Make Send and Sync impls an opt-in feature

ext/Cargo.toml

@@ -14,10 +14,16 @@ tokio = ["dep:tokio", "dep:async-timer"]
 all-arch = ["wasmtime/all-arch"]
 ruby-api = []
 winch = ["wasmtime/winch"]
+unsafe-impl-sync = []
+unsafe-impl-send = []
+unsafe-impl-send-sync = ["unsafe-impl-send", "unsafe-impl-sync"]
 
 [dependencies]
 lazy_static = "1.4.0"
-magnus = { version = "0.6", features = ["rb-sys", "deprecated-send-sync-value"] }
+magnus = { version = "0.6", features = [
+  "rb-sys",
+  "deprecated-send-sync-value",
+] }
 rb-sys = { version = "*", default-features = false, features = [
   "stable-api-compiled-fallback",
 ] }

ext/src/helpers/macros.rs

@@ -10,3 +10,20 @@ macro_rules! define_rb_intern {
         )*
     };
 }
+
+/// Boilerplate for defining send and sync on a Magnus struct when the feature is enabled.
+#[macro_export]
+macro_rules! unsafe_impl_send_sync {
+    ($struct:ident) => {
+        #[cfg(feature = "unsafe-impl-send")]
+        unsafe impl Send for $struct {}
+        #[cfg(feature = "unsafe-impl-sync")]
+        unsafe impl Sync for $struct {}
+    };
+    ($struct:ident <'_>) => {
+        #[cfg(feature = "unsafe-impl-send")]
+        unsafe impl Send for $struct<'_> {}
+        #[cfg(feature = "unsafe-impl-sync")]
+        unsafe impl Sync for $struct<'_> {}
+    };
+}

ext/src/ruby_api/caller.rs

@@ -1,4 +1,5 @@
 use super::{convert::WrapWasmtimeType, externals::Extern, root, store::StoreData};
+use crate::{error, unsafe_impl_send_sync};
 use magnus::{
     class,
     gc::{Compactor, Marker},
@@ -143,7 +144,7 @@ impl<'a> Caller<'a> {
     }
 }
 
-unsafe impl Send for Caller<'_> {}
+unsafe_impl_send_sync!(Caller);
 
 pub fn init() -> Result<(), Error> {
     let klass = root().define_class("Caller", class::object())?;

ext/src/ruby_api/convert.rs

@@ -1,4 +1,4 @@
-use crate::{define_rb_intern, err, error, helpers::SymbolEnum};
+use crate::{define_rb_intern, err, error, helpers::SymbolEnum, unsafe_impl_send_sync};
 use lazy_static::lazy_static;
 use magnus::{prelude::*, Error, IntoValue, RArray, Ruby, Symbol, TryConvert, TypedData, Value};
 use wasmtime::{ExternRef, Val, ValType};
@@ -95,8 +95,8 @@ impl From<Value> for ExternRefValue {
         Self(v)
     }
 }
-unsafe impl Send for ExternRefValue {}
-unsafe impl Sync for ExternRefValue {}
+
+unsafe_impl_send_sync!(ExternRefValue);
 
 pub trait ToExtern {
     fn to_extern(&self, ruby: &Ruby) -> Result<wasmtime::Extern, Error>;

ext/src/ruby_api/instance.rs

@@ -5,7 +5,7 @@ use super::{
     root,
     store::{Store, StoreContextValue, StoreData},
 };
-use crate::err;
+use crate::{err, unsafe_impl_send_sync};
 use magnus::{
     class, function, gc::Marker, method, prelude::*, scan_args, typed_data::Obj, DataTypeFunctions,
     Error, Object, RArray, RHash, RString, Ruby, TryConvert, TypedData, Value,
@@ -22,7 +22,7 @@ pub struct Instance {
     store: Obj<Store>,
 }
 
-unsafe impl Send for Instance {}
+unsafe_impl_send_sync!(Instance);
 
 impl DataTypeFunctions for Instance {
     fn mark(&self, marker: &Marker) {

ext/src/ruby_api/linker.rs

@@ -9,7 +9,7 @@ use super::{
     root,
     store::{Store, StoreContextValue, StoreData},
 };
-use crate::{define_rb_intern, err, error};
+use crate::{define_rb_intern, err, error, unsafe_impl_send_sync};
 use magnus::{
     block::Proc, class, function, gc::Marker, method, prelude::*, scan_args, scan_args::scan_args,
     typed_data::Obj, DataTypeFunctions, Error, Object, RArray, RHash, RString, Ruby, TypedData,
@@ -32,7 +32,7 @@ pub struct Linker {
     has_wasi: bool,
 }
 
-unsafe impl Send for Linker {}
+unsafe_impl_send_sync!(Linker);
 
 impl DataTypeFunctions for Linker {
     fn mark(&self, marker: &Marker) {

ext/src/ruby_api/memory.rs

@@ -5,7 +5,7 @@ use super::{
     root,
     store::{Store, StoreContextValue},
 };
-use crate::{define_rb_intern, error};
+use crate::{define_rb_intern, error, unsafe_impl_send_sync};
 use magnus::{
     class, function, gc::Marker, method, r_string::RString, scan_args, typed_data::Obj,
     DataTypeFunctions, Error, Module as _, Object, Ruby, TypedData, Value,
@@ -31,12 +31,13 @@ pub struct Memory<'a> {
     inner: ManuallyTracked<MemoryImpl>,
 }
 
+unsafe_impl_send_sync!(Memory<'_>);
+
 impl DataTypeFunctions for Memory<'_> {
     fn mark(&self, marker: &Marker) {
         self.store.mark(marker)
     }
 }
-unsafe impl Send for Memory<'_> {}
 
 impl<'a> Memory<'a> {
     /// @yard

ext/src/ruby_api/module.rs

@@ -14,7 +14,7 @@ pub struct Module {
     _track_memory_usage: ManuallyTracked<()>,
 }
 
-// Needed for ManuallyTracked
+#[cfg(feature = "unsafe-impl-send")]
 unsafe impl Send for Module {}
 
 impl Module {

ext/src/ruby_api/store.rs

@@ -1,6 +1,6 @@
 use super::errors::wasi_exit_error;
 use super::{caller::Caller, engine::Engine, root, trap::Trap, wasi_ctx_builder::WasiCtxBuilder};
-use crate::{define_rb_intern, error};
+use crate::{define_rb_intern, error, unsafe_impl_send_sync};
 use magnus::rb_sys::AsRawValue;
 use magnus::Class;
 use magnus::{
@@ -96,8 +96,7 @@ impl DataTypeFunctions for Store {
     }
 }
 
-unsafe impl Send for Store {}
-unsafe impl Send for StoreData {}
+unsafe_impl_send_sync!(Store);
 
 impl Store {
     /// @yard