util: Consolidate and improve workarounds for clang-tidy issue 58992

We have several workarounds for a clang-tidy bug where the checker doesn't
recognize that a number of system calls write to - and therefore initialise
- a socket address.  We can't neatly use a suppression, because the bogus
warning shows up some time after the actual system call, when we access
a field of the socket address which clang-tidy erroneously thinks is
uninitialised.

Consolidate these workarounds into one place by using macros to implement
wrappers around affected system calls which add a memset() of the sockaddr
to silence clang-tidy.  This removes the need for the individual memset()
workarounds at the callers - and the somewhat longwinded explanatory
comments.

We can then use a #define to not include the hack in "real" builds, but
only consider it for clang-tidy.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

tcp.c

@@ -2752,19 +2752,13 @@ void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
 			const struct timespec *now)
 {
 	struct sockaddr_storage sa;
+	socklen_t sl = sizeof(sa);
 	union tcp_conn *conn;
-	socklen_t sl;
 	int s;
 
 	if (c->no_tcp || c->tcp.conn_count >= TCP_MAX_CONNS)
 		return;
 
-	sl = sizeof(sa);
-	/* FIXME: Workaround clang-tidy not realizing that accept4()
-	 * writes the socket address.  See
-	 * https://github.com/llvm/llvm-project/issues/58992
-	 */
-	memset(&sa, 0, sizeof(struct sockaddr_in6));
 	s = accept4(ref.fd, (struct sockaddr *)&sa, &sl, SOCK_NONBLOCK);
 	if (s < 0)
 		return;