once override then all override

otherwise clang will throw a lot of warnings and hence CIs will die

src/shogun/labels/BinaryLabels.h

@@ -88,13 +88,13 @@ class CBinaryLabels : public CDenseLabels
 	*
 	* @param context optional message to convey the context
 	 */
-	virtual void ensure_valid(const char * context = NULL);
+	virtual void ensure_valid(const char * context = NULL) override;
 
 	/** get label type
 	 *
 	 * @return label type binary
 	 */
-	virtual ELabelType get_label_type() const;
+	virtual ELabelType get_label_type() const override;
 
 	/** Converts all scores to calibrated probabilities by fitting a
 	 * sigmoid function using the method described in
@@ -117,13 +117,13 @@ class CBinaryLabels : public CDenseLabels
 	void scores_to_probabilities(float64_t a = 0, float64_t b = 0);
 
 	/** @return object name */
-	virtual const char * get_name() const
+	virtual const char * get_name() const override
 	{
 		return "BinaryLabels";
 	}
 
 #ifndef SWIG // SWIG should skip this part
-	virtual CLabels* shallow_subset_copy();
+	virtual CLabels* shallow_subset_copy() override;
 #endif
 };
 

src/shogun/labels/DenseLabels.h

@@ -56,7 +56,7 @@ namespace shogun
 		CDenseLabels(CFile* loader);
 
 		/** destructor */
-		virtual ~CDenseLabels();
+		virtual ~CDenseLabels() override;
 
 		virtual bool is_valid() const override;
 
@@ -74,15 +74,15 @@ namespace shogun
 		 *
 		 * @param loader File object via which to load data
 		 */
-		virtual void load(CFile* loader);
+		virtual void load(CFile* loader) override;
 
 		/** save labels to file
 		 *
 		 * not possible with subset
 		 *
 		 * @param writer File object via which to save data
 		 */
-		virtual void save(CFile* writer);
+		virtual void save(CFile* writer) override;
 
 		/** set label
 		 *

src/shogun/labels/LatentLabels.h

@@ -1,7 +1,7 @@
 /*
  * This software is distributed under BSD 3-clause license (see LICENSE file).
  *
- * Authors: Viktor Gal, Evgeniy Andreev, Yuyu Zhang, Fernando Iglesias, 
+ * Authors: Viktor Gal, Evgeniy Andreev, Yuyu Zhang, Fernando Iglesias,
  *          Sergey Lisitsyn, Soeren Sonnenburg
  */
 
@@ -39,7 +39,7 @@ namespace shogun
 			CLatentLabels(CLabels* labels);
 
 			/** destructor */
-			virtual ~CLatentLabels();
+			virtual ~CLatentLabels() override;
 
 			/** get all the stored latent labels
 			 *
@@ -76,25 +76,25 @@ namespace shogun
 			 *
 			 * @param context optional message to convey the context
 			 */
-			virtual void ensure_valid(const char* context=NULL);
+			virtual void ensure_valid(const char* context=NULL) override;
 
 			/** get label type
 			 *
 			 * @return label type (binary, multiclass, ...)
 			 */
-			virtual ELabelType get_label_type() const { return LT_LATENT; }
+			virtual ELabelType get_label_type() const override { return LT_LATENT; }
 
 			/** Returns the name of the SGSerializable instance.
 			 *
 			 * @return name of the SGSerializable
 			 */
-			virtual const char* get_name() const { return "LatentLabels"; }
+			virtual const char* get_name() const override { return "LatentLabels"; }
 
 			/** get the number of stored labels
 			 *
 			 * @return the number of labels
 			 */
-			virtual int32_t get_num_labels() const;
+			virtual int32_t get_num_labels() const override;
 
 			/** set labels
 			 *

src/shogun/labels/MultilabelLabels.h

@@ -84,13 +84,13 @@ class CMultilabelLabels : public CLabels
 	 *
 	 * @return label type multiclass
 	 */
-	virtual ELabelType get_label_type() const
+	virtual ELabelType get_label_type() const override
 	{
 		return LT_SPARSE_MULTILABEL;
 	}
 
 	/** @return object name */
-	virtual const char * get_name() const
+	virtual const char * get_name() const override
 	{
 		return "MultilabelLabels";
 	}
@@ -99,13 +99,13 @@ class CMultilabelLabels : public CLabels
 	 *
 	 * @return the number of labels
 	 */
-	virtual int32_t get_num_labels() const;
+	virtual int32_t get_num_labels() const override;
 
 	/** return number of classes (per label)
 	 *
 	 * @return number of classes
 	 */
-	virtual int32_t  get_num_classes() const;
+	virtual int32_t get_num_classes() const override;
 
 	/** set labels
 	 *

src/shogun/labels/StructuredLabels.h

@@ -1,7 +1,7 @@
 /*
  * This software is distributed under BSD 3-clause license (see LICENSE file).
  *
- * Authors: Fernando Iglesias, Thoralf Klein, Evgeniy Andreev, Yuyu Zhang, 
+ * Authors: Fernando Iglesias, Thoralf Klein, Evgeniy Andreev, Yuyu Zhang,
  *          Bjoern Esser
  */
 
@@ -37,7 +37,7 @@ class CStructuredLabels : public CLabels
 		CStructuredLabels(int32_t num_labels);
 
 		/** destructor */
-		virtual ~CStructuredLabels();
+		virtual ~CStructuredLabels() override;
 
 		virtual bool is_valid() const override;
 
@@ -47,7 +47,7 @@ class CStructuredLabels : public CLabels
 		 *
 		 * @return if labeling is valid
 		 */
-		virtual void ensure_valid(const char* context = NULL);
+		virtual void ensure_valid(const char* context = NULL) override;
 
 		/**
 		 * add a new label to the vector of labels, effectively
@@ -57,7 +57,7 @@ class CStructuredLabels : public CLabels
 		 *
 		 * @param label label to add
 		 */
-		virtual void add_label(CStructuredData* label);
+		virtual void add_label(CStructuredData* label) override;
 
 		/** get labels
 		 *
@@ -73,7 +73,7 @@ class CStructuredLabels : public CLabels
 		 *
 		 * @return label object
 		 */
-		virtual CStructuredData* get_label(int32_t idx);
+		virtual CStructuredData* get_label(int32_t idx) override;
 
 		/**
 		 * set label, possible with subset. This method should be used
@@ -85,22 +85,22 @@ class CStructuredLabels : public CLabels
 		 *
 		 * @return if setting was successful
 		 */
-		virtual bool set_label(int32_t idx, CStructuredData* label);
+		virtual bool set_label(int32_t idx, CStructuredData* label) override;
 
 		/** get number of labels, depending on wheter a subset is set
 		 *
 		 * @return number of labels
 		 */
-		virtual int32_t get_num_labels() const;
+		virtual int32_t get_num_labels() const override;
 
 		/** @return object name */
-		virtual const char* get_name() const { return "StructuredLabels"; }
+		virtual const char* get_name() const override { return "StructuredLabels"; }
 
 		/** get label type
 		 *
 		 * @return label type LT_STRUCTURED
 		 */
-		virtual ELabelType get_label_type() const { return LT_STRUCTURED; }
+		virtual ELabelType get_label_type() const override { return LT_STRUCTURED; }
 
 		/** get structured data type the labels are composed of
 		 *