gdiplus plugin: make 'FileStream' destructor virtual

`FileStream::Release` optionally deletes `this`. This is OK because nothing
inherits from `FileStream`, but the compiler believes this is dangerous because
this class participates in an inheritance hierarchy and does not have a virtual
destructor. By giving it one, we silence the -Wdelete-non-virtual-dtor warning,
make it safer to inherit from this class in future, and make it safe to delete
a `FileStream` through an `IStream` pointer.

diff --git a/plugin/gdiplus/FileStream.h b/plugin/gdiplus/FileStream.h
index 0157d738f1a990cd1cd76d91e3218f046dab2d35..2de81e76e862e388961ba0f30947ef2bb533e432 100644 (file)
--- a/plugin/gdiplus/FileStream.h
+++ b/plugin/gdiplus/FileStream.h
@@ -81,6 +81,8 @@ public:
        virtual HRESULT STDMETHODCALLTYPE  Clone( 
                IStream **ppstm);
         
+       virtual ~FileStream() = default;
+
 private:
        FileStream(char *name, FILE *file);