Andrii Nakryiko <andriin@xxxxxx> writes:
> LIBBPF_OPTS is implemented as a mix of field declaration and memset
> + assignment. This makes it neither variable declaration nor purely
> statements, which is a problem, because you can't mix it with either
> other variable declarations nor other function statements, because C90
> compiler mode emits warning on mixing all that together.
>
> This patch changes LIBBPF_OPTS into a strictly declaration of variable
> and solves this problem, as can be seen in case of bpftool, which
> previously would emit compiler warning, if done this way (LIBBPF_OPTS as
> part of function variables declaration block).
>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> ---
> tools/bpf/bpftool/prog.c | 6 +++---
> tools/lib/bpf/libbpf.h | 13 +++++++------
> 2 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 27da96a797ab..1a7e8ddf8232 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -1093,6 +1093,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> {
> struct bpf_object_load_attr load_attr = { 0 };
> enum bpf_prog_type common_prog_type = BPF_PROG_TYPE_UNSPEC;
> + LIBBPF_OPTS(bpf_object_open_opts, open_opts,
> + .relaxed_maps = relaxed_maps,
> + );
> enum bpf_attach_type expected_attach_type;
> struct map_replace *map_replace = NULL;
> struct bpf_program *prog = NULL, *pos;
> @@ -1106,9 +1109,6 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> const char *file;
> int idx, err;
>
> - LIBBPF_OPTS(bpf_object_open_opts, open_opts,
> - .relaxed_maps = relaxed_maps,
> - );
>
> if (!REQ_ARGS(2))
> return -1;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 0fdf086beba7..bf105e9e866f 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -77,12 +77,13 @@ struct bpf_object_open_attr {
> * bytes, but that's the best way I've found and it seems to work in practice.
> */
> #define LIBBPF_OPTS(TYPE, NAME, ...) \
> - struct TYPE NAME; \
> - memset(&NAME, 0, sizeof(struct TYPE)); \
> - NAME = (struct TYPE) { \
> - .sz = sizeof(struct TYPE), \
> - __VA_ARGS__ \
> - }
> + struct TYPE NAME = ({ \
> + memset(&NAME, 0, sizeof(struct TYPE)); \
> + (struct TYPE) { \
> + .sz = sizeof(struct TYPE), \
Wait, you can stick arbitrary code inside a variable initialisation
block like this? How does that work? Is everything before the (struct
type) just ignored (and is that a cast)?
-Toke
