Make FuncRef nullable at the API level

examples/table.rs

@@ -118,7 +118,7 @@ fn main() -> anyhow::Result<()> {
     );
     // Now demonstarte that the function we grew the table with is actually in the table.
     for table_index in 3..6 {
-        if let Value::FuncRef(f) = guest_table.get(table_index as _).unwrap() {
+        if let Value::FuncRef(Some(f)) = guest_table.get(table_index as _).unwrap() {
             let result = f.call(&[Value::I32(1), Value::I32(9)])?;
             assert_eq!(result[0], Value::I32(10));
         } else {
@@ -140,7 +140,7 @@ fn main() -> anyhow::Result<()> {
     // Now demonstrate that the host and guest see the same table and that both
     // get the same result.
     for table_index in 3..6 {
-        if let Value::FuncRef(f) = guest_table.get(table_index as _).unwrap() {
+        if let Value::FuncRef(Some(f)) = guest_table.get(table_index as _).unwrap() {
             let result = f.call(&[Value::I32(1), Value::I32(9)])?;
             assert_eq!(result[0], Value::I32(10));
         } else {

lib/api/src/types.rs

@@ -19,9 +19,10 @@ pub type Val = Value<Function>;
 impl StoreObject for Val {
     fn comes_from_same_store(&self, store: &Store) -> bool {
         match self {
-            Self::FuncRef(f) => Store::same(store, f.store()),
+            Self::FuncRef(None) => true,
+            Self::FuncRef(Some(f)) => Store::same(store, f.store()),
             Self::ExternRef(ExternRef::Ref(_)) | Self::ExternRef(ExternRef::Other(_)) => false,
-            Self::ExternRef(ExternRef::Null) => true,
+            Self::ExternRef(ExternRef::Null) => todo!("update this code"),
             Self::I32(_) | Self::I64(_) | Self::F32(_) | Self::F64(_) | Self::V128(_) => true,
         }
     }
@@ -29,7 +30,7 @@ impl StoreObject for Val {
 
 impl From<Function> for Val {
     fn from(val: Function) -> Self {
-        Self::FuncRef(val)
+        Self::FuncRef(Some(val))
     }
 }
 
@@ -60,21 +61,29 @@ impl ValFuncRef for Val {
             return Err(RuntimeError::new("cross-`Store` values are not supported"));
         }
         Ok(match self {
-            Self::ExternRef(ExternRef::Null) => wasmer_vm::VMCallerCheckedAnyfunc {
+            Self::ExternRef(ExternRef::Null) => todo!("Extern ref not yet implemented"), /*wasmer_vm::VMCallerCheckedAnyfunc {
+            func_ptr: ptr::null(),
+            type_index: wasmer_vm::VMSharedSignatureIndex::default(),
+            vmctx: wasmer_vm::VMFunctionEnvironment {
+            host_env: ptr::null_mut(),
+            },
+            },*/
+            Self::FuncRef(None) => wasmer_vm::VMCallerCheckedAnyfunc {
                 func_ptr: ptr::null(),
                 type_index: wasmer_vm::VMSharedSignatureIndex::default(),
                 vmctx: wasmer_vm::VMFunctionEnvironment {
                     host_env: ptr::null_mut(),
                 },
             },
-            Self::FuncRef(f) => f.checked_anyfunc(),
+            Self::FuncRef(Some(f)) => f.checked_anyfunc(),
-            _ => return Err(RuntimeError::new("val is not funcref")),
+            _ => return Err(RuntimeError::new("val is not reference")),
         })
     }
 
     fn from_checked_anyfunc(item: wasmer_vm::VMCallerCheckedAnyfunc, store: &Store) -> Self {
+        // TODO: use `is_null()`?
         if item.type_index == wasmer_vm::VMSharedSignatureIndex::default() {
-            return Self::ExternRef(ExternRef::Null);
+            return Self::FuncRef(None);
         }
         let signature = store
             .engine()
@@ -96,7 +105,7 @@ impl ValFuncRef for Val {
             },
         };
         let f = Function::from_vm_export(store, export);
-        Self::FuncRef(f)
+        Self::FuncRef(Some(f))
     }
 
     fn into_table_reference(
@@ -107,16 +116,28 @@ impl ValFuncRef for Val {
             return Err(RuntimeError::new("cross-`Store` values are not supported"));
         }
         Ok(match self {
-            Self::ExternRef(ExternRef::Null) => wasmer_vm::TableReference::FuncRef(wasmer_vm::VMCallerCheckedAnyfunc {
+            Self::ExternRef(ExternRef::Null) =>
+            /*wasmer_vm::TableReference::FuncRef(wasmer_vm::VMCallerCheckedAnyfunc {
                 func_ptr: ptr::null(),
                 type_index: wasmer_vm::VMSharedSignatureIndex::default(),
                 vmctx: wasmer_vm::VMFunctionEnvironment {
                     host_env: ptr::null_mut(),
                 },
-            }),
+            }),*/
             // existing code uses `ExtenRef` for null pointers
-            //todo!("extern ref not yet supported"),
+            {
-            Self::FuncRef(f) => wasmer_vm::TableReference::FuncRef(f.checked_anyfunc()),
+                todo!("extern ref not yet supported")
+            }
+            Self::FuncRef(None) => {
+                wasmer_vm::TableReference::FuncRef(wasmer_vm::VMCallerCheckedAnyfunc {
+                    func_ptr: ptr::null(),
+                    type_index: wasmer_vm::VMSharedSignatureIndex::default(),
+                    vmctx: wasmer_vm::VMFunctionEnvironment {
+                        host_env: ptr::null_mut(),
+                    },
+                })
+            }
+            Self::FuncRef(Some(f)) => wasmer_vm::TableReference::FuncRef(f.checked_anyfunc()),
             _ => return Err(RuntimeError::new("val is not reference")),
         })
     }

lib/api/tests/externals.rs

@@ -67,7 +67,7 @@ fn table_new() -> Result<()> {
         maximum: None,
     };
     let f = Function::new_native(&store, || {});
-    let table = Table::new(&store, table_type, Value::FuncRef(f))?;
+    let table = Table::new(&store, table_type, Value::FuncRef(Some(f)))?;
     assert_eq!(*table.ty(), table_type);
 
     // Anyrefs not yet supported
@@ -92,7 +92,7 @@ fn table_get() -> Result<()> {
         maximum: Some(1),
     };
     let f = Function::new_native(&store, |num: i32| num + 1);
-    let table = Table::new(&store, table_type, Value::FuncRef(f.clone()))?;
+    let table = Table::new(&store, table_type, Value::FuncRef(Some(f.clone())))?;
     assert_eq!(*table.ty(), table_type);
     let _elem = table.get(0).unwrap();
     // assert_eq!(elem.funcref().unwrap(), f);
@@ -115,13 +115,13 @@ fn table_grow() -> Result<()> {
         maximum: Some(10),
     };
     let f = Function::new_native(&store, |num: i32| num + 1);
-    let table = Table::new(&store, table_type, Value::FuncRef(f.clone()))?;
+    let table = Table::new(&store, table_type, Value::FuncRef(Some(f.clone())))?;
     // Growing to a bigger maximum should return None
-    let old_len = table.grow(12, Value::FuncRef(f.clone()));
+    let old_len = table.grow(12, Value::FuncRef(Some(f.clone())));
     assert!(old_len.is_err());
 
     // Growing to a bigger maximum should return None
-    let old_len = table.grow(5, Value::FuncRef(f.clone()))?;
+    let old_len = table.grow(5, Value::FuncRef(Some(f.clone())))?;
     assert_eq!(old_len, 0);
 
     Ok(())

lib/vm/src/vmcontext.rs

@@ -762,6 +762,17 @@ pub struct VMCallerCheckedAnyfunc {
     // If more elements are added here, remember to add offset_of tests below!
 }
 
+impl VMCallerCheckedAnyfunc {
+    /// Check if this anyfunc is a null funcref.
+    // TODO: we probably want to clean this up before shipping, maybe actually add
+    // an extra layer of indirection
+    pub fn is_null(&self) -> bool {
+        self.func_ptr == std::ptr::null()
+            && self.type_index == VMSharedSignatureIndex::default()
+            && self.vmctx.is_null()
+    }
+}
+
 #[cfg(test)]
 mod test_vmcaller_checked_anyfunc {
     use super::VMCallerCheckedAnyfunc;

lib/wasmer-types/src/values.rs

@@ -31,7 +31,7 @@ pub enum Value<T> {
     ExternRef(ExternRef),
 
     /// A first-class reference to a WebAssembly function.
-    FuncRef(T),
+    FuncRef(Option<T>),
 
     /// A 128-bit number
     V128(u128),
@@ -120,7 +120,7 @@ impl<T> Value<T> {
         (I64(i64) i64 unwrap_i64 *e)
         (F32(f32) f32 unwrap_f32 *e)
         (F64(f64) f64 unwrap_f64 *e)
-        (FuncRef(&T) funcref unwrap_funcref e)
+        (FuncRef(&Option<T>) funcref unwrap_funcref e)
         (V128(u128) v128 unwrap_v128 *e)
     }
 

tests/lib/wast/src/spectest.rs

@@ -23,7 +23,7 @@ pub fn spectest_importobject(store: &Store) -> ImportObject {
     let global_f64 = Global::new(store, Val::F64(f64::from_bits(0x4084_d000_0000_0000)));
 
     let ty = TableType::new(ValType::FuncRef, 10, Some(20));
-    let table = Table::new(store, ty, Val::ExternRef(ExternRef::Null)).unwrap();
+    let table = Table::new(store, ty, Val::FuncRef(None)).unwrap();
 
     let ty = MemoryType::new(1, Some(2), false);
     let memory = Memory::new(store, ty).unwrap();