Re: selftests: hid: trouble building with clang due to missing header

[Nick Desaulniers]

+ Ben, author of commit dbb60c8a26da ("selftests: add tests for the
HID-bpf initial implementation")

On Tue, Aug 22, 2023 at 1:34 PM Justin Stitt <justinstitt@xxxxxxxxxx> wrote:
>
> Hi, I'd like to get some help with building the kselftest target.
>
> I am running into some warnings within the hid tree:
> | progs/hid_bpf_helpers.h:9:38: error: declaration of 'struct
> hid_bpf_ctx' will \
> |       not be visible outside of this function [-Werror,-Wvisibility]
> |     9 | extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
> |       |                                      ^
> | progs/hid.c:23:35: error: incompatible pointer types passing 'struct
> hid_bpf_ctx *' \
> |       to parameter of type 'struct hid_bpf_ctx *'
> [-Werror,-Wincompatible-pointer-types]
> |    23 |         __u8 *rw_data = hid_bpf_get_data(hid_ctx, 0 /*
> offset */, 3 /* size */);
>
> This warning, amongst others, is due to some symbol not being included.
> In this case, `struct hid_bpf_ctx` is not being defined anywhere that I
> can see inside of the testing tree itself.
>
> Instead, `struct hid_bpf_ctx` is defined and implemented at
> `include/linux/hid_bpf.h`. AFAIK, I cannot just include this header as
> the tools directory is a separate entity from kbuild and these tests are
> meant to be built/ran without relying on kernel headers. Am I correct in
> this assumption? At any rate, the include itself doesn't work. How can I
> properly include this struct definition and fix the warning(s)?
>
> Please note that we cannot just forward declare the struct as it is
> being dereferenced and would then yield a completely different
> error/warning for an incomplete type. We need the entire implementation
> for the struct included.
>
> Other symbols also defined in `include/linux/hid_bpf.h` that we need are
> `struct hid_report_type` and `HID_BPF_FLAG...`
>
> Here's the invocation I am running to build kselftest:
> `$ make LLVM=1 ARCH=x86_64 mrproper headers && make LLVM=1 ARCH=x86_64
> -j128 V=1 -C tools/testing/selftests`
>
> If anyone is currently getting clean builds of kselftest with clang,
> what invocation works for you?
>
>
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1698
> Full-build-log:
> https://gist.github.com/JustinStitt/b217f6e47c1d762e5e1cc6c3532f1bbb
> (V=1)
>
> Thanks.
> Justin



-- 
Thanks,
~Nick Desaulniers