Re: [PATCH] libbpf: export inline helpers as symbols for xsk

On Mon, Apr 26, 2021 at 1:22 PM Kumar Kartikeya Dwivedi
[off-list ref] wrote:

This helps people writing language bindings to not have to rewrite C
wrappers for inline functions in the headers. We force inline the
definition from the header for C and C++ consumers, but also export a
symbol in the library for others. This keeps the performance
advantages similar to using static inline, while also allowing tools
like Rust's bindgen to generate wrappers for the functions.

Also see
https://lore.kernel.org/bpf/CAJ8uoz0QqR97qEYYK=VVCE9A=V=k2tKnH6wNM48jeak2RAmL0A@mail.gmail.com/ (local)
for some context.

Also see https://github.com/xdp-project/xdp-tools/pull/97 for more
discussion on the same.

extern inline is used as it's slightly better since it warns when an
inline definition is missing.

The fvisibility attribute goes on the inline definition, as essentially
it acts as a declaration for the function, while the extern inline
declaration ends up acting as a definition.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---

xsk is moving into libxdp, why not do this there, instead of exporting
a lot of symbols that we'll be deprecating very soon. It will also
incentivise customers to make a move more promptly.

Bjorn, Magnus, what's the status of libxsk in libxdp?

 tools/lib/bpf/libbpf.map | 16 ++++++++++++++
 tools/lib/bpf/xsk.c      | 24 +++++++++++++++++++++
 tools/lib/bpf/xsk.h      | 45 +++++++++++++++++++++++-----------------
 3 files changed, 66 insertions(+), 19 deletions(-)

[...]