rust: fix unsound `OwningDirstateMap`
As per the previous patch, `OwningDirstateMap` is unsound. Self-referential
structs are difficult to implement correctly in Rust since the compiler is
free to move structs around as much as it wants to. They are also very rarely
needed in practice, so the state-of-the-art on how they should be done within
the Rust rules is still a bit new.
The crate `ouroboros` is an attempt at providing a safe way (in the Rust sense)
of declaring self-referential structs. It is getting a lot attention and was
improved very quickly when soundness issues were found in the past: rather than
relying on our own (limited) review circle, we might as well use the de-facto
common crate to fix this problem. This will give us a much better chance of
finding issues should any new ones be discovered as well as the benefit of
fewer `unsafe` APIs of our own.
I was starting to think about how I would present a safe API to the old struct
but soon realized that the callback-based approach was already done in
`ouroboros`, along with a lot more care towards refusing incorrect structs.
In short: we don't return a mutable reference to the `DirstateMap` anymore, we
expect users of its API to pass a `FnOnce` that takes the map as an argument.
This allows our `OwningDirstateMap` to control the input and output lifetimes
of the code that modifies it to prevent such issues.
Changing to `ouroboros` meant changing every API with it, but it is relatively
low churn in the end. It correctly identified the example buggy modification of
`copy_map_insert` outlined in the previous patch as violating the borrow rules.
Differential Revision: https://phab.mercurial-scm.org/D12429
#!/usr/bin/env python3
# fsmonitor-run-tests.py - Run Mercurial tests with fsmonitor enabled
#
# Copyright 2017 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# This is a wrapper around run-tests.py that spins up an isolated instance of
# Watchman and runs the Mercurial tests against it. This ensures that the global
# version of Watchman isn't affected by anything this test does.
from __future__ import absolute_import
from __future__ import print_function
import argparse
import contextlib
import json
import os
import shutil
import subprocess
import sys
import tempfile
import uuid
osenvironb = getattr(os, 'environb', os.environ)
if sys.version_info > (3, 5, 0):
PYTHON3 = True
xrange = range # we use xrange in one place, and we'd rather not use range
def _sys2bytes(p):
return p.encode('utf-8')
elif sys.version_info >= (3, 0, 0):
print(
'%s is only supported on Python 3.5+ and 2.7, not %s'
% (sys.argv[0], '.'.join(str(v) for v in sys.version_info[:3]))
)
sys.exit(70) # EX_SOFTWARE from `man 3 sysexit`
else:
PYTHON3 = False
# In python 2.x, path operations are generally done using
# bytestrings by default, so we don't have to do any extra
# fiddling there. We define the wrapper functions anyway just to
# help keep code consistent between platforms.
def _sys2bytes(p):
return p
def getparser():
"""Obtain the argument parser used by the CLI."""
parser = argparse.ArgumentParser(
description='Run tests with fsmonitor enabled.',
epilog='Unrecognized options are passed to run-tests.py.',
)
# - keep these sorted
# - none of these options should conflict with any in run-tests.py
parser.add_argument(
'--keep-fsmonitor-tmpdir',
action='store_true',
help='keep temporary directory with fsmonitor state',
)
parser.add_argument(
'--watchman',
help='location of watchman binary (default: watchman in PATH)',
default='watchman',
)
return parser
@contextlib.contextmanager
def watchman(args):
basedir = tempfile.mkdtemp(prefix='hg-fsmonitor')
try:
# Much of this configuration is borrowed from Watchman's test harness.
cfgfile = os.path.join(basedir, 'config.json')
# TODO: allow setting a config
with open(cfgfile, 'w') as f:
f.write(json.dumps({}))
logfile = os.path.join(basedir, 'log')
clilogfile = os.path.join(basedir, 'cli-log')
if os.name == 'nt':
sockfile = '\\\\.\\pipe\\watchman-test-%s' % uuid.uuid4().hex
else:
sockfile = os.path.join(basedir, 'sock')
pidfile = os.path.join(basedir, 'pid')
statefile = os.path.join(basedir, 'state')
argv = [
args.watchman,
'--sockname',
sockfile,
'--logfile',
logfile,
'--pidfile',
pidfile,
'--statefile',
statefile,
'--foreground',
'--log-level=2', # debug logging for watchman
]
envb = osenvironb.copy()
envb[b'WATCHMAN_CONFIG_FILE'] = _sys2bytes(cfgfile)
with open(clilogfile, 'wb') as f:
proc = subprocess.Popen(
argv, env=envb, stdin=None, stdout=f, stderr=f
)
try:
yield sockfile
finally:
proc.terminate()
proc.kill()
finally:
if args.keep_fsmonitor_tmpdir:
print('fsmonitor dir available at %s' % basedir)
else:
shutil.rmtree(basedir, ignore_errors=True)
def run():
parser = getparser()
args, runtestsargv = parser.parse_known_args()
with watchman(args) as sockfile:
osenvironb[b'WATCHMAN_SOCK'] = _sys2bytes(sockfile)
# Indicate to hghave that we're running with fsmonitor enabled.
osenvironb[b'HGFSMONITOR_TESTS'] = b'1'
runtestdir = os.path.dirname(__file__)
runtests = os.path.join(runtestdir, 'run-tests.py')
blacklist = os.path.join(runtestdir, 'blacklists', 'fsmonitor')
runtestsargv.insert(0, runtests)
runtestsargv.extend(
[
'--extra-config',
'extensions.fsmonitor=',
# specify fsmonitor.mode=paranoid always in order to force
# fsmonitor extension execute "paranoid" code path
#
# TODO: make fsmonitor-run-tests.py accept specific options
'--extra-config',
'fsmonitor.mode=paranoid',
'--blacklist',
blacklist,
]
)
return subprocess.call(runtestsargv)
if __name__ == '__main__':
sys.exit(run())