Mercurial > hg
view tests/test-mq-qdiff.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> |
---|---|
date | Tue, 05 Apr 2022 10:55:28 +0200 |
parents | e955549cd045 |
children |
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$ cat <<EOF >> $HGRCPATH > [extensions] > mq = > [mq] > git = keep > EOF $ hg init a $ cd a $ echo 'base' > base $ hg ci -Ambase adding base $ hg qnew -mmqbase mqbase $ echo 'patched' > base $ hg qrefresh qdiff: $ hg qdiff diff -r d20a80d4def3 base --- a/base Thu Jan 01 00:00:00 1970 +0000 +++ b/base* (glob) @@ -1,1 +1,1 @@ -base +patched qdiff dirname: $ hg qdiff --nodates . diff -r d20a80d4def3 base --- a/base +++ b/base @@ -1,1 +1,1 @@ -base +patched qdiff filename: $ hg qdiff --nodates base diff -r d20a80d4def3 base --- a/base +++ b/base @@ -1,1 +1,1 @@ -base +patched $ hg revert -a $ hg qpop popping mqbase patch queue now empty $ hg qdelete mqbase $ printf '1\n2\n3\n4\nhello world\ngoodbye world\n7\n8\n9\n' > lines $ hg ci -Amlines -d '2 0' adding lines $ hg qnew -mmqbase2 mqbase2 $ printf '\n\n1\n2\n3\n4\nhello world\n goodbye world\n7\n8\n9\n' > lines $ hg qdiff --nodates -U 1 diff -r b0c220e1cf43 lines --- a/lines +++ b/lines @@ -1,1 +1,3 @@ + + 1 @@ -4,4 +6,4 @@ 4 -hello world -goodbye world +hello world + goodbye world 7 $ hg qdiff --nodates -b diff -r b0c220e1cf43 lines --- a/lines +++ b/lines @@ -1,9 +1,11 @@ + + 1 2 3 4 hello world -goodbye world + goodbye world 7 8 9 $ hg qdiff --nodates -U 1 -B diff -r b0c220e1cf43 lines --- a/lines +++ b/lines @@ -4,4 +4,4 @@ 4 -hello world -goodbye world +hello world + goodbye world 7 $ hg qdiff --nodates -w diff -r b0c220e1cf43 lines --- a/lines +++ b/lines @@ -1,3 +1,5 @@ + + 1 2 3 $ hg qdiff --nodates --reverse diff -r b0c220e1cf43 lines --- a/lines +++ b/lines @@ -1,11 +1,9 @@ - - 1 2 3 4 -hello world - goodbye world +hello world +goodbye world 7 8 9 qdiff preserve existing git flag: $ hg qrefresh --git $ echo a >> lines $ hg qdiff diff --git a/lines b/lines --- a/lines +++ b/lines @@ -1,9 +1,12 @@ + + 1 2 3 4 -hello world -goodbye world +hello world + goodbye world 7 8 9 +a $ hg qdiff --stat lines | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) $ hg qrefresh qdiff when file deleted (but not removed) in working dir: $ hg qnew deleted-file $ echo a > newfile $ hg add newfile $ hg qrefresh $ rm newfile $ hg qdiff $ cd ..