Fix deinit against uninited InstanceEntity

Author: kateinoigakukun

Sources/WasmKit/Execution/StoreAllocator.swift

@@ -56,6 +56,15 @@ class BumpAllocator<T> {
         currentOffset += 1
         return pointer
     }
+
+    /// Deallocates a just-allocated pointer.
+    ///
+    /// - Parameter pointer: The pointer to deallocate.
+    /// - Precondition: The pointer must be the last allocated pointer.
+    func deallocate(_ pointer: UnsafeMutablePointer<T>) {
+        currentOffset -= 1
+        assert(pointer == currentPage.baseAddress!.advanced(by: currentOffset), "Deallocating a pointer out of order.")
+    }
 }
 
 protocol ValidatableEntity {
@@ -256,6 +265,14 @@ extension StoreAllocator {
         let types = module.types
         // Uninitialized instance
         let instancePointer = instances.allocate()
+        var instanceInitialized = false
+        defer {
+            // If the instance is not initialized due to an exception, deallocate the buffer but don't
+            // deinitalize it.
+            if !instanceInitialized {
+                instances.deallocate(instancePointer)
+            }
+        }
         let instanceHandle = InternalInstance(unsafe: instancePointer)
         var importedFunctions: [InternalFunction] = []
         var importedTables: [InternalTable] = []
@@ -430,6 +447,7 @@ extension StoreAllocator {
             hasDataCount: module.hasDataCount
         )
         instancePointer.initialize(to: instanceEntity)
+        instanceInitialized = true
         return instanceHandle
     }