Test case showing that modifications in child process are not visible to parent

dbm_fork_test.py (text/x-python), 941 bytes, created by Zac Medico on 2020-08-09 05:18:43 UTC

#!/usr/bin/python
# Demo for https://bugs.gentoo.org/736473.

import dbm.gnu
import multiprocessing
import os
import tempfile

expected = {
	b'child_key': b'child_value',
	b'parent_key': b'parent_value',
}

with tempfile.NamedTemporaryFile() as temp_db:

	db_path = temp_db.name

	db = dbm.gnu.open(db_path, 'wu')
	db[b'parent_key'] = expected[b'parent_key']

	def modify_db():
		db[b'child_key'] = expected[b'child_key']

	proc = multiprocessing.Process(target=modify_db)
	proc.start()
	proc.join()

	# All keys are visible if we re-open db here.
	# db = dbm.gnu.open(db_path, 'wu')
	db_keys = set(db.keys())

	for k in expected:
		if k not in db_keys:
			raise AssertionError('db has missing key {}'.format(k))

	for k in db_keys:
		if k not in expected:
			raise AssertionError('db has unexpected key {}'.format(k))
		if db[k] != expected[k]:
			raise AssertionError('unexpected value for key {}, {} != {}'.format(k, db[k], expected[k]))