netdev - [iproute2, PATCH v2 1/2] arpd: use designated initializers for msghdr structure

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Message-ID: <20240928090312.1079952-1-dario.binacchi@amarulasolutions.com>
Date: Sat, 28 Sep 2024 11:03:11 +0200
From: Dario Binacchi <dario.binacchi@...rulasolutions.com>
To: netdev@...r.kernel.org
Cc: Stephen Hemminger <stephen@...workplumber.org>,
	linux-amarula@...rulasolutions.com,
	Dario Binacchi <dario.binacchi@...rulasolutions.com>
Subject: [iproute2, PATCH v2 1/2] arpd: use designated initializers for msghdr structure

This patch fixes the following error:

arpd.c:442:17: error: initialization of 'int' from 'void *' makes integer from pointer without a cast [-Wint-conversion]
  442 |                 NULL,   0,

raised by Buildroot autobuilder [1].

In the case in question, the analysis of socket.h [2] containing the
msghdr structure shows that it has been modified with the addition of
padding fields, which cause the compilation error. The use of designated
initializers allows the issue to be fixed.

struct msghdr {
	void *msg_name;
	socklen_t msg_namelen;
	struct iovec *msg_iov;
#if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __BIG_ENDIAN
	int __pad1;
#endif
	int msg_iovlen;
#if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __LITTLE_ENDIAN
	int __pad1;
#endif
	void *msg_control;
#if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __BIG_ENDIAN
	int __pad2;
#endif
	socklen_t msg_controllen;
#if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __LITTLE_ENDIAN
	int __pad2;
#endif
	int msg_flags;
};

[1] http://autobuild.buildroot.org/results/e4cdfa38ae9578992f1c0ff5c4edae3cc0836e3c/
[2] iproute2/host/mips64-buildroot-linux-musl/sysroot/usr/include/sys/socket.h

Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
---
Changes v1 -> v2:
 - Put one field per line.
 - Drop (void *) cast for msg_control field.

 misc/arpd.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/misc/arpd.c b/misc/arpd.c
index e77ef53928a2..91f0006a60aa 100644
--- a/misc/arpd.c
+++ b/misc/arpd.c
@@ -437,10 +437,13 @@ static void get_kern_msg(void)
 	struct iovec iov;
 	char   buf[8192];
 	struct msghdr msg = {
-		(void *)&nladdr, sizeof(nladdr),
-		&iov,	1,
-		NULL,	0,
-		0
+		.msg_name = &nladdr,
+		.msg_namelen = sizeof(nladdr),
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = NULL,
+		.msg_controllen = 0,
+		.msg_flags = 0
 	};
 
 	iov.iov_base = buf;
-- 
2.43.0