From 973e698d7d5ea4d9ad6b056491eec2d5c5eee059 Mon Sep 17 00:00:00 2001
From: landerlyoung <landerlyoung@gmail.com>
Date: Sat, 27 May 2023 14:42:26 +0800
Subject: [PATCH] add fine-grained operation to control V8 Platform instance
 lifecycle.

---
 backend/V8/V8Helper.hpp  | 26 ++++++++++++++++++++++++++
 backend/V8/V8Platform.cc | 17 +++++++++++++++++
 backend/V8/V8Platform.h  |  2 ++
 3 files changed, 45 insertions(+)

diff --git a/backend/V8/V8Helper.hpp b/backend/V8/V8Helper.hpp
index ca6812a9..e4234b10 100644
--- a/backend/V8/V8Helper.hpp
+++ b/backend/V8/V8Helper.hpp
@@ -97,6 +97,32 @@ struct v8_interop {
   static ArgumentsData extractArguments(const Arguments& args) {
     return ArgumentsData{args.callbackInfo_.first, args.callbackInfo_.second};
   }
+
+  struct Critical {
+    /**
+     * DANGEROUS OPERATION!!!
+     * By default the v8 platform is a process-level singleton, which will be destroyed during
+     * process exit. In some C++ guide, it's recommended not to relay on static variable
+     * destruction.
+     *
+     * By call this method, it is guaranteed not to destroy the platform instance (actually by
+     * making the singleton leak).
+     */
+    static void neverDestroyPlatform();
+
+    /**
+     * DANGEROUS OPERATION!!!
+     * By default the v8 platform is a process-level singleton, which will be destroyed during
+     * process exit. In some case, if you are sure not to use V8 in the process again (never
+     * re-create a instance), you can call this method to destroy the platform immediately. Once
+     * destroyed, V8 usually shuts down thread pool, etc to release resources.
+     *
+     * In face, if there is still running V8Engine instance, the platform will be destroy
+     * afterwords.
+     *
+     */
+    static void immediatelyDestroyPlatform();
+  };
 };
 
 }  // namespace script
\ No newline at end of file
diff --git a/backend/V8/V8Platform.cc b/backend/V8/V8Platform.cc
index 07138764..06c1df22 100644
--- a/backend/V8/V8Platform.cc
+++ b/backend/V8/V8Platform.cc
@@ -17,8 +17,10 @@
 
 #include "V8Platform.h"
 #include <libplatform/libplatform.h>
+#include <type_traits>
 #include "../../src/Utils.h"
 #include "V8Engine.h"
+#include "V8Helper.hpp"
 
 namespace script::v8_backend {
 
@@ -198,3 +200,18 @@ bool V8Platform::OnCriticalMemoryPressure(size_t length) {
 #endif
 
 }  // namespace script::v8_backend
+
+void script::v8_interop::Critical::neverDestroyPlatform() {
+  using script::v8_backend::V8Platform;
+  auto platform = V8Platform::getPlatform();
+
+  // make the shared_ptr leak
+  std::aligned_storage_t<sizeof(std::shared_ptr<V8Platform>)> buffer;
+  new (&buffer) std::shared_ptr<V8Platform>(platform);
+}
+
+void script::v8_interop::Critical::immediatelyDestroyPlatform() {
+  using script::v8_backend::V8Platform;
+  std::lock_guard<std::mutex> lock(V8Platform::lock_);
+  V8Platform::singletonInstance_ = nullptr;
+}
diff --git a/backend/V8/V8Platform.h b/backend/V8/V8Platform.h
index 161103bd..8db71957 100644
--- a/backend/V8/V8Platform.h
+++ b/backend/V8/V8Platform.h
@@ -144,6 +144,8 @@ class V8Platform : public v8::Platform {
   void addEngineInstance(v8::Isolate* isolate, V8Engine* engine);
 
   void removeEngineInstance(v8::Isolate* isolate);
+
+  friend struct script::v8_interop;
 };
 
 }  // namespace script::v8_backend