Use [[maybe_unused]] attribute (C++17) and specify -Wunused-variable

CMakeLists.txt

@@ -15,6 +15,8 @@ endif()
 
 include (CheckCXXCompilerFlag)
 
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wunused-variable")
+
 CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
 CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
 if(COMPILER_SUPPORTS_CXX11)

include/openbabel/base.h

@@ -28,15 +28,6 @@ GNU General Public License for more details.
 #include <iostream>
 #include <openbabel/tokenst.h>
 
-#ifdef UNUSED
-#elif (__GNUC__ == 4)
-# define UNUSED(x) UNUSED_ ## x __attribute__((unused))
-#elif defined(__LCLINT__)
-# define UNUSED(x) /*@unused@*/ x
-#else
-# define UNUSED(x) x
-#endif
-
 namespace OpenBabel
 {
 
@@ -283,7 +274,7 @@ class OBConversion; //used only as pointer
       //! \brief  Base type does nothing
       //! Made virtual around r3535 to simplify code which passes around OBBase*.
       //Currently no title data member in base class.
-      virtual const char  *GetTitle(bool UNUSED(replaceNewlines) = true) const { return "";}
+      virtual const char  *GetTitle(OB_UNUSED bool replaceNewlines = true) const { return "";}
       virtual void  SetTitle(const char *) {}
 
       //! \name Generic data handling methods (via OBGenericData)

include/openbabel/forcefield.h

@@ -910,56 +910,56 @@ const double GAS_CONSTANT = 8.31446261815324e-3 / KCAL_TO_KJ;  //!< kcal mol^-1
      *    OBFF_LOGLVL_MEDIUM: energy for individual energy terms \n
      *    OBFF_LOGLVL_HIGH:   energy for individual energy interactions \n
      */
-    virtual double Energy(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double Energy(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Bond stretching energy.
      *   \par Output to log:
      *    see Energy()
      */
-    virtual double E_Bond(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_Bond(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Angle bending energy.
      *  \par Output to log:
      *   see Energy()
      */
-    virtual double E_Angle(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_Angle(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Stretch bending energy.
      *   \par Output to log:
      *    see Energy()
      */
-    virtual double E_StrBnd(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_StrBnd(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Torsional energy.
      *    \par Output to log:
      *	  see Energy()
      */
-    virtual double E_Torsion(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_Torsion(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Out-Of-Plane bending energy.
      *   \par Output to log:
      *	  see Energy()
      */
-    virtual double E_OOP(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_OOP(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Van der Waals energy.
      *   \par Output to log:
      *	  see Energy()
      */
-    virtual double E_VDW(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_VDW(OB_UNUSED bool gradients = true) { return 0.0f; }
     /*! \param gradients Set to true when the gradients need to be calculated
      *  (needs to be done before calling GetGradient()).
      *  \return Electrostatic energy.
      *   \par Output to log:
      *	  see Energy()
      */
-    virtual double E_Electrostatic(bool UNUSED(gradients) = true) { return 0.0f; }
+    virtual double E_Electrostatic(OB_UNUSED bool gradients = true) { return 0.0f; }
     //@}
 
     /////////////////////////////////////////////////////////////////////////

include/openbabel/rotor.h

@@ -24,15 +24,6 @@ GNU General Public License for more details.
 #include <openbabel/typer.h>
 #include <openbabel/bitvec.h>
 
-#ifdef UNUSED
-#elif (__GNUC__ == 4)
-# define UNUSED(x) UNUSED_ ## x __attribute__((unused))
-#elif defined(__LCLINT__)
-# define UNUSED(x) /*@unused@*/ x
-#else
-# define UNUSED(x) x
-#endif
-
 namespace OpenBabel
 {
   class OBRing;
@@ -425,7 +416,7 @@ namespace OpenBabel
     ///@name Deprecated
     ///@{
     /** @deprecated Has no effect. */
-    void SetDelta(double UNUSED(d)) {}
+    void SetDelta(OB_UNUSED double d) {}
     /** @deprecated Has no effect. */
     double GetDelta() { return 10.0; }
     /** @deprecated */
@@ -441,7 +432,7 @@ namespace OpenBabel
     /** @deprecated Bad name, see GetTorsionValues() */
     std::vector<double> &GetResolution() { return _torsionAngles; }
     /** @deprecated */
-    void SetNumCoords(int UNUSED(nc)) {}
+    void SetNumCoords(OB_UNUSED int nc) {}
     ///@}
 
   };

src/config.h.cmake

@@ -31,6 +31,13 @@
  #define OB_HIDDEN
 #endif
 
+// maybe_unused attribute (C++17)
+#if __cplusplus >= 201402L && defined(__has_cpp_attribute) && __has_cpp_attribute(maybe_unused) >= 201603L && !defined(SWIG)
+  #define OB_UNUSED [[maybe_unused]]
+#else
+  #define OB_UNUSED
+#endif
+
 /* Used to export symbols for DLL / shared library builds */
 #if defined(MAKE_OBDLL) // e.g. in src/main.cpp
  #ifndef EXTERN