MYNEWT-702 dbg: Erase mempool entries during free.

This behavior only takes effect when BLE_HS_DEBUG is enabled.  When a
host mempool entry is freed, it is memset to 0xff.  This will hopefully
help catch dangling pointer bugs.

X-Original-Commit: b8380e94765005b48bfeebe06dee2c2ac924da96

nimble/host/src/ble_att_svr.c

@@ -2170,6 +2170,9 @@ ble_att_svr_prep_free(struct ble_att_prep_entry *entry)
 {
     if (entry != NULL) {
         os_mbuf_free_chain(entry->bape_value);
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+        memset(entry, 0xff, sizeof *entry);
+#endif
         os_memblock_put(&ble_att_svr_prep_entry_pool, entry);
     }
 }

nimble/host/src/ble_gattc.c

@@ -710,6 +710,9 @@ ble_gattc_proc_free(struct ble_gattc_proc *proc)
             break;
         }
 
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+        memset(proc, 0xff, sizeof *proc);
+#endif
         rc = os_memblock_put(&ble_gattc_proc_pool, proc);
         BLE_HS_DBG_ASSERT_EVAL(rc == 0);
     }

nimble/host/src/ble_hs_conn.c

@@ -217,6 +217,9 @@ ble_hs_conn_free(struct ble_hs_conn *conn)
         ble_hs_conn_delete_chan(conn, chan);
     }
 
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+    memset(conn, 0xff, sizeof *conn);
+#endif
     rc = os_memblock_put(&ble_hs_conn_pool, conn);
     BLE_HS_DBG_ASSERT_EVAL(rc == 0);
 

nimble/host/src/ble_l2cap.c

@@ -81,6 +81,9 @@ ble_l2cap_chan_free(struct ble_l2cap_chan *chan)
     os_mbuf_free_chain(chan->rx_buf);
     ble_l2cap_coc_cleanup_chan(chan);
 
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+    memset(chan, 0xff, sizeof *chan);
+#endif
     rc = os_memblock_put(&ble_l2cap_chan_pool, chan);
     BLE_HS_DBG_ASSERT_EVAL(rc == 0);
 

nimble/host/src/ble_l2cap_sig.c

@@ -206,6 +206,9 @@ ble_l2cap_sig_proc_free(struct ble_l2cap_sig_proc *proc)
     if (proc != NULL) {
         ble_l2cap_sig_dbg_assert_proc_not_inserted(proc);
 
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+        memset(proc, 0xff, sizeof *proc);
+#endif
         rc = os_memblock_put(&ble_l2cap_sig_proc_pool, proc);
         BLE_HS_DBG_ASSERT_EVAL(rc == 0);
     }

nimble/host/src/ble_sm.c

@@ -393,7 +393,9 @@ ble_sm_proc_free(struct ble_sm_proc *proc)
 
     if (proc != NULL) {
         ble_sm_dbg_assert_not_inserted(proc);
-
+#if MYNEWT_VAL(BLE_HS_DEBUG)
+        memset(proc, 0xff, sizeof *proc);
+#endif
         rc = os_memblock_put(&ble_sm_proc_pool, proc);
         BLE_HS_DBG_ASSERT_EVAL(rc == 0);
     }