On 7/11/23 6:02 AM, Andrii Nakryiko wrote:
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 :)
It does, I've used this in BPF code for Cilium, too. ;)
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.
Agree, changed into ...
/* Helper macro to clear and optionally reinitialize libbpf options struct
*
* Small helper macro to reset all fields and to reinitialize the common
* structure size member. Values provided by users in struct initializer-
* syntax as varargs can be provided as well to reinitialize options struct
* specific members.
*/
#define LIBBPF_OPTS_RESET(NAME, ...) \
do { \
memset(&NAME, 0, sizeof(NAME)); \
NAME = (typeof(NAME)) { \
.sz = sizeof(NAME), \
__VA_ARGS__ \
}; \
} while (0)
... and updated all the test cases.
Thanks,
Daniel
