Index: ps/trunk/source/simulation2/helpers/Grid.h
===================================================================
--- ps/trunk/source/simulation2/helpers/Grid.h	(revision 22544)
+++ ps/trunk/source/simulation2/helpers/Grid.h	(revision 22545)
@@ -1,289 +1,290 @@
 /* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 2 of the License, or
  * (at your option) any later version.
  *
  * 0 A.D. is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef INCLUDED_GRID
 #define INCLUDED_GRID
 
 #include <cstring>
 
 #ifdef NDEBUG
 #define GRID_BOUNDS_DEBUG 0
 #else
 #define GRID_BOUNDS_DEBUG 1
 #endif
 
 /**
  * Basic 2D array, intended for storing tile data, plus support for lazy updates
  * by ICmpObstructionManager.
  * @c T must be a POD type that can be initialised with 0s.
  */
 template<typename T>
 class Grid
 {
 public:
 	Grid() : m_W(0), m_H(0), m_Data(NULL), m_DirtyID(0)
 	{
 	}
 
 	Grid(u16 w, u16 h) : m_W(w), m_H(h), m_Data(NULL), m_DirtyID(0)
 	{
 		if (m_W || m_H)
 			m_Data = new T[m_W * m_H];
 		reset();
 	}
 
 	Grid(const Grid& g) : m_W(0), m_H(0), m_Data(NULL), m_DirtyID(0)
 	{
 		*this = g;
 	}
 
 	Grid& operator=(const Grid& g)
 	{
 		if (this == &g)
 			return *this;
 
 		m_DirtyID = g.m_DirtyID;
 		if (m_W == g.m_W && m_H == g.m_H)
 		{
 			memcpy(m_Data, g.m_Data, m_W*m_H*sizeof(T));
 			return *this;
 		}
 
 		m_W = g.m_W;
 		m_H = g.m_H;
 		delete[] m_Data;
 		if (g.m_Data)
 		{
 			m_Data = new T[m_W * m_H];
 			memcpy(m_Data, g.m_Data, m_W*m_H*sizeof(T));
 		}
 		else
 			m_Data = NULL;
 		return *this;
 	}
 
 	void swap(Grid& g)
 	{
 		std::swap(m_DirtyID, g.m_DirtyID);
 		std::swap(m_Data, g.m_Data);
 		std::swap(m_H, g.m_H);
 		std::swap(m_W, g.m_W);
 	}
 
 	~Grid()
 	{
 		delete[] m_Data;
 	}
 
 	bool operator==(const Grid& g) const
 	{
 		if (!compare_sizes(&g) || m_DirtyID != g.m_DirtyID)
 			return false;
 
 		return memcmp(m_Data, g.m_Data, m_W*m_H*sizeof(T)) == 0;
 	}
 
 	bool blank() const
 	{
 		return m_W == 0 && m_H == 0;
 	}
 
 	bool any_set_in_square(int i0, int j0, int i1, int j1) const
 	{
 	#if GRID_BOUNDS_DEBUG
 		ENSURE(i0 >= 0 && j0 >= 0 && i1 <= m_W && j1 <= m_H);
 	#endif
 		for (int j = j0; j < j1; ++j)
 		{
 			int sum = 0;
 			for (int i = i0; i < i1; ++i)
 				sum += m_Data[j*m_W + i];
 			if (sum > 0)
 				return true;
 		}
 		return false;
 	}
 
 	void reset()
 	{
 		if (m_Data)
 			memset(m_Data, 0, m_W*m_H*sizeof(T));
 	}
 
 	// Add two grids of the same size
 	void add(const Grid& g)
 	{
 #if GRID_BOUNDS_DEBUG
 		ENSURE(g.m_W == m_W && g.m_H == m_H);
 #endif
 		for (int i=0; i < m_H*m_W; ++i)
 			m_Data[i] += g.m_Data[i];
 	}
 
 	void bitwise_or(const Grid& g)
 	{
 		if (this == &g)
 			return;
 
 #if GRID_BOUNDS_DEBUG
 		ENSURE(g.m_W == m_W && g.m_H == m_H);
 #endif
 		for (int i = 0; i < m_H*m_W; ++i)
 			m_Data[i] |= g.m_Data[i];
 	}
 
 	void set(int i, int j, const T& value)
 	{
 #if GRID_BOUNDS_DEBUG
 		ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
 #endif
 		m_Data[j*m_W + i] = value;
 	}
 
 	T& get(int i, int j) const
 	{
 #if GRID_BOUNDS_DEBUG
 		ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
 #endif
 		return m_Data[j*m_W + i];
 	}
 
 	template<typename U>
 	bool compare_sizes(const Grid<U>* g) const
 	{
 		return g && m_W == g->m_W && m_H == g->m_H;
 	}
 
 	u16 m_W, m_H;
 	T* m_Data;
 
 	size_t m_DirtyID; // if this is < the id maintained by ICmpObstructionManager then it needs to be updated
 };
 
 /**
  * Similar to Grid, except optimised for sparse usage (the grid is subdivided into
  * buckets whose contents are only initialised on demand, to save on memset cost).
  */
 template<typename T>
 class SparseGrid
 {
 	NONCOPYABLE(SparseGrid);
 
 	enum { BucketBits = 4, BucketSize = 1 << BucketBits };
 
 	T* GetBucket(int i, int j)
 	{
 		size_t b = (j >> BucketBits) * m_BW + (i >> BucketBits);
 		if (!m_Data[b])
 		{
 			m_Data[b] = new T[BucketSize*BucketSize]();
 		}
 		return m_Data[b];
 	}
 
 public:
 	SparseGrid(u16 w, u16 h) : m_W(w), m_H(h), m_DirtyID(0)
 	{
 		ENSURE(m_W && m_H);
 
 		m_BW = (u16)((m_W + BucketSize-1) >> BucketBits);
 		m_BH = (u16)((m_H + BucketSize-1) >> BucketBits);
 
 		m_Data = new T*[m_BW*m_BH]();
 	}
 
 	~SparseGrid()
 	{
 		reset();
 		delete[] m_Data;
 	}
 
 	void reset()
 	{
 		for (size_t i = 0; i < (size_t)(m_BW*m_BH); ++i)
 			delete[] m_Data[i];
 
-		m_Data = new T*[m_BW*m_BH]();
+		// Reset m_Data by value-constructing in place with placement new.
+		m_Data = new (m_Data) T*[m_BW*m_BH]();
 	}
 
 	void set(int i, int j, const T& value)
 	{
 #if GRID_BOUNDS_DEBUG
 		ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
 #endif
 		GetBucket(i, j)[(j % BucketSize)*BucketSize + (i % BucketSize)] = value;
 	}
 
 	T& get(int i, int j)
 	{
 #if GRID_BOUNDS_DEBUG
 		ENSURE(0 <= i && i < m_W && 0 <= j && j < m_H);
 #endif
 		return GetBucket(i, j)[(j % BucketSize)*BucketSize + (i % BucketSize)];
 	}
 
 	u16 m_W, m_H;
 	u16 m_BW, m_BH;
 	T** m_Data;
 
 	size_t m_DirtyID; // if this is < the id maintained by ICmpObstructionManager then it needs to be updated
 };
 
 /**
  * Structure holding grid dirtiness informations, for clever updates.
  */
 struct GridUpdateInformation
 {
 	bool dirty;
 	bool globallyDirty;
 	Grid<u8> dirtinessGrid;
 
 	/**
 	 * Update the information with additionnal needed updates, then erase the source of additions.
 	 * This can usually be optimized through a careful memory management.
 	 */
 	void MergeAndClear(GridUpdateInformation& b)
 	{
 		ENSURE(dirtinessGrid.compare_sizes(&b.dirtinessGrid));
 
 		bool wasDirty = dirty;
 
 		dirty |= b.dirty;
 		globallyDirty |= b.globallyDirty;
 
 		// If the current grid is useless, swap it
 		if (!wasDirty)
 			dirtinessGrid.swap(b.dirtinessGrid);
 		// If the new grid isn't used, don't bother updating it
 		else if (dirty && !globallyDirty)
 			dirtinessGrid.bitwise_or(b.dirtinessGrid);
 
 		b.Clean();
 	}
 
 	/**
 	 * Mark everything as clean
 	 */
 	void Clean()
 	{
 		dirty = false;
 		globallyDirty = false;
 		dirtinessGrid.reset();
 	}
 };
 
 #endif // INCLUDED_GRID