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Rederive the shared source pointer through an unwinding set_layout

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This commit is contained in:
Dennis Kobert
2026-09-08 13:15:13 +00:00
parent 5e388cb38f
commit 2b5845464c
1 changed files with 15 additions and 3 deletions
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18
node-graph/libraries/core-types/src/registry.rs
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@@ -127,12 +127,22 @@ impl<N: ?Sized> SharedSource<N> {
/// Re-derives the cached pointer from the owned payload. An exclusive
/// re-borrow of the payload invalidates the pointer taken before it, so
/// every mutation through `own` ends here.
/// every mutation through `own` ends here, an unwinding one included.
pub fn rederive(&mut self) {
self.ptr = std::ptr::NonNull::from(&*self.own);
}
}
/// Re-derives on the way out of an exclusive re-borrow, so a mutation that
/// panics cannot leave the cached pointer retired for a caller that catches.
struct Rederive<'a, N: ?Sized>(&'a mut SharedSource<N>);
impl<N: ?Sized> Drop for Rederive<'_, N> {
fn drop(&mut self) {
self.0.rederive();
}
}
// SAFETY: `ptr` is derived from the owned Arc and never mutated through, so the source is exactly as
// thread safe as the payload it shares.
unsafe impl<N: ?Sized + Send + Sync> Send for SharedSource<N> {}
@@ -224,9 +234,11 @@ impl SourceHandle {
layout: |edge| Node::<ContextImpl>::layout(edge.downcast_ref::<SharedSource<N>>().expect("layout hook matches the stored edge type")),
set_layout: |edge, layout| {
let shared = edge.downcast_mut::<SharedSource<N>>().expect("set_layout hook matches the stored edge type");
let node = std::sync::Arc::get_mut(&mut shared.own).expect("layout is installed before the node is shared");
// The re-borrow below retires the cached pointer, so the rederive
// is a guard: a panicking `set_layout` must not leave it stale.
let guard = Rederive(shared);
let node = std::sync::Arc::get_mut(&mut guard.0.own).expect("layout is installed before the node is shared");
Node::<ContextImpl>::set_layout(node, layout);
shared.rederive();
},
ty,
}