From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Shelley Vohr <shelley.vohr@gmail.com>
Date: Mon, 9 Aug 2021 18:42:15 +0200
Subject: repl: fix crash when SharedArrayBuffer disabled

It's possible for SharedArrayBuffers to be disabled with
--no-harmony-sharedarraybuffer so we first need to check that this
isn't the case before attempting to use them in the repl or a crash occurs.

Upstreamed at https://github.com/nodejs/node/pull/39718.

diff --git a/benchmark/worker/atomics-wait.js b/benchmark/worker/atomics-wait.js
index a771b1813731edf4f0dd60f3505799e389f1d876..b9461677e2d7d1df192e752496e62cca837717b5 100644
--- a/benchmark/worker/atomics-wait.js
+++ b/benchmark/worker/atomics-wait.js
@@ -7,6 +7,10 @@ const bench = common.createBenchmark(main, {
 });
 
 function main({ n }) {
+  if (typeof SharedArrayBuffer === 'undefined') {
+    throw new Error('SharedArrayBuffers must be enabled to run this benchmark');
+  }
+
   const i32arr = new Int32Array(new SharedArrayBuffer(4));
   bench.start();
   for (let i = 0; i < n; i++)
diff --git a/lib/internal/main/worker_thread.js b/lib/internal/main/worker_thread.js
index 71a07a63a3636ab211746004ebab24a0058b08fc..e3ce67987ee3185a93750ebad72beab304c71e3a 100644
--- a/lib/internal/main/worker_thread.js
+++ b/lib/internal/main/worker_thread.js
@@ -9,7 +9,7 @@ const {
   ArrayPrototypeSplice,
   ObjectDefineProperty,
   PromisePrototypeCatch,
-  globalThis: { Atomics },
+  globalThis: { Atomics, SharedArrayBuffer },
 } = primordials;
 
 const {
@@ -142,6 +142,9 @@ port.on('message', (message) => {
     const originalCwd = process.cwd;
 
     process.cwd = function() {
+      // SharedArrayBuffers can be disabled with --no-harmony-sharedarraybuffer.
+      if (typeof SharedArrayBuffer === 'undefined') return originalCwd();
+
       const currentCounter = Atomics.load(cwdCounter, 0);
       if (currentCounter === lastCounter)
         return cachedCwd;
diff --git a/lib/internal/worker.js b/lib/internal/worker.js
index 1d2cd8cefd2996c6a4f84ea08e6b4c53a22dc418..28b1a9a53b13036297a2ed3271c36cbe14c51a32 100644
--- a/lib/internal/worker.js
+++ b/lib/internal/worker.js
@@ -90,7 +90,8 @@ let cwdCounter;
 
 const environmentData = new SafeMap();
 
-if (isMainThread) {
+// SharedArrayBuffers can be disabled with --no-harmony-sharedarraybuffer.
+if (isMainThread && typeof SharedArrayBuffer !== 'undefined') {
   cwdCounter = new Uint32Array(new SharedArrayBuffer(4));
   const originalChdir = process.chdir;
   process.chdir = function(path) {
