On Mon, Jul 10, 2023 at 1:12 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> Add a small and generic LIBBPF_OPTS_CLEAR() helper macros which clears
> an opts structure and reinitializes its .sz member to place the structure
> size. I found this very useful when developing selftests, but it is also
> generic enough as a macro next to the existing LIBBPF_OPTS() which hides
> the .sz initialization, too.
>
> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf_common.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf_common.h b/tools/lib/bpf/libbpf_common.h
> index 9a7937f339df..eb180023aa97 100644
> --- a/tools/lib/bpf/libbpf_common.h
> +++ b/tools/lib/bpf/libbpf_common.h
> @@ -70,4 +70,15 @@
> }; \
> })
>
> +/* Helper macro to clear a libbpf options struct
> + *
> + * Small helper macro to reset all fields and to reinitialize the common
> + * structure size member.
> + */
> +#define LIBBPF_OPTS_CLEAR(NAME) \
> + do { \
> + memset(&NAME, 0, sizeof(NAME)); \
> + NAME.sz = sizeof(NAME); \
> + } while (0)
> +
This is fine, but I think you can go a half-step further and have
something even more universal and useful. Something like this:
#define LIBBPF_OPTS_RESET(NAME, ...)
do {
memset(&NAME, 0, sizeof(NAME));
NAME = (typeof(NAME)) {
.sz = sizeof(struct TYPE),
__VA_ARGS__
};
while (0);
I actually haven't tried if that typeof() trick works, but I hope it does :)
Then your LIBBPF_OPTS_CLEAR() is just LIBBPF_OPTS_RESET(x). But you
can also re-initialize:
LIBBPF_OPTS_RESET(x, .flags = 123, .prog_fd = 456);
It's more in line with LIBBPF_OPTS() itself in capabilities, except it
works on existing variable.
> #endif /* __LIBBPF_LIBBPF_COMMON_H */
> --
> 2.34.1
>
