lib: do not crash using workers with disabled shared array buffers

This allows the repl to function normally while using the
`--no-harmony-sharedarraybuffer` V8 flag.
It also fixes using workers while using the
`--no-harmony-atomics` V8 flag.
Fixes: #39717
Signed-off-by: Ruben Bridgewater <ruben@bridgewater.de>
Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>
PR-URL: #41023
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: 2 people

benchmark/worker/atomics-wait.js

@@ -1,5 +1,12 @@
 'use strict';
-/* global SharedArrayBuffer */
+
+if(typeofSharedArrayBuffer==='undefined'){
+thrownewError('SharedArrayBuffers must be enabled to run this benchmark');
+}
+
+if(typeofAtomics==='undefined'){
+thrownewError('Atomics must be enabled to run this benchmark');
+}
 
 constcommon=require('../common.js');
 constbench=common.createBenchmark(main,{

lib/internal/main/worker_thread.js

@@ -10,7 +10,10 @@ const {
  ObjectDefineProperty,
  PromisePrototypeThen,
  RegExpPrototypeExec,
-globalThis: { Atomics },
+globalThis: {
+ Atomics,
+ SharedArrayBuffer,
+},
 }=primordials;
 
 const{
@@ -105,21 +108,23 @@ port.on('message', (message) => {
 
 require('internal/worker').assignEnvironmentData(environmentData);
 
-// The counter is only passed to the workers created by the main thread, not
-// to workers created by other workers.
-letcachedCwd='';
-letlastCounter=-1;
-constoriginalCwd=process.cwd;
-
-process.cwd=function(){
-constcurrentCounter=Atomics.load(cwdCounter,0);
-if(currentCounter===lastCounter)
+if(SharedArrayBuffer!==undefined&&Atomics!==undefined){
+// The counter is only passed to the workers created by the main thread,
+// not to workers created by other workers.
+letcachedCwd='';
+letlastCounter=-1;
+constoriginalCwd=process.cwd;
+
+process.cwd=function(){
+constcurrentCounter=Atomics.load(cwdCounter,0);
+if(currentCounter===lastCounter)
+returncachedCwd;
+lastCounter=currentCounter;
+cachedCwd=originalCwd();
 returncachedCwd;
-lastCounter=currentCounter;
-cachedCwd=originalCwd();
-returncachedCwd;
-};
-workerIo.sharedCwdCounter=cwdCounter;
+};
+workerIo.sharedCwdCounter=cwdCounter;
+}
 
 if(manifestSrc){
 require('internal/process/policy').setup(manifestSrc,manifestURL);

lib/internal/worker.js

@@ -91,7 +91,9 @@ let cwdCounter;
 
 constenvironmentData=newSafeMap();
 
-if(isMainThread){
+// SharedArrayBuffers can be disabled with --no-harmony-sharedarraybuffer.
+// Atomics can be disabled with --no-harmony-atomics.
+if(isMainThread&&SharedArrayBuffer!==undefined&&Atomics!==undefined){
 cwdCounter=newUint32Array(newSharedArrayBuffer(4));
 constoriginalChdir=process.chdir;
 process.chdir=function(path){

test/parallel/test-worker-no-atomics.js

@@ -0,0 +1,21 @@
+// Flags: --no-harmony-atomics
+
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+const{ Worker }=require('worker_threads');
+
+// Regression test for https://github.com/nodejs/node/issues/39717.
+
+// Do not use isMainThread so that this test itself can be run inside a Worker.
+if(!process.env.HAS_STARTED_WORKER){
+process.env.HAS_STARTED_WORKER=1;
+constw=newWorker(__filename);
+
+w.on('exit',common.mustCall((status)=>{
+assert.strictEqual(status,2);
+}));
+}else{
+process.exit(2);
+}

test/parallel/test-worker-no-sab.js

@@ -0,0 +1,21 @@
+// Flags: --no-harmony-sharedarraybuffer
+
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+const{ Worker }=require('worker_threads');
+
+// Regression test for https://github.com/nodejs/node/issues/39717.
+
+// Do not use isMainThread so that this test itself can be run inside a Worker.
+if(!process.env.HAS_STARTED_WORKER){
+process.env.HAS_STARTED_WORKER=1;
+constw=newWorker(__filename);
+
+w.on('exit',common.mustCall((status)=>{
+assert.strictEqual(status,2);
+}));
+}else{
+process.exit(2);
+}