feat: implement Ephemeron API and Trace trait additions for boa integration

oscars/Cargo.toml

@@ -8,6 +8,13 @@ hashbrown = "0.16.1"
 oscars_derive = { path = "../oscars_derive", version = "0.1.0" }
 rustc-hash = "2.1.1"
 thin-vec = { version = "0.2", optional = true }
+# Optional Trace/Finalize impls for external types.
+# Uses remote git dependency for standalone compilation.
+# Override locally via `[patch]` in workspace root.
+boa_string = { git = "https://github.com/boa-dev/boa.git", branch = "main", optional = true }
+icu_locale_core = { version = "2.2.0", default-features = false, optional = true }
+either = { version = "1.16.0", optional = true }
+arrayvec = { version = "0.7.6", optional = true }
 
 [dev-dependencies]
 criterion = { version = "0.5", features = ["html_reports"] }
@@ -39,3 +46,7 @@ mark_sweep_branded = ["mark_sweep"]
 null_collector = ["mark_sweep"]
 null_collector_branded = ["mark_sweep"]
 thin-vec = ["dep:thin-vec", "mark_sweep"]
+boa_string = ["dep:boa_string", "mark_sweep"]
+icu = ["dep:icu_locale_core", "mark_sweep"]
+either = ["dep:either", "mark_sweep"]
+arrayvec = ["dep:arrayvec", "mark_sweep"]

oscars/src/alloc/arena2/alloc.rs

@@ -48,6 +48,7 @@ impl<T: ?Sized> ArenaHeapItem<T> {
     ///
     /// This avoids creating a `&mut self` reference, which can lead to stacked borrows
     /// if shared references to the heap item exist
+    #[allow(dead_code)]
     pub(crate) fn as_value_ptr(ptr: NonNull<Self>) -> *mut T {
         // SAFETY: `&raw mut` computes the field address without creating a reference
         unsafe { &raw mut (*ptr.as_ptr()).value }
@@ -147,6 +148,7 @@ impl<'arena> ErasedArenaPointer<'arena> {
     /// SAFETY:
     ///
     /// safe because the gc collector owns the arena and keeps it alive
+    #[allow(dead_code)]
     pub(crate) unsafe fn extend_lifetime(self) -> ErasedArenaPointer<'static> {
         ErasedArenaPointer(self.0, PhantomData)
     }
@@ -202,6 +204,7 @@ impl<'arena, T> ArenaPointer<'arena, T> {
     /// SAFETY:
     ///
     /// safe because the gc collector owns the arena and keeps it alive
+    #[allow(dead_code)]
     pub(crate) unsafe fn extend_lifetime(self) -> ArenaPointer<'static, T> {
         // SAFETY: upheld by caller
         ArenaPointer(unsafe { self.0.extend_lifetime() }, PhantomData)

oscars/src/alloc/mempool3/alloc.rs

@@ -107,7 +107,7 @@ impl<'pool, T: ?Sized> PoolPointer<'pool, T> {
     }
 }
 
-impl<'pool, T> PoolPointer<'pool, T> {
+impl<'pool, T: ?Sized> PoolPointer<'pool, T> {
     pub(crate) unsafe fn from_raw(raw: NonNull<PoolItem<T>>) -> Self {
         Self(raw, PhantomData)
     }

oscars/src/collectors/mark_sweep/internals/mod.rs

@@ -4,6 +4,7 @@ mod gc_header;
 mod vtable;
 
 pub(crate) use ephemeron::Ephemeron;
+#[allow(unused_imports)]
 pub(crate) use gc_header::{GcHeader, HeaderColor};
 pub(crate) use vtable::{DropFn, FinalizeFn, TraceFn, VTable, vtable_of};
 

oscars/src/collectors/mark_sweep/trace.rs

@@ -54,6 +54,14 @@ pub unsafe trait Trace: Finalize {
     /// - An incorrect implementation may cause undefined behavior
     unsafe fn trace(&self, color: TraceColor);
 
+    /// Unroots handles located in the GC heap.
+    ///
+    /// # Safety
+    ///
+    /// Must only be called by the garbage collector.
+    #[inline]
+    unsafe fn trace_non_roots(&self) {}
+
     fn run_finalizer(&self);
 }
 

oscars/src/collectors/mark_sweep_branded/cell.rs

@@ -65,10 +65,9 @@ impl<T: Trace> DerefMut for GcRefMut<'_, T> {
 impl<T: Trace> Finalize for GcRefCell<T> {}
 
 unsafe impl<T: Trace> Trace for GcRefCell<T> {
+    #[inline]
     unsafe fn trace(&self, tracer: &mut Tracer) {
         let val = unsafe { &*self.inner.as_ptr() };
-        unsafe {
-            val.trace(tracer);
-        }
+        unsafe { val.trace(tracer) };
     }
 }

oscars/src/collectors/mark_sweep_branded/gc.rs

@@ -60,7 +60,7 @@ impl<'gc, T: Trace + 'gc> Deref for Gc<'gc, T> {
     }
 }
 
-impl<T: Trace> Finalize for Gc<'_, T> {}
+impl<T: Trace + ?Sized> Finalize for Gc<'_, T> {}
 unsafe impl<T: Trace> Trace for Gc<'_, T> {
     unsafe fn trace(&self, tracer: &mut crate::collectors::mark_sweep_branded::trace::Tracer) {
         tracer.mark(self);

oscars/src/collectors/mark_sweep_branded/tests/mod.rs

@@ -6,6 +6,7 @@ struct JsObject {
     value: i32,
 }
 
+// SAFETY: JsObject contains no Gc pointers; tracing is a no-op.
 unsafe impl crate::collectors::mark_sweep_branded::Trace for JsObject {
     unsafe fn trace(&self, _tracer: &mut crate::collectors::mark_sweep_branded::trace::Tracer) {}
 }

oscars/src/collectors/mark_sweep_branded/tests/uaf.rs

@@ -5,6 +5,7 @@ use core::cell::Cell;
 
 struct DetectDrop<'a>(&'a Cell<bool>);
 
+// SAFETY: DetectDrop contains no Gc pointers; tracing is a no-op.
 unsafe impl<'a> Trace for DetectDrop<'a> {
     unsafe fn trace(&self, _tracer: &mut crate::collectors::mark_sweep_branded::trace::Tracer) {}
 }