Move component value support behind a feature flag (#1131)

* Move component `value` support behind a feature flag

Support for the `value` type in the component model is somewhat
best-effort right now in implementations like Wasmtime's. Additionally
there's open questions in the upstream specification about what to do
with `value`, especially around `post-return` and ABI details. For now
this adds a separate feature gate for the `value` type to have
first-class errors about its usage in the binary encoding rather than
possible panics in Wasmtime, for example.

* Update fuzzers

* Fix benchmark build

crates/wasm-shrink/src/lib.rs

@@ -235,6 +235,7 @@ impl ShrinkRun {
             component_model: false,
             function_references: false,
             gc: false,
+            component_model_values: false,
 
             floats: true,
             memory_control: true,

crates/wasm-smith/tests/core.rs

@@ -309,6 +309,7 @@ fn parser_features_from_config(config: &impl Config) -> WasmFeatures {
         function_references: false,
         memory_control: false,
         gc: false,
+        component_model_values: false,
     }
 }
 

crates/wasmparser/benches/benchmark.rs

@@ -254,6 +254,7 @@ fn define_benchmarks(c: &mut Criterion) {
             function_references: true,
             memory_control: true,
             gc: true,
+            component_model_values: true,
         })
     }
 

crates/wasmparser/src/validator.rs

@@ -247,6 +247,8 @@ pub struct WasmFeatures {
     pub memory_control: bool,
     /// The WebAssembly gc proposal
     pub gc: bool,
+    /// Support for the `value` type in the component model proposal.
+    pub component_model_values: bool,
 }
 
 impl WasmFeatures {
@@ -336,6 +338,7 @@ impl Default for WasmFeatures {
             function_references: false,
             memory_control: false,
             gc: false,
+            component_model_values: false,
 
             // On-by-default features (phase 4 or greater).
             mutable_global: true,
@@ -1062,11 +1065,11 @@ impl Validator {
                 current.instances.reserve(count as usize);
                 Ok(())
             },
-            |components, types, _, instance, offset| {
+            |components, types, features, instance, offset| {
                 components
                     .last_mut()
                     .unwrap()
-                    .add_instance(instance, types, offset)
+                    .add_instance(instance, features, types, offset)
             },
         )
     }
@@ -1082,8 +1085,8 @@ impl Validator {
             section,
             "alias",
             |_, _, _, _| Ok(()), // maximums checked via `add_alias`
-            |components, types, _, alias, offset| -> Result<(), BinaryReaderError> {
-                ComponentState::add_alias(components, alias, types, offset)
+            |components, types, features, alias, offset| -> Result<(), BinaryReaderError> {
+                ComponentState::add_alias(components, alias, features, types, offset)
             },
         )
     }
@@ -1181,6 +1184,7 @@ impl Validator {
             f.func_index,
             &f.arguments,
             f.results,
+            &self.features,
             &self.types,
             range.start,
         )
@@ -1197,11 +1201,11 @@ impl Validator {
             section,
             "import",
             |_, _, _, _| Ok(()), // add_import will check limits
-            |components, types, _, import, offset| {
+            |components, types, features, import, offset| {
                 components
                     .last_mut()
                     .unwrap()
-                    .add_import(import, types, offset)
+                    .add_import(import, features, types, offset)
             },
         )
     }
@@ -1228,12 +1232,13 @@ impl Validator {
                 current.exports.reserve(count as usize);
                 Ok(())
             },
-            |components, types, _, export, offset| {
+            |components, types, features, export, offset| {
                 let current = components.last_mut().unwrap();
-                let ty = current.export_to_entity_type(&export, types, offset)?;
+                let ty = current.export_to_entity_type(&export, features, types, offset)?;
                 current.add_export(
                     export.name,
                     ty,
+                    features,
                     types,
                     offset,
                     false, /* checked above */

crates/wasmparser/src/validator/component.rs

@@ -410,13 +410,15 @@ impl ComponentState {
     pub fn add_import(
         &mut self,
         import: crate::ComponentImport,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<()> {
-        let mut entity = self.check_type_ref(&import.ty, types, offset)?;
+        let mut entity = self.check_type_ref(&import.ty, features, types, offset)?;
         self.add_entity(
             &mut entity,
             Some((import.name.as_str(), ExternKind::Import)),
+            features,
             types,
             offset,
         )?;
@@ -437,6 +439,7 @@ impl ComponentState {
         &mut self,
         ty: &mut ComponentEntityType,
         name_and_kind: Option<(&str, ExternKind)>,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<()> {
@@ -464,6 +467,7 @@ impl ComponentState {
                 (self.function_count(), MAX_WASM_FUNCTIONS, "functions")
             }
             ComponentEntityType::Value(ty) => {
+                self.check_value_support(features, offset)?;
                 let value_used = match kind {
                     Some(ExternKind::Import) | None => false,
                     Some(ExternKind::Export) => true,
@@ -868,6 +872,7 @@ impl ComponentState {
         &mut self,
         name: ComponentExternName<'_>,
         mut ty: ComponentEntityType,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
         check_limit: bool,
@@ -878,6 +883,7 @@ impl ComponentState {
         self.add_entity(
             &mut ty,
             Some((name.as_str(), ExternKind::Export)),
+            features,
             types,
             offset,
         )?;
@@ -1037,16 +1043,23 @@ impl ComponentState {
     pub fn add_instance(
         &mut self,
         instance: crate::ComponentInstance,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<()> {
         let instance = match instance {
             crate::ComponentInstance::Instantiate {
                 component_index,
                 args,
-            } => self.instantiate_component(component_index, args.into_vec(), types, offset)?,
+            } => self.instantiate_component(
+                component_index,
+                args.into_vec(),
+                features,
+                types,
+                offset,
+            )?,
             crate::ComponentInstance::FromExports(exports) => {
-                self.instantiate_exports(exports.into_vec(), types, offset)?
+                self.instantiate_exports(exports.into_vec(), features, types, offset)?
             }
         };
 
@@ -1058,6 +1071,7 @@ impl ComponentState {
     pub fn add_alias(
         components: &mut [Self],
         alias: crate::ComponentAlias,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<()> {
@@ -1070,6 +1084,7 @@ impl ComponentState {
                 instance_index,
                 kind,
                 name,
+                features,
                 types,
                 offset,
             ),
@@ -1106,9 +1121,16 @@ impl ComponentState {
         func_index: u32,
         args: &[u32],
         results: u32,
+        features: &WasmFeatures,
         types: &TypeList,
         offset: usize,
     ) -> Result<()> {
+        if !features.component_model_values {
+            bail!(
+                offset,
+                "support for component model `value`s is not enabled"
+            );
+        }
         if self.has_start {
             return Err(BinaryReaderError::new(
                 "component cannot have more than one start function",
@@ -1281,6 +1303,7 @@ impl ComponentState {
     fn check_type_ref(
         &mut self,
         ty: &ComponentTypeRef,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<ComponentEntityType> {
@@ -1302,6 +1325,7 @@ impl ComponentState {
                 ComponentEntityType::Func(id)
             }
             ComponentTypeRef::Value(ty) => {
+                self.check_value_support(features, offset)?;
                 let ty = match ty {
                     crate::ComponentValType::Primitive(ty) => ComponentValType::Primitive(*ty),
                     crate::ComponentValType::Type(index) => {
@@ -1348,6 +1372,7 @@ impl ComponentState {
     pub fn export_to_entity_type(
         &mut self,
         export: &crate::ComponentExport,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<ComponentEntityType> {
@@ -1359,6 +1384,7 @@ impl ComponentState {
                 ComponentEntityType::Func(self.function_at(export.index, offset)?)
             }
             ComponentExternalKind::Value => {
+                self.check_value_support(features, offset)?;
                 ComponentEntityType::Value(*self.value_at(export.index, offset)?)
             }
             ComponentExternalKind::Type => {
@@ -1378,7 +1404,7 @@ impl ComponentState {
         };
 
         let ascribed = match &export.ty {
-            Some(ty) => self.check_type_ref(ty, types, offset)?,
+            Some(ty) => self.check_type_ref(ty, features, types, offset)?,
             None => return Ok(actual),
         };
 
@@ -1466,17 +1492,17 @@ impl ComponentState {
                 }
                 crate::ComponentTypeDeclaration::Export { name, ty } => {
                     let current = components.last_mut().unwrap();
-                    let ty = current.check_type_ref(&ty, types, offset)?;
-                    current.add_export(name, ty, types, offset, true)?;
+                    let ty = current.check_type_ref(&ty, features, types, offset)?;
+                    current.add_export(name, ty, features, types, offset, true)?;
                 }
                 crate::ComponentTypeDeclaration::Import(import) => {
                     components
                         .last_mut()
                         .unwrap()
-                        .add_import(import, types, offset)?;
+                        .add_import(import, features, types, offset)?;
                 }
                 crate::ComponentTypeDeclaration::Alias(alias) => {
-                    Self::add_alias(components, alias, types, offset)?;
+                    Self::add_alias(components, alias, features, types, offset)?;
                 }
             };
         }
@@ -1503,11 +1529,11 @@ impl ComponentState {
                 }
                 crate::InstanceTypeDeclaration::Export { name, ty } => {
                     let current = components.last_mut().unwrap();
-                    let ty = current.check_type_ref(&ty, types, offset)?;
-                    current.add_export(name, ty, types, offset, true)?;
+                    let ty = current.check_type_ref(&ty, features, types, offset)?;
+                    current.add_export(name, ty, features, types, offset, true)?;
                 }
                 crate::InstanceTypeDeclaration::Alias(alias) => {
-                    Self::add_alias(components, alias, types, offset)?;
+                    Self::add_alias(components, alias, features, types, offset)?;
                 }
             };
         }
@@ -1690,6 +1716,7 @@ impl ComponentState {
         &mut self,
         component_index: u32,
         component_args: Vec<crate::ComponentInstantiationArg>,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<TypeId> {
@@ -1712,6 +1739,7 @@ impl ComponentState {
                     ComponentEntityType::Func(self.function_at(component_arg.index, offset)?)
                 }
                 ComponentExternalKind::Value => {
+                    self.check_value_support(features, offset)?;
                     ComponentEntityType::Value(*self.value_at(component_arg.index, offset)?)
                 }
                 ComponentExternalKind::Type => {
@@ -1957,6 +1985,7 @@ impl ComponentState {
     fn instantiate_exports(
         &mut self,
         exports: Vec<crate::ComponentExport>,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<TypeId> {
@@ -2003,6 +2032,7 @@ impl ComponentState {
                     ComponentEntityType::Func(self.function_at(export.index, offset)?)
                 }
                 ComponentExternalKind::Value => {
+                    self.check_value_support(features, offset)?;
                     ComponentEntityType::Value(*self.value_at(export.index, offset)?)
                 }
                 ComponentExternalKind::Type => {
@@ -2229,9 +2259,13 @@ impl ComponentState {
         instance_index: u32,
         kind: ComponentExternalKind,
         name: &str,
+        features: &WasmFeatures,
         types: &mut TypeAlloc,
         offset: usize,
     ) -> Result<()> {
+        if let ComponentExternalKind::Value = kind {
+            self.check_value_support(features, offset)?;
+        }
         let mut ty = match types[self.instance_at(instance_index, offset)?]
             .unwrap_component_instance()
             .exports
@@ -2266,7 +2300,7 @@ impl ComponentState {
             );
         }
 
-        self.add_entity(&mut ty, None, types, offset)?;
+        self.add_entity(&mut ty, None, features, types, offset)?;
         Ok(())
     }
 
@@ -2869,6 +2903,16 @@ impl ComponentState {
 
         Ok(ty)
     }
+
+    fn check_value_support(&self, features: &WasmFeatures, offset: usize) -> Result<()> {
+        if !features.component_model_values {
+            bail!(
+                offset,
+                "support for component model `value`s is not enabled"
+            );
+        }
+        Ok(())
+    }
 }
 
 impl KebabNameContext {

fuzz/fuzz_targets/validate.rs

@@ -39,6 +39,7 @@ fuzz_target!(|data: &[u8]| {
         memory_control: (byte3 & 0b0000_0001) != 0,
         function_references: (byte3 & 0b0000_0010) != 0,
         gc: (byte3 & 0b0000_0100) != 0,
+        component_model_values: (byte3 & 0b0000_1000) != 0,
     });
     let use_maybe_invalid = byte3 & 0b0000_1000 != 0;
 

src/bin/wasm-tools/validate.rs

@@ -106,6 +106,7 @@ fn parse_features(arg: &str) -> Result<WasmFeatures> {
         ("multi-value", |f| &mut f.multi_value),
         ("tail-call", |f| &mut f.tail_call),
         ("component-model", |f| &mut f.component_model),
+        ("component-model-values", |f| &mut f.component_model_values),
         ("multi-memory", |f| &mut f.multi_memory),
         ("exception-handling", |f| &mut f.exceptions),
         ("memory64", |f| &mut f.memory64),