Dmitry V. Levin <ldv@altlinux.org>
> > Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> > Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>
> > Cc: stable@vger.kernel.org
> > ---
> > tools/include/linux/string.h | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
> > index 980cb9266718..99ede7f5dfb8 100644
> > --- a/tools/include/linux/string.h
> > +++ b/tools/include/linux/string.h
> > @@ -17,7 +17,10 @@ int strtobool(const char *s, bool *res);
> > * However uClibc headers also define __GLIBC__ hence the hack below
> > */
> > #if defined(__GLIBC__) && !defined(__UCLIBC__)
> > +#pragma GCC diagnostic push
> > +#pragma GCC diagnostic ignored "-Wredundant-decls"
> > extern size_t strlcpy(char *dest, const char *src, size_t size);
> > +#pragma GCC diagnostic pop
> > #endif
> >
> > char *str_error_r(int errnum, char *buf, size_t buflen);

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