node-api: run finalizers directly from GC

PR-URL: #42651 Reviewed-By: Gabriel Schulhof <[email protected]> Reviewed-By: Michael Dawson <[email protected]>
nodejs · Oct 3, 2023 · b38e312 · b38e312
1 parent 344d3c4
commit b38e312
Show file tree

Hide file tree

Showing 10 changed files with 477 additions and 40 deletions.
diff --git a/doc/api/n-api.md b/doc/api/n-api.md
@@ -5428,6 +5428,42 @@ invocation. If it is deleted before then, then the finalize callback may never
 be invoked. Therefore, when obtaining a reference a finalize callback is also
 required in order to enable correct disposal of the reference.
 
+#### `node_api_post_finalizer`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+```c
+napi_status node_api_post_finalizer(napi_env env,
+                                    napi_finalize finalize_cb,
+                                    void* finalize_data,
+                                    void* finalize_hint);
+```
+
+* `[in] env`: The environment that the API is invoked under.
+* `[in] finalize_cb`: Native callback that will be used to free the
+  native data when the JavaScript object has been garbage-collected.
+  [`napi_finalize`][] provides more details.
+* `[in] finalize_data`: Optional data to be passed to `finalize_cb`.
+* `[in] finalize_hint`: Optional contextual hint that is passed to the
+  finalize callback.
+
+Returns `napi_ok` if the API succeeded.
+
+Schedules a `napi_finalize` callback to be called asynchronously in the
+event loop.
+
+Normally, finalizers are called while the GC (garbage collector) collects
+objects. At that point calling any Node-API that may cause changes in the GC
+state will be disabled and will crash Node.js.
+
+`node_api_post_finalizer` helps to work around this limitation by allowing the
+add-on to defer calls to such Node-APIs to a point in time outside of the GC
+finalization.
+
 ## Simple asynchronous operations
 
 Addon modules often need to leverage async helpers from libuv as part of their

diff --git a/src/js_native_api.h b/src/js_native_api.h
@@ -517,6 +517,16 @@ NAPI_EXTERN napi_status NAPI_CDECL napi_add_finalizer(napi_env env,
 
 #endif  // NAPI_VERSION >= 5
 
+#ifdef NAPI_EXPERIMENTAL
+
+NAPI_EXTERN napi_status NAPI_CDECL
+node_api_post_finalizer(napi_env env,
+                        napi_finalize finalize_cb,
+                        void* finalize_data,
+                        void* finalize_hint);
+
+#endif  // NAPI_EXPERIMENTAL
+
 #if NAPI_VERSION >= 6
 
 // BigInt