fix clang error

src/ngraph/runtime/allocator.cpp

@@ -16,6 +16,8 @@
 
 #include "ngraph/runtime/allocator.hpp"
 
+ngraph::runtime::Allocator::~Allocator() {}
+
 class DefaultNgraphAllocator : public ngraph::runtime::Allocator
 {
 public:

src/ngraph/runtime/allocator.hpp

@@ -37,6 +37,7 @@ namespace ngraph
 class ngraph::runtime::Allocator
 {
 public:
+    virtual ~Allocator() = 0;
     /// \brief allocates memory with the given size and alignment requirement
     /// \param size exact size of bytes to allocate
     /// \param alignment specifies the alignment. Must be a valid alignment supported by the implementation.

src/ngraph/runtime/backend.hpp

@@ -124,17 +124,17 @@ public:
     virtual Allocator* get_host_memory_allocator()
     {
         return ngraph::runtime::get_ngraph_allocator();
-    };
+    }
 
     /// \brief Set the host memory allocator to be used by the backend
-    /// \param pointer to host memory allocator object
-    virtual void set_host_memory_allocator(Allocator* allocator){};
+    /// \param allocator is pointer to host memory allocator object
+    virtual void set_host_memory_allocator(Allocator* allocator){}
 
     /// \brief Returns memory allocator used by backend for device allocations
     virtual Allocator* get_device_memory_allocator()
     {
         return ngraph::runtime::get_ngraph_allocator();
-    };
+    }
 
     /// \brief method for each supported backend to determine if the passed pointer is in device pinned memory or not
     /// \param ptr pointer to the memory to determine if its in device memory or not

src/ngraph/runtime/cpu/cpu_backend.cpp

@@ -156,7 +156,7 @@ runtime::Allocator* runtime::cpu::CPU_Backend::get_host_memory_allocator()
     }
     else
     {
-        runtime::get_ngraph_allocator();
+        return runtime::get_ngraph_allocator();
     }
 }