process,worker: ensure code after exit() effectless

lib/internal/process/per_thread.js

@@ -104,6 +104,8 @@ function hrtimeBigInt() {
   return hrBigintValues[0];
 }
 
+function nop() {}
+
 // The execution of this function itself should not cause any side effects.
 function wrapProcessMethods(binding) {
   const {
@@ -195,6 +197,16 @@ function wrapProcessMethods(binding) {
     // in the user land. Either document it, or deprecate it in favor of a
     // better public alternative.
     process.reallyExit(process.exitCode || kNoFailure);
+
+    // If this is a worker, v8::Isolate::TerminateExecution() is called above.
+    // That function spoofs the stack pointer to cause the stack guard
+    // check to throw the termination exception. Because v8 performs
+    // stack guard check upon every function call, we give it a chance.
+    //
+    // Without this, user code after `process.exit()` would take effect.
+    // test/parallel/test-worker-voluntarily-exit-followed-by-addition.js
+    // test/parallel/test-worker-voluntarily-exit-followed-by-throw.js
+    nop();
   }
 
   function kill(pid, sig) {

src/js_native_api_v8.cc

@@ -308,6 +308,9 @@ class CallbackWrapperBase : public CallbackWrapper {
     env->CallIntoModule([&](napi_env env) { result = cb(env, cbinfo_wrapper); },
                         [&](napi_env env, v8::Local<v8::Value> value) {
                           exceptionOccurred = true;
+                          if (env->terminatedOrTerminating()) {
+                            return;
+                          }
                           env->isolate->ThrowException(value);
                         });
 

src/js_native_api_v8.h

@@ -72,9 +72,20 @@ struct napi_env__ {
   }
 
   static inline void HandleThrow(napi_env env, v8::Local<v8::Value> value) {
+    if (env->terminatedOrTerminating()) {
+      return;
+    }
     env->isolate->ThrowException(value);
   }
 
+  // i.e. whether v8 exited or is about to exit
+  inline bool terminatedOrTerminating() {
+    return this->isolate->IsExecutionTerminating() || !can_call_into_js();
+  }
+
+  // v8 uses a special exception to indicate termination, the
+  // `handle_exception` callback should identify such case using
+  // terminatedOrTerminating() before actually handle the exception
   template <typename T, typename U = decltype(HandleThrow)>
   inline void CallIntoModule(T&& call, U&& handle_exception = HandleThrow) {
     int open_handle_scopes_before = open_handle_scopes;

src/node_api.cc

@@ -82,6 +82,9 @@ template <bool enforceUncaughtExceptionPolicy, typename T>
 void node_napi_env__::CallbackIntoModule(T&& call) {
   CallIntoModule(call, [](napi_env env_, v8::Local<v8::Value> local_err) {
     node_napi_env__* env = static_cast<node_napi_env__*>(env_);
+    if (env->terminatedOrTerminating()) {
+      return;
+    }
     node::Environment* node_env = env->node_env();
     if (!node_env->options()->force_node_api_uncaught_exceptions_policy &&
         !enforceUncaughtExceptionPolicy) {

test/cctest/test_environment.cc

@@ -553,7 +553,9 @@ TEST_F(EnvironmentTest, ExitHandlerTest) {
     callback_calls++;
     node::Stop(*env);
   });
-  node::LoadEnvironment(*env, "process.exit(42)").ToLocalChecked();
+  // When terminating, v8 throws makes the current embedder call bail out
+  // with MaybeLocal<>()
+  EXPECT_TRUE(node::LoadEnvironment(*env, "process.exit(42)").IsEmpty());
   EXPECT_EQ(callback_calls, 1);
 }
 

test/node-api/test_worker_terminate/test.js

@@ -19,8 +19,8 @@ if (isMainThread) {
   const { Test } = require(`./build/${common.buildType}/test_worker_terminate`);
 
   const { counter } = workerData;
-  // Test() tries to call a function twice and asserts that the second call does
-  // not work because of a pending exception.
+  // Test() tries to call a function and asserts it fails because of a
+  // pending termination exception.
   Test(() => {
     Atomics.add(counter, 0, 1);
     process.exit();

test/node-api/test_worker_terminate/test_worker_terminate.c

@@ -17,8 +17,6 @@ napi_value Test(napi_env env, napi_callback_info info) {
   NODE_API_ASSERT(env, t == napi_function,
       "Wrong first argument, function expected.");
 
-  status = napi_call_function(env, recv, argv[0], 0, NULL, NULL);
-  assert(status == napi_ok);
   status = napi_call_function(env, recv, argv[0], 0, NULL, NULL);
   assert(status == napi_pending_exception);
 

test/parallel/test-async-hooks-worker-asyncfn-terminate-4.js

@@ -12,6 +12,7 @@ const { Worker } = require('worker_threads');
 const workerData = new Int32Array(new SharedArrayBuffer(4));
 const w = new Worker(`
 const { createHook } = require('async_hooks');
+const { workerData } = require('worker_threads');
 
 setImmediate(async () => {
   createHook({ init() {} }).enable();

test/parallel/test-worker-voluntarily-exit-followed-by-addition.js

@@ -0,0 +1,18 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { Worker, isMainThread } = require('worker_threads');
+
+if (isMainThread) {
+  const workerData = new Int32Array(new SharedArrayBuffer(4));
+  new Worker(__filename, {
+    workerData,
+  });
+  process.on('beforeExit', common.mustCall(() => {
+    assert.strictEqual(workerData[0], 0);
+  }));
+} else {
+  const { workerData } = require('worker_threads');
+  process.exit();
+  workerData[0] = 1;
+}

test/parallel/test-worker-voluntarily-exit-followed-by-throw.js

@@ -0,0 +1,23 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { Worker, isMainThread } = require('worker_threads');
+
+if (isMainThread) {
+  const workerData = new Int32Array(new SharedArrayBuffer(4));
+  new Worker(__filename, {
+    workerData,
+  });
+  process.on('beforeExit', common.mustCall(() => {
+    assert.strictEqual(workerData[0], 0);
+  }));
+} else {
+  const { workerData } = require('worker_threads');
+  try {
+    process.exit();
+    throw new Error('xxx');
+    // eslint-disable-next-line no-unused-vars
+  } catch (err) {
+    workerData[0] = 1;
+  }
+}