src: unload addons when environment quits

This is an alternative to https://github.com/nodejs/node/pull/23319
which attaches the loaded addons to the environment and closes them
when the environment is destroyed.

PR-URL: https://github.com/nodejs/node/pull/24861
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

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

@@ -276,6 +276,11 @@ 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

@@ -30,6 +30,7 @@
 #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"
@@ -37,11 +38,12 @@
 #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;
 
@@ -637,6 +639,9 @@ 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();
@@ -923,6 +928,7 @@ 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
@@ -127,32 +123,9 @@ 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)
+DLib::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);
-};
-
 #ifdef __POSIX__
 bool DLib::Open() {
   handle_ = dlopen(filename_.c_str(), flags_);
@@ -248,8 +221,8 @@ void DLOpen(const FunctionCallbackInfo<Value>& args) {
   }
 
   node::Utf8Value filename(env->isolate(), args[1]);  // Cast
-  DLib dlib(*filename, flags);
-  bool is_opened = dlib.Open();
+  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
@@ -259,37 +232,39 @@ void DLOpen(const FunctionCallbackInfo<Value>& args) {
     uv_key_set(&thread_local_modpending, nullptr);
 
     if (!is_opened) {
-    Local<String> errmsg = OneByteString(env->isolate(), dlib.errmsg_.c_str());
-    dlib.Close();
+      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());
 #endif  // _WIN32
       env->isolate()->ThrowException(Exception::Error(errmsg));
-    return;
+      return false;
     }
 
     if (mp == nullptr) {
-    if (auto callback = GetInitializerCallback(&dlib)) {
+      if (auto callback = GetInitializerCallback(dlib)) {
         callback(exports, module, context);
-    } else if (auto napi_callback = GetNapiInitializerCallback(&dlib)) {
+      } else if (auto napi_callback = GetNapiInitializerCallback(dlib)) {
         napi_module_register_by_symbol(exports, module, context, napi_callback);
       } else {
-      dlib.Close();
+        dlib->Close();
         env->ThrowError("Module did not self-register.");
+        return false;
       }
-    return;
+      return true;
     }
 
     // -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)) {
+      // 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;
+        return true;
       }
       char errmsg[1024];
       snprintf(errmsg,
@@ -306,17 +281,17 @@ void DLOpen(const FunctionCallbackInfo<Value>& args) {
 
       // NOTE: `mp` is allocated inside of the shared library's memory, calling
       // `dlclose` will deallocate it
-    dlib.Close();
+      dlib->Close();
       env->ThrowError(errmsg);
-    return;
+      return false;
     }
     if (mp->nm_flags & NM_F_BUILTIN) {
-    dlib.Close();
+      dlib->Close();
       env->ThrowError("Built-in module self-registered.");
-    return;
+      return false;
     }
 
-  mp->nm_dso_handle = dlib.handle_;
+    mp->nm_dso_handle = dlib->handle_;
     mp->nm_link = modlist_addon;
     modlist_addon = mp;
 
@@ -325,11 +300,14 @@ void DLOpen(const FunctionCallbackInfo<Value>& args) {
     } else if (mp->nm_register_func != nullptr) {
       mp->nm_register_func(exports, module, mp->nm_priv);
     } else {
-    dlib.Close();
+      dlib->Close();
       env->ThrowError("Module has no declared entry point.");
-    return;
+      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)});
 

test/addons/at-exit/binding.cc

@@ -9,6 +9,19 @@ using v8::Isolate;
 using v8::Local;
 using v8::Object;
 
+#if defined(_MSC_VER)
+#pragma section(".CRT$XPU", read)
+#define NODE_C_DTOR(fn)                                               \
+  NODE_CTOR_PREFIX void __cdecl fn(void);                             \
+  __declspec(dllexport, allocate(".CRT$XPU"))                         \
+      void (__cdecl*fn ## _)(void) = fn;                              \
+  NODE_CTOR_PREFIX void __cdecl fn(void)
+#else
+#define NODE_C_DTOR(fn)                                               \
+  NODE_CTOR_PREFIX void fn(void) __attribute__((destructor));         \
+  NODE_CTOR_PREFIX void fn(void)
+#endif
+
 static char cookie[] = "yum yum";
 static int at_exit_cb1_called = 0;
 static int at_exit_cb2_called = 0;
@@ -27,7 +40,7 @@ static void at_exit_cb2(void* arg) {
   at_exit_cb2_called++;
 }
 
-static void sanity_check(void) {
+NODE_C_DTOR(sanity_check) {
   assert(at_exit_cb1_called == 1);
   assert(at_exit_cb2_called == 2);
 }
@@ -36,7 +49,6 @@ void init(Local<Object> exports) {
   AtExit(at_exit_cb1, exports->GetIsolate());
   AtExit(at_exit_cb2, cookie);
   AtExit(at_exit_cb2, cookie);
-  atexit(sanity_check);
 }
 
 NODE_MODULE(NODE_GYP_MODULE_NAME, init)

test/addons/uv-handle-leak/binding.cc

@@ -41,8 +41,7 @@ void LeakHandle(const FunctionCallbackInfo<Value>& args) {
   uv_unref(reinterpret_cast<uv_handle_t*>(leaked_timer));
 }
 
-void Initialize(v8::Local<v8::Object> exports) {
+// This module gets loaded multiple times in some tests so it must support that.
+NODE_MODULE_INIT(/*exports, module, context*/) {
   NODE_SET_METHOD(exports, "leakHandle", LeakHandle);
 }
-
-NODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)