Fix leak in test

Author: alexcrichton

crates/c-api/include/wasmtime/exnref.h

@@ -128,20 +128,17 @@ wasmtime_exnref_field(wasmtime_context_t *store, const wasmtime_exnref_t *exn,
 /**
  * \brief Sets the pending exception on the store and returns a trap.
  *
- * This transfers ownership of `exn` to the store. After this call,
- * the caller must not use or free `exn`.
- *
  * Returns a `wasm_trap_t` that the host callback MUST return to signal
  * to the Wasm runtime that an exception was thrown. The caller owns
  * the returned trap.
  *
  * \param store the store context
- * \param exn the exception to throw (ownership transferred)
+ * \param exn the exception to throw
  * \return a trap to return from the host callback (caller-owned)
  */
 WASM_API_EXTERN wasm_trap_t *
 wasmtime_context_set_exception(wasmtime_context_t *store,
-                               wasmtime_exnref_t *exn);
+                               const wasmtime_exnref_t *exn);
 
 /**
  * \brief Takes the pending exception from the store, if any.

crates/c-api/include/wasmtime/store.hh

@@ -44,9 +44,7 @@ inline Store::Context::Context(Caller *caller) : Context(*caller) {}
 
 #ifdef WASMTIME_FEATURE_GC
 inline Trap Store::Context::throw_exception(ExnRef exn) {
-  auto *ret = wasmtime_context_set_exception(capi(), exn.capi());
-  wasmtime_exnref_set_null(exn.capi());
-  return Trap(ret);
+  return Trap(wasmtime_context_set_exception(capi(), exn.capi()));
 }
 
 inline std::optional<ExnRef> Store::Context::take_exception() {

crates/c-api/src/exnref.rs

@@ -83,7 +83,7 @@ pub unsafe extern "C" fn wasmtime_exnref_field(
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn wasmtime_context_set_exception(
     mut store: WasmtimeStoreContextMut<'_>,
-    exn: &mut wasmtime_exnref_t,
+    exn: &wasmtime_exnref_t,
 ) -> Option<Box<wasm_trap_t>> {
     let mut scope = RootScope::new(&mut store);
     let rooted = exn.as_wasmtime()?.to_rooted(&mut scope);

crates/c-api/tests/exception.cc

@@ -98,7 +98,7 @@ TEST(Exception, HostThrowWasmCatch) {
 
                   std::vector<Val> fields = {Val(int32_t(99))};
                   auto exn = ExnRef::create(cx2, tag, fields).unwrap();
-                  return cx2.throw_exception(std::move(exn));
+                  return cx2.throw_exception(exn);
                 });
 
   std::vector<Extern> imports = {throw_fn, tag};