Properly implement _idf as static variable

src/modules/EventLoaderALiBaVa/ALiBaVa/DataFileRoot.cpp

@@ -31,6 +31,7 @@ void _A_got_intr(int);
 void _A_got_intr(int) {
     _A_do_run = false;
 }
+std::string DataFileRoot::_idf;
 
 DataFileRoot::DataFileRoot(const char*, const char* pedfile, const char*)
     : _nchan(MAX_NCHAN), _seedcut(5.), _neighcut(3.), _average_gain(1.), _version(2), _polarity(1), _t1(0.0), _t2(99999.),
@@ -295,7 +296,7 @@ DataFileRoot* DataFileRoot::OpenFile(const char* nam, const char* pedfile, const
     char buf[5] = {'\0'};
     ifile.read(buf, 4);
     ifile.close();
-    std::string _idf(buf + 1);
+    _idf = std::string(buf + 1);
 
     if(_idf == "HDF")
         return new HDFRoot(nam, pedfile, gainfile);

src/modules/EventLoaderALiBaVa/ALiBaVa/DataFileRoot.h

@@ -60,7 +60,7 @@ protected: // This is ugly but comfortable
     double _cnoise_roi;
 
     EventDataBlock _data;
-    const std::string _idf;
+    static std::string _idf;
     double _mean_temp_pedestal = std::numeric_limits<double>::quiet_NaN();
 
 protected: