Mercurial > hg
view tests/test-issue586.t @ 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> |
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date | Tue, 05 Apr 2022 10:55:28 +0200 |
parents | eb586ed5d8ce |
children |
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Issue586: removing remote files after merge appears to corrupt the dirstate $ hg init a $ cd a $ echo a > a $ hg ci -Ama adding a $ hg init ../b $ cd ../b $ echo b > b $ hg ci -Amb adding b $ hg pull -f ../a pulling from ../a searching for changes warning: repository is unrelated requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets cb9a9f314b8b (run 'hg heads' to see heads, 'hg merge' to merge) $ hg merge 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg rm -f a $ hg ci -Amc $ hg st -A C b $ cd .. Issue1433: Traceback after two unrelated pull, two move, a merge and a commit (related to issue586) create test repos $ hg init repoa $ touch repoa/a $ hg -R repoa ci -Am adda adding a $ hg init repob $ touch repob/b $ hg -R repob ci -Am addb adding b $ hg init repoc $ cd repoc $ hg pull ../repoa pulling from ../repoa requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files new changesets 7132ab4568ac (run 'hg update' to get a working copy) $ hg update 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ mkdir tst $ hg mv * tst $ hg ci -m "import a in tst" $ hg pull -f ../repob pulling from ../repob searching for changes warning: repository is unrelated requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files (+1 heads) new changesets 5ddceb349652 (run 'hg heads' to see heads, 'hg merge' to merge) merge both repos $ hg merge 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ mkdir src move b content $ hg mv b src $ hg ci -m "import b in src" $ hg manifest src/b tst/a $ cd ..