avoid implicit destructor in BSplineBase.h

allows BSplineBase.h to be included by itself when the explicit
instantation will be linked from elsewhere.
create v2.2.

BSpline/BSpline.dox

@@ -50,6 +50,11 @@ The HTML documentation is generated from the source files by Doxygen
 
 @section releasenotes Release Notes
 
+<h2>Release 2.2</h2>
+
+Restore the explicit destructor so BSplineBase.h can be used by itself when
+explicit instantiations will be linked from a library.
+
 <h2>Release 2.1</h2>
 
 Fix missing assignment operator bug in BSplineBase.  Thanks to @@AlexRockliff

BSpline/BSplineBase.cpp

@@ -175,6 +175,15 @@ BSplineBase<T>::BSplineBase(const T* x, int nx, double wl, int bc,
     setDomain(x, nx, wl, bc, num_nodes);
 }
 
+// The destructor is declared in the class definition but not defined so the
+// compiler does not try to generate it when the full implementation is not
+// available.  The implicit destructor fails to instantiate when BSplineBaseP
+// is still incomplete, because the std::unique_ptr<BSplineBaseP> destructor
+// cannot be instantiated.  To fully instantiate BSplineBase, this file has to
+// be included.  The header alone can be used when the template is explicitly
+// instantiated elsewhere.
+template <class T> BSplineBase<T>::~BSplineBase() {}
+
 template <class T>
 bool
 BSplineBase<T>::setDomain(const T* x, int nx, double wl, int bc, int num_nodes)

BSpline/BSplineBase.h

@@ -208,6 +208,10 @@ template <class T> class BSplineBase
     /// Assignment operator
     BSplineBase& operator=(const BSplineBase& right);
 
+    // Declare the destructor so it is not implicitly instantiated.  It can
+    // only be instantiated with the full implementation in BSplineBase.cpp.
+    ~BSplineBase();
+
     /**
      * Change the domain of this base.  [If this is part of a BSpline
      * object, this method {\em will not} change the existing curve or

BSpline/BSplineVersion.h

@@ -20,7 +20,7 @@
 #define bspline_str(s) #s
 #define BSPLINE_VERSION bspline_xstr(BSPLINE_AUTO_REVISION)
 #else
-#define BSPLINE_VERSION "v2.1-x"
+#define BSPLINE_VERSION "v2.2"
 #endif
 
 #define BSPLINE_URL "https://github.com/NCAR/bspline"