pyergo segfaults after call to pyergo_end_session

[ryejeff]

Describe the bug
If pyergo_end_session is ever called, later calls to pyergo may segfault, even if a new session is started with pyergo_start_session.

To Reproduce
Steps to reproduce the behavior:

1. Call pyergo_start_session.
2. Call pyergo_end_session.
3. Call pyergo_start_session.
4. Repeatedly call pyergo_command.

• Usually this causes a segfault on the first invocation. Sometimes it requires a few calls.

See the attached Python script (and input files) for a reproducible test case.

Expected behavior
After the second pyergo_start_session, the pyergo_command should succeed without causing a segfault.

Screenshots
Not applicable.

Desktop (please complete the following information):

• OS: MacOS
• Version: ErgoAI 3.0, installed using ergoAI_3.0.run from https://github.com/ErgoAI/.github/releases

Also evokes a segfault in a Docker image with debian:bookworm as a base and installed using ergoAI_3.0.run from https://github.com/ErgoAI/.github/releases.

Additional context
We encountered this in testing when we tried to make separate pyergo sessions for each test.

[ryejeff]

GitHub won't allow attachments with the .py or .flr extensions, so here are the file contents to reproduce this bug.

pyergo_segfault.py:

#!/usr/bin/env python3

import os
import sys

PYERGO = os.getenv("PYERGO")
XSBARCHDIR = os.getenv("XSBARCHDIR")
ERGOROOT = os.getenv("ERGOROOT")

sys.path.append(PYERGO)
import pyergo

print("Relevant environment variables:")
print(f"  {PYERGO=}")
print(f"  {XSBARCHDIR=}")
print(f"  {ERGOROOT=}")

print("Starting pyergo session")
pyergo.pyergo_start_session(XSBARCHDIR, ERGOROOT)

print("Checking for active ergo session")
print(f"{pyergo.ergo_session_active=}")
pyergo.check_active_ergo_session()

# This is not strictly necessary for reproducing the segfault. It is here to
# show verify that the load command succeeds.
#
cmd = "['first.flr']."
print(f"Executing a pyergo command: {cmd}")
pyergo.pyergo_command(cmd)

# If we end the session, we will get the segfault in one of the steps below. If
# we remove this, we do not get the segfault.
#
print("Ending pyergo session")
pyergo.pyergo_end_session()

# This shows that the session is still active. I did not expect it to be after
# we ended the session.
#
print("Checking for active ergo session")
print(f"{pyergo.ergo_session_active=}")
pyergo.check_active_ergo_session()

# This has no impact. We segfault whether this is included or not.
#
print("Starting pyergo session")
pyergo.pyergo_start_session(XSBARCHDIR, ERGOROOT)

print("Checking for active ergo session")
print(f"{pyergo.ergo_session_active=}")
pyergo.check_active_ergo_session()

# Notice that this file has more statements in it. If we reload the
# `first.flr` file we still sometimes get the segfault. But the larger file
# yields the segfault every time.
#
cmd = "['second.flr']."
for step in range(100):
    print(f"Step {step} - Executing a pyergo command: {cmd}")
    pyergo.pyergo_command(cmd)

print("Done")

first.flr:

Tweety:bird.

second.flr:

Tweety:bird.
Smokey:ostrich.
Sam:bird.
Fred:ostrich.