fix debug_name handling in buffer_pool

- possible bug discovered by coverity

lib/include/srslte/common/buffer_pool.h

@@ -76,7 +76,7 @@ public:
   {
     printf("%d buffers in queue\n", (int) used.size());
     for (uint32_t i=0;i<used.size();i++) {
-      printf("%s\n", used[i]->debug_name?used[i]->debug_name:"Undefined");              
+      printf("%s\n", strlen(used[i]->debug_name)?used[i]->debug_name:"Undefined");
     }
   }
   
@@ -97,7 +97,8 @@ public:
       }
 #ifdef SRSLTE_BUFFER_POOL_LOG_ENABLED
     if (debug_name) {
-      strncpy(b->debug_name, debug_name, 128);
+      strncpy(b->debug_name, debug_name, SRSLTE_BUFFER_POOL_LOG_NAME_LEN);
+      b->debug_name[SRSLTE_BUFFER_POOL_LOG_NAME_LEN-1] = 0;
     }
 #endif
       

lib/include/srslte/common/common.h

@@ -54,6 +54,7 @@
 
 #ifdef SRSLTE_BUFFER_POOL_LOG_ENABLED
 #define pool_allocate (pool->allocate(__FUNCTION__))
+#define SRSLTE_BUFFER_POOL_LOG_NAME_LEN 128
 #else
 #define pool_allocate (pool->allocate())
 #endif
@@ -121,7 +122,7 @@ public:
     uint8_t     buffer[SRSLTE_MAX_BUFFER_SIZE_BYTES];
     uint8_t    *msg;
 #ifdef SRSLTE_BUFFER_POOL_LOG_ENABLED
-    char        debug_name[128];
+    char        debug_name[SRSLTE_BUFFER_POOL_LOG_NAME_LEN];
 #endif
 
     byte_buffer_t():N_bytes(0)
@@ -129,6 +130,9 @@ public:
       timestamp_is_set = false; 
       msg  = &buffer[SRSLTE_BUFFER_HEADER_OFFSET];
       next = NULL; 
+#ifdef SRSLTE_BUFFER_POOL_LOG_ENABLED
+      debug_name[0] = 0;
+#endif
     }
     byte_buffer_t(const byte_buffer_t& buf)
     {