netdev - [PATCH bpf-next v6 5/8] libbpf: Add helper macro to clear opts structs

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Message-Id: <20230719140858.13224-6-daniel@iogearbox.net>
Date: Wed, 19 Jul 2023 16:08:55 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: ast@...nel.org
Cc: andrii@...nel.org,
	martin.lau@...ux.dev,
	razor@...ckwall.org,
	sdf@...gle.com,
	john.fastabend@...il.com,
	kuba@...nel.org,
	dxu@...uu.xyz,
	joe@...ium.io,
	toke@...nel.org,
	davem@...emloft.net,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf-next v6 5/8] libbpf: Add helper macro to clear opts structs

Add a small and generic LIBBPF_OPTS_RESET() helper macros which clears an
opts structure and reinitializes its .sz member to place the structure
size. Additionally, the user can pass option-specific data to reinitialize
via varargs.

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@...earbox.net>
---
 tools/lib/bpf/libbpf_common.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tools/lib/bpf/libbpf_common.h b/tools/lib/bpf/libbpf_common.h
index 9a7937f339df..b7060f254486 100644
--- a/tools/lib/bpf/libbpf_common.h
+++ b/tools/lib/bpf/libbpf_common.h
@@ -70,4 +70,20 @@
 		};							    \
 	})
 
+/* 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)
+
 #endif /* __LIBBPF_LIBBPF_COMMON_H */
-- 
2.34.1