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nodejs/src/js_native_api_v8_internals.h
Gabriel Schulhof 53ca0b9ae1 src: render N-API weak callbacks as cleanup hooks
Since worker threads are complete Node.js environments, including the
ability to load native addons, and since those native addons can
allocate resources to be freed when objects go out of scope, and since,
upon worker thread exit, the engine does not invoke the weak callbacks
responsible for freeing resources which still have references, this
modification introduces tracking for weak references such that a list
of outstanding weak references is maintained. This list is traversed
during environment teardown. The callbacks for the remaining weak
references are called.

This change is also relevant for Node.js embedder scenarios, because in
those cases the process also outlives the `node::Environment` and
therefore weak callbacks should also be rendered as environment cleanup
hooks to ensure proper cleanup after native addons. This changes
introduces the means by which this can be accomplished.

A benchmark is included which measures the time it takes to execute the
weak reference callback for a given number of weak references.

Re: https://github.com/tc39/proposal-weakrefs/issues/125#issuecomment-535832130
PR-URL: https://github.com/nodejs/node/pull/28428
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
2019-10-13 00:07:43 -07:00

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#ifndef SRC_JS_NATIVE_API_V8_INTERNALS_H_
#define SRC_JS_NATIVE_API_V8_INTERNALS_H_
// The V8 implementation of N-API, including `js_native_api_v8.h` uses certain
// idioms which require definition here. For example, it uses a variant of
// persistent references which need not be reset in the constructor. It is the
// responsibility of this file to define these idioms. Optionally, this file
// may also define `NAPI_VERSION` and set it to the version of N-API to be
// exposed.
// In the case of the Node.js implementation of N-API some of the idioms are
// imported directly from Node.js by including `node_internals.h` below. Others
// are bridged to remove references to the `node` namespace. `node_version.h`,
// included below, defines `NAPI_VERSION`.
#include "node_version.h"
#include "env.h"
#include "node_internals.h"
#define NAPI_ARRAYSIZE(array) \
node::arraysize((array))
#define NAPI_FIXED_ONE_BYTE_STRING(isolate, string) \
node::FIXED_ONE_BYTE_STRING((isolate), (string))
#define NAPI_PRIVATE_KEY(context, suffix) \
(node::Environment::GetCurrent((context))->napi_ ## suffix())
namespace v8impl {
class RefTracker {
public:
RefTracker() {}
virtual ~RefTracker() {}
virtual void Finalize(bool isEnvTeardown) {}
typedef RefTracker RefList;
inline void Link(RefList* list) {
prev_ = list;
next_ = list->next_;
if (next_ != nullptr) {
next_->prev_ = this;
}
list->next_ = this;
}
inline void Unlink() {
if (prev_ != nullptr) {
prev_->next_ = next_;
}
if (next_ != nullptr) {
next_->prev_ = prev_;
}
prev_ = nullptr;
next_ = nullptr;
}
static void FinalizeAll(RefList* list) {
while (list->next_ != nullptr) {
list->next_->Finalize(true);
}
}
private:
RefList* next_ = nullptr;
RefList* prev_ = nullptr;
};
template <typename T>
using Persistent = v8::Global<T>;
using PersistentToLocal = node::PersistentToLocal;
} // end of namespace v8impl
#endif // SRC_JS_NATIVE_API_V8_INTERNALS_H_