[dart:io][windows] Make unicode characters display correctly.

runtime/bin/platform_win.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 "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/platform.h"
 
 #include "bin/file.h"
 #include "bin/log.h"
 #if !defined(DART_IO_DISABLED) && !defined(PLATFORM_DISABLE_SOCKET)
 #include "bin/socket.h"
 #endif
 #include "bin/utils.h"
 #include "bin/utils_win.h"
 
 namespace dart {
 
 // Defined in vm/os_thread_win.cc
 extern bool private_flag_windows_run_tls_destructors;
 
 namespace bin {
 
 const char* Platform::executable_name_ = NULL;
 char* Platform::resolved_executable_name_ = NULL;
 int Platform::script_index_ = 1;
 char** Platform::argv_ = NULL;
 
+static int old_output_cp = -1;
+
 bool Platform::Initialize() {
+  ASSERT(old_output_cp == -1);
+  old_output_cp = GetConsoleOutputCP();
+  SetConsoleOutputCP(CP_UTF8);
   SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOOPENFILEERRORBOX);
   return true;
 }
 
 
 int Platform::NumberOfProcessors() {
   SYSTEM_INFO info;
   GetSystemInfo(&info);
   return info.dwNumberOfProcessors;
 }
@@ skipping 76 matching lines @@
   char* path = StringUtilsWin::WideToUtf8(tmp_buffer);
   // Return the canonical path as the returned path might contain symlinks.
   const char* canon_path = File::GetCanonicalPath(path);
   return canon_path;
 }
 
 
 void Platform::Exit(int exit_code) {
   // TODO(zra): Remove once VM shuts down cleanly.
   ::dart::private_flag_windows_run_tls_destructors = false;
+  // Restore the console's output code page
+  if (old_output_cp != -1) {
+    SetConsoleOutputCP(old_output_cp);

[Florian Schneider, 2017/02/21 20:34:50]

Can there be multiple threads calling Platform::Exit? If yes, another thread
could have reset old_output_cp to -1 before this call here.

[zra, 2017/02/21 21:26:46]

Yes. This can happen if multiple isolates call Platform.exit() at the same time.
I've added a mutex to protect old_output_cp.

+    old_output_cp = -1;
+  }
   // On Windows we use ExitProcess so that threads can't clobber the exit_code.
   // See: https://code.google.com/p/nativeclient/issues/detail?id=2870
   ::ExitProcess(exit_code);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)