dart2js: Use unique instance as exit signal.

pkg/compiler/lib/src/dart2js.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cmdline;
 
 import 'dart:async'
     show Future, EventSink;
 import 'dart:convert' show UTF8, LineSplitter;
 import 'dart:io'
@@ skipping 408 matching lines @@
   options.add('--out=$out');
   options.add('--source-map=$sourceMapOut');
 
   RandomAccessFileOutputProvider outputProvider =
       new RandomAccessFileOutputProvider(
           out, sourceMapOut, onInfo: diagnosticHandler.info, onFailure: fail);
 
   api.CompilationResult compilationDone(api.CompilationResult result) {
     if (analyzeOnly) return result;
     if (!result.isSuccess) {
       fail('Compilation failed.');

[ahe, 2015/01/13 08:35:20]

This throws _EXIT_SIGNAL.

     }
     writeString(Uri.parse('$out.deps'),
                 getDepsOutput(inputProvider.sourceFiles));
     diagnosticHandler.info(
          'Compiled ${inputProvider.dartCharactersRead} characters Dart '
          '-> ${outputProvider.totalCharactersWritten} characters '
          '$outputLanguage in '
          '${relativize(currentDirectory, out, Platform.isWindows)}');
     if (diagnosticHandler.verbose) {
       String input = uriPathToNative(arguments[0]);
@@ skipping 211 matching lines @@
 Future<api.CompilationResult> internalMain(List<String> arguments) {
   Future onError(exception, trace) {
     try {
       print('The compiler crashed: $exception');
     } catch (ignored) {
       print('The compiler crashed: error while printing exception');
     }
 
     try {
       if (trace != null) {
         print(trace);

[ahe, 2015/01/13 08:35:20]

This prints the stack trace associated with _EXIT_SIGNAL.

       }
     } finally {
       exitFunc(253); // 253 is recognized as a crash by our test scripts.
     }
     return new Future.error(exception, trace);
   }
 
   try {
     return compilerMain(arguments).catchError(onError);

[ahe, 2015/01/13 08:35:20]

This calls compile which calls compilationDone.

   } catch (exception, trace) {
     return onError(exception, trace);
   }
 }
 
-const _EXIT_SIGNAL = const Object();
+class _ExitSignal {
+  const _ExitSignal();
+}
+
+const _EXIT_SIGNAL = const _ExitSignal();
 
 void batchMain(List<String> batchArguments) {
   int exitCode;
   exitFunc = (errorCode) {
     // Since we only throw another part of the compiler might intercept our
     // exception and try to exit with a different code.
     if (exitCode == 0) {
       exitCode = errorCode;
     }
     throw _EXIT_SIGNAL;
   };
 
   var stream = stdin.transform(UTF8.decoder).transform(new LineSplitter());
   var subscription;
   subscription = stream.listen((line) {
     new Future.sync(() {
       subscription.pause();
       exitCode = 0;
       if (line == null) exit(0);
       List<String> args = <String>[];
       args.addAll(batchArguments);
       args.addAll(splitLine(line, windows: Platform.isWindows));
       return internalMain(args);

[ahe, 2015/01/13 08:35:20]

Calling internalMain here.

     }).catchError((exception, trace) {
       if (!identical(exception, _EXIT_SIGNAL)) {
         exitCode = 253;
       }
     }).whenComplete(() {
       // The testing framework waits for a status line on stdout and
       // stderr before moving to the next test.
       if (exitCode == 0){
         print(">>> TEST OK");
       } else if (exitCode == 253) {
         print(">>> TEST CRASH");
       } else {
         print(">>> TEST FAIL");
       }
       stderr.writeln(">>> EOF STDERR");
       subscription.resume();
     });
   });
 }