Mercurial > hg
view tests/cgienv @ 49000:dd6b67d5c256 stable
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 | aa3f726a2bdb |
children |
line wrap: on
line source
DOCUMENT_ROOT="/var/www/hg"; export DOCUMENT_ROOT GATEWAY_INTERFACE="CGI/1.1"; export GATEWAY_INTERFACE HTTP_ACCEPT="text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"; export HTTP_ACCEPT HTTP_ACCEPT_CHARSET="ISO-8859-1,utf-8;q=0.7,*;q=0.7"; export HTTP_ACCEPT_CHARSET HTTP_ACCEPT_ENCODING="gzip,deflate"; export HTTP_ACCEPT_ENCODING HTTP_ACCEPT_LANGUAGE="en-us,en;q=0.5"; export HTTP_ACCEPT_LANGUAGE HTTP_CACHE_CONTROL="max-age=0"; export HTTP_CACHE_CONTROL HTTP_CONNECTION="keep-alive"; export HTTP_CONNECTION HTTP_HOST="hg.omnifarious.org"; export HTTP_HOST HTTP_KEEP_ALIVE="300"; export HTTP_KEEP_ALIVE HTTP_USER_AGENT="Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.8.0.4) Gecko/20060608 Ubuntu/dapper-security Firefox/1.5.0.4"; export HTTP_USER_AGENT PATH_INFO="/"; export PATH_INFO PATH_TRANSLATED="/var/www/hg/index.html"; export PATH_TRANSLATED QUERY_STRING=""; export QUERY_STRING REMOTE_ADDR="127.0.0.2"; export REMOTE_ADDR REMOTE_PORT="44703"; export REMOTE_PORT REQUEST_METHOD="GET"; export REQUEST_METHOD REQUEST_URI="/test/"; export REQUEST_URI SCRIPT_FILENAME="/home/hopper/hg_public/test.cgi"; export SCRIPT_FILENAME SCRIPT_NAME="/test"; export SCRIPT_NAME SCRIPT_URI="http://hg.omnifarious.org/test/"; export SCRIPT_URI SCRIPT_URL="/test/"; export SCRIPT_URL SERVER_ADDR="127.0.0.1"; export SERVER_ADDR SERVER_ADMIN="eric@localhost"; export SERVER_ADMIN SERVER_NAME="hg.omnifarious.org"; export SERVER_NAME SERVER_PORT="80"; export SERVER_PORT SERVER_PROTOCOL="HTTP/1.1"; export SERVER_PROTOCOL SERVER_SIGNATURE="<address>Apache/2.0.53 (Fedora) Server at hg.omnifarious.org Port 80</address>"; export SERVER_SIGNATURE SERVER_SOFTWARE="Apache/2.0.53 (Fedora)"; export SERVER_SOFTWARE