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Date:   Mon, 30 Jul 2018 12:35:09 -0700
From:   Jakub Kicinski <jakub.kicinski@netronome.com>
To:     Thomas Richter <tmricht@linux.ibm.com>
Cc:     daniel@iogearbox.net, ast@kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, heiko.carstens@de.ibm.com,
        brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com
Subject: Re: [PATCH v3] perf build: Build error in libbpf with
 EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2"
Message-ID: <20180730123509.0ffa4737@cakuba.netronome.com>
In-Reply-To: <20180730085323.75738-1-tmricht@linux.ibm.com>
References: <20180730085323.75738-1-tmricht@linux.ibm.com>
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On Mon, 30 Jul 2018 10:53:23 +0200, Thomas Richter wrote:
> commit 531b014e7a2f ("tools: bpf: make use of reallocarray")
> causes a compiler error when building the perf tool in the linux-next
> tree.  Compile file tools/lib/bpf/libbpf.c on a FEDORA 28
> installation with gcc compiler
> version: gcc (GCC) 8.0.1 20180324 (Red Hat 8.0.1-0.20)
> shows this error message:
>=20
> [root@p23lp27] # make V=3D1 EXTRA_CFLAGS=3D"-Wp,-D_FORTIFY_SOURCE=3D2 -O2"
> [...]
> make -f /home6/tmricht/linux-next/tools/build/Makefile.build
> 	dir=3D./util/scripting-engines obj=3Dlibperf
> libbpf.c: In function =E2=80=98bpf_object__elf_collect=E2=80=99:
> libbpf.c:811:15: error: ignoring return value of =E2=80=98strerror_r=E2=
=80=99,
> 		declared with attribute warn_unused_result [-Werror=3Dunused-result]
>      strerror_r(-err, errmsg, sizeof(errmsg));
>                ^
> cc1: all warnings being treated as errors
> mv: cannot stat './.libbpf.o.tmp': No such file or directory
> /home6/tmricht/linux-next/tools/build/Makefile.build:96: recipe for targe=
t 'libbpf.o' failed
>=20
> Replace all occurrences of strerror() by calls to strerror_r().
> To keep the compiler quiet also use the return value from strerror_r()
> otherwise a 'variable set but not use' warning which is treated as error
> terminates the compile.
>=20
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
> Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
> Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>

Conversion looks correct, thank you!

Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>