Re: [PATCH] selftests: bpf: fix urandom_read build issue

[Y Song]

On Thu, Jun 7, 2018 at 3:57 AM, Anders Roxell <anders.roxell@xxxxxxxxxx> wrote:
> gcc complains that urandom_read gets built twice.
>
> gcc -o tools/testing/selftests/bpf/urandom_read
> -static urandom_read.c -Wl,--build-id
> gcc -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf
> -I../../../../include/generated  -I../../../include    urandom_read.c
> urandom_read -lcap -lelf -lrt -lpthread -o
> tools/testing/selftests/bpf/urandom_read
> gcc: fatal error: input file
> âtools/testing/selftests/bpf/urandom_readâ is the
> same as output file
> compilation terminated.
> ../lib.mk:110: recipe for target
> 'tools/testing/selftests/bpf/urandom_read' failed

What is the build/make command to reproduce the above failure?

> To fix this issue remove the urandom_read target and so target
> TEST_CUSTOM_PROGS gets used.
>
> Fixes: 81f77fd0deeb ("bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID")
> Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/Makefile | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 607ed8729c06..67285591ffd7 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -16,10 +16,8 @@ LDLIBS += -lcap -lelf -lrt -lpthread
>  TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
>  all: $(TEST_CUSTOM_PROGS)
>
> -$(TEST_CUSTOM_PROGS): urandom_read
> -
> -urandom_read: urandom_read.c
> -       $(CC) -o $(TEST_CUSTOM_PROGS) -static $< -Wl,--build-id
> +$(TEST_CUSTOM_PROGS): $(OUTPUT)/%: %.c
> +       $(CC) -o $@ -static $< -Wl,--build-id
>
>  # Order correspond to 'make run_tests' order
>  TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
> --
> 2.17.1
>