Very simple version of Isolates.

runtime/bin/main.cc

 // Copyright (c) 2012, 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.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_debugger_api.h"
@@ skipping 845 matching lines @@
                          Dart_GetError(result));
       }
     }
     if (has_print_script) {
       result = GenerateScriptSource();
       if (Dart_IsError(result)) {
         return DartErrorExit(result);
       }
     } else {
       // Lookup and invoke the top level main function.
-      Dart_Handle main_args[1];
+      // The top-level function may accept up to two arguments:
+      //   main(List<String> args, var message).
+      // However most commonly it either accepts one (the args list) or
+      // none.
+      // If the message is optional, main(args, [message]), it is invoked with
+      // one argument only.
+      Dart_Handle main_args[2];
       main_args[0] = CreateRuntimeOptions(&dart_options);
+      main_args[1] = Dart_Null();
+      // First try with 1 argument.

[Lasse Reichstein Nielsen, 2013/10/25 09:42:49]

Could we inspect the function to see its signature, instead of trying to invoke
and failing? Or is trying to invoke efficient enough that it's not an overhead
(with the TODO below fixed)?

[floitsch, 2013/10/25 13:11:01]

It will be fixed. The TODO below is from Ivan. This is just a temporary
solution.

       result = Dart_Invoke(library, DartUtils::NewString("main"), 1, main_args);
       // TODO(iposva): Return a special error type for mismatched argument
       // counts from Dart_Invoke to avoid the string comparison.
       const char* expected_error = "Dart_Invoke: wrong argument count for "
-          "function 'main': 1 passed, 0 expected.";
+          "function 'main': ";
+      intptr_t length = strlen(expected_error);
       if (Dart_IsError(result) &&
-          strcmp(expected_error, Dart_GetError(result)) == 0) {
-        result = Dart_Invoke(library, DartUtils::NewString("main"), 0, NULL);
+          strncmp(expected_error, Dart_GetError(result), length) == 0) {
+        // Try with two arguments.

[Lasse Reichstein Nielsen, 2013/10/25 09:42:49]

Say why we try two before zero.

We really want to pass the first argument (which we have), and don't care about
passing the second (which we don't have anyway).

[floitsch, 2013/10/25 13:11:01]

See comment above.

+        result =
+            Dart_Invoke(library, DartUtils::NewString("main"), 2, main_args);
+        if (Dart_IsError(result) &&
+            strncmp(expected_error, Dart_GetError(result), length) == 0) {
+          // Finally try with 0 arguments.
+          result = Dart_Invoke(library, DartUtils::NewString("main"), 0, NULL);
+        }
       }
       if (Dart_IsError(result)) {
         return DartErrorExit(result);
       }
 
       // Keep handling messages until the last active receive port is closed.
       result = Dart_RunLoop();
       if (Dart_IsError(result)) {
         return DartErrorExit(result);
       }
@@ skipping 15 matching lines @@
 
   return Process::GlobalExitCode();
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   return dart::bin::main(argc, argv);
 }