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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
author | Raphaël Gomès <rgomes@octobus.net> |
---|---|
date | Tue, 05 Apr 2022 10:55:28 +0200 |
parents | c102b704edb5 |
children | 6000f5b25c9b |
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#!/usr/bin/env python3 """ Utility for inspecting files in various ways. This tool is like the collection of tools found in a unix environment but are cross platform and stable and suitable for our needs in the test suite. This can be used instead of tools like: [ dd find head hexdump ls md5sum readlink sha1sum stat tail test readlink.py md5sum.py """ from __future__ import absolute_import import binascii import glob import hashlib import optparse import os import re import sys # Python 3 adapters ispy3 = sys.version_info[0] >= 3 if ispy3: def iterbytes(s): for i in range(len(s)): yield s[i : i + 1] else: iterbytes = iter def visit(opts, filenames, outfile): """Process filenames in the way specified in opts, writing output to outfile.""" for f in sorted(filenames): isstdin = f == '-' if not isstdin and not os.path.lexists(f): outfile.write(b'%s: file not found\n' % f.encode('utf-8')) continue quiet = opts.quiet and not opts.recurse or isstdin isdir = os.path.isdir(f) islink = os.path.islink(f) isfile = os.path.isfile(f) and not islink dirfiles = None content = None facts = [] if isfile: if opts.type: facts.append(b'file') if any((opts.hexdump, opts.dump, opts.md5, opts.sha1, opts.sha256)): with open(f, 'rb') as fobj: content = fobj.read() elif islink: if opts.type: facts.append(b'link') content = os.readlink(f).encode('utf8') elif isstdin: content = getattr(sys.stdin, 'buffer', sys.stdin).read() if opts.size: facts.append(b'size=%d' % len(content)) elif isdir: if opts.recurse or opts.type: dirfiles = glob.glob(f + '/*') facts.append(b'directory with %d files' % len(dirfiles)) elif opts.type: facts.append(b'type unknown') if not isstdin: stat = os.lstat(f) if opts.size and not isdir: facts.append(b'size=%d' % stat.st_size) if opts.mode and not islink: facts.append(b'mode=%o' % (stat.st_mode & 0o777)) if opts.links: facts.append(b'links=%d' % stat.st_nlink) if opts.newer: # mtime might be in whole seconds so newer file might be same if stat.st_mtime >= os.stat(opts.newer).st_mtime: facts.append( b'newer than %s' % opts.newer.encode('utf8', 'replace') ) else: facts.append( b'older than %s' % opts.newer.encode('utf8', 'replace') ) if opts.md5 and content is not None: h = hashlib.md5(content) facts.append(b'md5=%s' % binascii.hexlify(h.digest())[: opts.bytes]) if opts.sha1 and content is not None: h = hashlib.sha1(content) facts.append( b'sha1=%s' % binascii.hexlify(h.digest())[: opts.bytes] ) if opts.sha256 and content is not None: h = hashlib.sha256(content) facts.append( b'sha256=%s' % binascii.hexlify(h.digest())[: opts.bytes] ) if isstdin: outfile.write(b', '.join(facts) + b'\n') elif facts: outfile.write(b'%s: %s\n' % (f.encode('utf-8'), b', '.join(facts))) elif not quiet: outfile.write(b'%s:\n' % f.encode('utf-8')) if content is not None: chunk = content if not islink: if opts.lines: if opts.lines >= 0: chunk = b''.join(chunk.splitlines(True)[: opts.lines]) else: chunk = b''.join(chunk.splitlines(True)[opts.lines :]) if opts.bytes: if opts.bytes >= 0: chunk = chunk[: opts.bytes] else: chunk = chunk[opts.bytes :] if opts.hexdump: for i in range(0, len(chunk), 16): s = chunk[i : i + 16] outfile.write( b'%04x: %-47s |%s|\n' % ( i, b' '.join(b'%02x' % ord(c) for c in iterbytes(s)), re.sub(b'[^ -~]', b'.', s), ) ) if opts.dump: if not quiet: outfile.write(b'>>>\n') outfile.write(chunk) if not quiet: if chunk.endswith(b'\n'): outfile.write(b'<<<\n') else: outfile.write(b'\n<<< no trailing newline\n') if opts.recurse and dirfiles: assert not isstdin visit(opts, dirfiles, outfile) if __name__ == "__main__": parser = optparse.OptionParser("%prog [options] [filenames]") parser.add_option( "-t", "--type", action="store_true", help="show file type (file or directory)", ) parser.add_option( "-m", "--mode", action="store_true", help="show file mode" ) parser.add_option( "-l", "--links", action="store_true", help="show number of links" ) parser.add_option( "-s", "--size", action="store_true", help="show size of file" ) parser.add_option( "-n", "--newer", action="store", help="check if file is newer (or same)" ) parser.add_option( "-r", "--recurse", action="store_true", help="recurse into directories" ) parser.add_option( "-S", "--sha1", action="store_true", help="show sha1 hash of the content", ) parser.add_option( "", "--sha256", action="store_true", help="show sha256 hash of the content", ) parser.add_option( "-M", "--md5", action="store_true", help="show md5 hash of the content" ) parser.add_option( "-D", "--dump", action="store_true", help="dump file content" ) parser.add_option( "-H", "--hexdump", action="store_true", help="hexdump file content" ) parser.add_option( "-B", "--bytes", type="int", help="number of characters to dump" ) parser.add_option( "-L", "--lines", type="int", help="number of lines to dump" ) parser.add_option( "-q", "--quiet", action="store_true", help="no default output" ) (opts, filenames) = parser.parse_args(sys.argv[1:]) if not filenames: filenames = ['-'] visit(opts, filenames, getattr(sys.stdout, 'buffer', sys.stdout))