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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 | d4ba4d51f85f |
children | 6000f5b25c9b |
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#!/usr/bin/env python3 # # hggettext - carefully extract docstrings for Mercurial # # Copyright 2009 Olivia Mackall <olivia@selenic.com> and others # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. # The normalize function is taken from pygettext which is distributed # with Python under the Python License, which is GPL compatible. """Extract docstrings from Mercurial commands. Compared to pygettext, this script knows about the cmdtable and table dictionaries used by Mercurial, and will only extract docstrings from functions mentioned therein. Use xgettext like normal to extract strings marked as translatable and join the message cataloges to get the final catalog. """ from __future__ import absolute_import, print_function import inspect import os import re import sys def escape(s): # The order is important, the backslash must be escaped first # since the other replacements introduce new backslashes # themselves. s = s.replace('\\', '\\\\') s = s.replace('\n', '\\n') s = s.replace('\r', '\\r') s = s.replace('\t', '\\t') s = s.replace('"', '\\"') return s def normalize(s): # This converts the various Python string types into a format that # is appropriate for .po files, namely much closer to C style. lines = s.split('\n') if len(lines) == 1: s = '"' + escape(s) + '"' else: if not lines[-1]: del lines[-1] lines[-1] = lines[-1] + '\n' lines = map(escape, lines) lineterm = '\\n"\n"' s = '""\n"' + lineterm.join(lines) + '"' return s def poentry(path, lineno, s): return ( '#: %s:%d\n' % (path, lineno) + 'msgid %s\n' % normalize(s) + 'msgstr ""\n' ) doctestre = re.compile(r'^ +>>> ', re.MULTILINE) def offset(src, doc, name, lineno, default): """Compute offset or issue a warning on stdout.""" # remove doctest part, in order to avoid backslash mismatching m = doctestre.search(doc) if m: doc = doc[: m.start()] # Backslashes in doc appear doubled in src. end = src.find(doc.replace('\\', '\\\\')) if end == -1: # This can happen if the docstring contains unnecessary escape # sequences such as \" in a triple-quoted string. The problem # is that \" is turned into " and so doc wont appear in src. sys.stderr.write( "%s:%d:warning:" " unknown docstr offset, assuming %d lines\n" % (name, lineno, default) ) return default else: return src.count('\n', 0, end) def importpath(path): """Import a path like foo/bar/baz.py and return the baz module.""" if path.endswith('.py'): path = path[:-3] if path.endswith('/__init__'): path = path[:-9] path = path.replace('/', '.') mod = __import__(path) for comp in path.split('.')[1:]: mod = getattr(mod, comp) return mod def docstrings(path): """Extract docstrings from path. This respects the Mercurial cmdtable/table convention and will only extract docstrings from functions mentioned in these tables. """ mod = importpath(path) if not path.startswith('mercurial/') and mod.__doc__: with open(path) as fobj: src = fobj.read() lineno = 1 + offset(src, mod.__doc__, path, 1, 7) print(poentry(path, lineno, mod.__doc__)) functions = list(getattr(mod, 'i18nfunctions', [])) functions = [(f, True) for f in functions] cmdtable = getattr(mod, 'cmdtable', {}) if not cmdtable: # Maybe we are processing mercurial.commands? cmdtable = getattr(mod, 'table', {}) functions.extend((c[0], False) for c in cmdtable.values()) for func, rstrip in functions: if func.__doc__: docobj = func # this might be a proxy to provide formatted doc func = getattr(func, '_origfunc', func) funcmod = inspect.getmodule(func) extra = '' if funcmod.__package__ == funcmod.__name__: extra = '/__init__' actualpath = '%s%s.py' % (funcmod.__name__.replace('.', '/'), extra) src = inspect.getsource(func) lineno = inspect.getsourcelines(func)[1] doc = docobj.__doc__ origdoc = getattr(docobj, '_origdoc', '') if rstrip: doc = doc.rstrip() origdoc = origdoc.rstrip() if origdoc: lineno += offset(src, origdoc, actualpath, lineno, 1) else: lineno += offset(src, doc, actualpath, lineno, 1) print(poentry(actualpath, lineno, doc)) def rawtext(path): with open(path) as f: src = f.read() print(poentry(path, 1, src)) if __name__ == "__main__": # It is very important that we import the Mercurial modules from # the source tree where hggettext is executed. Otherwise we might # accidentally import and extract strings from a Mercurial # installation mentioned in PYTHONPATH. sys.path.insert(0, os.getcwd()) from mercurial import demandimport demandimport.enable() for path in sys.argv[1:]: if path.endswith('.txt'): rawtext(path) else: docstrings(path)