Use a singleton instead of a global for MojoWaitManyState

mojo/dart/embedder/mojo_natives.cc

Index: mojo/dart/embedder/mojo_natives.cc
diff --git a/mojo/dart/embedder/mojo_natives.cc b/mojo/dart/embedder/mojo_natives.cc
index 02eb5956ab4c5495bbe69f9989bfae0d028cd7ab..22f270872a454612e7bd07816483c46789c87f7a 100644
--- a/mojo/dart/embedder/mojo_natives.cc
+++ b/mojo/dart/embedder/mojo_natives.cc
@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/singleton.h"
 #include "dart/runtime/include/dart_api.h"
 #include "mojo/dart/embedder/builtin.h"
 #include "mojo/dart/embedder/mojo_dart_state.h"
@@ -727,25 +728,32 @@ struct MojoWaitManyState {
   std::vector<uint32_t> signals;
   std::vector<uint32_t> out_index;
   std::vector<MojoHandleSignalsState> out_signals;
+
+  static MojoWaitManyState* GetInstance();
 };
 
 // This global is safe because it is only accessed by the single handle watcher
 // isolate. If multiple handle watcher isolates are ever needed, it will need
 // to be replicated.
-static MojoWaitManyState handle_watcher_wait_state;
+MojoWaitManyState* MojoWaitManyState::GetInstance() {
+  return Singleton<MojoWaitManyState>::get();

[jamesr, 2015/10/09 23:42:32]

Singleton<> here is providing thread-safe initialization, which you don't need
as this code isn't threadsafe anyway. do this instead:

  static MojoWaitManyState* state = new MojoWaitManyState;
  return state;

and remove the //base/memory/singleton.h dependency

[jsimmons1, 2015/10/09 23:50:46]

Done.

+}
 
 void MojoHandleWatcher_GrowStateArrays(Dart_NativeArguments arguments) {
   int64_t new_length;
   CHECK_INTEGER_ARGUMENT(arguments, 0, &new_length, InvalidArgument);
 
-  handle_watcher_wait_state.handles.resize(new_length);
-  handle_watcher_wait_state.signals.resize(new_length);
-  handle_watcher_wait_state.out_index.resize(1);
-  handle_watcher_wait_state.out_signals.resize(new_length);
+  MojoWaitManyState* handle_watcher_wait_state =

[jamesr, 2015/10/09 23:42:32]

Make this a reference and you won't have to change the following lines. it can
never be null

[abarth-chromium, 2015/10/09 23:45:46]

If you make this a reference, please add DISALLOW_COPY_AND_ASSIGN to
MojoWaitManyState.  (You might want to do that anyway.)

[jsimmons1, 2015/10/09 23:50:46]

Done.

+      MojoWaitManyState::GetInstance();
+
+  handle_watcher_wait_state->handles.resize(new_length);
+  handle_watcher_wait_state->signals.resize(new_length);
+  handle_watcher_wait_state->out_index.resize(1);
+  handle_watcher_wait_state->out_signals.resize(new_length);
 
   Dart_Handle dart_handles = Dart_NewExternalTypedData(
-      Dart_TypedData_kUint32, handle_watcher_wait_state.handles.data(),
-      handle_watcher_wait_state.handles.size());
+      Dart_TypedData_kUint32, handle_watcher_wait_state->handles.data(),
+      handle_watcher_wait_state->handles.size());
   if (Dart_IsError(dart_handles)) {
     Dart_PropagateError(dart_handles);
   }
@@ -755,8 +763,8 @@ void MojoHandleWatcher_GrowStateArrays(Dart_NativeArguments arguments) {
   }
 
   Dart_Handle dart_signals = Dart_NewExternalTypedData(
-      Dart_TypedData_kUint32, handle_watcher_wait_state.signals.data(),
-      handle_watcher_wait_state.signals.size());
+      Dart_TypedData_kUint32, handle_watcher_wait_state->signals.data(),
+      handle_watcher_wait_state->signals.size());
   if (Dart_IsError(dart_signals)) {
     Dart_PropagateError(dart_signals);
   }
@@ -766,8 +774,8 @@ void MojoHandleWatcher_GrowStateArrays(Dart_NativeArguments arguments) {
   }
 
   Dart_Handle dart_out_index = Dart_NewExternalTypedData(
-      Dart_TypedData_kUint32, handle_watcher_wait_state.out_index.data(),
-      handle_watcher_wait_state.out_index.size());
+      Dart_TypedData_kUint32, handle_watcher_wait_state->out_index.data(),
+      handle_watcher_wait_state->out_index.size());
   if (Dart_IsError(dart_out_index)) {
     Dart_PropagateError(dart_out_index);
   }
@@ -777,8 +785,8 @@ void MojoHandleWatcher_GrowStateArrays(Dart_NativeArguments arguments) {
   }
 
   Dart_Handle dart_out_signals = Dart_NewExternalTypedData(
-      Dart_TypedData_kUint64, handle_watcher_wait_state.out_signals.data(),
-      handle_watcher_wait_state.out_signals.size());
+      Dart_TypedData_kUint64, handle_watcher_wait_state->out_signals.data(),
+      handle_watcher_wait_state->out_signals.size());
   if (Dart_IsError(dart_out_signals)) {
     Dart_PropagateError(dart_out_signals);
   }
@@ -801,11 +809,14 @@ void MojoHandleWatcher_WaitMany(Dart_NativeArguments arguments) {
   CHECK_INTEGER_ARGUMENT(arguments, 0, &handles_len, InvalidArgument);
   CHECK_INTEGER_ARGUMENT(arguments, 1, &deadline, InvalidArgument);
 
-  uint32_t* handles = handle_watcher_wait_state.handles.data();
-  uint32_t* signals = handle_watcher_wait_state.signals.data();
-  uint32_t* out_index = handle_watcher_wait_state.out_index.data();
+  MojoWaitManyState* handle_watcher_wait_state =
+      MojoWaitManyState::GetInstance();
+
+  uint32_t* handles = handle_watcher_wait_state->handles.data();
+  uint32_t* signals = handle_watcher_wait_state->signals.data();
+  uint32_t* out_index = handle_watcher_wait_state->out_index.data();
   MojoHandleSignalsState* out_signals =
-      handle_watcher_wait_state.out_signals.data();
+      handle_watcher_wait_state->out_signals.data();
 
   Dart_IsolateBlocked();
   MojoResult mojo_result = MojoWaitMany(handles, signals, handles_len, deadline,