Fix C++ warnings (#156)

* Fix C++ warnings

Signed-off-by: Christian Vetter <[email protected]>

Author: VeaaC

flatdata-cpp/examples/coappearances/coappearances.cpp

@@ -220,7 +220,7 @@ convert( const char* json_path, const char* archive_path )
 // Note: The linear search below is slow for big graphs for obvious reasons, where it is much better
 // to build a lookup table. However, for our small graph this works fine.
 std::vector< uint32_t >
-get_neighbors( co::Graph graph, uint32_t vertex_ref )
+get_neighbors( const co::Graph& graph, uint32_t vertex_ref )
 {
     std::vector< uint32_t > neighbors;
     for ( auto e : graph.edges( ) )
@@ -238,7 +238,7 @@ get_neighbors( co::Graph graph, uint32_t vertex_ref )
 }
 
 size_t
-calculate_num_connected_components( co::Graph graph )
+calculate_num_connected_components( const co::Graph& graph )
 {
     size_t num_connected_components = 0;
 

flatdata-cpp/examples/fibonacci.cpp

@@ -77,7 +77,7 @@ main( int argc, char const* argv[] )
             return 1;
         }
     }
-    catch ( std::runtime_error err )
+    catch ( const std::runtime_error& err )
     {
         std::cerr << "Error: " << err.what( ) << std::endl;
     }

flatdata-cpp/examples/graph.cpp

@@ -95,7 +95,7 @@ main( int argc, char const* argv[] )
             return 1;
         }
     }
-    catch ( std::runtime_error err )
+    catch ( const std::runtime_error& err )
     {
         std::cerr << "Error: " << err.what( ) << std::endl;
     }

flatdata-cpp/include/flatdata/Archive.h

@@ -3,6 +3,8 @@
  * See the LICENSE file in the root of this project for license details.
  */
 
+#pragma once
+
 #include "ResourceStorage.h"
 
 #include <boost/optional.hpp>

flatdata-cpp/include/flatdata/internal/ArchiveUtils.h

@@ -3,6 +3,8 @@
  * See the LICENSE file in the root of this project for license details.
  */
 
+#pragma once
+
 #include <string>
 
 namespace flatdata