On Tue, Mar 12, 2024 at 5:08 PM Kui-Feng Lee <sinquersw@xxxxxxxxx> wrote:
>
>
>
> On 3/12/24 15:47, Andrii Nakryiko wrote:
> > On Mon, Mar 11, 2024 at 6:38 PM Kui-Feng Lee <thinker.li@xxxxxxxxx> wrote:
> >>
> >> According to a report, skeletons fail to assign shadow pointers when being
> >> compiled with C++ programs. Unlike C doing implicit casting for void
> >> pointers, C++ requires an explicit casting.
> >>
> >> To support C++, we do explicit casting for each shadow pointer.
> >>
> >> Cc: yhs@xxxxxxxx
> >> Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
> >> ---
> >> tools/bpf/bpftool/gen.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> >> index 4fa4ade1ce74..dedafea0c127 100644
> >> --- a/tools/bpf/bpftool/gen.c
> >> +++ b/tools/bpf/bpftool/gen.c
> >> @@ -1131,7 +1131,7 @@ static void gen_st_ops_shadow_init(struct btf *btf, struct bpf_object *obj)
> >> continue;
> >> codegen("\
> >> \n\
> >> - obj->struct_ops.%1$s = bpf_map__initial_value(obj->maps.%1$s, NULL);\n\
> >> + obj->struct_ops.%1$s = (typeof(obj->struct_ops.%1$s))bpf_map__initial_value(obj->maps.%1$s, NULL);\n\
> >
> > Given we have a named struct type for this and we use explicit type
> > names in other parts of generated skeleton code, let's maybe use
> > "struct %s__%s__%s" explicitly here (passing in obj_name, ident,
> > type_name)?
>
> I have considered about this solution. But, C++ works differently. It
> has nested namespaces. That means it should be referred as
> "XXX_skeleton::OOO_st_ops_map" in C++. Then, we need #if #else #endif
> directives to provide two separated casting.
>
we cast to (struct <skeleton> *) by name of the skeleton, so it should
be fine, I don't see why we'd need to do something C++ specific here
> >
> > No strong preferences, but feels like a consistent approach here would be nice.
> >
> >> \n\
> >> ", ident);
> >> }
> >> --
> >> 2.34.1
> >>
