contrib/rdmacm-mux: remove Wno-format-truncation flag

The flag is not recognized by some CLANG versions.
Add proper constraints in code instead.

Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Tested-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190118124614.24548-2-marcel.apfelbaum@gmail.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>

contrib/rdmacm-mux/Makefile.objs

@@ -1,4 +1,4 @@
 ifdef CONFIG_PVRDMA
-CFLAGS += -libumad -Wno-format-truncation
+CFLAGS += -libumad
 rdmacm-mux-obj-y = main.o
 endif

contrib/rdmacm-mux/main.c

@@ -42,6 +42,8 @@
 
 /* The below can be override by command line parameter */
 #define UNIX_SOCKET_PATH "/var/run/rdmacm-mux"
+/* Has format %s-%s-%d" <path>-<rdma-dev--name>-<port> */
+#define SOCKET_PATH_MAX (PATH_MAX - NAME_MAX - sizeof(int) - 2)
 #define RDMA_PORT_NUM 1
 
 typedef struct RdmaCmServerArgs {
@@ -95,7 +97,7 @@ static void help(const char *progname)
 static void parse_args(int argc, char *argv[])
 {
     int c;
-    char unix_socket_path[PATH_MAX];
+    char unix_socket_path[SOCKET_PATH_MAX];
 
     strcpy(server.args.rdma_dev_name, "");
     strcpy(unix_socket_path, UNIX_SOCKET_PATH);
@@ -113,7 +115,7 @@ static void parse_args(int argc, char *argv[])
 
         case 's':
             /* This is temporary, final name will build below */
-            strncpy(unix_socket_path, optarg, PATH_MAX);
+            strncpy(unix_socket_path, optarg, SOCKET_PATH_MAX);
             break;
 
         case 'p':