Python crushes while traversing entities to the top level

Current Behavior

Getting python crush (segmentation fault) while traversing entities to the top level entity.

Steps to Reproduce

Execute the following script:

#!/usr/bin/env python
#
from ydk.services import CRUDService
from ydk.providers import NetconfServiceProvider
from ydk.models.cisco_ios_xr import Cisco_IOS_XR_ipv4_bgp_oper as xr_ipv4_bgp_oper

import logging

def enable_logging(level):
    log = logging.getLogger('ydk')
    log.setLevel(level)
    handler = logging.StreamHandler()
    formatter = logging.Formatter(
            "%(asctime)s - %(name)s - %(levelname)s - %(message)s")
    handler.setFormatter(formatter)
    log.addHandler(handler)

def build_bgp_instance_obj():
    bgp_oper_obj = xr_ipv4_bgp_oper.Bgp()

    bgp_oper_instance_list_obj = xr_ipv4_bgp_oper.Bgp.Instances.Instance()
    bgp_oper_instance_list_obj.instance_name = 'default'
    bgp_oper_obj.instances.instance.append(bgp_oper_instance_list_obj)
    return bgp_oper_instance_list_obj

if __name__ == '__main__':

    enable_logging(logging.INFO)

    provider = NetconfServiceProvider(
        address='sbx-iosxr-mgmt.cisco.com',
        port=10000,
        username='admin',
        password='C1sco12345')

    crud = CRUDService()

    bgp_instance_obj = build_bgp_instance_obj()

    bgp_oper = crud.read(provider, bgp_instance_obj)

Getting the following output:

/Users/ygorelik/venv/bin/python /Users/ygorelik/ydk-gen/scripts/community/xr_bgp_oper.py
2020-11-03 10:02:39,216 - ydk - INFO - Path where models are to be downloaded: /Users/ygorelik/.ydk/sbx-iosxr-mgmt.cisco.com
2020-11-03 10:02:39,250 - ydk - INFO - Connected to sbx-iosxr-mgmt.cisco.com on port 10000 using ssh with timeout of -1

Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

Script debugging showed that Python crushes in function ydk.entity_utils._traverse_to_top_entity:

def _traverse_to_top_entity(entity):
    while entity.parent is not None:
        entity = entity.parent    # crushes on execution of this line
    return entity

Note. No issues observed when crud.read called on top level object _bgp_operobj .

System Information

YDK-0.8.5

This is erroneous script, because by the time the function _build_bgp_instanceobj finished the top level object _bgp_operobj is released from memory by the Python garbage collector. That causes the script to crash.

The correct and working script would be:

#!/usr/bin/env python
#
from ydk.services import CRUDService
from ydk.providers import NetconfServiceProvider
from ydk.models.cisco_ios_xr import Cisco_IOS_XR_ipv4_bgp_oper as xr_ipv4_bgp_oper

import logging

def enable_logging(level):
    log = logging.getLogger('ydk')
    log.setLevel(level)
    handler = logging.StreamHandler()
    formatter = logging.Formatter(
            "%(asctime)s - %(name)s - %(levelname)s - %(message)s")
    handler.setFormatter(formatter)
    log.addHandler(handler)

def build_bgp_instance_obj(bgp_oper_obj_):
    bgp_oper_instance_list_obj = xr_ipv4_bgp_oper.Bgp.Instances.Instance()
    bgp_oper_instance_list_obj.instance_name = "default"
    bgp_oper_obj_.instances.instance.append(bgp_oper_instance_list_obj)
    return bgp_oper_instance_list_obj

if __name__ == '__main__':

    enable_logging(logging.INFO)

    provider = NetconfServiceProvider(
        address='sbx-iosxr-mgmt.cisco.com',
        port=10000,
        username='admin',
        password='C1sco12345')

    crud = CRUDService()

    bgp_oper_obj = xr_ipv4_bgp_oper.Bgp()
    bgp_instance_obj = build_bgp_instance_obj(bgp_oper_obj)

    bgp_oper = crud.read(provider, bgp_instance_obj)
    if bgp_oper:
        print("Got BGP config")
    else:
        print("No BGP config found")

It produces this result:

2023-02-22 16:56:23,886 - ydk - INFO - Path where models are to be downloaded: /Users/ygorelik/.ydk/sbx-iosxr-mgmt.cisco.com
2023-02-22 16:56:23,898 - ydk - INFO - Connected to sbx-iosxr-mgmt.cisco.com on port 10000 using ssh with timeout of -1
2023-02-22 16:56:23,927 - ydk - INFO - Executing CRUD read operation on [Cisco-IOS-XR-ipv4-bgp-oper:bgp]
2023-02-22 16:56:23,927 - ydk - INFO - Executing 'get' RPC on [Cisco-IOS-XR-ipv4-bgp-oper:bgp]
2023-02-22 16:56:27,184 - ydk - INFO - ============= Sending RPC to device =============
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"><get xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <filter><bgp xmlns="http://cisco.com/ns/yang/Cisco-IOS-XR-ipv4-bgp-oper">
  <instances>
    <instance>
      <instance-name>default</instance-name>
    </instance>
  </instances>
</bgp></filter>
</get>
</rpc>
No BGP config found
2023-02-22 16:56:28,425 - ydk - INFO - ============= Received RPC from device =============
<?xml version="1.0"?>
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1">
  <data/>
</rpc-reply>

2023-02-22 16:56:28,426 - ydk - INFO - Found empty data tag, meaning requested data are not found on Netconf server
2023-02-22 16:56:28,470 - ydk - INFO - Disconnected from device

CiscoDevNet / ydk-gen