src: unload native addons when the environment is destroyed

doc/api/addons.md

@@ -234,6 +234,23 @@ NODE_MODULE_INIT(/* exports, module, context */) {
 }
 ```
 
+#### Worker support
+
+In order to support [`Worker`][] threads, addons need to clean up any resources
+they may have allocated when such a thread exists. This can be achieved through
+the usage of the `AddEnvironmentCleanupHook()` function:
+
+```c++
+void AddEnvironmentCleanupHook(v8::Isolate* isolate,
+                               void (*fun)(void* arg),
+                               void* arg);
+```
+
+This function adds a hook that will run before a given Node.js instance shuts
+down. If necessary, such hooks can be removed using
+`RemoveEnvironmentCleanupHook()` before they are run, which has the same
+signature.
+
 ### Building
 
 Once the source code has been written, it must be compiled into the binary
@@ -1349,6 +1366,7 @@ Test in JavaScript by running:
 require('./build/Release/addon');
 ```
 
+[`Worker`]: worker_threads.html#worker_threads_class_worker
 [Electron]: https://electronjs.org/
 [Embedder's Guide]: https://github.com/v8/v8/wiki/Embedder's%20Guide
 [Linking to Node.js' own dependencies]: #addons_linking_to_node_js_own_dependencies

src/env-inl.h

@@ -396,6 +396,16 @@ inline uv_loop_t* Environment::event_loop() const {
   return isolate_data()->event_loop();
 }
 
+inline void Environment::TryLoadAddon(
+    const char* filename,
+    int flags,
+    std::function<bool(binding::DLib*)> was_loaded) {
+  loaded_addons_.emplace_back(filename, flags);
+  if (!was_loaded(&loaded_addons_.back())) {
+    loaded_addons_.pop_back();
+  }
+}
+
 inline Environment::AsyncHooks* Environment::async_hooks() {
   return &async_hooks_;
 }

src/env.cc

@@ -267,6 +267,11 @@ Environment::~Environment() {
 
   TRACE_EVENT_NESTABLE_ASYNC_END0(
     TRACING_CATEGORY_NODE1(environment), "Environment", this);
+
+  // Dereference all addons that were loaded into this environment.
+  for (binding::DLib& addon : loaded_addons_) {
+    addon.Close();
+  }
 }
 
 void Environment::Start(const std::vector<std::string>& args,

src/env.h

@@ -30,18 +30,20 @@
 #endif
 #include "handle_wrap.h"
 #include "node.h"
+#include "node_binding.h"
 #include "node_http2_state.h"
 #include "node_options.h"
 #include "req_wrap.h"
 #include "util.h"
 #include "uv.h"
 #include "v8.h"
 
-#include <list>
 #include <stdint.h>
-#include <vector>
+#include <functional>
+#include <list>
 #include <unordered_map>
 #include <unordered_set>
+#include <vector>
 
 struct nghttp2_rcbuf;
 
@@ -636,6 +638,9 @@ class Environment {
   inline v8::Isolate* isolate() const;
   inline uv_loop_t* event_loop() const;
   inline uint32_t watched_providers() const;
+  inline void TryLoadAddon(const char* filename,
+                           int flags,
+                           std::function<bool(binding::DLib*)> was_loaded);
 
   static inline Environment* from_timer_handle(uv_timer_t* handle);
   inline uv_timer_t* timer_handle();
@@ -921,6 +926,7 @@ class Environment {
   inline void ThrowError(v8::Local<v8::Value> (*fun)(v8::Local<v8::String>),
                          const char* errmsg);
 
+  std::list<binding::DLib> loaded_addons_;
   v8::Isolate* const isolate_;
   IsolateData* const isolate_data_;
   uv_timer_t timer_handle_;

src/node_binding.cc

@@ -2,10 +2,6 @@
 #include "node_internals.h"
 #include "node_native_module.h"
 
-#if defined(__POSIX__)
-#include <dlfcn.h>
-#endif
-
 #if HAVE_OPENSSL
 #define NODE_BUILTIN_OPENSSL_MODULES(V) V(crypto) V(tls_wrap)
 #else
@@ -126,31 +122,8 @@ extern "C" void node_module_register(void* m) {
 
 namespace binding {
 
-class DLib {
- public:
-#ifdef __POSIX__
-  static const int kDefaultFlags = RTLD_LAZY;
-#else
-  static const int kDefaultFlags = 0;
-#endif
-
-  inline DLib(const char* filename, int flags)
-      : filename_(filename), flags_(flags), handle_(nullptr) {}
-
-  inline bool Open();
-  inline void Close();
-  inline void* GetSymbolAddress(const char* name);
-
-  const std::string filename_;
-  const int flags_;
-  std::string errmsg_;
-  void* handle_;
-#ifndef __POSIX__
-  uv_lib_t lib_;
-#endif
- private:
-  DISALLOW_COPY_AND_ASSIGN(DLib);
-};
+DLib::DLib(const char* filename, int flags)
+    : filename_(filename), flags_(flags), handle_(nullptr) {}
 
 #ifdef __POSIX__
 bool DLib::Open() {
@@ -247,87 +220,92 @@ void DLOpen(const FunctionCallbackInfo<Value>& args) {
   }
 
   node::Utf8Value filename(env->isolate(), args[1]);  // Cast
-  DLib dlib(*filename, flags);
-  bool is_opened = dlib.Open();
-
-  // Objects containing v14 or later modules will have registered themselves
-  // on the pending list.  Activate all of them now.  At present, only one
-  // module per object is supported.
-  node_module* const mp =
-      static_cast<node_module*>(uv_key_get(&thread_local_modpending));
-  uv_key_set(&thread_local_modpending, nullptr);
-
-  if (!is_opened) {
-    Local<String> errmsg = OneByteString(env->isolate(), dlib.errmsg_.c_str());
-    dlib.Close();
+  env->TryLoadAddon(*filename, flags, [&](DLib* dlib) {
+    const bool is_opened = dlib->Open();
+
+    // Objects containing v14 or later modules will have registered themselves
+    // on the pending list.  Activate all of them now.  At present, only one
+    // module per object is supported.
+    node_module* const mp =
+        static_cast<node_module*>(uv_key_get(&thread_local_modpending));
+    uv_key_set(&thread_local_modpending, nullptr);
+
+    if (!is_opened) {
+      Local<String> errmsg =
+          OneByteString(env->isolate(), dlib->errmsg_.c_str());
+      dlib->Close();
 #ifdef _WIN32
-    // Windows needs to add the filename into the error message
-    errmsg = String::Concat(
-        env->isolate(), errmsg, args[1]->ToString(context).ToLocalChecked());
+      // Windows needs to add the filename into the error message
+      errmsg = String::Concat(
+          env->isolate(), errmsg, args[1]->ToString(context).ToLocalChecked());
 #endif  // _WIN32
-    env->isolate()->ThrowException(Exception::Error(errmsg));
-    return;
-  }
+      env->isolate()->ThrowException(Exception::Error(errmsg));
+      return false;
+    }
 
-  if (mp == nullptr) {
-    if (auto callback = GetInitializerCallback(&dlib)) {
-      callback(exports, module, context);
-    } else if (auto napi_callback = GetNapiInitializerCallback(&dlib)) {
-      napi_module_register_by_symbol(exports, module, context, napi_callback);
-    } else {
-      dlib.Close();
-      env->ThrowError("Module did not self-register.");
+    if (mp == nullptr) {
+      if (auto callback = GetInitializerCallback(dlib)) {
+        callback(exports, module, context);
+      } else if (auto napi_callback = GetNapiInitializerCallback(dlib)) {
+        napi_module_register_by_symbol(exports, module, context, napi_callback);
+      } else {
+        dlib->Close();
+        env->ThrowError("Module did not self-register.");
+        return false;
+      }
+      return true;
     }
-    return;
-  }
 
-  // -1 is used for N-API modules
-  if ((mp->nm_version != -1) && (mp->nm_version != NODE_MODULE_VERSION)) {
-    // Even if the module did self-register, it may have done so with the wrong
-    // version. We must only give up after having checked to see if it has an
-    // appropriate initializer callback.
-    if (auto callback = GetInitializerCallback(&dlib)) {
-      callback(exports, module, context);
-      return;
+    // -1 is used for N-API modules
+    if ((mp->nm_version != -1) && (mp->nm_version != NODE_MODULE_VERSION)) {
+      // Even if the module did self-register, it may have done so with the
+      // wrong version. We must only give up after having checked to see if it
+      // has an appropriate initializer callback.
+      if (auto callback = GetInitializerCallback(dlib)) {
+        callback(exports, module, context);
+        return true;
+      }
+      char errmsg[1024];
+      snprintf(errmsg,
+               sizeof(errmsg),
+               "The module '%s'"
+               "\nwas compiled against a different Node.js version using"
+               "\nNODE_MODULE_VERSION %d. This version of Node.js requires"
+               "\nNODE_MODULE_VERSION %d. Please try re-compiling or "
+               "re-installing\nthe module (for instance, using `npm rebuild` "
+               "or `npm install`).",
+               *filename,
+               mp->nm_version,
+               NODE_MODULE_VERSION);
+
+      // NOTE: `mp` is allocated inside of the shared library's memory, calling
+      // `dlclose` will deallocate it
+      dlib->Close();
+      env->ThrowError(errmsg);
+      return false;
+    }
+    if (mp->nm_flags & NM_F_BUILTIN) {
+      dlib->Close();
+      env->ThrowError("Built-in module self-registered.");
+      return false;
     }
-    char errmsg[1024];
-    snprintf(errmsg,
-             sizeof(errmsg),
-             "The module '%s'"
-             "\nwas compiled against a different Node.js version using"
-             "\nNODE_MODULE_VERSION %d. This version of Node.js requires"
-             "\nNODE_MODULE_VERSION %d. Please try re-compiling or "
-             "re-installing\nthe module (for instance, using `npm rebuild` "
-             "or `npm install`).",
-             *filename,
-             mp->nm_version,
-             NODE_MODULE_VERSION);
-
-    // NOTE: `mp` is allocated inside of the shared library's memory, calling
-    // `dlclose` will deallocate it
-    dlib.Close();
-    env->ThrowError(errmsg);
-    return;
-  }
-  if (mp->nm_flags & NM_F_BUILTIN) {
-    dlib.Close();
-    env->ThrowError("Built-in module self-registered.");
-    return;
-  }
 
-  mp->nm_dso_handle = dlib.handle_;
-  mp->nm_link = modlist_addon;
-  modlist_addon = mp;
+    mp->nm_dso_handle = dlib->handle_;
+    mp->nm_link = modlist_addon;
+    modlist_addon = mp;
 
-  if (mp->nm_context_register_func != nullptr) {
-    mp->nm_context_register_func(exports, module, context, mp->nm_priv);
-  } else if (mp->nm_register_func != nullptr) {
-    mp->nm_register_func(exports, module, mp->nm_priv);
-  } else {
-    dlib.Close();
-    env->ThrowError("Module has no declared entry point.");
-    return;
-  }
+    if (mp->nm_context_register_func != nullptr) {
+      mp->nm_context_register_func(exports, module, context, mp->nm_priv);
+    } else if (mp->nm_register_func != nullptr) {
+      mp->nm_register_func(exports, module, mp->nm_priv);
+    } else {
+      dlib->Close();
+      env->ThrowError("Module has no declared entry point.");
+      return false;
+    }
+
+    return true;
+  });
 
   // Tell coverity that 'handle' should not be freed when we return.
   // coverity[leaked_storage]

src/node_binding.h

@@ -3,8 +3,14 @@
 
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
+#if defined(__POSIX__)
+#include <dlfcn.h>
+#endif
+
 #include "node.h"
+#define NAPI_EXPERIMENTAL
 #include "node_api.h"
+#include "util.h"
 #include "uv.h"
 #include "v8.h"
 
@@ -46,6 +52,32 @@ extern bool node_is_initialized;
 
 namespace binding {
 
+class DLib {
+ public:
+#ifdef __POSIX__
+  static const int kDefaultFlags = RTLD_LAZY;
+#else
+  static const int kDefaultFlags = 0;
+#endif
+
+  DLib(const char* filename, int flags);
+
+  bool Open();
+  void Close();
+  void* GetSymbolAddress(const char* name);
+
+  const std::string filename_;
+  const int flags_;
+  std::string errmsg_;
+  void* handle_;
+#ifndef __POSIX__
+  uv_lib_t lib_;
+#endif
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DLib);
+};
+
 // Call _register<module_name> functions for all of
 // the built-in modules. Because built-in modules don't
 // use the __attribute__((constructor)). Need to
@@ -60,5 +92,7 @@ void DLOpen(const v8::FunctionCallbackInfo<v8::Value>& args);
 
 }  // namespace node
 
+#include "node_binding.h"
+
 #endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 #endif  // SRC_NODE_BINDING_H_

test/abort/test-addon-uv-handle-leak.js

@@ -18,6 +18,16 @@ if (!fs.existsSync(bindingPath))
   common.skip('binding not built yet');
 
 if (process.argv[2] === 'child') {
+
+  // The worker thread loads and then unloads `bindingPath`. Because of this the
+  // symbols in `bindingPath` are lost when the worker thread quits, but the
+  // number of open handles in the worker thread's event loop is assessed in the
+  // main thread afterwards, and the names of the callbacks associated with the
+  // open handles is retrieved at that time as well. Thus, we require
+  // `bindingPath` here so that the symbols and their names survive the life
+  // cycle of the worker thread.
+  require(bindingPath);
+
   new Worker(`
   const binding = require(${JSON.stringify(bindingPath)});