[PATCH] tools lib: Disable redundant-delcs error for strlcpy

[PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Vitaly Chikunov]

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);
-- 
2.11.0

Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Dmitry V. Levin]

[-- Attachment #1: Type: text/plain, Size: 1221 bytes --]

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

Apparently, this patch also addresses
https://bugzilla.kernel.org/show_bug.cgi?id=118481


-- 
ldv

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Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Vitaly Chikunov]

Arnaldo,

Ping. Can you accept or comment on this patch? There is further
explanations of it:

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);

Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Arnaldo Carvalho de Melo]

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);

Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Vitaly Chikunov]

Arnaldo,

On Tue, Dec 17, 2019 at 05:04:20PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Dec 17, 2019 at 03:23:32PM +0300, Vitaly Chikunov escreveu:
> > Arnaldo,

(Btw, you didn't include me into the To: of your reply).

> > Ping. Can you accept or comment on this patch? There is further
> > explanations of it:
> 
> Will this work when building with clang

Clang doesn't produce this warning:

  https://clang.llvm.org/docs/DiagnosticsReference.html#wredundant-decls
  "-Wredundant-decls
  This diagnostic flag exists for GCC compatibility, and has no effect
  in Clang."

Thus, this change doesn't affect clang. (When building the kernel objtool
compiles OK).

But, compilation with clang fails compiling perf with:

    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,
         ^
  1 error generated.

This warning could be disabled with this:

diff --git tools/lib/string.c tools/lib/string.c
index f2ae1b87c719..65b569014446 100644
--- tools/lib/string.c
+++ tools/lib/string.c
@@ -96,6 +96,8 @@ int strtobool(const char *s, bool *res)
  * If libc has strlcpy() then that version will override this
  * implementation:
  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wignored-attributes"
 size_t __weak strlcpy(char *dest, const char *src, size_t size)
 {
        size_t ret = strlen(src);
@@ -107,6 +109,7 @@ size_t __weak strlcpy(char *dest, const char *src, size_t size)
        }
        return ret;
 }
+#pragma GCC diagnostic pop

 /**
  * skip_spaces - Removes leading whitespace from @str.

If this is acceptable I will resend v2 with this.

Thanks,

> 
> - 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);
> 

Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Arnaldo Carvalho de Melo]

Em Fri, Dec 20, 2019 at 05:52:36AM +0300, Vitaly Chikunov escreveu:
> Arnaldo,
> 
> On Tue, Dec 17, 2019 at 05:04:20PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Tue, Dec 17, 2019 at 03:23:32PM +0300, Vitaly Chikunov escreveu:
> > > Arnaldo,
> 
> (Btw, you didn't include me into the To: of your reply).
> 
> > > Ping. Can you accept or comment on this patch? There is further
> > > explanations of it:
> > 
> > Will this work when building with clang
> 
> Clang doesn't produce this warning:
> 
>   https://clang.llvm.org/docs/DiagnosticsReference.html#wredundant-decls
>   "-Wredundant-decls
>   This diagnostic flag exists for GCC compatibility, and has no effect
>   in Clang."
> 
> Thus, this change doesn't affect clang. (When building the kernel objtool
> compiles OK).
> 
> But, compilation with clang fails compiling perf with:
> 
>     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,
>          ^
>   1 error generated.
> 
> This warning could be disabled with this:
> 
> diff --git tools/lib/string.c tools/lib/string.c
> index f2ae1b87c719..65b569014446 100644
> --- tools/lib/string.c
> +++ tools/lib/string.c
> @@ -96,6 +96,8 @@ int strtobool(const char *s, bool *res)
>   * If libc has strlcpy() then that version will override this
>   * implementation:
>   */
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Wignored-attributes"
>  size_t __weak strlcpy(char *dest, const char *src, size_t size)
>  {
>         size_t ret = strlen(src);
> @@ -107,6 +109,7 @@ size_t __weak strlcpy(char *dest, const char *src, size_t size)
>         }
>         return ret;
>  }
> +#pragma GCC diagnostic pop
> 
>  /**
>   * skip_spaces - Removes leading whitespace from @str.
> 
> If this is acceptable I will resend v2 with this.

Go ahead, and please let me know if there is any container image for
Altlinux, as I test with clang on all the distros I have container
images for, and this hasn't appeared on my radar, i.e. clang + strlcpy
warnings :-)

- Arnaldo
 
> Thanks,
> 
> > 
> > - 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);
> > 

-- 

- Arnaldo

Re: [PATCH] tools lib: Disable redundant-delcs error for strlcpy

[Vitaly Chikunov]

Arnaldo,

On Fri, Dec 20, 2019 at 09:31:36AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Dec 20, 2019 at 05:52:36AM +0300, Vitaly Chikunov escreveu:
> > If this is acceptable I will resend v2 with this.
> 
> Go ahead, and please let me know if there is any container image for
> Altlinux, as I test with clang on all the distros I have container
> images for, and this hasn't appeared on my radar, i.e. clang + strlcpy
> warnings :-)

ALT Linux container micro how-to:

Docker: https://en.altlinux.org/Docker
  Quick start:
    # docker run -it alt:sisyphus
    [root@28fd15798968 /]# apt-get update
    [root@28fd15798968 /]# apt-get install clang rpm-build

  It will install clang-7.0.

systemd-nspawn:
   Images are at http://ftp.altlinux.org/pub/distributions/ALTLinux/images/Sisyphus/cloud/
   Quick start:
   # machinectl pull-tar --verify=no http://ftp.altlinux.org/pub/distributions/ALTLinux/images/Sisyphus/cloud/alt-sisyphus-rootfs-systemd-x86_64.tar.xz alttest
   # systemd-nspawn -M alttest
   [root@alttest ~]# apt-get update
   [root@alttest ~]# apt-get install clang rpm-build

There is also LXD support: https://en.altlinux.org/LXD

ps. If you going to use binary clang from http://releases.llvm.org/download.html#9.0.0
I would recommend version clang+llvm-9.0.0-x86_64-linux-gnu-ubuntu-14.04.tar.xz
and `ln -snf x86_64-alt-linux /usr/lib64/gcc/x86_64-unknown-linux` to
workaround `cannot find -lgcc` error.

Thanks,

> 
> - Arnaldo
>  
> > Thanks,
> > 
> > > 
> > > - 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);
> > > 
> 
> -- 
> 
> - Arnaldo