Re: [PATCH bpf-next] bpf: Cast helper IDs to the helper type in bpf_helper_defs.h

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Tue, Oct 20, 2026 at 03:12 AM Maxim Skokov <skokovmaksimevg@gmail.com> wrote:
> Converting void * to a function pointer is a GNU extension in C (gcc
> -pedantic: "ISO C forbids initialization between function pointer and
> 'void *'") and an error in C++, so BPF programs written in C++ can't
> include bpf_helpers.h.

What C++ programs you have in mind?
Since today there is one as a selftest.
C++ is far from being supported.

... and including the header doesn't get them far. bpf_for() and bpf_repeat()
in bpf_helpers.h initialize 'struct bpf_iter_num *___p' with (void *)0,
which is an error in C++. The bpf_iter_num_*() externs there have no
extern "C", so the kfunc names get mangled. vmlinux.h doesn't compile
as C++ at all: struct page has a field named private and struct device
has one named class.

> Tested: the generated header compiles with clang for the bpf target as
> C, gnu++20 and c++17, and with gcc as C; with gcc -pedantic the 211
> function pointer warnings are gone. All 1082 selftests BPF programs
> build to byte-identical objects with the old and the new header.

Those are all C programs.

It feels to me that you're scratching the surface.
We have to see full roadmap to decide whether we should even bother
making these steps.

pw-bot: cr