selftests/net: suppress clang's "variable-sized type not at the end" warning

[PATCH v2] selftests/net: suppress clang's "variable-sized type not at the end" warning

Posted by John Hubbard 3 months, 3 weeks ago

When building with clang, via:

    make LLVM=1 -C tools/testing/selftest

...clang warns that "a variable sized type not at the end of a struct or
class is a GNU extension".

These cases are not easily changed, because they involve structs that
are part of the API. Fortunately, however, the tests seem to be doing
just fine (specifically, neither affected test runs any differently with
gcc vs. clang builds, on my test system) regardless of the warning. So,
all the warning is doing is preventing a clean build of selftests/net.

Fix this by suppressing this particular clang warning for the
selftests/net suite.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---

Changes since the first version:

1) Rebased onto Linux 6.10-rc1

thanks,
John Hubbard


 tools/testing/selftests/net/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index bd01e4a0be2c..9a3b766c8781 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -6,6 +6,10 @@ CFLAGS += -I../../../../usr/include/ $(KHDR_INCLUDES)
 # Additional include paths needed by kselftest.h
 CFLAGS += -I../
 
+ifneq ($(LLVM),)
+    CFLAGS += -Wno-gnu-variable-sized-type-not-at-end
+endif
+
 TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh \
 	      rtnetlink.sh xfrm_policy.sh test_blackhole_dev.sh
 TEST_PROGS += fib_tests.sh fib-onlink-tests.sh pmtu.sh udpgso.sh ip_defrag.sh

base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b
-- 
2.45.1

Re: [PATCH v2] selftests/net: suppress clang's "variable-sized type not at the end" warning

Posted by Nathan Chancellor 3 months, 3 weeks ago

On Mon, May 27, 2024 at 02:36:41PM -0700, John Hubbard wrote:
> When building with clang, via:
> 
>     make LLVM=1 -C tools/testing/selftest
> 
> ...clang warns that "a variable sized type not at the end of a struct or
> class is a GNU extension".
> 
> These cases are not easily changed, because they involve structs that
> are part of the API. Fortunately, however, the tests seem to be doing
> just fine (specifically, neither affected test runs any differently with
> gcc vs. clang builds, on my test system) regardless of the warning. So,
> all the warning is doing is preventing a clean build of selftests/net.
> 
> Fix this by suppressing this particular clang warning for the
> selftests/net suite.
> 
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> 
> Changes since the first version:
> 
> 1) Rebased onto Linux 6.10-rc1
> 
> thanks,
> John Hubbard
> 
> 
>  tools/testing/selftests/net/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> index bd01e4a0be2c..9a3b766c8781 100644
> --- a/tools/testing/selftests/net/Makefile
> +++ b/tools/testing/selftests/net/Makefile
> @@ -6,6 +6,10 @@ CFLAGS += -I../../../../usr/include/ $(KHDR_INCLUDES)
>  # Additional include paths needed by kselftest.h
>  CFLAGS += -I../
>  
> +ifneq ($(LLVM),)
> +    CFLAGS += -Wno-gnu-variable-sized-type-not-at-end

For what it's worth, the main kernel has -Wno-gnu because there is
little point in warning about the use of GNU extensions when building
with '-std=gnu...'. It may be worth doing this anywhere that uses a GNU
standard in the selftests but I guess it depends on how noisy things
are.

> +endif
> +
>  TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh \
>  	      rtnetlink.sh xfrm_policy.sh test_blackhole_dev.sh
>  TEST_PROGS += fib_tests.sh fib-onlink-tests.sh pmtu.sh udpgso.sh ip_defrag.sh
> 
> base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b
> -- 
> 2.45.1
> 
>

Re: [PATCH v2] selftests/net: suppress clang's "variable-sized type not at the end" warning

Posted by John Hubbard 3 months, 3 weeks ago

On 5/28/24 1:39 PM, Nathan Chancellor wrote:
> On Mon, May 27, 2024 at 02:36:41PM -0700, John Hubbard wrote:
...
>> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
>> index bd01e4a0be2c..9a3b766c8781 100644
>> --- a/tools/testing/selftests/net/Makefile
>> +++ b/tools/testing/selftests/net/Makefile
>> @@ -6,6 +6,10 @@ CFLAGS += -I../../../../usr/include/ $(KHDR_INCLUDES)
>>   # Additional include paths needed by kselftest.h
>>   CFLAGS += -I../
>>   
>> +ifneq ($(LLVM),)
>> +    CFLAGS += -Wno-gnu-variable-sized-type-not-at-end
> 
> For what it's worth, the main kernel has -Wno-gnu because there is
> little point in warning about the use of GNU extensions when building
> with '-std=gnu...'. It may be worth doing this anywhere that uses a GNU
> standard in the selftests but I guess it depends on how noisy things
> are.

I think there might be one or two other cases like this that I haven't
gotten around to, so yes you are right, this probably should be moved
into lib.mk instead.

I'll do that in a v3.

> 
>> +endif
>> +
>>   TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh \
>>   	      rtnetlink.sh xfrm_policy.sh test_blackhole_dev.sh
>>   TEST_PROGS += fib_tests.sh fib-onlink-tests.sh pmtu.sh udpgso.sh ip_defrag.sh
>>
>> base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b
>> -- 
>> 2.45.1
>>
>>

thanks,
-- 
John Hubbard
NVIDIA

Re: [PATCH v2] selftests/net: suppress clang's "variable-sized type not at the end" warning

Posted by MPTCP CI 3 months, 3 weeks ago

Hi John,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal: Success! ✅
- KVM Validation: debug: Success! ✅
- KVM Validation: btf (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/9260539047

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/31d0136a686c
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=856310


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)