Nanobing leak warnings

[ENAC-Robotique]

Hello,
I'm using the python bindings for ecal6 on Ubuntu 22.04, installed from pypi.

When my application stops, it prints a lot of warnings from nanobind.
I don't know the severity of this issue, but is it possible to at least silence those warnings ?

Nanobind leak warnings

Protobuf version: 4.25.2
[eCAL][Config] Yaml configuration loaded from "/etc/ecal/ecal.yaml".
^Cnanobind: leaked 5 instances!
 - leaked instance 0x7d6287b9c228 of type "ecal.nanobind_core.DataTypeInformation"
 - leaked instance 0x7d628712c408 of type "ecal.nanobind_core.Subscriber"
 - leaked instance 0x7d62877aa768 of type "ecal.nanobind_core.SubscriberConfiguration"
 - leaked instance 0x7d62872c13a8 of type "ecal.nanobind_core.SubscriberConfiguration"
 - leaked instance 0x7d6287b02548 of type "ecal.nanobind_core.SubscriberConfiguration"
nanobind: leaked 5 types!
 - leaked type "ecal.nanobind_core.TopicId"
 - leaked type "ecal.nanobind_core.ReceiveCallbackData"
 - leaked type "ecal.nanobind_core.DataTypeInformation"
 - leaked type "ecal.nanobind_core.Subscriber"
 - leaked type "ecal.nanobind_core.SubscriberConfiguration"
nanobind: leaked 37 functions!
 - leaked function ""
 - leaked function ""
 - leaked function "__repr__"
 - leaked function "__lt__"
 - leaked function "get_topic_name"
 - leaked function "set_receive_callback"
 - leaked function ""
 - leaked function ""
 - leaked function "__lt__"
 - leaked function ""
 - leaked function ""
 - leaked function "__eq__"
 - leaked function "get_data_type_information"
 - leaked function ""
 - leaked function ""
 - leaked function ""
 - leaked function "remove_receive_callback"
 - leaked function ""
 - leaked function "get_publisher_count"
 - leaked function "__init__"
 - leaked function ""
 - leaked function ""
 - leaked function "__init__"
 - leaked function ""
 - leaked function "get_topic_id"
 - leaked function "__hash__"
 - leaked function ""
 - leaked function "__init__"
 - leaked function "__init__"
 - leaked function "__hash__"
 - leaked function "__init__"
 - leaked function "__repr__"
 - leaked function ""
 - leaked function "__eq__"
 - leaked function ""
 - leaked function ""
 - leaked function "__repr__"
nanobind: this is likely caused by a reference counting issue in the binding code.
See https://nanobind.readthedocs.io/en/latest/refleaks.htmldouble free or corruption (!prev)
Aborted

[KerstinKeller]

As far as I know, it's not possible to silence the warnings. However, what is your exact usage of eCAL? E.g. when you have global variables (ecal publishers / ecal subscribers) the warning may occur, due to how Python is doing its cleanup routines. If you have the variables inside a function (e.g. def main():) the warnings should not occur.
The same might happen with subscribers that register (but do not unregister) callbacks.

Do you have sample code? You can also take a look at the ecal samples (nanobind_core subfolder in lang/python/samples), which do not issue any warnings.

[ENAC-Robotique]

Ok, unregistering callbacks solve the issue, I will do that !

I wrote a small sample application adapted to my messages.
Commenting line 35 self.sub.remove_receive_callback() reveals the warnings.

Thank you for your answer, and thank you for making eCAL available on pypi, it solves a lot of venv headaches on our side!

import ecal.nanobind_core as ecal_core
from ecal.msg.proto.core import Subscriber as ProtobufSubscriber
from ecal.msg.common.core import ReceiveCallbackData
import lidar_data_pb2 as lidar_pb
import time


class LidarWatcher:
    def __init__(self):
        if not ecal_core.is_initialized():
            # Initialize eCAL. You always have to initialize eCAL before using its API.
            # The name of our eCAL Process will be "ecal test rcv". 
            # This name will be visible in the eCAL Monitor, once the process is running.
            ecal_core.initialize("ecal test rcv")
        
        # Set the state for the program.
        # You can vary between different states like healthy, warning, critical ...
        # This can be used to communicate the application state to applications like eCAL Monitor/Sys.
        ecal_core.process.set_state(ecal_core.process.Severity.HEALTHY, ecal_core.process.SeverityLevel.LEVEL1, "I feel good!")


        # Creating the eCAL Subscriber. An eCAL Process can create multiple subscribers (and publishers).
        # The topic we are going to receive is called "lidar_data".
        self.sub = ProtobufSubscriber[lidar_pb.Lidar](lidar_pb.Lidar, "lidar_data")
        self.sub.set_receive_callback(self.data_callback)
    
    def data_callback(self, pub_id : ecal_core.TopicId, data : ReceiveCallbackData[lidar_pb.Lidar]) -> None:
        mean_dist = sum(data.message.distances) / len(data.message.distances)
        min_angle = data.message.angles[0]
        max_angle = data.message.angles[-1]
        print(f"[{min_angle:.2f}-{max_angle:.2f}]{mean_dist: .0f} mm")
    
    def stop(self):
        # ne devrait pas être necessaire, mais il y a plein de warnings si on ne fait pas ça...
        self.sub.remove_receive_callback()
        # Finalize eCAL.
        # You should always do that before your application exits.
        ecal_core.finalize()


def main():
    lw = LidarWatcher()

    # Creating an infinite loop.
    # eCAL Supports a stop signal; when an eCAL Process is stopped, eCAL::Ok() will return false.
    try:
        while ecal_core.ok():
            time.sleep(0.5) # Sleep for 500ms to reduce CPU usage.
    except KeyboardInterrupt:
        pass
    finally:
        lw.stop()

if __name__ == '__main__':
    main()

[KerstinKeller]

Happy to help!