From 38afbed3704c5d21db26758d9ce78078710abaa8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dan=20Vr=C3=A1til?= <dvratil@redhat.com>
Date: Sat, 7 Feb 2015 17:51:41 +0100
Subject: Async: don't leak Executors

We now hold executors in shared pointers. We cannot easilly delete them, as they
are referenced from two objects (the Job they belong to, and the next job), and
the lifetime of the jobs is unclear.
---
 async/src/async.cpp |  4 ++--
 async/src/async.h   | 58 ++++++++++++++++++++++++++---------------------------
 2 files changed, 30 insertions(+), 32 deletions(-)

(limited to 'async')

diff --git a/async/src/async.cpp b/async/src/async.cpp
index 921a6b5..c9fedc7 100644
--- a/async/src/async.cpp
+++ b/async/src/async.cpp
@@ -24,7 +24,7 @@
 
 using namespace Async;
 
-Private::ExecutorBase::ExecutorBase(ExecutorBase* parent)
+Private::ExecutorBase::ExecutorBase(const ExecutorBasePtr &parent)
     : mPrev(parent)
     , mResult(0)
 {
@@ -36,7 +36,7 @@ Private::ExecutorBase::~ExecutorBase()
 }
 
 
-JobBase::JobBase(Private::ExecutorBase *executor)
+JobBase::JobBase(const Private::ExecutorBasePtr &executor)
     : mExecutor(executor)
 {
 }
diff --git a/async/src/async.h b/async/src/async.h
index 753a44f..d15373b 100644
--- a/async/src/async.h
+++ b/async/src/async.h
@@ -29,10 +29,12 @@
 
 #include <QVector>
 #include <QObject>
+#include <QSharedPointer>
 
 
 /*
- * TODO: on .then and potentially others: support for ThenTask without future argument and return value which makes it implicitly a sync continuation. Useful for typical value consumer continuations.
+ * TODO: on .then and potentially others: support for ThenTask without future argument and return value which makes it implicitly a sync continuation.
+ * Useful for typical value consumer continuations.
  * TODO: error continuation on .then and others.
  * TODO: instead of passing the future objects callbacks could be provided for result reporting (we can still use the future object internally
  */
@@ -57,6 +59,10 @@ using ErrorHandler = std::function<void(int, const QString &)>;
 namespace Private
 {
 
+class ExecutorBase;
+typedef QSharedPointer<ExecutorBase> ExecutorBasePtr;
+
+
 template<typename ... T>
 struct PreviousOut {
     using type = typename std::tuple_element<0, std::tuple<T ..., void>>::type;
@@ -77,9 +83,9 @@ public:
     }
 
 protected:
-    ExecutorBase(ExecutorBase *parent);
+    ExecutorBase(const ExecutorBasePtr &parent);
 
-    ExecutorBase *mPrev;
+    ExecutorBasePtr mPrev;
     FutureBase *mResult;
 };
 
@@ -87,7 +93,7 @@ template<typename PrevOut, typename Out, typename ... In>
 class Executor : public ExecutorBase
 {
 protected:
-    Executor(ExecutorBase *parent)
+    Executor(const Private::ExecutorBasePtr &parent)
         : ExecutorBase(parent)
         , mPrevFuture(0)
     {}
@@ -106,7 +112,7 @@ template<typename Out, typename ... In>
 class ThenExecutor: public Executor<typename PreviousOut<In ...>::type, Out, In ...>
 {
 public:
-    ThenExecutor(ThenTask<Out, In ...> then, ErrorHandler errorHandler = ErrorHandler(), ExecutorBase *parent = nullptr);
+    ThenExecutor(ThenTask<Out, In ...> then, ErrorHandler errorHandler = ErrorHandler(), const ExecutorBasePtr &parent = ExecutorBasePtr());
     void previousFutureReady();
 };
 
@@ -114,7 +120,7 @@ template<typename PrevOut, typename Out, typename In>
 class EachExecutor : public Executor<PrevOut, Out, In>
 {
 public:
-    EachExecutor(EachTask<Out, In> each, ExecutorBase *parent);
+    EachExecutor(EachTask<Out, In> each, const ExecutorBasePtr &parent);
     void previousFutureReady();
 
 private:
@@ -122,11 +128,10 @@ private:
 };
 
 template<typename Out, typename In>
-class ReduceExecutor : public Executor<In, Out, In>
+class ReduceExecutor : public ThenExecutor<Out, In>
 {
 public:
-    ReduceExecutor(ReduceTask<Out, In> reduce, ExecutorBase *parent);
-    void previousFutureReady();
+    ReduceExecutor(ReduceTask<Out, In> reduce, const ExecutorBasePtr &parent);
 };
 
 } // namespace Private
@@ -175,11 +180,11 @@ class JobBase
     friend class Job;
 
 public:
-    JobBase(Private::ExecutorBase *executor);
+    JobBase(const Private::ExecutorBasePtr &executor);
     ~JobBase();
 
 protected:
-    Private::ExecutorBase *mExecutor;
+    Private::ExecutorBasePtr mExecutor;
 };
 
 /**
@@ -237,9 +242,8 @@ public:
     template<typename OutOther, typename ... InOther>
     Job<OutOther, InOther ...> then(ThenTask<OutOther, InOther ...> func, ErrorHandler errorFunc = ErrorHandler())
     {
-        //FIXME are we leaking the executor?
-        //The executor is copied with ever job instance, so use a sharedpointer?
-        return Job<OutOther, InOther ...>(new Private::ThenExecutor<OutOther, InOther ...>(func, errorFunc, mExecutor));
+        return Job<OutOther, InOther ...>(Private::ExecutorBasePtr(
+            new Private::ThenExecutor<OutOther, InOther ...>(func, errorFunc, mExecutor)));
     }
 
     template<typename OutOther, typename InOther>
@@ -249,7 +253,8 @@ public:
                       "The 'Each' task can only be connected to a job that returns a list or an array.");
         static_assert(detail::isIterable<OutOther>::value,
                       "The result type of 'Each' task must be a list or an array.");
-        return Job<OutOther, InOther>(new Private::EachExecutor<Out, OutOther, InOther>(func, mExecutor));
+        return Job<OutOther, InOther>(Private::ExecutorBasePtr(
+            new Private::EachExecutor<Out, OutOther, InOther>(func, mExecutor)));
     }
 
     template<typename OutOther, typename InOther>
@@ -259,7 +264,8 @@ public:
                       "The 'Result' task can only be connected to a job that returns a list or an array");
         static_assert(std::is_same<typename Out::value_type, typename InOther::value_type>::value,
                       "The return type of previous task must be compatible with input type of this task");
-        return Job<OutOther, InOther>(new Private::ReduceExecutor<OutOther, InOther>(func, mExecutor));
+        return Job<OutOther, InOther>(Private::ExecutorBasePtr(
+            new Private::ReduceExecutor<OutOther, InOther>(func, mExecutor)));
     }
 
     Async::Future<Out> exec()
@@ -274,7 +280,7 @@ public:
     }
 
 private:
-    Job(Private::ExecutorBase *executor)
+    Job(Private::ExecutorBasePtr executor)
         : JobBase(executor)
     {}
 };
@@ -289,8 +295,7 @@ namespace Async {
 template<typename Out>
 Job<Out> start(ThenTask<Out> func)
 {
-    //FIXME we're leaking the exucutor, use a shared pointer
-    return Job<Out>(new Private::ThenExecutor<Out>(func));
+    return Job<Out>(Private::ExecutorBasePtr(new Private::ThenExecutor<Out>(func)));
 }
 
 namespace Private {
@@ -326,7 +331,7 @@ void Executor<PrevOut, Out, In ...>::exec()
 }
 
 template<typename Out, typename ... In>
-ThenExecutor<Out, In ...>::ThenExecutor(ThenTask<Out, In ...> then, ErrorHandler error, ExecutorBase* parent)
+ThenExecutor<Out, In ...>::ThenExecutor(ThenTask<Out, In ...> then, ErrorHandler error, const ExecutorBasePtr &parent)
     : Executor<typename PreviousOut<In ...>::type, Out, In ...>(parent)
 {
     this->mFunc = then;
@@ -356,7 +361,7 @@ void ThenExecutor<Out, In ...>::previousFutureReady()
 }
 
 template<typename PrevOut, typename Out, typename In>
-EachExecutor<PrevOut, Out, In>::EachExecutor(EachTask<Out, In> each, ExecutorBase* parent)
+EachExecutor<PrevOut, Out, In>::EachExecutor(EachTask<Out, In> each, const ExecutorBasePtr &parent)
     : Executor<PrevOut, Out, In>(parent)
 {
     this->mFunc = each;
@@ -393,18 +398,11 @@ void EachExecutor<PrevOut, Out, In>::previousFutureReady()
 }
 
 template<typename Out, typename In>
-ReduceExecutor<Out, In>::ReduceExecutor(ReduceTask<Out, In> reduce, ExecutorBase* parent)
-    : Executor<In, Out, In>(parent)
+ReduceExecutor<Out, In>::ReduceExecutor(ReduceTask<Out, In> reduce, const ExecutorBasePtr &parent)
+    : ThenExecutor<Out, In>(reduce, ErrorHandler(), parent)
 {
-    this->mFunc = reduce;
 }
 
-template<typename Out, typename In>
-void ReduceExecutor<Out, In>::previousFutureReady()
-{
-    assert(this->mPrevFuture->isFinished());
-    this->mFunc(this->mPrevFuture->value(), *static_cast<Async::Future<Out>*>(this->mResult));
-}
 
 } // namespace Private
 
-- 
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