GridBase: Define virtual destructor in .cpp file

This fixes compiler warnings from clang:

src/textord/bbgrid.h:53:7: warning:
 'GridBase' has no out-of-line virtual method definitions;
 its vtable will be emitted in every translation unit [-Wweak-vtables]

Signed-off-by: Stefan Weil <[email protected]>

Author: stweil

src/textord/bbgrid.cpp

@@ -31,6 +31,11 @@ GridBase::GridBase(int gridsize, const ICOORD& bleft, const ICOORD& tright) {
   Init(gridsize, bleft, tright);
 }
 
+// Destructor.
+// It is defined here, so the compiler can create a single vtable
+// instead of weak vtables in every compilation unit.
+GridBase::~GridBase() = default;
+
 // (Re)Initialize the grid. The gridsize is the size in pixels of each cell,
 // and bleft, tright are the bounding box of everything to go in it.
 void GridBase::Init(int gridsize, const ICOORD& bleft, const ICOORD& tright) {

src/textord/bbgrid.h

@@ -54,7 +54,7 @@ class GridBase {
  public:
   GridBase() = default;
   GridBase(int gridsize, const ICOORD& bleft, const ICOORD& tright);
-  virtual ~GridBase() = default;
+  virtual ~GridBase();
 
   // (Re)Initialize the grid. The gridsize is the size in pixels of each cell,
   // and bleft, tright are the bounding box of everything to go in it.