Use = default for virtual constructors.

src/solver/check_sat_result.h

@@ -45,7 +45,7 @@ protected:
     double      m_time;
 public:
     check_sat_result():m_ref_count(0), m_status(l_undef), m_time(0) {}
-    virtual ~check_sat_result() {}
+    virtual ~check_sat_result() = default;
     void inc_ref() { m_ref_count++; }
     void dec_ref() { SASSERT(m_ref_count > 0); m_ref_count--; if (m_ref_count == 0) dealloc(this); }
     lbool set_status(lbool r) { return m_status = r; }

src/solver/progress_callback.h

@@ -20,7 +20,7 @@ Revision History:
 
 class progress_callback {
 public:
-    virtual ~progress_callback() {}
+    virtual ~progress_callback() = default;
     
     // Called on every check for resource limit exceeded (much more frequent).
     virtual void fast_progress_sample() {}

src/solver/solver.h

@@ -29,7 +29,7 @@ class model_converter;
 
 class solver_factory {
 public:
-    virtual ~solver_factory() {}
+    virtual ~solver_factory() = default;
     virtual solver * operator()(ast_manager & m, params_ref const & p, bool proofs_enabled, bool models_enabled, bool unsat_core_enabled, symbol const & logic) = 0;
 };
 
@@ -113,7 +113,7 @@ public:
     virtual void set_phase(expr* e) = 0;
     virtual void move_to_front(expr* e) = 0; 
 
-    class phase { public: virtual ~phase() {} };
+    class phase { public: virtual ~phase() = default; };
     
     virtual phase* get_phase() = 0;