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Mark query_captures function as unsafe

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It's easy to mistakenly use-after-free the cursor and captures iterator
here because of the transmute. Ideally this could be fixed upstream in
tree-sitter by introducing an API with lifetimes/types that reflect the
lifetimes of the underlying data.

Co-authored-by: Pascal Kuthe <pascal.kuthe@semimod.de>
This commit is contained in:
Michael Davis 2022-12-21 09:27:50 -06:00
parent 68f7b87519
commit 1a5eb55477
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1 changed files with 20 additions and 14 deletions
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34
helix-core/src/syntax.rs
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@ -1079,7 +1079,8 @@ pub struct TsParser {
/// Creates an iterator over the captures in a query within the given range,
/// re-using a cursor from the pool if available.
fn query_captures<'a, 'tree>(
/// SAFETY: The `QueryCaptures` must be droped before the `QueryCursor` is dropped.
unsafe fn query_captures<'a, 'tree>(
query: &'a Query,
root: Node<'tree>,
source: RopeSlice<'a>,
@ -1094,10 +1095,11 @@ fn query_captures<'a, 'tree>(
highlighter.cursors.pop().unwrap_or_default()
});
// This is the unsafe line:
// The `captures` iterator borrows the `Tree` and the `QueryCursor`, which
// prevents them from being moved. But both of these values are really just
// pointers, so it's actually ok to move them.
let cursor_ref = unsafe { mem::transmute::<_, &'static mut QueryCursor>(&mut cursor) };
let cursor_ref = mem::transmute::<_, &'static mut QueryCursor>(&mut cursor);
// if reusing cursors & no range this resets to whole range
cursor_ref.set_byte_range(range.unwrap_or(0..usize::MAX));
@ -1460,12 +1462,14 @@ fn query_iter<'a, F>(
.layers
.iter()
.filter_map(|(_, layer)| {
let (cursor, captures) = query_captures(
query_fn(&layer.config),
layer.tree().root_node(),
source,
range.clone(),
);
let (cursor, captures) = unsafe {
query_captures(
query_fn(&layer.config),
layer.tree().root_node(),
source,
range.clone(),
)
};
let mut captures = captures.peekable();
// If there aren't any captures for this layer, skip the layer.
@ -1497,12 +1501,14 @@ pub fn highlight_iter<'a>(
.filter_map(|(_, layer)| {
// TODO: if range doesn't overlap layer range, skip it
let (cursor, captures) = query_captures(
&layer.config.query,
layer.tree().root_node(),
source,
range.clone(),
);
let (cursor, captures) = unsafe {
query_captures(
&layer.config.query,
layer.tree().root_node(),
source,
range.clone(),
)
};
let mut captures = captures.peekable();
// If there are no captures, skip the layer