Repository: nodejs/node
Pull request: src: store `Local` for `CallbackScope` on stack

##### ~~src: track async resources via pointers to stack-allocated handles~~

(Split out into https://github.com/nodejs/node/pull/59704)

~~This addresses an existing `TODO` to remove the need for a separate
`LocalVector`. Since all relevant handles are already present on the
stack, we can track their addresses instead of storing the objects
in a separate container.~~

##### src: store `Local` for `CallbackScope` on stack

This is a requirement of the V8 API, but requires a separate
semver-major change (as it is ABI-breaking) to address.

(There's also a similar requirement for `napi_open_callback_scope`
that would not be easily addressable without breaking ABI compatibility
there as well. In real-world situations, it seems extremely unlikely
that the `CallbackScope` would be the only reference to the resource
object.)


<!--
Before submitting a pull request, please read:

- the CONTRIBUTING guide at https://github.com/nodejs/node/blob/HEAD/CONTRIBUTING.md
- the commit message formatting guidelines at
  https://github.com/nodejs/node/blob/HEAD/doc/contributing/pull-requests.md#commit-message-guidelines

For code changes:
1. Include tests for any bug fixes or new features.
2. Update documentation if relevant.
3. Ensure that `make -j4 test` (UNIX), or `vcbuild test` (Windows) passes.

If you believe this PR should be highlighted in the Node.js CHANGELOG
please add the `notable-change` label.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.
-->


Changed files:
filename: src/api/callback.cc
patch: @@ -26,10 +26,10 @@ CallbackScope::CallbackScope(Isolate* isolate,
 CallbackScope::CallbackScope(Environment* env,
                              Local<Object> object,
                              async_context asyncContext)
-  : private_(new InternalCallbackScope(env,
-                                       object,
-                                       asyncContext)),
-    try_catch_(env->isolate()) {
+    : resource_storage_(object),
+      private_(
+          new InternalCallbackScope(env, &resource_storage_, asyncContext)),
+      try_catch_(env->isolate()) {
   try_catch_.SetVerbose(true);
 }
 

filename: src/node.h
patch: @@ -1452,6 +1452,8 @@ class NODE_EXTERN CallbackScope {
   CallbackScope(CallbackScope&&) = delete;
 
  private:
+  void* reserved_;
+  v8::Local<v8::Object> resource_storage_;
   InternalCallbackScope* private_;
   v8::TryCatch try_catch_;
 };