prepare for folly::Executor taking folly::Function

Summary:
A bunch of small changes that are necessary before we change
the definition of folly::Func from std::function<void()> to
folly::Function<void()>.

Reviewed By: yfeldblum, mzlee

Differential Revision: D3706210

fbshipit-source-id: 198d8a391ef6f545ad4411d316ba9e271ea795e3

folly/futures/ManualExecutor.cpp

@@ -26,7 +26,7 @@ namespace folly {
 
 void ManualExecutor::add(Func callback) {
   std::lock_guard<std::mutex> lock(lock_);
-  funcs_.push(std::move(callback));
+  funcs_.emplace(std::move(callback));
   sem_.post();
 }
 
@@ -42,7 +42,7 @@ size_t ManualExecutor::run() {
       auto& sf = scheduledFuncs_.top();
       if (sf.time > now_)
         break;
-      funcs_.push(sf.func);
+      funcs_.emplace(sf.moveOutFunc());
       scheduledFuncs_.pop();
     }
 

folly/futures/ManualExecutor.h

@@ -118,7 +118,7 @@ namespace folly {
     struct ScheduledFunc {
       TimePoint time;
       size_t ordinal;
-      Func func;
+      Func mutable func;
 
       ScheduledFunc(TimePoint const& t, Func&& f)
         : time(t), func(std::move(f))
@@ -132,6 +132,10 @@ namespace folly {
           return ordinal < b.ordinal;
         return time < b.time;
       }
+
+      Func&& moveOutFunc() const {
+        return std::move(func);
+      }
     };
     std::priority_queue<ScheduledFunc> scheduledFuncs_;
     TimePoint now_ = now_.min();

folly/futures/QueuedImmediateExecutor.cpp

@@ -30,7 +30,7 @@ void QueuedImmediateExecutor::addStatic(Func callback) {
       q_->pop();
     }
   } else {
-    q_->push(callback);
+    q_->push(std::move(callback));
   }
 }
 

folly/futures/test/ViaTest.cpp

@@ -31,7 +31,7 @@ struct ManualWaiter : public DrivableExecutor {
   explicit ManualWaiter(std::shared_ptr<ManualExecutor> ex) : ex(ex) {}
 
   void add(Func f) override {
-    ex->add(f);
+    ex->add(std::move(f));
   }
 
   void drive() override {

folly/io/async/EventBase.h

@@ -50,7 +50,7 @@
 
 namespace folly {
 
-typedef std::function<void()> Cob;
+using Cob = Func; // defined in folly/Executor.h
 template <typename MessageT>
 class NotificationQueue;
 

folly/test/SingletonTest.cpp

@@ -495,7 +495,7 @@ class TestEagerInitParallelExecutor : public folly::Executor {
 
   virtual void add(folly::Func func) override {
     const auto index = (counter_ ++) % eventBases_.size();
-    eventBases_[index]->add(func);
+    eventBases_[index]->add(std::move(func));
   }
 
  private: