various fixes in the file handler thread

src/OutputFileHandler.h

@@ -11,13 +11,13 @@
 class OutputFileHandler {
 
 public:
-  OutputFileHandler(const std::string base_path,
-                    const std::string filename_prefix)
+  OutputFileHandler(const std::string &base_path,
+                    const std::string &filename_prefix)
       : base_path_(base_path), filename_prefix_(filename_prefix),
         working_files_base_path_(base_path_ + "/" + working_dir_),
         current_run_number_(0), current_index_(0), current_filename_(""),
-        current_file_(0), close_and_rename_(base_path),
-        t(std::thread(close_and_rename_)) {
+        current_file_(0), close_and_rename_(base_path_), t{} {
+    t = std::thread(close_and_rename_);
     create_output_directory_maybe(working_files_base_path_);
   }
 
@@ -30,6 +30,8 @@ public:
 
   FILE *getFile(uint32_t run, uint32_t index);
 
+  bool hasFile() { return current_file_ != 0; }
+
 private:
   void create_output_directory_maybe(std::string &output_directory);
 
@@ -44,7 +46,7 @@ private:
 
   class close_and_rename {
   public:
-    close_and_rename(std::string base_path) : base_path_(base_path) {}
+    close_and_rename(std::string &base_path) : base_path_(base_path) {}
 
     void operator()() const;