Mercurial > hg
view tests/test-empty-group.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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# A B # # 3 4 3 # |\/| |\ # |/\| | \ # 1 2 1 2 # \ / \ / # 0 0 # # if the result of the merge of 1 and 2 # is the same in 3 and 4, no new manifest # will be created and the manifest group # will be empty during the pull # # (plus we test a failure where outgoing # wrongly reported the number of csets) $ hg init a $ cd a $ touch init $ hg ci -A -m 0 adding init $ touch x y $ hg ci -A -m 1 adding x adding y $ hg update 0 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ touch x y $ hg ci -A -m 2 adding x adding y created new head $ hg merge 1 0 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -A -m m1 $ hg update -C 1 0 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg merge 2 0 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg ci -A -m m2 created new head $ cd .. $ hg clone -r 3 a b adding changesets adding manifests adding file changes added 4 changesets with 3 changes to 3 files new changesets 5fcb73622933:d15a0c284984 updating to branch default 3 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg clone -r 4 a c adding changesets adding manifests adding file changes added 4 changesets with 3 changes to 3 files new changesets 5fcb73622933:1ec3c74fc0e0 updating to branch default 3 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg -R a outgoing b comparing with b searching for changes changeset: 4:1ec3c74fc0e0 tag: tip parent: 1:79f9e10cd04e parent: 2:8e1bb01c1a24 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m2 $ hg -R a outgoing c comparing with c searching for changes changeset: 3:d15a0c284984 parent: 2:8e1bb01c1a24 parent: 1:79f9e10cd04e user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m1 $ hg -R b outgoing c comparing with c searching for changes changeset: 3:d15a0c284984 tag: tip parent: 2:8e1bb01c1a24 parent: 1:79f9e10cd04e user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m1 $ hg -R c outgoing b comparing with b searching for changes changeset: 3:1ec3c74fc0e0 tag: tip parent: 1:79f9e10cd04e parent: 2:8e1bb01c1a24 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: m2 $ hg -R b pull a pulling from a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 0 changes to 0 files (+1 heads) new changesets 1ec3c74fc0e0 (run 'hg heads' to see heads, 'hg merge' to merge) $ hg -R c pull a pulling from a searching for changes adding changesets adding manifests adding file changes added 1 changesets with 0 changes to 0 files (+1 heads) new changesets d15a0c284984 (run 'hg heads' to see heads, 'hg merge' to merge)