add new_with_user_state

crates/runtime/src/externref.rs

@@ -669,7 +669,7 @@ impl VMExternRefActivationsTable {
         // The current `precise_stack_roots` becomes our new over-appoximated
         // set for the next GC cycle.
         let mut over_approximated = self.over_approximated_stack_roots.borrow_mut();
-        mem::swap(&mut *precise_stack_roots, &mut *over_approximated);
+        mem::swap(precise_stack_roots, &mut *over_approximated);
 
         // And finally, the new `precise_stack_roots` should be cleared and
         // remain empty until the next GC cycle.

crates/wasmtime/src/instance.rs

@@ -1,8 +1,10 @@
+use crate::frame_info::GlobalFrameInfoRegistration;
 use crate::trampoline::StoreInstanceHandle;
 use crate::{Engine, Export, Extern, Func, Global, Memory, Module, Store, Table, Trap};
 use anyhow::{anyhow, bail, Context, Error, Result};
 use std::any::Any;
 use std::mem;
+use std::sync::Arc;
 use wasmtime_environ::EntityIndex;
 use wasmtime_jit::CompiledModule;
 use wasmtime_runtime::{
@@ -102,7 +104,47 @@ pub struct Instance {
     module: Module,
 }
 
+pub struct HostState {
+    #[allow(dead_code)]
+    frame_info_registration: Option<Arc<GlobalFrameInfoRegistration>>,
+    pub user_state: Option<Box<dyn Any>>,
+}
+
 impl Instance {
+    /// allows the caller to specify customimzed user_state, which can be accessed by
+    /// instance.host_state().downcast_ref::<HostState>.user_state
+    pub fn new_with_user_state(
+        store: &Store,
+        module: &Module,
+        imports: &[Extern],
+        user_state: Option<Box<dyn Any>>,
+    ) -> Result<Instance, Error> {
+        if !Engine::same(store.engine(), module.engine()) {
+            bail!("cross-`Engine` instantiation is not currently supported");
+        }
+
+        let host_info = Box::new({
+            let frame_info_registration = module.register_frame_info();
+            store.register_jit_code(&module);
+            store.register_stack_maps(&module);
+
+            HostState {
+                frame_info_registration,
+                user_state,
+            }
+        });
+
+        let handle = with_imports(store, module.compiled_module(), imports, |imports| {
+            instantiate(store, module.compiled_module(), imports, host_info)
+        })?;
+
+        Ok(Instance {
+            handle,
+            store: store.clone(),
+            module: module.clone(),
+        })
+    }
+
     /// Creates a new [`Instance`] from the previously compiled [`Module`] and
     /// list of `imports` specified.
     ///
@@ -157,26 +199,7 @@ impl Instance {
     /// [issue]: https://github.com/bytecodealliance/wasmtime/issues/727
     /// [`ExternType`]: crate::ExternType
     pub fn new(store: &Store, module: &Module, imports: &[Extern]) -> Result<Instance, Error> {
-        if !Engine::same(store.engine(), module.engine()) {
-            bail!("cross-`Engine` instantiation is not currently supported");
-        }
-
-        let host_info = Box::new({
-            let frame_info_registration = module.register_frame_info();
-            store.register_jit_code(&module);
-            store.register_stack_maps(&module);
-            frame_info_registration
-        });
-
-        let handle = with_imports(store, module.compiled_module(), imports, |imports| {
-            instantiate(store, module.compiled_module(), imports, host_info)
-        })?;
-
-        Ok(Instance {
-            handle,
-            store: store.clone(),
-            module: module.clone(),
-        })
+        Instance::new_with_user_state(store, module, imports, None)
     }
 
     /// Returns the associated [`Store`] that this `Instance` is compiled into.