diff --git a/FWCore/ParameterSet/interface/ANDGroupDescription.h b/FWCore/ParameterSet/interface/ANDGroupDescription.h
index 697696a8d90a8..02c87c8a8db4c 100644
--- a/FWCore/ParameterSet/interface/ANDGroupDescription.h
+++ b/FWCore/ParameterSet/interface/ANDGroupDescription.h
@@ -29,43 +29,43 @@ namespace edm {
     ANDGroupDescription(std::unique_ptr<ParameterDescriptionNode> node_left,
                         std::unique_ptr<ParameterDescriptionNode> node_right);
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ANDGroupDescription(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool hasNestedContent_() const {
+    bool hasNestedContent_() const override {
       return true;
     }
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
 
     void throwIfDuplicateLabels(std::set<std::string> const& labelsLeft,
diff --git a/FWCore/ParameterSet/interface/AllowedLabelsDescription.h b/FWCore/ParameterSet/interface/AllowedLabelsDescription.h
index 9c763f694ab77..372462f9482a2 100644
--- a/FWCore/ParameterSet/interface/AllowedLabelsDescription.h
+++ b/FWCore/ParameterSet/interface/AllowedLabelsDescription.h
@@ -34,15 +34,15 @@ namespace edm {
     {
     }
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new AllowedLabelsDescription(*this);
     }
 
   private:
 
-    virtual void validateAllowedLabel_(std::string const& allowedLabel,
-                                       ParameterSet & pset,
-                                       std::set<std::string> & validatedLabels) const {
+    void validateAllowedLabel_(std::string const& allowedLabel,
+                               ParameterSet & pset,
+                               std::set<std::string> & validatedLabels) const override {
       if (pset.existsAs<T>(allowedLabel, isTracked())) {
         validatedLabels.insert(allowedLabel);
       }
@@ -67,17 +67,17 @@ namespace edm {
                              ParameterSetDescription const& value,
                              bool isTracked);
 
-    virtual ParameterDescriptionNode* clone() const;
+    ParameterDescriptionNode* clone() const override;
 
   private:
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & helper) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & helper) const override;
 
-    virtual void validateAllowedLabel_(std::string const& allowedLabel,
-                                       ParameterSet & pset,
-                                       std::set<std::string> & validatedLabels) const;
+    void validateAllowedLabel_(std::string const& allowedLabel,
+                               ParameterSet & pset,
+                               std::set<std::string> & validatedLabels) const override;
 
     value_ptr<ParameterSetDescription> psetDesc_;
   };
@@ -100,17 +100,17 @@ namespace edm {
                              ParameterSetDescription const& value,
                              bool isTracked);
 
-    virtual ParameterDescriptionNode* clone() const;
+    ParameterDescriptionNode* clone() const override;
 
   private:
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & helper) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & helper) const override;
 
-    virtual void validateAllowedLabel_(std::string const& allowedLabel,
-                                       ParameterSet & pset,
-                                       std::set<std::string> & validatedLabels) const;
+    void validateAllowedLabel_(std::string const& allowedLabel,
+                               ParameterSet & pset,
+                               std::set<std::string> & validatedLabels) const override;
 
     value_ptr<ParameterSetDescription> psetDesc_;
   };
diff --git a/FWCore/ParameterSet/interface/AllowedLabelsDescriptionBase.h b/FWCore/ParameterSet/interface/AllowedLabelsDescriptionBase.h
index c132d9b6007c2..56fe118f8c420 100644
--- a/FWCore/ParameterSet/interface/AllowedLabelsDescriptionBase.h
+++ b/FWCore/ParameterSet/interface/AllowedLabelsDescriptionBase.h
@@ -16,7 +16,7 @@ namespace edm {
   class AllowedLabelsDescriptionBase : public ParameterDescriptionNode {
   public:
 
-    virtual ~AllowedLabelsDescriptionBase();
+    ~AllowedLabelsDescriptionBase() override;
 
     ParameterTypes type() const { return type_; }
     bool isTracked() const { return isTracked_; }
@@ -33,36 +33,36 @@ namespace edm {
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     virtual void validateAllowedLabel_(std::string const& allowedLabel,
                                        ParameterSet & pset,
diff --git a/FWCore/ParameterSet/interface/EmptyGroupDescription.h b/FWCore/ParameterSet/interface/EmptyGroupDescription.h
index 7f084b07b5598..bc80d4d6e7e95 100644
--- a/FWCore/ParameterSet/interface/EmptyGroupDescription.h
+++ b/FWCore/ParameterSet/interface/EmptyGroupDescription.h
@@ -16,35 +16,35 @@ namespace edm {
   public:
     EmptyGroupDescription();
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new EmptyGroupDescription(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
   };
 }
 #endif
diff --git a/FWCore/ParameterSet/interface/IfExistsDescription.h b/FWCore/ParameterSet/interface/IfExistsDescription.h
index 5cb12dc719ab4..6d939e0aa85d9 100644
--- a/FWCore/ParameterSet/interface/IfExistsDescription.h
+++ b/FWCore/ParameterSet/interface/IfExistsDescription.h
@@ -29,43 +29,43 @@ namespace edm {
     IfExistsDescription(std::unique_ptr<ParameterDescriptionNode> node_left,
                         std::unique_ptr<ParameterDescriptionNode> node_right);
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new IfExistsDescription(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool hasNestedContent_() const {
+    bool hasNestedContent_() const override {
       return true;
     }
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     void throwIfDuplicateLabels(std::set<std::string> const& labelsLeft,
                                 std::set<std::string> const& labelsRight) const;
diff --git a/FWCore/ParameterSet/interface/ORGroupDescription.h b/FWCore/ParameterSet/interface/ORGroupDescription.h
index 1aeeb00dd293e..aabcd1d4ed178 100644
--- a/FWCore/ParameterSet/interface/ORGroupDescription.h
+++ b/FWCore/ParameterSet/interface/ORGroupDescription.h
@@ -29,43 +29,43 @@ namespace edm {
     ORGroupDescription(std::unique_ptr<ParameterDescriptionNode> node_left,
                        std::unique_ptr<ParameterDescriptionNode> node_right);
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ORGroupDescription(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool hasNestedContent_() const {
+    bool hasNestedContent_() const override {
       return true;
     }
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     void throwIfDuplicateLabels(std::set<std::string> const& labelsLeft,
                                 std::set<std::string> const& labelsRight) const;
diff --git a/FWCore/ParameterSet/interface/ParameterDescription.h b/FWCore/ParameterSet/interface/ParameterDescription.h
index a7dc630294d70..4270313a78aad 100644
--- a/FWCore/ParameterSet/interface/ParameterDescription.h
+++ b/FWCore/ParameterSet/interface/ParameterDescription.h
@@ -160,9 +160,9 @@ namespace edm {
       value_() {
     }
 
-    virtual ~ParameterDescription() { }
+    ~ParameterDescription() override { }
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ParameterDescription(*this);
     }
 
@@ -170,28 +170,28 @@ namespace edm {
 
   private:
 
-    virtual bool exists_(ParameterSet const& pset) const {
+    bool exists_(ParameterSet const& pset) const override {
       return pset.existsAs<T>(label(), isTracked());
     }
 
-    virtual bool hasNestedContent_() const {
+    bool hasNestedContent_() const override {
       if (!hasDefault()) return false;
       return writeParameterValue::hasNestedContent(value_);
     }
 
-    virtual void writeCfi_(std::ostream& os, int indentation) const {
+    void writeCfi_(std::ostream& os, int indentation) const override {
       writeParameterValue::writeValue(os, indentation, value_, writeParameterValue::CFI);
     }
 
-    virtual void writeDoc_(std::ostream& os, int indentation) const {
+    void writeDoc_(std::ostream& os, int indentation) const override {
       writeParameterValue::writeValue(os, indentation, value_, writeParameterValue::DOC);
     }
 
-    virtual bool exists_(ParameterSet const& pset, bool isTracked) const {
+    bool exists_(ParameterSet const& pset, bool isTracked) const override {
       return pset.existsAs<T>(label(), isTracked);
     }
 
-    virtual void insertDefault_(ParameterSet& pset) const {
+    void insertDefault_(ParameterSet& pset) const override {
       if (isTracked()) {
         pset.addParameter(label(), value_);
       }
@@ -218,40 +218,40 @@ namespace edm {
                          bool isTracked,
                          Comment const& iComment = Comment());
 
-    virtual ~ParameterDescription();
+    ~ParameterDescription() override;
 
-    virtual ParameterSetDescription const* parameterSetDescription() const;
-    virtual ParameterSetDescription * parameterSetDescription();
+    ParameterSetDescription const* parameterSetDescription() const override;
+    ParameterSetDescription * parameterSetDescription() override;
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ParameterDescription(*this);
     }
 
   private:
 
-    virtual void validate_(ParameterSet& pset,
-                           std::set<std::string>& validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet& pset,
+                   std::set<std::string>& validatedLabels,
+                   bool optional) const override;
 
-    virtual void printDefault_(std::ostream& os,
-                                 bool writeToCfi,
-                                 DocFormatHelper& dfh) const;
+    void printDefault_(std::ostream& os,
+                       bool writeToCfi,
+                       DocFormatHelper& dfh) const override;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
-    virtual void printNestedContent_(std::ostream& os,
-                                     bool optional,
-                                     DocFormatHelper& dfh) const;
+    void printNestedContent_(std::ostream& os,
+                             bool optional,
+                             DocFormatHelper& dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual void writeCfi_(std::ostream& os, int indentation) const;
+    void writeCfi_(std::ostream& os, int indentation) const override;
 
-    virtual void writeDoc_(std::ostream& os, int indentation) const;
+    void writeDoc_(std::ostream& os, int indentation) const override;
 
-    virtual bool exists_(ParameterSet const& pset, bool isTracked) const;
+    bool exists_(ParameterSet const& pset, bool isTracked) const override;
 
-    virtual void insertDefault_(ParameterSet& pset) const;
+    void insertDefault_(ParameterSet& pset) const override;
 
     value_ptr<ParameterSetDescription> psetDesc_;
   };
@@ -283,12 +283,12 @@ namespace edm {
                          bool isTracked,
                          Comment const& iComment = Comment());
 
-    virtual ~ParameterDescription();
+    ~ParameterDescription() override;
 
-    virtual ParameterSetDescription const* parameterSetDescription() const;
-    virtual ParameterSetDescription * parameterSetDescription();
+    ParameterSetDescription const* parameterSetDescription() const override;
+    ParameterSetDescription * parameterSetDescription() override;
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ParameterDescription(*this);
     }
 
@@ -296,29 +296,29 @@ namespace edm {
 
   private:
 
-    virtual void validate_(ParameterSet& pset,
-                           std::set<std::string>& validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet& pset,
+                   std::set<std::string>& validatedLabels,
+                   bool optional) const override;
 
-    virtual void printDefault_(std::ostream& os,
-                               bool writeToCfi,
-                               DocFormatHelper& dfh) const;
+    void printDefault_(std::ostream& os,
+                       bool writeToCfi,
+                       DocFormatHelper& dfh) const override;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
-    virtual void printNestedContent_(std::ostream& os,
-                                     bool optional,
-                                     DocFormatHelper& dfh) const;
+    void printNestedContent_(std::ostream& os,
+                             bool optional,
+                             DocFormatHelper& dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual void writeCfi_(std::ostream& os, int indentation) const;
+    void writeCfi_(std::ostream& os, int indentation) const override;
 
-    virtual void writeDoc_(std::ostream& os, int indentation) const;
+    void writeDoc_(std::ostream& os, int indentation) const override;
 
-    virtual bool exists_(ParameterSet const& pset, bool isTracked) const;
+    bool exists_(ParameterSet const& pset, bool isTracked) const override;
 
-    virtual void insertDefault_(ParameterSet& pset) const;
+    void insertDefault_(ParameterSet& pset) const override;
 
     static void writeOneElementToCfi(ParameterSet const& pset,
                                      std::ostream& os,
diff --git a/FWCore/ParameterSet/interface/ParameterDescriptionBase.h b/FWCore/ParameterSet/interface/ParameterDescriptionBase.h
index a0937c8c802d4..c401b4e356f20 100644
--- a/FWCore/ParameterSet/interface/ParameterDescriptionBase.h
+++ b/FWCore/ParameterSet/interface/ParameterDescriptionBase.h
@@ -33,15 +33,15 @@ namespace edm {
   class ParameterDescriptionBase : public ParameterDescriptionNode 
   {
   public:
-    virtual ~ParameterDescriptionBase();
+    ~ParameterDescriptionBase() override;
 
     std::string const& label() const { return label_; }
     ParameterTypes type() const { return type_; }
     bool isTracked() const { return isTracked_; }
     bool hasDefault() const { return hasDefault_; }
 
-    virtual ParameterSetDescription const* parameterSetDescription() const { return 0; }
-    virtual ParameterSetDescription * parameterSetDescription() { return 0; }
+    virtual ParameterSetDescription const* parameterSetDescription() const { return nullptr; }
+    virtual ParameterSetDescription * parameterSetDescription() { return nullptr; }
 
   protected:
     void throwParameterWrongTrackiness() const;
@@ -64,39 +64,39 @@ namespace edm {
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     virtual void writeCfi_(std::ostream & os, int indentation) const = 0;
 
     virtual void writeDoc_(std::ostream & os, int indentation) const = 0;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
     virtual void printDefault_(std::ostream & os,
-                                 bool writeToCfi,
-                                 DocFormatHelper & dfh) const;
+                               bool writeToCfi,
+                               DocFormatHelper & dfh) const;
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
     using ParameterDescriptionNode::exists_;
     virtual bool exists_(ParameterSet const& pset, bool isTracked) const = 0;
diff --git a/FWCore/ParameterSet/interface/ParameterSetDescriptionFiller.h b/FWCore/ParameterSet/interface/ParameterSetDescriptionFiller.h
index 4645ad6e319a0..c08559c34b210 100644
--- a/FWCore/ParameterSet/interface/ParameterSetDescriptionFiller.h
+++ b/FWCore/ParameterSet/interface/ParameterSetDescriptionFiller.h
@@ -35,16 +35,16 @@ namespace edm {
   public:
     ParameterSetDescriptionFiller() {}
 
-    virtual void fill(ConfigurationDescriptions & descriptions) const {
+    void fill(ConfigurationDescriptions & descriptions) const override {
       T::fillDescriptions(descriptions);
       T::prevalidate(descriptions);
     }
 
-    virtual const std::string& baseType() const {
+    const std::string& baseType() const override {
       return T::baseType();
     }
 
-    virtual const std::string& extendedBaseType() const {
+    const std::string& extendedBaseType() const override {
       const T* type = nullptr;
       return ParameterSetDescriptionFillerBase::extendedBaseType(type);
     }
@@ -130,7 +130,7 @@ namespace edm {
 
     // If T has a fillDescriptions function then just call that, otherwise
     // put in an "unknown description" as a default.
-    virtual void fill(ConfigurationDescriptions & descriptions) const {
+    void fill(ConfigurationDescriptions & descriptions) const override {
       std::conditional_t<edm::fillDetails::has_fillDescriptions_function<T>::value,
                          edm::fillDetails::DoFillDescriptions<T>,
                          edm::fillDetails::DoFillAsUnknown<T>> fill_descriptions;
@@ -140,11 +140,11 @@ namespace edm {
       //prevalidateService(descriptions);
     }
 
-    virtual const std::string& baseType() const {
+    const std::string& baseType() const override {
       return kBaseForService;
     }
 
-    virtual const std::string& extendedBaseType() const {
+    const std::string& extendedBaseType() const override {
       return kEmpty;
     }
 
@@ -162,7 +162,7 @@ namespace edm {
 
     // If T has a fillDescriptions function then just call that, otherwise
     // put in an "unknown description" as a default.
-    virtual void fill(ConfigurationDescriptions & descriptions) const {
+    void fill(ConfigurationDescriptions & descriptions) const override {
       std::conditional_t<edm::fillDetails::has_fillDescriptions_function<T>::value,
                          edm::fillDetails::DoFillDescriptions<T>,
                          edm::fillDetails::DoFillAsUnknown<T>> fill_descriptions;
@@ -174,11 +174,11 @@ namespace edm {
       prevalidate(descriptions);
     }
 
-    virtual const std::string& baseType() const {
+    const std::string& baseType() const override {
       return kBaseForESSource;
     }
 
-    virtual const std::string& extendedBaseType() const {
+    const std::string& extendedBaseType() const override {
       return kEmpty;
     }
 
@@ -195,7 +195,7 @@ namespace edm {
 
     // If T has a fillDescriptions function then just call that, otherwise
     // put in an "unknown description" as a default.
-    virtual void fill(ConfigurationDescriptions & descriptions) const {
+    void fill(ConfigurationDescriptions & descriptions) const override {
       std::conditional_t<edm::fillDetails::has_fillDescriptions_function<T>::value,
                          edm::fillDetails::DoFillDescriptions<T>,
                          edm::fillDetails::DoFillAsUnknown<T>> fill_descriptions;
@@ -207,11 +207,11 @@ namespace edm {
       prevalidate(descriptions);
     }
 
-    virtual const std::string& baseType() const {
+    const std::string& baseType() const override {
       return kBaseForESProducer;
     }
 
-    virtual const std::string& extendedBaseType() const {
+    const std::string& extendedBaseType() const override {
       return kEmpty;
     }
 
diff --git a/FWCore/ParameterSet/interface/ParameterSwitch.h b/FWCore/ParameterSet/interface/ParameterSwitch.h
index cd2dc28d96e2f..5acc79e2ea786 100644
--- a/FWCore/ParameterSet/interface/ParameterSwitch.h
+++ b/FWCore/ParameterSet/interface/ParameterSwitch.h
@@ -38,24 +38,24 @@ namespace edm {
       }
     }
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ParameterSwitch(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const {
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override {
 
       std::set<std::string> caseLabels;
       std::set<ParameterTypes> caseParameterTypes;
       std::set<ParameterTypes> caseWildcardTypes;
       for_all(cases_, std::bind(&ParameterSwitch::checkCaseLabels,
-                                  std::placeholders::_1,
-                                  std::ref(caseLabels),
-                                  std::ref(caseParameterTypes),
-                                  std::ref(caseWildcardTypes)));
+                                std::placeholders::_1,
+                                std::ref(caseLabels),
+                                std::ref(caseParameterTypes),
+                                std::ref(caseWildcardTypes)));
 
       insertAndCheckLabels(switch_.label(),
                            usedLabels,
@@ -72,9 +72,9 @@ namespace edm {
       }
     }
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const {
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override {
 
       switch_.validate(pset, validatedLabels, optional);
       if (switch_.exists(pset)) {
@@ -109,10 +109,10 @@ namespace edm {
       }
     }
 
-    virtual void writeCfi_(std::ostream & os,
-                          bool & startWithComma,
-                          int indentation,
-                          bool & wroteSomething) const {
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override {
       switch_.writeCfi(os, startWithComma, indentation, wroteSomething);
 
       typename CaseMap::const_iterator selectedCase = cases_.find(switch_.getDefaultValue());
@@ -121,27 +121,27 @@ namespace edm {
       }
     }
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const {
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override {
       printBase(os, optional, writeToCfi, dfh, switch_.label(), switch_.isTracked(), parameterTypeEnumToString(switch_.type()));
     }
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const {
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override {
 
       DocFormatHelper new_dfh(dfh);
       printNestedContentBase(os, dfh, new_dfh, switch_.label());
 
       switch_.print(os, optional, true, new_dfh);
       for_all(cases_, std::bind(&ParameterSwitchBase::printCaseT<T>,
-                                  std::placeholders::_1,
-                                  std::ref(os),
-                                  optional,
-                                  std::ref(new_dfh),
-                                  std::cref(switch_.label())));
+                                std::placeholders::_1,
+                                std::ref(os),
+                                optional,
+                                std::ref(new_dfh),
+                                std::cref(switch_.label())));
 
       new_dfh.setPass(1);
       new_dfh.setCounter(0);
@@ -168,7 +168,7 @@ namespace edm {
                                   std::cref(switch_.label())));
     }
 
-    virtual bool exists_(ParameterSet const& pset) const { return switch_.exists(pset); }
+    bool exists_(ParameterSet const& pset) const override { return switch_.exists(pset); }
 
     static void checkCaseLabels(std::pair<T, edm::value_ptr<ParameterDescriptionNode> > const& thePair,
                                 std::set<std::string> & labels,
diff --git a/FWCore/ParameterSet/interface/ParameterSwitchBase.h b/FWCore/ParameterSet/interface/ParameterSwitchBase.h
index c94f2675003ca..7c22517ae0741 100644
--- a/FWCore/ParameterSet/interface/ParameterSwitchBase.h
+++ b/FWCore/ParameterSet/interface/ParameterSwitchBase.h
@@ -15,7 +15,7 @@ namespace edm {
 
   class ParameterSwitchBase : public ParameterDescriptionNode {
   public:
-    virtual ~ParameterSwitchBase();
+    ~ParameterSwitchBase() override;
 
   protected:
     void insertAndCheckLabels(std::string const& switchLabel,
@@ -23,10 +23,10 @@ namespace edm {
                               std::set<std::string> & labels) const;
 
     void insertAndCheckTypes(ParameterTypes switchType,
-                      std::set<ParameterTypes> const& caseParameterTypes,
-                      std::set<ParameterTypes> const& caseWildcardTypes,
-                      std::set<ParameterTypes> & parameterTypes,
-		      std::set<ParameterTypes> & wildcardTypes) const;
+                             std::set<ParameterTypes> const& caseParameterTypes,
+                             std::set<ParameterTypes> const& caseWildcardTypes,
+                             std::set<ParameterTypes> & parameterTypes,
+                             std::set<ParameterTypes> & wildcardTypes) const;
 
     void throwDuplicateCaseValues(std::string const& switchLabel) const;
 
@@ -42,7 +42,7 @@ namespace edm {
                    bool isTracked,
                    std::string const& typeString) const;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
     void printNestedContentBase(std::ostream & os,
                                 DocFormatHelper & dfh,
@@ -78,9 +78,9 @@ namespace edm {
                           DocFormatHelper & dfh,
                           std::string const& switchLabel);
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
   };
 }
diff --git a/FWCore/ParameterSet/interface/ParameterWildcard.h b/FWCore/ParameterSet/interface/ParameterWildcard.h
index 448941e5a4c04..5faa8c72c3d34 100644
--- a/FWCore/ParameterSet/interface/ParameterWildcard.h
+++ b/FWCore/ParameterSet/interface/ParameterWildcard.h
@@ -33,30 +33,30 @@ namespace edm {
       throwIfInvalidPattern(pattern);
     }
 
-    virtual ~ParameterWildcard() { }
+    ~ParameterWildcard() override { }
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new ParameterWildcard(*this);
     }
 
   private:
    
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const {
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override {
 
       std::vector<std::string> parameterNames  = pset.getParameterNamesForType<T>(isTracked());
       validateMatchingNames(parameterNames, validatedLabels, optional);
 
     }
 
-    virtual bool exists_(ParameterSet const& pset) const {
+    bool exists_(ParameterSet const& pset) const override {
 
       if (criteria() == RequireZeroOrMore) return true;
 
       std::vector<std::string> parameterNames  = pset.getParameterNamesForType<T>(isTracked());
 
-      if (criteria() == RequireAtLeastOne) return parameterNames.size() >= 1U;
+      if (criteria() == RequireAtLeastOne) return !parameterNames.empty();
       return parameterNames.size() == 1U;
     }
 
@@ -76,23 +76,23 @@ namespace edm {
     ParameterWildcard(char const* pattern, WildcardValidationCriteria criteria, bool isTracked,
                       ParameterSetDescription const& desc);
 
-    virtual ~ParameterWildcard();
+    ~ParameterWildcard() override;
 
-    virtual ParameterDescriptionNode* clone() const;
+    ParameterDescriptionNode* clone() const override;
 
   private:
    
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & helper) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & helper) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
     void validateDescription(std::string const& parameterName, ParameterSet & pset) const;
 
@@ -112,23 +112,23 @@ namespace edm {
     ParameterWildcard(char const* pattern, WildcardValidationCriteria criteria, bool isTracked,
                       ParameterSetDescription const& desc);
 
-    virtual ~ParameterWildcard();
+    ~ParameterWildcard() override;
 
-    virtual ParameterDescriptionNode* clone() const;
+    ParameterDescriptionNode* clone() const override;
 
   private:
    
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual bool hasNestedContent_() const;
+    bool hasNestedContent_() const override;
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
     void validatePSetVector(std::string const& parameterName, ParameterSet & pset) const;
 
diff --git a/FWCore/ParameterSet/interface/ParameterWildcardBase.h b/FWCore/ParameterSet/interface/ParameterWildcardBase.h
index 2780ef7fef927..8e5443b1826ed 100644
--- a/FWCore/ParameterSet/interface/ParameterWildcardBase.h
+++ b/FWCore/ParameterSet/interface/ParameterWildcardBase.h
@@ -24,7 +24,7 @@ namespace edm {
   class ParameterWildcardBase : public ParameterDescriptionNode 
   {
   public:
-    virtual ~ParameterWildcardBase();
+    ~ParameterWildcardBase() override;
 
     ParameterTypes type() const { return type_; }
     bool isTracked() const { return isTracked_; }
@@ -45,23 +45,23 @@ namespace edm {
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     ParameterTypes type_;
     bool isTracked_;
diff --git a/FWCore/ParameterSet/interface/XORGroupDescription.h b/FWCore/ParameterSet/interface/XORGroupDescription.h
index afbf4b1fc888b..ab49cf290e7d9 100644
--- a/FWCore/ParameterSet/interface/XORGroupDescription.h
+++ b/FWCore/ParameterSet/interface/XORGroupDescription.h
@@ -29,43 +29,43 @@ namespace edm {
     XORGroupDescription(std::unique_ptr<ParameterDescriptionNode> node_left,
                         std::unique_ptr<ParameterDescriptionNode> node_right);
 
-    virtual ParameterDescriptionNode* clone() const {
+    ParameterDescriptionNode* clone() const override {
       return new XORGroupDescription(*this);
     }
 
   private:
 
-    virtual void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
-                                            std::set<ParameterTypes> & parameterTypes,
-                                            std::set<ParameterTypes> & wildcardTypes) const;
+    void checkAndGetLabelsAndTypes_(std::set<std::string> & usedLabels,
+                                    std::set<ParameterTypes> & parameterTypes,
+                                    std::set<ParameterTypes> & wildcardTypes) const override;
 
-    virtual void validate_(ParameterSet & pset,
-                           std::set<std::string> & validatedLabels,
-                           bool optional) const;
+    void validate_(ParameterSet & pset,
+                   std::set<std::string> & validatedLabels,
+                   bool optional) const override;
 
-    virtual void writeCfi_(std::ostream & os,
-                           bool & startWithComma,
-                           int indentation,
-                           bool & wroteSomething) const;
+    void writeCfi_(std::ostream & os,
+                   bool & startWithComma,
+                   int indentation,
+                   bool & wroteSomething) const override;
 
-    virtual void print_(std::ostream & os,
-                        bool optional,
-                        bool writeToCfi,
-                        DocFormatHelper & dfh) const;
+    void print_(std::ostream & os,
+                bool optional,
+                bool writeToCfi,
+                DocFormatHelper & dfh) const override;
 
-    virtual bool hasNestedContent_() const {
+    bool hasNestedContent_() const override {
       return true;
     }
 
-    virtual void printNestedContent_(std::ostream & os,
-                                     bool optional,
-                                     DocFormatHelper & dfh) const;
+    void printNestedContent_(std::ostream & os,
+                             bool optional,
+                             DocFormatHelper & dfh) const override;
 
-    virtual bool exists_(ParameterSet const& pset) const;
+    bool exists_(ParameterSet const& pset) const override;
 
-    virtual bool partiallyExists_(ParameterSet const& pset) const;
+    bool partiallyExists_(ParameterSet const& pset) const override;
 
-    virtual int howManyXORSubNodesExist_(ParameterSet const& pset) const;
+    int howManyXORSubNodesExist_(ParameterSet const& pset) const override;
 
     void throwMoreThanOneParameter() const;
     void throwAfterValidation() const;
diff --git a/FWCore/ParameterSet/src/ParameterDescription.cc b/FWCore/ParameterSet/src/ParameterDescription.cc
index 1b8314a1e1cc7..0548004be3e64 100644
--- a/FWCore/ParameterSet/src/ParameterDescription.cc
+++ b/FWCore/ParameterSet/src/ParameterDescription.cc
@@ -324,11 +324,11 @@ namespace edm {
     if(partOfDefaultOfVPSet_) subsectionOffset = 1;
 
     if(hasDefault()) {
-      if(vPset_.size() == 0U) os << "The default VPSet is empty.\n";
+      if(vPset_.empty()) os << "The default VPSet is empty.\n";
       else if(vPset_.size() == 1U) os << "The default VPSet has 1 element.\n";
       else os << "The default VPSet has " << vPset_.size() << " elements.\n";
 
-      if(vPset_.size() > 0U) {
+      if(!vPset_.empty()) {
         for(unsigned i = 0; i < vPset_.size(); ++i) {
           printSpaces(os, indentation + DocFormatHelper::offsetSectionContent());
           os << "[" << (i) << "]: see Section " << dfh.section()
@@ -487,7 +487,7 @@ namespace edm {
         std::string resultLessPrecision = s.str();
 
         if(resultLessPrecision.size() < result.size() - 2) {
-          double test = std::strtod(resultLessPrecision.c_str(), 0);
+          double test = std::strtod(resultLessPrecision.c_str(), nullptr);
           if(test == value) {
             result = resultLessPrecision;
           }
@@ -645,11 +645,11 @@ namespace edm {
       std::ios_base::fmtflags ff = os.flags(std::ios_base::dec);
       char oldFill = os.fill();
       os.width(0);
-      if(value_.size() == 0U && format == DOC) {
+      if(value_.empty() && format == DOC) {
         os << "empty";
       } else if(value_.size() == 1U && format == CFI) {
         writeValueInVector<T>(os, value_[0], format);
-      } else if(value_.size() >= 1U) {
+      } else if(!value_.empty()) {
         if(format == DOC) os << "(vector size = " << value_.size() << ")";
         if(format == CFI and value_.size() > 255U) os << " *(";
         os.fill(' ');