diff --git a/qucs-powercombining/qucspowercombiningtool.cpp b/qucs-powercombining/qucspowercombiningtool.cpp
index 67c1d8f5e..fba602ea5 100644
--- a/qucs-powercombining/qucspowercombiningtool.cpp
+++ b/qucs-powercombining/qucspowercombiningtool.cpp
@@ -787,7 +787,7 @@ QString QucsPowerCombiningTool::calcChebyLines(double RL, double Z0, double gamm
     {
         QMessageBox::warning(0, QObject::tr("Error"),
                              QObject::tr("Chebyshev weighting for N>7 is not available"));
-        return QString("");
+        return QString();
     }
     QString s;
     double sec_theta_m;// = cosh((1/(1.*N))*acosh((1/gamma)*fabs((RL-Z0)/(Z0+RL))) );
@@ -2065,7 +2065,7 @@ QString QucsPowerCombiningTool::ConvertLengthFromM(double len)
           return QString("%1 mm").arg(RoundVariablePrecision(conv));
   }
   }while(true);
-  return QString("");
+  return QString();
 }
 
 // Copied from Qucs misc class
diff --git a/qucs/components/component.cpp b/qucs/components/component.cpp
index 15b97e817..c05f2d4e8 100644
--- a/qucs/components/component.cpp
+++ b/qucs/components/component.cpp
@@ -763,7 +763,7 @@ QString Component::spice_netlist(bool) {
 }
 
 QString Component::va_code() {
-    return QString(""); // ignore if not implemented
+    return QString(); // ignore if not implemented
 }
 
 // -------------------------------------------------------
@@ -772,7 +772,7 @@ QString Component::getNetlist() {
         case COMP_IS_ACTIVE:
             return netlist();
         case COMP_IS_OPEN:
-            return QString("");
+            return QString();
     }
 
     // Component is shortened.
@@ -795,7 +795,7 @@ QString Component::getSpiceNetlist(bool isXyce) {
             s.replace(" gnd ", " 0 ");
             return s;
         case COMP_IS_OPEN:
-            return QString("");
+            return QString();
     }
 
     // Component is shortened.
@@ -820,16 +820,16 @@ QString Component::getVerilogACode() {
             return s;
         case COMP_IS_OPEN:
         default:
-            return QString("");
+            return QString();
     }
 }
 
 QString Component::getExpression(bool) {
-    return QString("");
+    return QString();
 }
 
 QString Component::getEquations(QString, QStringList &) {
-    return QString("");
+    return QString();
 }
 
 QStringList Component::getExtraVariables() {
@@ -837,35 +837,35 @@ QStringList Component::getExtraVariables() {
 }
 
 QString Component::getProbeVariable(bool) {
-    return QString("");
+    return QString();
 }
 
 QString Component::getSpiceModel() {
-    return QString("");
+    return QString();
 }
 
 QString Component::getNgspiceBeforeSim(QString sim, int lvl) {
     Q_UNUSED(sim) // To suppress warning
     Q_UNUSED(lvl)
-    return QString("");
+    return QString();
 }
 
 QString Component::getNgspiceAfterSim(QString sim, int lvl) {
     Q_UNUSED(sim) // To suppress warning
     Q_UNUSED(lvl)
-    return QString("");
+    return QString();
 }
 
 // -------------------------------------------------------
 QString Component::verilogCode(int) {
-    return QString("");   // no digital model
+    return QString();   // no digital model
 }
 
 // -------------------------------------------------------
 QString Component::get_Verilog_Code(int NumPorts) {
     switch (isActive) {
         case COMP_IS_OPEN:
-            return QString("");
+            return QString();
         case COMP_IS_ACTIVE:
             return verilogCode(NumPorts);
     }
@@ -882,14 +882,14 @@ QString Component::get_Verilog_Code(int NumPorts) {
 
 // -------------------------------------------------------
 QString Component::vhdlCode(int) {
-    return QString("");   // no digital model
+    return QString();   // no digital model
 }
 
 // -------------------------------------------------------
 QString Component::get_VHDL_Code(int NumPorts) {
     switch (isActive) {
         case COMP_IS_OPEN:
-            return QString("");
+            return QString();
         case COMP_IS_ACTIVE:
             return vhdlCode(NumPorts);
     }
diff --git a/qucs/components/component.h b/qucs/components/component.h
index cc98bd096..64966355e 100644
--- a/qucs/components/component.h
+++ b/qucs/components/component.h
@@ -49,11 +49,11 @@ class Component : public Element {
   virtual QStringList getExtraVariables();
   virtual QString getProbeVariable(bool isXyce = false);
   virtual QString getSpiceModel();
-  virtual QString getSpiceLibrary() { return QString(""); }
+  virtual QString getSpiceLibrary() { return QString(); }
   virtual QString getNgspiceBeforeSim(QString sim, int lvl=0);
   virtual QString getNgspiceAfterSim(QString sim, int lvl=0);
-  virtual QString getVAvariables() {return QString("");};
-  virtual QString getVAExpressions() {return QString("");};
+  virtual QString getVAvariables() {return QString();};
+  virtual QString getVAExpressions() {return QString();};
   virtual void getExtraVANodes(QStringList& ) {};
   QString get_VHDL_Code(int);
   QString get_Verilog_Code(int);
diff --git a/qucs/components/d_flipflop.cpp b/qucs/components/d_flipflop.cpp
index e1d59d548..40076cec3 100644
--- a/qucs/components/d_flipflop.cpp
+++ b/qucs/components/d_flipflop.cpp
@@ -122,7 +122,7 @@ Element* D_FlipFlop::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString D_FlipFlop::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/dff_SR.cpp b/qucs/components/dff_SR.cpp
index 2f1463d77..d93427fbb 100644
--- a/qucs/components/dff_SR.cpp
+++ b/qucs/components/dff_SR.cpp
@@ -177,7 +177,7 @@ QString dff_SR::verilogCode( int )
 
 QString dff_SR::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/equation.cpp b/qucs/components/equation.cpp
index 6bbfd508f..b45432f8a 100644
--- a/qucs/components/equation.cpp
+++ b/qucs/components/equation.cpp
@@ -124,7 +124,7 @@ QString Equation::getVAExpressions()
  */
 QString Equation::getExpression(bool isXyce)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QStringList ng_vars,ngsims;
     getNgnutmegVars(ng_vars,ngsims);
@@ -172,7 +172,7 @@ QString Equation::getExpression(bool isXyce)
  */
 QString Equation::getEquations(QString sim, QStringList &dep_vars)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QStringList ng_vars,ngsims;
     getNgnutmegVars(ng_vars,ngsims);
@@ -214,7 +214,7 @@ QString Equation::getNgspiceScript()
 
     QString s;
     s.clear();
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     for (int i=0;i<Props.count()-1;i++) {
         QStringList tokens;
diff --git a/qucs/components/ground.cpp b/qucs/components/ground.cpp
index 33e5e73d9..9d3c06124 100644
--- a/qucs/components/ground.cpp
+++ b/qucs/components/ground.cpp
@@ -63,10 +63,10 @@ Element* Ground::info(QString& Name, char* &BitmapFile, bool getNewOne)
 // -------------------------------------------------------
 QString Ground::netlist()
 {
-  return QString("");
+  return QString();
 }
 
 QString Ground::spice_netlist(bool)
 {
-    return QString("");
+    return QString();
 }
diff --git a/qucs/components/jkff_SR.cpp b/qucs/components/jkff_SR.cpp
index ab9606617..28ac2bd70 100644
--- a/qucs/components/jkff_SR.cpp
+++ b/qucs/components/jkff_SR.cpp
@@ -186,7 +186,7 @@ QString jkff_SR::verilogCode( int )
 
 QString jkff_SR::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/logical_buf.cpp b/qucs/components/logical_buf.cpp
index 11d83b917..219e659d2 100644
--- a/qucs/components/logical_buf.cpp
+++ b/qucs/components/logical_buf.cpp
@@ -137,7 +137,7 @@ Element* Logical_Buf::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString Logical_Buf::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/logical_inv.cpp b/qucs/components/logical_inv.cpp
index 4cc57be46..158735b10 100644
--- a/qucs/components/logical_inv.cpp
+++ b/qucs/components/logical_inv.cpp
@@ -154,7 +154,7 @@ Element* Logical_Inv::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString Logical_Inv::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/param_sweep.cpp b/qucs/components/param_sweep.cpp
index 2a8f69a9d..411c940e6 100644
--- a/qucs/components/param_sweep.cpp
+++ b/qucs/components/param_sweep.cpp
@@ -81,7 +81,7 @@ void Param_Sweep::recreate(Schematic*)
 
 QString Param_Sweep::getNgspiceBeforeSim(QString sim, int lvl)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s,unit;
     QStringList parameter_list = getProperty("Param")->Value.split( this->param_split_str );
@@ -166,7 +166,7 @@ QString Param_Sweep::getNgspiceBeforeSim(QString sim, int lvl)
 
 QString Param_Sweep::getNgspiceAfterSim(QString sim, int lvl)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     QStringList parameter_list = getProperty("Param")->Value.split( this->param_split_str );
diff --git a/qucs/components/spicefile.cpp b/qucs/components/spicefile.cpp
index ae000a462..3fbd7edef 100644
--- a/qucs/components/spicefile.cpp
+++ b/qucs/components/spicefile.cpp
@@ -154,7 +154,7 @@ void SpiceFile::createSymbol()
 QString SpiceFile::netlist()
 {
   if(Props.at(1)->Value.isEmpty())
-    return QString("");  // no ports, no subcircuit instance
+    return QString();  // no ports, no subcircuit instance
 
   QString s = "Sub:"+Name;   // SPICE netlist is subcircuit
   for (Port *pp : Ports)
diff --git a/qucs/components/subcirport.cpp b/qucs/components/subcirport.cpp
index 4dd6e34f2..4ce4455ce 100644
--- a/qucs/components/subcirport.cpp
+++ b/qucs/components/subcirport.cpp
@@ -104,20 +104,20 @@ Element* SubCirPort::info(QString& Name, char* &BitmapFile, bool getNewOne)
 // -------------------------------------------------------
 QString SubCirPort::netlist()
 {
-  return QString("");
+  return QString();
 }
 
 // -------------------------------------------------------
 QString SubCirPort::spice_netlist(bool)
 {
-    return QString("");
+    return QString();
 }
 
 // -------------------------------------------------------
 QString SubCirPort::vhdlCode(int)
 {
   if(Props.at(1)->Value != "out")
-    return QString("");
+    return QString();
 
   // Insert dummy buffer to avoid reading from an output port.
   QString s = "  net_out";
@@ -130,5 +130,5 @@ QString SubCirPort::vhdlCode(int)
 // -------------------------------------------------------
 QString SubCirPort::verilogCode(int)
 {
-  return QString("");
+  return QString();
 }
diff --git a/qucs/components/tff_SR.cpp b/qucs/components/tff_SR.cpp
index 00d604f99..c89eac4a5 100644
--- a/qucs/components/tff_SR.cpp
+++ b/qucs/components/tff_SR.cpp
@@ -177,7 +177,7 @@ QString tff_SR::verilogCode( int )
 
 QString tff_SR::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name;
     QString tmp_model = "model_" + Name;
diff --git a/qucs/components/vacomponent.cpp b/qucs/components/vacomponent.cpp
index 83d853065..5f9213d45 100644
--- a/qucs/components/vacomponent.cpp
+++ b/qucs/components/vacomponent.cpp
@@ -298,7 +298,7 @@ void vacomponent::createSymbol(QJsonObject json)
 
 QString vacomponent::spice_netlist(bool isXyce)
 {
-    if (isXyce) return QString("");
+    if (isXyce) return QString();
 
     QString s = SpiceModel + Name + " ";
     for(const auto pp: Ports) {
diff --git a/qucs/components/verilogfile.cpp b/qucs/components/verilogfile.cpp
index 00c6bd7ec..8d682ce80 100644
--- a/qucs/components/verilogfile.cpp
+++ b/qucs/components/verilogfile.cpp
@@ -97,7 +97,7 @@ QString Verilog_File::loadFile()
 
   QFile f(File);
   if(!f.open(QIODevice::ReadOnly))
-    return QString("");
+    return QString();
 
   QTextStream stream(&f);
   File = stream.readAll();   // QString is better for "find" function
diff --git a/qucs/components/vhdlfile.cpp b/qucs/components/vhdlfile.cpp
index 07ce89f38..e303b01a5 100644
--- a/qucs/components/vhdlfile.cpp
+++ b/qucs/components/vhdlfile.cpp
@@ -104,7 +104,7 @@ QString VHDL_File::loadFile()
 
   QFile f(File);
   if(!f.open(QIODevice::ReadOnly))
-    return QString("");
+    return QString();
 
   QTextStream stream(&f);
   File = stream.readAll();   // QString is better for "find" function
@@ -332,11 +332,11 @@ QString VHDL_File_Info::parsePorts(QString s, int j)
   Expr.setPattern("\\bport\\b");  // start of interface definition
   i = s.indexOf(Expr, j+1);
   if(i < 0)
-    return QString("");
+    return QString();
   // find opening (
   i = s.indexOf('(', i+4) + 1;
   if(i <= 0)
-    return QString("");
+    return QString();
 
   // find closing (
   p = i;
@@ -344,7 +344,7 @@ QString VHDL_File_Info::parsePorts(QString s, int j)
   do {
     j = s.indexOf(')', j+1);
     if(j < 0)
-      return QString("");
+      return QString();
     p = s.indexOf('(', p+1);
     if(p >= 0 && p > j) p = -1;
   } while (p >= 0);
@@ -395,11 +395,11 @@ QString VHDL_File_Info::parseGenerics(QString s, int j)
   Expr.setPattern("\\bgeneric\\b");
   i = s.indexOf(Expr, j+1);
   if(i < 0)
-    return QString("");
+    return QString();
   // find opening (
   i = s.indexOf('(', i+4) + 1;
   if(i <= 0)
-    return QString("");
+    return QString();
 
   // find closing (
   p = i;
@@ -407,7 +407,7 @@ QString VHDL_File_Info::parseGenerics(QString s, int j)
   do {
     j = s.indexOf(')', j+1);
     if(j < 0)
-      return QString("");
+      return QString();
     p = s.indexOf('(', p+1);
     if(p >= 0 && p > j) p = -1;
   } while (p >= 0);
diff --git a/qucs/dialogs/matchdialog.cpp b/qucs/dialogs/matchdialog.cpp
index 2b3f324ef..7caa09815 100644
--- a/qucs/dialogs/matchdialog.cpp
+++ b/qucs/dialogs/matchdialog.cpp
@@ -817,7 +817,7 @@ QString MatchDialog::calcMatchingLC(double r_real, double r_imag, double Z0,
           0, tr("Error"),
           tr("Real part of impedance must be greater zero,\nbut is %1 !")
               .arg(Zreal));
-      return QString(""); // matching not possible
+      return QString(); // matching not possible
     }
 
     // In high-Q circuits, Zreal often becomes somewhat about -1e-16
@@ -1303,7 +1303,7 @@ QString MatchDialog::calcDoubleStub(double r_real, double r_imag, double Z0,
   {
     QMessageBox::warning(0, tr("Error"),
                 tr("It is not possible to match this load using the double stub method"));
-    return QString("");
+    return QString();
   }
 
   // Stubs susceptance
@@ -1432,7 +1432,7 @@ QString MatchDialog::calcChebyLines(double r_real, double r_imag, double Z0,
     QMessageBox::warning(
         0, QObject::tr("Error"),
         QObject::tr("Chebyshev weighting for N>7 is not available"));
-    return QString("");
+    return QString();
   }
 
   QString laddercode;
diff --git a/qucs/extsimkernels/ngspice.cpp b/qucs/extsimkernels/ngspice.cpp
index c411d6ff9..cc20a9ec0 100644
--- a/qucs/extsimkernels/ngspice.cpp
+++ b/qucs/extsimkernels/ngspice.cpp
@@ -400,7 +400,7 @@ QString Ngspice::getParentSWPscript(Component *pc_swp, QString sim, bool before,
             }
         }
     }
-    return QString("");
+    return QString();
 }
 
 /*!
diff --git a/qucs/extsimkernels/spicecompat.cpp b/qucs/extsimkernels/spicecompat.cpp
index 8c14cf344..dfd5de75a 100644
--- a/qucs/extsimkernels/spicecompat.cpp
+++ b/qucs/extsimkernels/spicecompat.cpp
@@ -344,7 +344,7 @@ QString spicecompat::convert_sweep_type(const QString& sweep)
 {
     if (sweep=="lin") return QString("lin");
     if (sweep=="log") return QString("dec");
-    return QString("");
+    return QString();
 }
 
 /*!
diff --git a/qucs/qucs_actions.cpp b/qucs/qucs_actions.cpp
index b6f0e03a7..a4123f5e6 100644
--- a/qucs/qucs_actions.cpp
+++ b/qucs/qucs_actions.cpp
@@ -821,7 +821,7 @@ void QucsApp::slotShowLastNetlist()
 // Is called to start the text editor.
 void QucsApp::slotCallEditor()
 {
-  editFile(QString(""));
+  editFile(QString());
 }
 
 // ------------------------------------------------------------------------
diff --git a/qucs/spicecomponents/BJT_SPICE.cpp b/qucs/spicecomponents/BJT_SPICE.cpp
index 6439b6e06..1ed509e6d 100644
--- a/qucs/spicecomponents/BJT_SPICE.cpp
+++ b/qucs/spicecomponents/BJT_SPICE.cpp
@@ -183,7 +183,7 @@ Element* BJT_SPICE::infoPNP5(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString BJT_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString BJT_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/C_SPICE.cpp b/qucs/spicecomponents/C_SPICE.cpp
index 8097d3c8a..f530fcceb 100644
--- a/qucs/spicecomponents/C_SPICE.cpp
+++ b/qucs/spicecomponents/C_SPICE.cpp
@@ -106,7 +106,7 @@ Element* C_SPICE::info_C3(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString C_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString C_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/DIODE_SPICE.cpp b/qucs/spicecomponents/DIODE_SPICE.cpp
index c42f832cf..e56f750c7 100644
--- a/qucs/spicecomponents/DIODE_SPICE.cpp
+++ b/qucs/spicecomponents/DIODE_SPICE.cpp
@@ -111,7 +111,7 @@ Element* DIODE_SPICE::info_DIODE3(QString& Name, char* &BitmapFile, bool getNewO
 
 QString DIODE_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString DIODE_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/Icouple.cpp b/qucs/spicecomponents/Icouple.cpp
index 9ed3a4205..7d7e76543 100644
--- a/qucs/spicecomponents/Icouple.cpp
+++ b/qucs/spicecomponents/Icouple.cpp
@@ -97,7 +97,7 @@ Element* Icouple::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString Icouple::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString Icouple::spice_netlist(bool)
diff --git a/qucs/spicecomponents/K_SPICE.cpp b/qucs/spicecomponents/K_SPICE.cpp
index 131a412fe..c68a21013 100644
--- a/qucs/spicecomponents/K_SPICE.cpp
+++ b/qucs/spicecomponents/K_SPICE.cpp
@@ -72,7 +72,7 @@ Element* K_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString K_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString K_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/LTL_SPICE.cpp b/qucs/spicecomponents/LTL_SPICE.cpp
index f355dd8a6..65e3863ef 100644
--- a/qucs/spicecomponents/LTL_SPICE.cpp
+++ b/qucs/spicecomponents/LTL_SPICE.cpp
@@ -85,7 +85,7 @@ Element* LTL_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString LTL_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString LTL_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/LTRA_SPICE.cpp b/qucs/spicecomponents/LTRA_SPICE.cpp
index 3cfdd26d4..7e0651ba9 100644
--- a/qucs/spicecomponents/LTRA_SPICE.cpp
+++ b/qucs/spicecomponents/LTRA_SPICE.cpp
@@ -91,7 +91,7 @@ Element* LTRA_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString LTRA_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString LTRA_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/L_SPICE.cpp b/qucs/spicecomponents/L_SPICE.cpp
index fa7f71608..1fb50b1da 100644
--- a/qucs/spicecomponents/L_SPICE.cpp
+++ b/qucs/spicecomponents/L_SPICE.cpp
@@ -80,7 +80,7 @@ Element* L_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString L_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString L_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/MESFET_SPICE.cpp b/qucs/spicecomponents/MESFET_SPICE.cpp
index acf80ca41..539c234f2 100644
--- a/qucs/spicecomponents/MESFET_SPICE.cpp
+++ b/qucs/spicecomponents/MESFET_SPICE.cpp
@@ -83,7 +83,7 @@ Element* MESFET_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString MESFET_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString MESFET_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/MOS_SPICE.cpp b/qucs/spicecomponents/MOS_SPICE.cpp
index 5af21e2a0..7c33b985e 100644
--- a/qucs/spicecomponents/MOS_SPICE.cpp
+++ b/qucs/spicecomponents/MOS_SPICE.cpp
@@ -176,7 +176,7 @@ Element* MOS_SPICE::info_PX4pin(QString& Name, char* &BitmapFile, bool getNewOne
 
 QString MOS_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 void MOS_SPICE::createSymbol()
diff --git a/qucs/spicecomponents/NJF_SPICE.cpp b/qucs/spicecomponents/NJF_SPICE.cpp
index 716ba9457..f11150b5b 100644
--- a/qucs/spicecomponents/NJF_SPICE.cpp
+++ b/qucs/spicecomponents/NJF_SPICE.cpp
@@ -90,7 +90,7 @@ Element* NJF_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString NJF_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString NJF_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/NMOS_SPICE.cpp b/qucs/spicecomponents/NMOS_SPICE.cpp
index c559936b9..3e483754e 100644
--- a/qucs/spicecomponents/NMOS_SPICE.cpp
+++ b/qucs/spicecomponents/NMOS_SPICE.cpp
@@ -99,7 +99,7 @@ Element* NMOS_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString NMOS_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString NMOS_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/NPN_SPICE.cpp b/qucs/spicecomponents/NPN_SPICE.cpp
index 800d0fcf4..3844a98cd 100644
--- a/qucs/spicecomponents/NPN_SPICE.cpp
+++ b/qucs/spicecomponents/NPN_SPICE.cpp
@@ -91,7 +91,7 @@ Element* NPN_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString NPN_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString NPN_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/PJF_SPICE.cpp b/qucs/spicecomponents/PJF_SPICE.cpp
index 302b6e945..bd9fd03a0 100644
--- a/qucs/spicecomponents/PJF_SPICE.cpp
+++ b/qucs/spicecomponents/PJF_SPICE.cpp
@@ -90,7 +90,7 @@ Element* PJF_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString PJF_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString PJF_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/PMF_MESFET_SPICE.cpp b/qucs/spicecomponents/PMF_MESFET_SPICE.cpp
index 29d56ab9f..5339a4bb5 100644
--- a/qucs/spicecomponents/PMF_MESFET_SPICE.cpp
+++ b/qucs/spicecomponents/PMF_MESFET_SPICE.cpp
@@ -83,7 +83,7 @@ Element* PMF_MESFET_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne
 
 QString PMF_MESFET_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString PMF_MESFET_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/PMOS_SPICE.cpp b/qucs/spicecomponents/PMOS_SPICE.cpp
index c9c352e2a..bebc6896d 100644
--- a/qucs/spicecomponents/PMOS_SPICE.cpp
+++ b/qucs/spicecomponents/PMOS_SPICE.cpp
@@ -99,7 +99,7 @@ Element* PMOS_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString PMOS_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString PMOS_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/PNP_SPICE.cpp b/qucs/spicecomponents/PNP_SPICE.cpp
index 66b67e2e3..1d3f0f226 100644
--- a/qucs/spicecomponents/PNP_SPICE.cpp
+++ b/qucs/spicecomponents/PNP_SPICE.cpp
@@ -92,7 +92,7 @@ Element* PNP_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString PNP_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString PNP_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/R_SPICE.cpp b/qucs/spicecomponents/R_SPICE.cpp
index bc030024a..974b7e4fa 100644
--- a/qucs/spicecomponents/R_SPICE.cpp
+++ b/qucs/spicecomponents/R_SPICE.cpp
@@ -110,7 +110,7 @@ Element* R_SPICE::info_R3(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString R_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString R_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/S4Q_Ieqndef.cpp b/qucs/spicecomponents/S4Q_Ieqndef.cpp
index 09235513a..368014814 100644
--- a/qucs/spicecomponents/S4Q_Ieqndef.cpp
+++ b/qucs/spicecomponents/S4Q_Ieqndef.cpp
@@ -83,7 +83,7 @@ Element* S4Q_Ieqndef::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString S4Q_Ieqndef::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString S4Q_Ieqndef::spice_netlist(bool)
diff --git a/qucs/spicecomponents/S4Q_S.cpp b/qucs/spicecomponents/S4Q_S.cpp
index 0373bfc99..181a00e0a 100644
--- a/qucs/spicecomponents/S4Q_S.cpp
+++ b/qucs/spicecomponents/S4Q_S.cpp
@@ -90,7 +90,7 @@ Element* S4Q_S::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 //QString S4Q_S::netlist()
 //{
- //   return QString("");
+ //   return QString();
 //}
 
 QString S4Q_S::spice_netlist(bool)
diff --git a/qucs/spicecomponents/SDTF.cpp b/qucs/spicecomponents/SDTF.cpp
index c0fc3688e..62b6cb609 100644
--- a/qucs/spicecomponents/SDTF.cpp
+++ b/qucs/spicecomponents/SDTF.cpp
@@ -80,7 +80,7 @@ Element* SDTF::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SDTF::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString SDTF::spice_netlist(bool)
diff --git a/qucs/spicecomponents/UDRCTL_SPICE.cpp b/qucs/spicecomponents/UDRCTL_SPICE.cpp
index 3c46c938f..38bf675d9 100644
--- a/qucs/spicecomponents/UDRCTL_SPICE.cpp
+++ b/qucs/spicecomponents/UDRCTL_SPICE.cpp
@@ -89,7 +89,7 @@ Element* UDRCTL_SPICE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString UDRCTL_SPICE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString UDRCTL_SPICE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/XAPWL.cpp b/qucs/spicecomponents/XAPWL.cpp
index ca46ded6d..888fe8273 100644
--- a/qucs/spicecomponents/XAPWL.cpp
+++ b/qucs/spicecomponents/XAPWL.cpp
@@ -80,7 +80,7 @@ Element* XAPWL::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString XAPWL::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString XAPWL::spice_netlist(bool)
diff --git a/qucs/spicecomponents/core.cpp b/qucs/spicecomponents/core.cpp
index a5d456ea7..7b163ac82 100644
--- a/qucs/spicecomponents/core.cpp
+++ b/qucs/spicecomponents/core.cpp
@@ -87,7 +87,7 @@ Element* core::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString core::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString core::spice_netlist(bool)
diff --git a/qucs/spicecomponents/eNL.cpp b/qucs/spicecomponents/eNL.cpp
index da9f44b74..39a3271b6 100644
--- a/qucs/spicecomponents/eNL.cpp
+++ b/qucs/spicecomponents/eNL.cpp
@@ -79,7 +79,7 @@ Element* eNL::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString eNL::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString eNL::spice_netlist(bool)
diff --git a/qucs/spicecomponents/gNL.cpp b/qucs/spicecomponents/gNL.cpp
index 1ea4007a9..f218c0e1f 100644
--- a/qucs/spicecomponents/gNL.cpp
+++ b/qucs/spicecomponents/gNL.cpp
@@ -78,7 +78,7 @@ Element* gNL::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString gNL::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString gNL::spice_netlist(bool)
diff --git a/qucs/spicecomponents/iAmpMod.cpp b/qucs/spicecomponents/iAmpMod.cpp
index 161672a5e..9eaacd590 100644
--- a/qucs/spicecomponents/iAmpMod.cpp
+++ b/qucs/spicecomponents/iAmpMod.cpp
@@ -86,7 +86,7 @@ Element* iAmpMod::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString iAmpMod::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString iAmpMod::spice_netlist(bool)
diff --git a/qucs/spicecomponents/iPWL.cpp b/qucs/spicecomponents/iPWL.cpp
index ce534f137..966c2a365 100644
--- a/qucs/spicecomponents/iPWL.cpp
+++ b/qucs/spicecomponents/iPWL.cpp
@@ -87,7 +87,7 @@ Element* iPWL::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString iPWL::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString iPWL::spice_netlist(bool)
@@ -111,7 +111,7 @@ QString Line_8= Props.at(7)->Value;
 QString Line_9= Props.at(8)->Value;
 QString Line_10= Props.at(9)->Value;
 
-    s += QString("");
+    s += QString();
  
     if(  PWL.length()    > 0)    s += QString("%1").arg(PWL);
     if(  Line_2.length() > 0 )   s += QString("\n%1").arg(Line_2);
diff --git a/qucs/spicecomponents/iTRNOISE.cpp b/qucs/spicecomponents/iTRNOISE.cpp
index e382dffed..db3bbf302 100644
--- a/qucs/spicecomponents/iTRNOISE.cpp
+++ b/qucs/spicecomponents/iTRNOISE.cpp
@@ -95,7 +95,7 @@ Element* iTRNOISE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString iTRNOISE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString iTRNOISE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/incl_script.cpp b/qucs/spicecomponents/incl_script.cpp
index 8074fc88a..cc589deb3 100644
--- a/qucs/spicecomponents/incl_script.cpp
+++ b/qucs/spicecomponents/incl_script.cpp
@@ -80,6 +80,6 @@ Element* InclScript::info(QString& Name, char* &BitmapFile, bool getNewOne)
 QString InclScript::getExpression(bool)
 {
     if (isActive != COMP_IS_ACTIVE)
-        return QString("");
+        return QString();
     return Props.at(0)->Value+"\n";
 }
diff --git a/qucs/spicecomponents/incl_script.h b/qucs/spicecomponents/incl_script.h
index 4871a437c..41748c07c 100644
--- a/qucs/spicecomponents/incl_script.h
+++ b/qucs/spicecomponents/incl_script.h
@@ -30,9 +30,9 @@ class InclScript : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/isffm.cpp b/qucs/spicecomponents/isffm.cpp
index 01fb3304d..7325ffe0d 100644
--- a/qucs/spicecomponents/isffm.cpp
+++ b/qucs/spicecomponents/isffm.cpp
@@ -86,7 +86,7 @@ Element* iSffm::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString iSffm::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString iSffm::spice_netlist(bool)
diff --git a/qucs/spicecomponents/sp_func.cpp b/qucs/spicecomponents/sp_func.cpp
index 451886bd6..e8869a1d6 100644
--- a/qucs/spicecomponents/sp_func.cpp
+++ b/qucs/spicecomponents/sp_func.cpp
@@ -72,7 +72,7 @@ Element* SpiceFunc::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SpiceFunc::getExpression(bool)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_func.h b/qucs/spicecomponents/sp_func.h
index af6778f4c..f942921e9 100644
--- a/qucs/spicecomponents/sp_func.h
+++ b/qucs/spicecomponents/sp_func.h
@@ -31,9 +31,9 @@ class SpiceFunc : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_globalpar.cpp b/qucs/spicecomponents/sp_globalpar.cpp
index 608e80154..4cb3d4d52 100644
--- a/qucs/spicecomponents/sp_globalpar.cpp
+++ b/qucs/spicecomponents/sp_globalpar.cpp
@@ -72,7 +72,7 @@ Element* SpiceGlobalParam::info(QString& Name, char* &BitmapFile, bool getNewOne
 
 QString SpiceGlobalParam::getExpression(bool)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_globalpar.h b/qucs/spicecomponents/sp_globalpar.h
index 710170c96..aee5cbb11 100644
--- a/qucs/spicecomponents/sp_globalpar.h
+++ b/qucs/spicecomponents/sp_globalpar.h
@@ -32,9 +32,9 @@ class SpiceGlobalParam : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_ic.cpp b/qucs/spicecomponents/sp_ic.cpp
index 7e5ef9d81..c9f535fd6 100644
--- a/qucs/spicecomponents/sp_ic.cpp
+++ b/qucs/spicecomponents/sp_ic.cpp
@@ -71,7 +71,7 @@ Element* SpiceIC::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SpiceIC::getExpression(bool)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_ic.h b/qucs/spicecomponents/sp_ic.h
index 722a361dd..a6b4b6439 100644
--- a/qucs/spicecomponents/sp_ic.h
+++ b/qucs/spicecomponents/sp_ic.h
@@ -31,9 +31,9 @@ class SpiceIC : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_include.cpp b/qucs/spicecomponents/sp_include.cpp
index 2f23b689b..a8c6d6b62 100644
--- a/qucs/spicecomponents/sp_include.cpp
+++ b/qucs/spicecomponents/sp_include.cpp
@@ -77,7 +77,7 @@ Element* S4Q_Include::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString S4Q_Include::getSpiceLibrary()
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
     QString s;
     s.clear();
 
diff --git a/qucs/spicecomponents/sp_include.h b/qucs/spicecomponents/sp_include.h
index 2126b2dcb..e457cfda4 100644
--- a/qucs/spicecomponents/sp_include.h
+++ b/qucs/spicecomponents/sp_include.h
@@ -31,9 +31,9 @@ class S4Q_Include : public Component  {
   QString getSpiceLibrary();
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_lib.cpp b/qucs/spicecomponents/sp_lib.cpp
index 82074e31e..b50c2fc7f 100644
--- a/qucs/spicecomponents/sp_lib.cpp
+++ b/qucs/spicecomponents/sp_lib.cpp
@@ -73,7 +73,7 @@ Element* S4Q_Lib::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString S4Q_Lib::getSpiceLibrary()
 {
-  if (isActive != COMP_IS_ACTIVE) return QString("");
+  if (isActive != COMP_IS_ACTIVE) return QString();
   QString s;
   s.clear();
 
diff --git a/qucs/spicecomponents/sp_lib.h b/qucs/spicecomponents/sp_lib.h
index df40fc685..4104548d5 100644
--- a/qucs/spicecomponents/sp_lib.h
+++ b/qucs/spicecomponents/sp_lib.h
@@ -31,9 +31,9 @@ class S4Q_Lib : public Component  {
   QString getSpiceLibrary();
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_model.cpp b/qucs/spicecomponents/sp_model.cpp
index 23349d819..5f64e7ed4 100644
--- a/qucs/spicecomponents/sp_model.cpp
+++ b/qucs/spicecomponents/sp_model.cpp
@@ -78,7 +78,7 @@ Element* S4Q_Model::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString S4Q_Model::getSpiceModel()
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_model.h b/qucs/spicecomponents/sp_model.h
index 3b3cc433d..f9932b69f 100644
--- a/qucs/spicecomponents/sp_model.h
+++ b/qucs/spicecomponents/sp_model.h
@@ -31,9 +31,9 @@ class S4Q_Model : public Component  {
   QString getSpiceModel();
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_nodeset.cpp b/qucs/spicecomponents/sp_nodeset.cpp
index ef18e27c7..5762cc965 100644
--- a/qucs/spicecomponents/sp_nodeset.cpp
+++ b/qucs/spicecomponents/sp_nodeset.cpp
@@ -71,7 +71,7 @@ Element* SpiceNodeset::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SpiceNodeset::getExpression(bool)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_nodeset.h b/qucs/spicecomponents/sp_nodeset.h
index 3ef76130c..cadf0f454 100644
--- a/qucs/spicecomponents/sp_nodeset.h
+++ b/qucs/spicecomponents/sp_nodeset.h
@@ -31,9 +31,9 @@ class SpiceNodeset : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_nutmeg.cpp b/qucs/spicecomponents/sp_nutmeg.cpp
index 3d2f92b05..2179bf926 100644
--- a/qucs/spicecomponents/sp_nutmeg.cpp
+++ b/qucs/spicecomponents/sp_nutmeg.cpp
@@ -74,7 +74,7 @@ Element* NutmegEquation::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString NutmegEquation::getEquations(QString sim, QStringList &dep_vars)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     QRegularExpression sim_rx("^\\w+\\d+");
diff --git a/qucs/spicecomponents/sp_nutmeg.h b/qucs/spicecomponents/sp_nutmeg.h
index 8457202e7..e07e5df8f 100644
--- a/qucs/spicecomponents/sp_nutmeg.h
+++ b/qucs/spicecomponents/sp_nutmeg.h
@@ -31,9 +31,9 @@ class NutmegEquation : public Component  {
   QString getEquations(QString sim, QStringList &dep_vars);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_options.cpp b/qucs/spicecomponents/sp_options.cpp
index 15e881222..a423e2df7 100644
--- a/qucs/spicecomponents/sp_options.cpp
+++ b/qucs/spicecomponents/sp_options.cpp
@@ -73,7 +73,7 @@ Element* SpiceOptions::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SpiceOptions::getExpression(bool isXyce)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_options.h b/qucs/spicecomponents/sp_options.h
index 97dfdfe24..05100a5fa 100644
--- a/qucs/spicecomponents/sp_options.h
+++ b/qucs/spicecomponents/sp_options.h
@@ -32,9 +32,9 @@ class SpiceOptions : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/sp_parameter.cpp b/qucs/spicecomponents/sp_parameter.cpp
index 7c6906878..bbe819ff8 100644
--- a/qucs/spicecomponents/sp_parameter.cpp
+++ b/qucs/spicecomponents/sp_parameter.cpp
@@ -71,7 +71,7 @@ Element* SpiceParam::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString SpiceParam::getExpression(bool)
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
 
     QString s;
     s.clear();
diff --git a/qucs/spicecomponents/sp_parameter.h b/qucs/spicecomponents/sp_parameter.h
index c29c079f6..571614732 100644
--- a/qucs/spicecomponents/sp_parameter.h
+++ b/qucs/spicecomponents/sp_parameter.h
@@ -32,9 +32,9 @@ class SpiceParam : public Component  {
   QString getExpression(bool isXyce);
 
 protected:
-  QString vhdlCode(int) { return QString(""); }
-  QString verilogCode(int) { return QString(""); }
-  QString netlist() { return QString(""); }
+  QString vhdlCode(int) { return QString(); }
+  QString verilogCode(int) { return QString(); }
+  QString netlist() { return QString(); }
 };
 
 #endif
diff --git a/qucs/spicecomponents/spicegeneric.cpp b/qucs/spicecomponents/spicegeneric.cpp
index d88d38aef..7de862615 100644
--- a/qucs/spicecomponents/spicegeneric.cpp
+++ b/qucs/spicecomponents/spicegeneric.cpp
@@ -131,7 +131,7 @@ void SpiceGeneric::createSymbol()
 // ---------------------------------------------------
 QString SpiceGeneric::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString SpiceGeneric::spice_netlist(bool)
diff --git a/qucs/spicecomponents/spicelibcomp.cpp b/qucs/spicecomponents/spicelibcomp.cpp
index c0acf0eef..e89845403 100644
--- a/qucs/spicecomponents/spicelibcomp.cpp
+++ b/qucs/spicecomponents/spicelibcomp.cpp
@@ -241,7 +241,7 @@ QString SpiceLibComp::spice_netlist(bool)
 
 QString SpiceLibComp::getSpiceLibrary()
 {
-    if (isActive != COMP_IS_ACTIVE) return QString("");
+    if (isActive != COMP_IS_ACTIVE) return QString();
     QString f = misc::properAbsFileName(Props.at(0)->Value, containingSchematic);
     QString s = QString(".INCLUDE \"%1\"\n").arg(f);
     return s;
diff --git a/qucs/spicecomponents/src_eqndef.cpp b/qucs/spicecomponents/src_eqndef.cpp
index 666745d7c..eaf0ec426 100644
--- a/qucs/spicecomponents/src_eqndef.cpp
+++ b/qucs/spicecomponents/src_eqndef.cpp
@@ -64,7 +64,7 @@ Element* Src_eqndef::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString Src_eqndef::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString Src_eqndef::spice_netlist(bool)
diff --git a/qucs/spicecomponents/vAmpMod.cpp b/qucs/spicecomponents/vAmpMod.cpp
index bcd47fada..ac0b35927 100644
--- a/qucs/spicecomponents/vAmpMod.cpp
+++ b/qucs/spicecomponents/vAmpMod.cpp
@@ -88,7 +88,7 @@ Element* vAmpMod::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString vAmpMod::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString vAmpMod::spice_netlist(bool)
diff --git a/qucs/spicecomponents/vPWL.cpp b/qucs/spicecomponents/vPWL.cpp
index 45c25ac58..f42946ad9 100644
--- a/qucs/spicecomponents/vPWL.cpp
+++ b/qucs/spicecomponents/vPWL.cpp
@@ -86,7 +86,7 @@ Element* vPWL::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString vPWL::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString vPWL::spice_netlist(bool)
@@ -110,7 +110,7 @@ QString Line_8= Props.at(7)->Value;
 QString Line_9= Props.at(8)->Value;
 QString Line_10= Props.at(9)->Value;
 
-    s += QString("");
+    s += QString();
   
     if(  PWL.length()  > 0)        s += QString("%1").arg(PWL);
     if(  Line_2.length() > 0 )     s += QString("\n%1").arg(Line_2);
diff --git a/qucs/spicecomponents/vTRNOISE.cpp b/qucs/spicecomponents/vTRNOISE.cpp
index 910a7ed48..8de541635 100644
--- a/qucs/spicecomponents/vTRNOISE.cpp
+++ b/qucs/spicecomponents/vTRNOISE.cpp
@@ -91,7 +91,7 @@ Element* vTRNOISE::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString vTRNOISE::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString vTRNOISE::spice_netlist(bool)
diff --git a/qucs/spicecomponents/vTRRANDOM.cpp b/qucs/spicecomponents/vTRRANDOM.cpp
index 9628924a2..a511937c3 100644
--- a/qucs/spicecomponents/vTRRANDOM.cpp
+++ b/qucs/spicecomponents/vTRRANDOM.cpp
@@ -93,7 +93,7 @@ Element* vTRRANDOM::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString vTRRANDOM::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString vTRRANDOM::spice_netlist(bool)
diff --git a/qucs/spicecomponents/vsffm.cpp b/qucs/spicecomponents/vsffm.cpp
index de576768c..2468a1b66 100644
--- a/qucs/spicecomponents/vsffm.cpp
+++ b/qucs/spicecomponents/vsffm.cpp
@@ -86,7 +86,7 @@ Element* vSffm::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString vSffm::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString vSffm::spice_netlist(bool)
diff --git a/qucs/spicecomponents/xsp_cmlib.cpp b/qucs/spicecomponents/xsp_cmlib.cpp
index d265ec623..cbef493e4 100644
--- a/qucs/spicecomponents/xsp_cmlib.cpp
+++ b/qucs/spicecomponents/xsp_cmlib.cpp
@@ -88,7 +88,7 @@ QString XSP_CMlib::getSpiceInit()
 
 QString XSP_CMlib::spice_netlist()
 {
-    return QString("");
+    return QString();
 }
 
 
diff --git a/qucs/spicecomponents/xsp_codemodel.cpp b/qucs/spicecomponents/xsp_codemodel.cpp
index 7bc21093d..c47dd34be 100644
--- a/qucs/spicecomponents/xsp_codemodel.cpp
+++ b/qucs/spicecomponents/xsp_codemodel.cpp
@@ -71,7 +71,7 @@ Element* XSP_CodeModel::info(QString& Name, char* &BitmapFile, bool getNewOne)
 
 QString XSP_CodeModel::spice_netlist()
 {
-    return QString("");
+    return QString();
 }
 
 
diff --git a/qucs/spicecomponents/xspicegeneric.cpp b/qucs/spicecomponents/xspicegeneric.cpp
index 10b855408..5ff748eae 100644
--- a/qucs/spicecomponents/xspicegeneric.cpp
+++ b/qucs/spicecomponents/xspicegeneric.cpp
@@ -142,7 +142,7 @@ void XspiceGeneric::createSymbol()
 // ---------------------------------------------------
 QString XspiceGeneric::netlist()
 {
-    return QString("");
+    return QString();
 }
 
 QString XspiceGeneric::spice_netlist(bool)