help compiler to apply RVO ( return the same object by value)

src/geometry_reprojection.cpp

@@ -170,82 +170,75 @@ struct geom_reproj_copy_visitor {
 
     geometry operator() (geometry_empty const&)
     {
-        return std::move(geometry_empty());
+        return geometry_empty();
     }
 
     geometry operator() (point const& p)
     {
+        geometry geom; // default empty
         unsigned int intial_err = n_err_;
         point new_p = reproject_internal(p, proj_trans_, n_err_);
-        if (n_err_ > intial_err)
+        if (n_err_ > intial_err) return geom;
-        {
+        geom = std::move(new_p);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_p);
     }
 
     geometry operator() (line_string const& ls)
     {
+        geometry geom; // default empty
         int intial_err = n_err_;
         line_string new_ls = reproject_internal(ls, proj_trans_, n_err_);
-        if (n_err_ > intial_err || new_ls.empty())
+        if (n_err_ > intial_err || new_ls.empty()) return geom;
-        {
+        geom = std::move(new_ls);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_ls);
     }
 
     geometry operator() (polygon const& poly)
     {
+        geometry geom; // default empty
         polygon new_poly = reproject_internal(poly, proj_trans_, n_err_);
-        if (new_poly.exterior_ring.empty())
+        if (new_poly.exterior_ring.empty()) return geom;
-        {
+        geom = std::move(new_poly);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_poly);
     }
 
     geometry operator() (multi_point const& mp)
     {
+        geometry geom; // default empty
         multi_point new_mp = reproject_internal(mp, proj_trans_, n_err_);
-        if (new_mp.empty())
+        if (new_mp.empty()) return geom;
-        {
+        geom = std::move(new_mp);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_mp);
     }
 
     geometry operator() (multi_line_string const& mls)
     {
+        geometry geom; // default empty
         multi_line_string new_mls = reproject_internal(mls, proj_trans_, n_err_);
-        if (new_mls.empty())
+        if (new_mls.empty()) return geom;
-        {
+        geom = std::move(new_mls);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_mls);
     }
 
     geometry operator() (multi_polygon const& mpoly)
     {
+        geometry geom; // default empty
         multi_polygon new_mpoly = reproject_internal(mpoly, proj_trans_, n_err_);
-        if (new_mpoly.empty())
+        if (new_mpoly.empty()) return geom;
-        {
+        geom = std::move(new_mpoly);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_mpoly);
     }
 
     geometry operator() (geometry_collection const& c)
     {
+        geometry geom; // default empty
         geometry_collection new_c = reproject_internal(c, proj_trans_, n_err_);
-        if (new_c.empty())
+        if (new_c.empty()) return geom;
-        {
+        geom = std::move(new_c);
-            return std::move(geometry_empty());
+        return geom;
-        }
-        return std::move(new_c);
     }
 
-  private:
+private:
     proj_transform const& proj_trans_;
     unsigned int & n_err_;
 
@@ -381,7 +374,7 @@ struct geom_reproj_visitor {
         return true;
     }
 
-  private:
+private:
     proj_transform const& proj_trans_;
 
 };