socket.c: suppress warnings

* ext/socket/socket.c (rsock_sys_fail_sockaddr): cast down explicitly
  to suppress warnings.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40155 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/socket.c

@@ -53,7 +53,7 @@ rsock_sys_fail_sockaddr(const char *mesg, VALUE addr)
 
     rai = rsock_addrinfo_new(
             (struct sockaddr *)RSTRING_PTR(addr),
-            RSTRING_LEN(addr),
+            (socklen_t)RSTRING_LEN(addr), /* overflow should be checked already */
             PF_UNSPEC, 0, 0, Qnil, Qnil);
 
     rsock_sys_fail_addrinfo(mesg, rai);