Fix compilation error on GCC 8.x due to usage of strncpy in zmq_imp_rx/tx.

Fixed also order in which zmq object is zero'ed out.

lib/src/phy/rf/rf_zmq_imp_rx.c

@@ -100,12 +100,13 @@ int rf_zmq_rx_open(rf_zmq_rx_t* q, char* id, void* zmq_ctx, char* sock_args)
   int ret = SRSLTE_ERROR;
 
   if (q) {
-    // Copy id
-    strncpy(q->id, id, 16);
-
     // Zero object
     bzero(q, sizeof(rf_zmq_tx_t));
 
+    // Copy id
+    strncpy(q->id, id, ZMQ_ID_STRLEN - 1);
+    q->id[ZMQ_ID_STRLEN - 1] = '\0';
+
     // Create socket
     q->sock = zmq_socket(zmq_ctx, ZMQ_REQ);
     if (!q->sock) {

lib/src/phy/rf/rf_zmq_imp_trx.h

@@ -38,9 +38,10 @@
 #define ZMQ_MAX_BUFFER_SIZE (NSAMPLES2NBYTES(3072000)) // 10 subframes at 20 MHz
 #define ZMQ_TIMEOUT_MS (1000)
 #define ZMQ_BASERATE_DEFAULT_HZ (23040000)
+#define ZMQ_ID_STRLEN 16
 
 typedef struct {
-  char            id[16];
+  char            id[ZMQ_ID_STRLEN];
   void*           sock;
   uint64_t        nsamples;
   bool            running;
@@ -49,7 +50,7 @@ typedef struct {
 } rf_zmq_tx_t;
 
 typedef struct {
-  char                id[16];
+  char                id[ZMQ_ID_STRLEN];
   void*               sock;
   uint64_t            nsamples;
   bool                running;

lib/src/phy/rf/rf_zmq_imp_tx.c

@@ -36,12 +36,13 @@ int rf_zmq_tx_open(rf_zmq_tx_t* q, const char* id, void* zmq_ctx, char* sock_arg
   int ret = SRSLTE_ERROR;
 
   if (q) {
-    // Copy id
-    strncpy(q->id, id, 16);
-
     // Zero object
     bzero(q, sizeof(rf_zmq_tx_t));
 
+    // Copy id
+    strncpy(q->id, id, ZMQ_ID_STRLEN - 1);
+    q->id[ZMQ_ID_STRLEN - 1] = '\0';
+
     // Create socket
     q->sock = zmq_socket(zmq_ctx, ZMQ_REP);
     if (!q->sock) {