Re: [PATCH 2/3] selftests: seccomp: use LDLIBS instead of LDFLAGS

From: sjpark
Date: Wed Jun 28 2017 - 17:40:43 EST

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In reply to: Fathi Boudra: "[PATCH 2/3] selftests: seccomp: use LDLIBS instead of LDFLAGS"
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Hi Fathi,

On Wed, 28 Jun 2017, Fathi Boudra wrote:

> seccomp_bpf fails to build due to undefined reference errors:
>
> aarch64-linaro-linux-gcc --sysroot=/build/tmp-rpb-glibc/sysroots/hikey
> -O2 -pipe -g -feliminate-unused-debug-types -Wl,-no-as-needed -Wall
> -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -lpthread seccomp_bpf.c -o
> /build/tmp-rpb-glibc/work/hikey-linaro-linux/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf
> /tmp/ccrlR3MW.o: In function `tsync_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1920: undefined reference to `sem_post'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1920: undefined reference to `sem_post'
> /tmp/ccrlR3MW.o: In function `TSYNC_setup':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1863: undefined reference to `sem_init'
> /tmp/ccrlR3MW.o: In function `TSYNC_teardown':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1904: undefined reference to `sem_destroy'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1897: undefined reference to `pthread_kill'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1898: undefined reference to `pthread_cancel'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1899: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_siblings_fail_prctl':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1978: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1990: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1992: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_two_siblings_with_ancestor':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2016: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2032: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2034: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_two_sibling_want_nnp':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2046: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2058: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2060: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_two_siblings_with_no_filter':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2073: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2098: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2100: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_two_siblings_with_one_divergence':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2125: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2143: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2145: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
> /tmp/ccrlR3MW.o: In function `TSYNC_two_siblings_not_under_filter':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2169: undefined reference to `sem_wait'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2202: undefined reference to `pthread_join'
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:2227: undefined reference to `pthread_join'
> /tmp/ccrlR3MW.o: In function `tsync_start_sibling':
> /usr/src/debug/kselftests/4.12-r0/linux-4.12-rc7/tools/testing/selftests/seccomp/seccomp_bpf.c:1941: undefined reference to `pthread_create'
>
> It's GNU Make and linker specific.
>
> The default Makefile rule looks like:
>
> $(CC) $(CFLAGS) $(LDFLAGS) $@ $^ $(LDLIBS)
>
> When linking is done by gcc itself, no issue, but when it needs to be passed
> to proper ld, only LDLIBS follows and then ld cannot know what libs to link
> with.
>
> More detail:
> https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
>
> LDFLAGS
> Extra flags to give to compilers when they are supposed to invoke the linker,
> âldâ, such as -L. Libraries (-lfoo) should be added to the LDLIBS variable
> instead.
>
> LDLIBS
> Library flags or names given to compilers when they are supposed to invoke the
> linker, âldâ. LOADLIBES is a deprecated (but still supported) alternative to
> LDLIBS. Non-library linker flags, such as -L, should go in the LDFLAGS
> variable.
>
> https://lkml.org/lkml/2010/2/10/362
>
> tools/perf: libraries must come after objects
>
> Link order matters, use LDLIBS instead of LDFLAGS to properly link against
> libpthread.
>
> Signed-off-by: Fathi Boudra <fathi.boudra@xxxxxxxxxx>
> ---
> tools/testing/selftests/seccomp/Makefile | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/seccomp/Makefile b/tools/testing/selftests/seccomp/Makefile
> index aeb0c805f3ca..d1c74ce70f08 100644
> --- a/tools/testing/selftests/seccomp/Makefile
> +++ b/tools/testing/selftests/seccomp/Makefile
> @@ -1,8 +1,8 @@
> TEST_GEN_PROGS := seccomp_bpf
> CFLAGS += -Wl,-no-as-needed -Wall
> -LDFLAGS += -lpthread
> +LDLIBS += -lpthread
>
> include ../lib.mk
>
> $(TEST_GEN_PROGS): seccomp_bpf.c ../kselftest_harness.h
> - $(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
> + $(CC) $(CFLAGS) $(LDLIBS) $< -o $@

Shouldn't $(LDLIBS) follow $< ?

Thanks,
SeongJae Park

> --
> 2.13.0
>
>

Next message: Shaohua Li: "Re: [PATCH V4 10/12] block: call __bio_free in bio_endio"
Previous message: Alexei Starovoitov: "Re: [PATCH v3 net-next 00/12] bpf: rewrite value tracking in verifier"
In reply to: Fathi Boudra: "[PATCH 2/3] selftests: seccomp: use LDLIBS instead of LDFLAGS"
Next in thread: Fathi Boudra: "Re: [PATCH 2/3] selftests: seccomp: use LDLIBS instead of LDFLAGS"
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