Re: [PATCH v3 bpf-next] bpftool: Make skeleton C++ compatible with explicit casts

[Yonghong Song <yonghong.song@linux.dev>]

On 1/3/26 6:14 PM, WanLi Niu wrote:
> From: WanLi Niu <niuwl1@chinatelecom.cn>
>
> Fix C++ compilation errors in generated skeleton by adding explicit
> pointer casts and using integer subtraction for offset calculation.
>
> Use struct outer::inner syntax under __cplusplus to access nested skeleton map
> structs, ensuring C++ compilation compatibility while preserving C support
>
> error: invalid conversion from 'void*' to '<obj_name>*' [-fpermissive]
>        |         skel = skel_alloc(sizeof(*skel));
>        |                ~~~~~~~~~~^~~~~~~~~~~~~~~
>        |                          |
>        |                          void*
>
> error: arithmetic on pointers to void
>        |         skel->ctx.sz = (void *)&skel->links - (void *)skel;
>        |                        ~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
>
> error: assigning to 'struct <obj_name>__<ident> *' from incompatible type 'void *'
>        |                 skel-><ident> = skel_prep_map_data((void *)data, 4096,
>        |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        |                                                 sizeof(data) - 1);
>        |                                                 ~~~~~~~~~~~~~~~~~
>
> error: assigning to 'struct <obj_name>__<ident> *' from incompatible type 'void *'
>        |         skel-><ident> = skel_finalize_map_data(&skel->maps.<ident>.initial_value,
>        |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        |                                         4096, PROT_READ | PROT_WRITE, skel->maps.<ident>.map_fd);
>        |                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Signed-off-by: WanLi Niu <niuwl1@chinatelecom.cn>
> Co-developed-by: Menglong Dong <dongml2@chinatelecom.cn>
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>

LGTM. Could you add a minimum reproducer in the commit message?

Acked-by: Yonghong Song <yonghong.song@linux.dev>