Validation: Check start function type

Author: kateinoigakukun

Sources/WasmKit/Module.swift

@@ -58,6 +58,7 @@ public struct Module {
     public let types: [FunctionType]
 
     let moduleImports: ModuleImports
+    let importedFunctionTypes: [TypeIndex]
     let memoryTypes: [MemoryType]
     let tableTypes: [TableType]
     let allocator: ISeqAllocator
@@ -92,19 +93,20 @@ public struct Module {
         self.features = features
         self.hasDataCount = hasDataCount
 
-        var functionTypeIndices: [TypeIndex] = []
+        var importedFunctionTypes: [TypeIndex] = []
         var globalTypes: [GlobalType] = []
         var memoryTypes: [MemoryType] = []
         var tableTypes: [TableType] = []
 
         self.moduleImports = ModuleImports.build(
             from: imports,
-            functionTypeIndices: &functionTypeIndices,
+            functionTypeIndices: &importedFunctionTypes,
             globalTypes: &globalTypes,
             memoryTypes: &memoryTypes,
             tableTypes: &tableTypes
         )
         self.types = types
+        self.importedFunctionTypes = importedFunctionTypes
         self.memoryTypes = memoryTypes + memories
         self.tableTypes = tableTypes + tables
     }
@@ -116,6 +118,19 @@ public struct Module {
         return typeSection[Int(index)]
     }
 
+    internal func resolveFunctionType(_ index: FunctionIndex) throws -> FunctionType {
+        guard Int(index) < functions.count + self.moduleImports.numberOfFunctions else {
+            throw TranslationError("Function index \(index) is out of range")
+        }
+        if Int(index) < self.moduleImports.numberOfFunctions {
+            return try Self.resolveType(
+                importedFunctionTypes[Int(index)],
+                typeSection: types
+            )
+        }
+        return functions[Int(index) - self.moduleImports.numberOfFunctions].type
+    }
+
     /// Instantiate this module in the given imports.
     ///
     /// - Parameters:

Sources/WasmKit/Validator.swift

@@ -61,6 +61,16 @@ struct ModuleValidator {
         for memoryType in module.memoryTypes {
             try Self.checkMemoryType(memoryType, features: module.features)
         }
+        try checkStartFunction()
+    }
+
+    func checkStartFunction() throws {
+        if let startFunction = module.start {
+            let type = try module.resolveFunctionType(startFunction)
+            guard type.parameters.isEmpty, type.results.isEmpty else {
+                throw ValidationError("Start function must have no parameters and no results")
+            }
+        }
     }
 
     static func checkMemoryType(_ type: MemoryType, features: WasmFeatureSet) throws {

Tests/WasmKitTests/SpectestTests.swift

@@ -22,7 +22,6 @@ final class SpectestTests: XCTestCase {
             path: Self.testPaths,
             include: [],
             exclude: [
-                "start.wast",
                 "table-sub.wast",
                 "table.wast",
                 "table_get.wast",