Fix StartupData memory leak (#131)

README.md

@@ -1,7 +1,5 @@
 # Rusty V8 Binding
 
-Status: Early development, not usable.
-
 V8 Version: 8.0.427
 
 [![ci](https://github.com/denoland/rusty_v8/workflows/ci/badge.svg?branch=master)](https://github.com/denoland/rusty_v8/actions)

src/binding.cc

@@ -666,6 +666,8 @@ void v8__SnapshotCreator__DESTRUCT(v8::SnapshotCreator& self) {
   self.~SnapshotCreator();
 }
 
+void v8__StartupData__DESTRUCT(v8::StartupData& self) { delete[] self.data; }
+
 v8::Isolate* v8__SnapshotCreator__GetIsolate(v8::SnapshotCreator& self) {
   return self.GetIsolate();
 }

src/snapshot.rs

@@ -3,6 +3,8 @@ use crate::Context;
 use crate::Isolate;
 use crate::Local;
 use std::mem::MaybeUninit;
+use std::ops::Deref;
+use std::ops::DerefMut;
 
 extern "C" {
   fn v8__SnapshotCreator__CONSTRUCT(buf: &mut MaybeUninit<SnapshotCreator>);
@@ -18,13 +20,33 @@ extern "C" {
     this: &mut SnapshotCreator,
     context: *mut Context,
   );
+  fn v8__StartupData__DESTRUCT(this: &mut StartupData);
 }
 
 #[derive(Debug)]
 #[repr(C)]
 pub struct StartupData {
-  pub data: *const u8,
-  pub raw_size: int,
+  data: *mut u8,
+  raw_size: int,
+}
+
+impl Deref for StartupData {
+  type Target = [u8];
+  fn deref(&self) -> &Self::Target {
+    unsafe { std::slice::from_raw_parts(self.data, self.raw_size as usize) }
+  }
+}
+
+impl DerefMut for StartupData {
+  fn deref_mut(&mut self) -> &mut Self::Target {
+    unsafe { std::slice::from_raw_parts_mut(self.data, self.raw_size as usize) }
+  }
+}
+
+impl Drop for StartupData {
+  fn drop(&mut self) {
+    unsafe { v8__StartupData__DESTRUCT(self) }
+  }
 }
 
 #[repr(C)]
@@ -66,14 +88,19 @@ impl SnapshotCreator {
 
   /// Creates a snapshot data blob.
   /// This must not be called from within a handle scope.
-  ///
-  /// Returns { nullptr, 0 } on failure, and a startup snapshot on success.
-  /// The caller acquires ownership of the data array in the return value.
   pub fn create_blob(
     &mut self,
     function_code_handling: FunctionCodeHandling,
-  ) -> StartupData {
-    unsafe { v8__SnapshotCreator__CreateBlob(self, function_code_handling) }
+  ) -> Option<StartupData> {
+    let blob =
+      unsafe { v8__SnapshotCreator__CreateBlob(self, function_code_handling) };
+    if blob.data.is_null() {
+      debug_assert!(blob.raw_size == 0);
+      None
+    } else {
+      debug_assert!(blob.raw_size > 0);
+      Some(blob)
+    }
   }
 
   /// Returns the isolate prepared by the snapshot creator.

tests/test_api.rs

@@ -1234,9 +1234,11 @@ fn snapshot_creator() {
       context.exit();
     }
 
-    snapshot_creator.create_blob(v8::FunctionCodeHandling::Clear)
+    snapshot_creator
+      .create_blob(v8::FunctionCodeHandling::Clear)
+      .unwrap()
   };
-  assert!(startup_data.raw_size > 0);
+  assert!(startup_data.len() > 0);
   // Now we try to load up the snapshot and check that 'a' has the correct
   // value.
   {
@@ -1259,8 +1261,5 @@ fn snapshot_creator() {
       context.exit();
     }
   }
-
-  // TODO(ry) startup_data is getting leaked and is not cleaned up properly!
-  // It must be freed using c++ delete.
   drop(g);
 }