gattlib-py: Fix some memory leaks

common/gattlib_common.c

@@ -191,3 +191,10 @@ void gattlib_handler_dispatch_to_thread(struct gattlib_handler* handler, void (*
 		return;
 	}
 }
+
+// Helper function to free memory from Python frontend
+void gattlib_free_mem(void *ptr) {
+	if (ptr != NULL) {
+		free(ptr);
+	}
+}

common/gattlib_eddystone.c

@@ -28,10 +28,10 @@ struct on_eddystone_discovered_device_arg {
 static void on_eddystone_discovered_device(void *adapter, const char* addr, const char* name, void *user_data)
 {
 	struct on_eddystone_discovered_device_arg *callback_data = user_data;
-	gattlib_advertisement_data_t *advertisement_data;
+	gattlib_advertisement_data_t *advertisement_data = NULL;
 	size_t advertisement_data_count;
 	uint16_t manufacturer_id;
-	uint8_t *manufacturer_data;
+	uint8_t *manufacturer_data = NULL;
 	size_t manufacturer_data_size;
 	int ret;
 
@@ -46,6 +46,13 @@ static void on_eddystone_discovered_device(void *adapter, const char* addr, cons
 			advertisement_data, advertisement_data_count,
 			manufacturer_id, manufacturer_data, manufacturer_data_size,
 			callback_data->user_data);
+
+	if (advertisement_data != NULL) {
+		free(advertisement_data);
+	}
+	if (manufacturer_data != NULL) {
+		free(manufacturer_data);
+	}
 }
 
 int gattlib_adapter_scan_eddystone(void *adapter, int16_t rssi_threshold, uint32_t eddystone_types,

gattlib-py/gattlib/__init__.py

@@ -217,3 +217,7 @@ class GattlibAdvertisementData(Structure):
 # int gattlib_mainloop_python(PyObject *handler, PyObject *user_data)
 gattlib_mainloop = gattlib.gattlib_mainloop_python
 gattlib_mainloop.argtypes = [py_object, py_object]
+
+# void gattlib_free_mem(void *ptr])
+gattlib_free_mem = gattlib.gattlib_free_mem
+gattlib_free_mem.argtypes = [c_void_p]

gattlib-py/gattlib/adapter.py

@@ -268,4 +268,7 @@ def gattlib_get_advertisement_data_from_mac(self, mac_address):
             for i in range(_manufacturer_data_len.value):
                 manufacturer_data[i] = c_bytearray.contents[i] & 0xFF
 
+        gattlib_free_mem(_advertisement_data)
+        gattlib_free_mem(_manufacturer_data)
+
         return advertisement_data, _manufacturer_id.value, manufacturer_data

gattlib-py/gattlib/device.py

@@ -40,7 +40,10 @@ def __init__(self, adapter: Adapter, addr: str, name: str = None):
             self._addr = addr
         self._name = name
         self._connection = None
+        # We use a lock because on disconnection, we will set self._connection to None
         self._connection_lock = threading.Lock()
+        # We use a lock on disconnection to ensure the memory is safely freed
+        self._disconnection_lock = threading.Lock()
 
         self.on_connection_callback = None
         self.on_connection_error_callback = None
@@ -51,6 +54,10 @@ def __init__(self, adapter: Adapter, addr: str, name: str = None):
         # Dictionnary for GATT characteristic callback
         self._gatt_characteristic_callbacks = {}
 
+        # Memory that could be allocated by native gattlib
+        self._services_ptr = None
+        self._characteristics_ptr = None
+
     @property
     def mac_address(self) -> str:
         """Return Device MAC Address"""
@@ -109,9 +116,24 @@ def register_on_disconnect(self, callback, user_data=None):
         self.disconnection_callback = callback
 
         def on_disconnection(user_data):
+            self._disconnection_lock.acquire()
+
             if self.disconnection_callback:
                 self.disconnection_callback()
 
+            # On disconnection, we do not need the list of GATT services and GATT characteristics
+            if self._services_ptr:
+                gattlib_free_mem(self._services_ptr)
+                self._services_ptr = None
+            if self._characteristics_ptr:
+                gattlib_free_mem(self._characteristics_ptr)
+                self._characteristics_ptr = None
+
+            # Reset the connection handler
+            self._connection = None
+
+            self._disconnection_lock.release()
+
         gattlib_register_on_disconnect(self.connection,
                                        gattlib_disconnected_device_python_callback,
                                        gattlib_python_callback_args(on_disconnection, user_data))
@@ -130,29 +152,29 @@ def discover(self):
         #
         # Discover GATT Services
         #
-        _services = POINTER(GattlibPrimaryService)()
+        self._services_ptr = POINTER(GattlibPrimaryService)()
         _services_count = c_int(0)
-        ret = gattlib_discover_primary(self.connection, byref(_services), byref(_services_count))
+        ret = gattlib_discover_primary(self.connection, byref(self._services_ptr), byref(_services_count))
         handle_return(ret)
 
         self._services = {}
         for i in range(0, _services_count.value):
-            service = GattService(self, _services[i])
+            service = GattService(self, self._services_ptr[i])
             self._services[service.short_uuid] = service
 
             logger.debug("Service UUID:0x%x" % service.short_uuid)
 
         #
         # Discover GATT Characteristics
         #
-        _characteristics = POINTER(GattlibCharacteristic)()
+        self._characteristics_ptr = POINTER(GattlibCharacteristic)()
         _characteristics_count = c_int(0)
-        ret = gattlib_discover_char(self.connection, byref(_characteristics), byref(_characteristics_count))
+        ret = gattlib_discover_char(self.connection, byref(self._characteristics_ptr), byref(_characteristics_count))
         handle_return(ret)
 
         self._characteristics = {}
         for i in range(0, _characteristics_count.value):
-            characteristic = GattCharacteristic(self, _characteristics[i])
+            characteristic = GattCharacteristic(self, self._characteristics_ptr[i])
             self._characteristics[characteristic.short_uuid] = characteristic
 
             logger.debug("Characteristic UUID:0x%x" % characteristic.short_uuid)
@@ -201,6 +223,9 @@ def get_advertisement_data(self):
             for i in range(_manufacturer_data_len.value):
                 manufacturer_data[i] = c_bytearray.contents[i] & 0xFF
 
+        gattlib_free_mem(_advertisement_data)
+        gattlib_free_mem(_manufacturer_data)
+
         return advertisement_data, _manufacturer_id.value, manufacturer_data
 
     @property