add lock_guard to protect against data races in initialization of scripting environment

rename function names to reduce camel case noise

extractor/extractor.cpp

@@ -155,7 +155,7 @@ int Extractor::Run(int argc, char *argv[])
             resulting_restrictions;
 
         // setup restriction parser
-        const RestrictionParser restriction_parser(scripting_environment.getLuaState());
+        const RestrictionParser restriction_parser(scripting_environment.get_lua_state());
 
         while (const osmium::memory::Buffer buffer = reader.read())
         {
@@ -181,12 +181,14 @@ int Extractor::Run(int argc, char *argv[])
                     ExtractionNode result_node;
                     ExtractionWay result_way;
 
+                    lua_State * local_state = scripting_environment.get_lua_state(); 
+
                     switch (entity->type())
                     {
                     case osmium::item_type::node:
                         ++number_of_nodes;
                         luabind::call_function<void>(
-                            scripting_environment.getLuaState(),
+                            local_state,
                             "node_function",
                             boost::cref(static_cast<const osmium::Node &>(*entity)),
                             boost::ref(result_node));
@@ -195,7 +197,7 @@ int Extractor::Run(int argc, char *argv[])
                     case osmium::item_type::way:
                         ++number_of_ways;
                         luabind::call_function<void>(
-                            scripting_environment.getLuaState(),
+                            local_state,
                             "way_function",
                             boost::cref(static_cast<const osmium::Way &>(*entity)),
                             boost::ref(result_way));

extractor/scripting_environment.cpp

@@ -60,13 +60,13 @@ int lua_error_callback(lua_State *L) // This is so I can use my own function as
 }
 
 
-ScriptingEnvironment::ScriptingEnvironment(const char *file_name)
+ScriptingEnvironment::ScriptingEnvironment(const std::string &file_name)
 : file_name(file_name)
 {
     SimpleLogger().Write() << "Using script " << file_name;
 }
 
-void ScriptingEnvironment::initLuaState(lua_State* lua_state)
+void ScriptingEnvironment::init_lua_state(lua_State* lua_state)
 {
     typedef double (osmium::Location::* location_member_ptr_type)() const;
 
@@ -129,18 +129,18 @@ void ScriptingEnvironment::initLuaState(lua_State* lua_state)
     }
 }
 
-lua_State *ScriptingEnvironment::getLuaState()
+lua_State *ScriptingEnvironment::get_lua_state()
 {
+    std::lock_guard<std::mutex> lock(init_mutex);
     bool initialized = false;
     auto& ref = script_contexts.local(initialized);
     if (!initialized)
     {
         std::shared_ptr<lua_State> state(luaL_newstate(), lua_close);
         ref = state;
-        initLuaState(ref.get());
+        init_lua_state(ref.get());
     }
     luabind::set_pcall_callback(&lua_error_callback);
 
     return ref.get();
 }
-

extractor/scripting_environment.hpp

@@ -30,6 +30,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <string>
 #include <memory>
+#include <mutex>
 #include <tbb/enumerable_thread_specific.h>
 
 struct lua_State;
@@ -38,13 +39,13 @@ class ScriptingEnvironment
 {
   public:
     ScriptingEnvironment() = delete;
-    explicit ScriptingEnvironment(const char *file_name);
+    explicit ScriptingEnvironment(const std::string &file_name);
 
-    lua_State *getLuaState();
+    lua_State *get_lua_state();
 
   private:
-    void initLuaState(lua_State* lua_state);
+    void init_lua_state(lua_State* lua_state);
-
+    std::mutex init_mutex; 
     std::string file_name;
     tbb::enumerable_thread_specific<std::shared_ptr<lua_State>> script_contexts;
 };