fix

src/binding.cc

@@ -1682,10 +1682,10 @@ void v8__Context__SetPromiseHooks(v8::Context& self, v8::Function& init_hook,
       ptr_to_local(&after_hook), ptr_to_local(&resolve_hook));
 }
 
-const v8::Context* v8__Context__FromSnapshot(v8::Isolate* isolate, 
+const v8::Context* v8__Context__FromSnapshot(v8::Isolate* isolate,
                                              size_t context_snapshot_index) {
-  v8::MaybeLocal<v8::Context> maybe_local = v8::Context::FromSnapshot(
-      isolate, context_snapshot_index);
+  v8::MaybeLocal<v8::Context> maybe_local =
+      v8::Context::FromSnapshot(isolate, context_snapshot_index);
   return maybe_local_to_ptr(maybe_local);
 }
 
@@ -2337,15 +2337,14 @@ void v8__Proxy__Revoke(const v8::Proxy& self) { ptr_to_local(&self)->Revoke(); }
 void v8__SnapshotCreator__CONSTRUCT(uninit_t<v8::SnapshotCreator>* buf,
                                     const intptr_t* external_references,
                                     v8::StartupData* existing_blob) {
-  construct_in_place<v8::SnapshotCreator>(buf, external_references, existing_blob);
+  construct_in_place<v8::SnapshotCreator>(buf, external_references,
+                                          existing_blob);
 }
 
 void v8__SnapshotCreator__DESTRUCT(v8::SnapshotCreator* self) {
   self->~SnapshotCreator();
 }
 
-void v8__StartupData__DESTRUCT(v8::StartupData* self) { delete[] self->data; }
-
 v8::Isolate* v8__SnapshotCreator__GetIsolate(const v8::SnapshotCreator& self) {
   // `v8::SnapshotCreator::GetIsolate()` is not declared as a const method, but
   // this appears to be a mistake.
@@ -3160,4 +3159,7 @@ const char* v8__CompiledWasmModule__SourceUrl(v8::CompiledWasmModule* self,
 void v8__CompiledWasmModule__DELETE(v8::CompiledWasmModule* self) {
   delete self;
 }
+
+void char__DELETE_ARRAY(const char* ptr[]) { delete[] ptr; }
+
 }  // extern "C"

src/snapshot.rs

@@ -3,12 +3,15 @@ use crate::scope::data::ScopeData;
 use crate::support::char;
 use crate::support::int;
 use crate::support::intptr_t;
+use crate::support::Allocated;
+use crate::support::CharArray;
 use crate::Context;
 use crate::Data;
 use crate::Isolate;
 use crate::Local;
 use crate::OwnedIsolate;
 
+use std::any::Any;
 use std::borrow::Borrow;
 use std::convert::TryFrom;
 use std::mem::MaybeUninit;
@@ -45,7 +48,6 @@ extern "C" {
     context: *const Context,
     data: *const Data,
   ) -> usize;
-  fn v8__StartupData__DESTRUCT(this: *mut StartupData);
 }
 
 // TODO(piscisaureus): merge this struct with
@@ -57,23 +59,18 @@ pub struct StartupData {
   raw_size: int,
 }
 
-impl From<Box<[u8]>> for StartupData {
-  fn from(slice: Box<[u8]>) -> Self {
-    let mut data: Vec<u8> = vec![];
-    data.copy_from_slice(&slice);
-    StartupData {
+impl StartupData {
+  pub fn from_static(data: &'static [u8]) -> Self {
+    Self {
       data: data.as_ptr() as *const char,
-      raw_size: data.len() as int,
+      raw_size: i32::try_from(data.len()).unwrap(),
     }
   }
 }
 
-impl From<&[u8]> for StartupData {
-  fn from(slice: &[u8]) -> Self {
-    StartupData {
-      data: slice.as_ptr() as *const char,
-      raw_size: slice.len() as int,
-    }
+impl From<&'static [u8]> for StartupData {
+  fn from(data: &'static [u8]) -> Self {
+    Self::from_static(data)
   }
 }
 
@@ -98,9 +95,51 @@ impl Borrow<[u8]> for StartupData {
   }
 }
 
-impl Drop for StartupData {
-  fn drop(&mut self) {
-    unsafe { v8__StartupData__DESTRUCT(self) }
+/// A `StartupData` object that owns the data it references, which is kept in a
+/// char array allocated in C++. This is what V8 returns when calling
+/// `SnapshotCreator::CreateBlob()`.
+pub struct OwnedStartupData {
+  inner: StartupData,
+  _owner: Box<dyn Any>,
+}
+
+impl OwnedStartupData {
+  pub fn new<T>(owned_data: T) -> Self
+  where
+    T: Deref<Target = [u8]> + 'static,
+  {
+    let inner = {
+      let slice = owned_data.deref();
+      let data = slice.as_ptr() as *const char;
+      let raw_size = int::try_from(slice.len()).unwrap();
+      StartupData { data, raw_size }
+    };
+    Self {
+      inner,
+      _owner: Box::new(owned_data),
+    }
+  }
+
+  fn from_raw_char_array(raw: StartupData) -> Self {
+    let char_array = unsafe { CharArray::from_ptr(raw.data) };
+    Self {
+      inner: raw,
+      _owner: Box::new(char_array),
+    }
+  }
+}
+
+impl Deref for OwnedStartupData {
+  type Target = StartupData;
+
+  fn deref(&self) -> &Self::Target {
+    &self.inner
+  }
+}
+
+impl Borrow<[u8]> for OwnedStartupData {
+  fn borrow(&self) -> &[u8] {
+    &**self
   }
 }
 
@@ -122,7 +161,7 @@ impl SnapshotCreator {
   #[inline(always)]
   pub fn new(
     external_references: Option<&'static ExternalReferences>,
-    existing_blob: Option<&StartupData>,
+    existing_blob: Option<impl Allocated<[u8]>>,
   ) -> Self {
     let mut snapshot_creator: MaybeUninit<Self> = MaybeUninit::uninit();
     let external_references_ptr = if let Some(er) = external_references {
@@ -205,7 +244,7 @@ impl SnapshotCreator {
   pub fn create_blob(
     &mut self,
     function_code_handling: FunctionCodeHandling,
-  ) -> Option<StartupData> {
+  ) -> Option<OwnedStartupData> {
     {
       let isolate = unsafe { &mut *v8__SnapshotCreator__GetIsolate(self) };
       ScopeData::get_root_mut(isolate);
@@ -217,7 +256,10 @@ impl SnapshotCreator {
       None
     } else {
       debug_assert!(blob.raw_size > 0);
-      Some(blob)
+      // Wrap the returned blob in a `OwnedStartupData`, which has a drop
+      // handler that will release the heap allocated `char[]` buffer that holds
+      // the snapshot blob returned by `v8::SnapshotCreator::CreateBlob()`.
+      Some(OwnedStartupData::from_raw_char_array(blob))
     }
   }
 

src/support.rs

@@ -365,6 +365,29 @@ fn assert_shared_ptr_use_count_eq<T: Shared>(
   );
 }
 
+extern "C" {
+  fn char__DELETE_ARRAY(ptr: *const char);
+}
+
+/// Wrapper around a C++ heap allocated `const char*` array. This wrapper calls
+/// `delete[]` in C++ when it is dropped.
+#[repr(transparent)]
+pub struct CharArray(*const char);
+
+impl CharArray {
+  pub unsafe fn from_ptr(ptr: *const char) -> Self {
+    Self(ptr)
+  }
+}
+
+impl Drop for CharArray {
+  fn drop(&mut self) {
+    if !self.0.is_null() {
+      unsafe { char__DELETE_ARRAY(self.0) };
+    }
+  }
+}
+
 /// A trait for values with static lifetimes that are allocated at a fixed
 /// address in memory. Practically speaking, that means they're either a
 /// `&'static` reference, or they're heap-allocated in a `Arc`, `Box`, `Rc`,

tests/test_api.rs

@@ -5225,7 +5225,7 @@ fn module_snapshot() {
       let result = eval(scope, "a === 3").unwrap();
       assert!(result.same_value(true_val));
 
-      let result = eval(scope, "a === 42").unwrap();
+      let result = eval(scope, "b === 42").unwrap();
       assert!(result.same_value(true_val));
     }
   }