fix --prof-process --preprocess flag

This is a one-line fix to prevent the --preprocess
option (used with --prof-process to output JSON)
to cause an isolate log file profiling process to crash.

PR-URL: https://github.com/nodejs/node/pull/14966
Reviewed-By: Luca Maraschi <luca.maraschi@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/v8_prof_processor.js

@@ -32,6 +32,7 @@ if (process.platform === 'darwin') {
 tickArguments.push.apply(tickArguments, process.argv.slice(1));
 script = `(function() {
   arguments = ${JSON.stringify(tickArguments)};
+  function write (s) { process.stdout.write(s) }
   ${script}
 })()`;
 eval(script);

test/tick-processor/test-tick-processor-preprocess-flag.js

@@ -0,0 +1,24 @@
+'use strict';
+const common = require('../common');
+
+if (!common.enoughTestCpu)
+  common.skip('test is CPU-intensive');
+
+if (common.isWindows ||
+    common.isSunOS ||
+    common.isAIX ||
+    common.isLinuxPPCBE ||
+    common.isFreeBSD)
+  common.skip('C++ symbols are not mapped for this os.');
+
+const base = require('./tick-processor-base.js');
+
+base.runTest({
+  pattern: /^{/,
+  code: `function f() {
+           require('vm').runInDebugContext('Debug');
+           setImmediate(function() { f(); });
+         };
+         f();`,
+  profProcessFlags: ['--preprocess']
+});

test/tick-processor/tick-processor-base.js

@@ -24,23 +24,25 @@ function runTest(test) {
 
   // Try to match after timeout
   setTimeout(() => {
-    match(test.pattern, proc, () => ticks);
+    match(test.pattern, proc, () => ticks, test.profProcessFlags);
   }, RETRY_TIMEOUT);
 }
 
-function match(pattern, parent, ticks) {
+function match(pattern, parent, ticks, flags = []) {
   // Store current ticks log
   fs.writeFileSync(LOG_FILE, ticks());
 
   const proc = cp.spawn(process.execPath, [
     '--prof-process',
     '--call-graph-size=10',
+    ...flags,
     LOG_FILE
   ], {
     stdio: [ 'ignore', 'pipe', 'inherit' ]
   });
 
   let out = '';
+
   proc.stdout.on('data', (chunk) => out += chunk);
   proc.stdout.once('end', () => {
     proc.once('exit', () => {