Segfault in CRUDService.read()

[knightjoel]

Hi. I'm seeing a segmentation fault in CRUDService.read() if I call this method multiple times in the same script:

from ydk.services import CRUDService
from ydk.providers import NetconfServiceProvider
from ydk.models.cisco_ios_xe import CISCO_CDP_MIB
from ydk.models.cisco_ios_xe import IF_MIB


address = '172.26.47.103'
username = 'admin'
password = 'cisco123'

provider = NetconfServiceProvider(address=address,
				  username=username,
				  password=password,
				  protocol='ssh',
				  port=830)

crud = CRUDService()

cdp = CISCO_CDP_MIB.CiscoCdpMib()
cdp = crud.read(provider, cdp)

if len(cdp.cdpcachetable.cdpcacheentry) > 0:
    print("**** CDP neighbor count: {}".format(len(cdp.cdpcachetable.cdpcacheentry)))
else:
    print("**** There are no CDP neighbors")

intf = IF_MIB.IfMib()
intf = crud.read(provider, intf)
print("**** Interface count: {}".format(len(intf.iftable.ifentry)))

The above script seg faults:

~/git/sdapov% python issue.py
**** CDP neighbor count: 1
[2]    59312 segmentation fault  python issue.py

However, if I reverse the order of operations and call crud.read() against the IF_MIB first, the script runs fine:

--- issue.py	2017-08-31 11:40:06.000000000 -0600
+++ issue2.py	2017-08-31 11:41:41.000000000 -0600
@@ -16,6 +16,10 @@

 crud = CRUDService()

+intf = IF_MIB.IfMib()
+intf = crud.read(provider, intf)
+print("**** Interface count: {}".format(len(intf.iftable.ifentry)))
+
 cdp = CISCO_CDP_MIB.CiscoCdpMib()
 cdp = crud.read(provider, cdp)

@@ -24,6 +28,3 @@
 else:
     print("**** There are no CDP neighbors")

-intf = IF_MIB.IfMib()
-intf = crud.read(provider, intf)
-print("**** Interface count: {}".format(len(intf.iftable.ifentry)))

~/git/sdapov% python issue2.py
**** Interface count: 74
**** CDP neighbor count: 1

I appologize, but I don't know how or where to start debugging this.

YDK-Py 0.6.0
libydk 0.6.0
Python 2.7.10
macOS 10.11.6

Python modules:
ncclient (0.5.3)
pip (9.0.1)
pybind11 (2.1.1)
setuptools (36.3.0)
six (1.10.0)
wheel (0.29.0)
ydk (0.6.0)
ydk-models-cisco-ios-xe (16.6.1)
ydk-models-cisco-ios-xr (6.2.2)
ydk-models-ietf (0.1.3)
ydk-models-openconfig (0.1.3)

[psykokwak4]

Thanks for catching these bugs, you can enabled logging following steps in documentation here.

Please use DEBUG level:

log.setLevel(logging.DEBUG)

[psykokwak4]

And also, the common causes for segfault would be:

1. Exceptions raised in C++ side not propagated to Python side.
2. Problems using pybind11 interface(for example, NetconfService.kill_session should accept unsigned integer instead of signed integer #528)

To reproduce segfault caused by the first reason, you could modify CMakeList.txt, add customized tests here. And use lldb/gdb for debugging.

[knightjoel]

debug log attached.

debug.txt

[knightjoel]

I had a go at running the unit tests but got stuck. The C++ instructions say to "cd ydk-gen/sdk/cpp/ydk" but that directory does not exist.

~/git% ll ydk-gen/sdk/cpp/
total 36
-rw-r--r--   1 jknight  staff      8  2 Sep 10:59 .gitignore
-rw-r--r--   1 jknight  staff   7314  2 Sep 10:59 CHANGES.md
-rw-r--r--   1 jknight  staff    713  2 Sep 10:59 Copyright
-rw-r--r--   1 jknight  staff  11357  2 Sep 10:59 LICENSE
-rw-r--r--   1 jknight  staff   4960  2 Sep 10:59 README.md
drwxr-xr-x  15 jknight  staff    510  2 Sep 11:11 core/
drwxr-xr-x   6 jknight  staff    204  2 Sep 10:59 install/
drwxr-xr-x  10 jknight  staff    340  2 Sep 10:59 packages/
drwxr-xr-x  21 jknight  staff    714  2 Sep 10:59 samples/
drwxr-xr-x  31 jknight  staff   1054  2 Sep 11:07 tests/

[psykokwak4]

Thanks for the log, but it seems like it is not helpful for this segfault issue, not sure the reason for segfault. The last log entry comes from path/root_data_node.cpp

Sorry, that C++ instructions seems outdated. Sharing my workflow:

# first install bundle you want to debug(xe)
$ cd sdk/cpp/core
$ mkdir build
$ cd build
$ cmake .. && sudo make install # install in libydk in debugging mode
$ cd ../../tests
# edit test files and CMakeLists.txt
$ mkdir build
$ cd build && cmake .. && make
$ lldb ./ydk_bundle_test <new-test-case-name>

[ghost]

Unable to reproduce on ydk 0.7.0