Re: [PATCH v3] perf build: Build error in libbpf with EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2"

On 07/30/2018 09:35 PM, Jakub Kicinski wrote:

On Mon, 30 Jul 2018 10:53:23 +0200, Thomas Richter wrote:

quoted

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:

[root@p23lp27] # make V=1 EXTRA_CFLAGS="-Wp,-D_FORTIFY_SOURCE=2 -O2"
[...]
make -f /home6/tmricht/linux-next/tools/build/Makefile.build
	dir=./util/scripting-engines obj=libperf
libbpf.c: In function ‘bpf_object__elf_collect’:
libbpf.c:811:15: error: ignoring return value of ‘strerror_r’,
		declared with attribute warn_unused_result [-Werror=unused-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 target 'libbpf.o' failed

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.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jakub Kicinski <redacted>
Suggested-by: Jakub Kicinski <redacted>
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Hendrik Brueckner <redacted>
Signed-off-by: Thomas Richter <redacted>

Applied to bpf-next, thanks Thomas!