Fix creation and access to elements of large matrices

Author: Florian Plaza Oñate

inst/include/Rcpp/Dimension.h

@@ -57,7 +57,7 @@ namespace Rcpp{
 	        return (int) dims.size() ;
 	    }
 	    inline int prod() const {
-	        return std::accumulate( dims.begin(), dims.end(), 1, std::multiplies<int>() ) ;
+	        return std::accumulate( dims.begin(), dims.end(), static_cast<R_xlen_t>(1), std::multiplies<R_xlen_t>() );
 	    }
 
 	    inline reference operator[](int i){

inst/include/Rcpp/vector/Matrix.h

@@ -58,7 +58,7 @@ class Matrix : public Vector<RTYPE, StoragePolicy>, public MatrixBase<RTYPE, tru
 
     template <typename Iterator>
     Matrix( const int& nrows_, const int& ncols, Iterator start ) :
-        VECTOR( start, start + (nrows_*ncols) ),
+        VECTOR( start, start + (static_cast<R_xlen_t>(nrows_)*ncols) ),
         nrows(nrows_)
     {
         VECTOR::attr( "dim" ) = Dimension( nrows, ncols ) ;
@@ -163,8 +163,7 @@ class Matrix : public Vector<RTYPE, StoragePolicy>, public MatrixBase<RTYPE, tru
 
 
 private:
-
-    inline R_xlen_t offset( int i, int j) const { return i + nrows * j ; }
+    inline R_xlen_t offset(const int i, const int j) const { return i + static_cast<R_xlen_t>(nrows) * j ; }
 
     template <typename U>
     void fill_diag__dispatch( traits::false_type, const U& u) {