add explicit deletion of forgetting objects

crates/main/src/lib.rs

@@ -57,6 +57,8 @@ pub use result::get_result_ptr;
 pub use result::get_result_size;
 pub use result::set_result_ptr;
 pub use result::set_result_size;
+pub use result::release_objects;
+pub use result::add_object_to_release;
 
 #[allow(unused_variables)]
 pub(crate) fn log<S: AsRef<str>>(msg: S) {

crates/main/src/result.rs

@@ -21,10 +21,13 @@
 use super::log;
 
 use std::sync::atomic::AtomicUsize;
+use std::cell::RefCell;
 
 static mut RESULT_PTR: AtomicUsize = AtomicUsize::new(0);
 static mut RESULT_SIZE: AtomicUsize = AtomicUsize::new(0);
 
+thread_local!(static OBJECTS_TO_RELEASE: RefCell<Vec<Box<dyn Drop>>> = RefCell::new(Vec::new()));
+
 #[no_mangle]
 pub unsafe fn get_result_ptr() -> usize {
     log(format!(
@@ -58,3 +61,20 @@ pub unsafe fn set_result_size(size: usize) {
 
     *RESULT_SIZE.get_mut() = size;
 }
+
+#[no_mangle]
+pub unsafe fn release_objects() {
+    OBJECTS_TO_RELEASE.with(|objects| {
+        let mut objects = objects.borrow_mut();
+        while let Some(object) = objects.pop() {
+            drop(object);
+        }
+    })
+}
+
+pub fn add_object_to_release(object: Box<dyn Drop>) {
+    OBJECTS_TO_RELEASE.with(|objects| {
+        let mut objects = objects.borrow_mut();
+        objects.push(object);
+    });
+}

crates/wit/src/parsed_type/fn_arg.rs

@@ -1,17 +1,17 @@
 /*
- * copyright 2020 fluence labs limited
+ * Copyright 2020 Fluence Labs Limited
  *
- * licensed under the apache license, version 2.0 (the "license");
- * you may not use this file except in compliance with the license.
- * you may obtain a copy of the license at
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *     http://www.apache.org/licenses/license-2.0
+ *     http://www.apache.org/licenses/LICENSE-2.0
  *
- * unless required by applicable law or agreed to in writing, software
- * distributed under the license is distributed on an "as is" basis,
- * without warranties or conditions of any kind, either express or implied.
- * see the license for the specific language governing permissions and
- * limitations under the license.
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
 use super::ParsedType;

crates/wit/src/parsed_type/fn_epilog.rs

@@ -133,9 +133,9 @@ fn generate_epilog(ty: &Option<ParsedType>) -> proc_macro2::TokenStream {
     }
 }
 
-/// If an export function returns a reference, probably this reference is to one
-/// of these function arguments. In this case they should preserve after the end
-/// of the function and then deleted by IT with explicitly call of deallocate.
+/// If an export function returns a reference, this is probably a reference to one
+/// of the function arguments. If that's the case, reference must be still valid after
+/// the end of the function. Their deletion will be handled by IT with calling `release_objects`.
 fn generate_mem_forget(
     args: &Vec<(String, ParsedType)>,
     converted_args: &Vec<syn::Ident>,
@@ -144,7 +144,7 @@ fn generate_mem_forget(
     let passing_style = ret_type.as_ref().map(passing_style_of);
 
     match passing_style {
-        Some(PassingStyle::ByValue) => mem_forget_by_ret_type(ret_type),
+        Some(PassingStyle::ByValue) => quote! { std::mem::forget(result); },
         Some(PassingStyle::ByRef) | Some(PassingStyle::ByMutRef) => {
             mem_forget_by_args(args, converted_args)
         }
@@ -152,13 +152,6 @@ fn generate_mem_forget(
     }
 }
 
-fn mem_forget_by_ret_type(ret_type: &Option<ParsedType>) -> proc_macro2::TokenStream {
-    match ret_type {
-        Some(_) => quote! { std::mem::forget(result); },
-        None => quote! {},
-    }
-}
-
 fn mem_forget_by_args(
     args: &Vec<(String, ParsedType)>,
     converted_args: &Vec<syn::Ident>,
@@ -171,7 +164,10 @@ fn mem_forget_by_args(
         match arg_passing_style {
             // such values will be deleted inside an export function because they are being moved
             PassingStyle::ByValue => {}
-            _ => res.extend(quote! { std::mem::forget(#converted_arg); }),
+            _ => res.extend(quote! {
+                fluence::internal::add_object_to_release(Box::new(#converted_arg));
+                std::mem::forget(#converted_arg);
+            }),
         }
     }
 

src/lib.rs

@@ -90,4 +90,5 @@ pub mod internal {
     pub use fluence_sdk_main::get_result_size;
     pub use fluence_sdk_main::set_result_ptr;
     pub use fluence_sdk_main::set_result_size;
+    pub use fluence_sdk_main::add_object_to_release;
 }