Add mutexed askedContains in placed of .asked.contains(). Issue #333 (dev::RangeMask<unsigned int>::contains), nextFetch clears m_asked concurrent to m_asked.contains() iteration.

alethzero/DownloadView.cpp

@@ -63,7 +63,7 @@ void DownloadView::paintEvent(QPaintEvent*)
 			unsigned h = 0;
 			m_man->foreachSub([&](DownloadSub const& sub)
 			{
-				if (sub.asked().contains(i))
+				if (sub.askedContains(i))
 					s = h;
 				h++;
 			});

libethereum/DownloadMan.h

@@ -54,6 +54,7 @@ public:
 	/// Nothing doing here.
 	void doneFetch() { resetFetch(); }
 
+	bool askedContains(unsigned _i) const { Guard l(m_fetch); return m_asked.contains(_i); }
 	RangeMask<unsigned> const& asked() const { return m_asked; }
 	RangeMask<unsigned> const& attemped() const { return m_attempted; }
 
@@ -69,7 +70,7 @@ private:
 
 	DownloadMan* m_man = nullptr;
 
-	Mutex m_fetch;
+	mutable Mutex m_fetch;
 	h256Set m_remaining;
 	std::map<h256, unsigned> m_indices;
 	RangeMask<unsigned> m_asked;