Create wxCoTaskMemPtr class

wxCoTaskMemPtr is a barebone RAII class for pointers
that must freed with ::CoTaskMemFree().

include/wx/msw/private/cotaskmemptr.h

@@ -0,0 +1,85 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/msw/private/cotaskmemptr.h
+// Purpose:     RAII class for pointers to be freed with ::CoTaskMemFree().
+// Author:      PB
+// Created:     2020-06-09
+// Copyright:   (c) 2020 wxWidgets team
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_MSW_PRIVATE_COTASKMEMPTR_H_
+#define _WX_MSW_PRIVATE_COTASKMEMPTR_H_
+
+// needed for ::CoTaskMem{Alloc|Free}()
+#include "wx/msw/wrapwin.h"
+
+// ----------------------------------------------------------------------------
+// wxCoTaskMemPtr: A barebone RAII class for pointers to be freed with ::CoTaskMemFree().
+// ----------------------------------------------------------------------------
+
+template <class T>
+class wxCoTaskMemPtr
+{
+public:
+    typedef T element_type;
+
+    wxCoTaskMemPtr()
+        : m_ptr(NULL)
+    {}
+
+    explicit wxCoTaskMemPtr(T* ptr)
+        : m_ptr(ptr)
+    {}
+
+    // Uses ::CoTaskMemAlloc() to allocate size bytes.    
+    explicit wxCoTaskMemPtr(size_t size)
+        : m_ptr(static_cast<T*>(::CoTaskMemAlloc(size)))
+    {}
+
+    ~wxCoTaskMemPtr()
+    {        
+        ::CoTaskMemFree(m_ptr);
+    }
+
+    void reset(T* ptr = NULL)
+    {
+        if ( m_ptr != ptr)
+        {                        
+            ::CoTaskMemFree(m_ptr);
+            m_ptr = ptr;
+        }
+    }
+
+    operator T*() const
+    {
+        return m_ptr;
+    }
+
+    // It would be better to forbid direct access completely but we do need it,
+    // so provide it but it can only be used to initialize the pointer,
+    // not to modify an existing one.
+    T** operator&()
+    {
+        wxASSERT_MSG(!m_ptr,
+                     wxS("Can't get direct access to initialized pointer"));
+
+        return &m_ptr;
+    }
+
+    // Gives up the ownership of the pointer,
+    // making the caller responsible for freeing it.
+    T* release()
+    {
+        T* ptr(m_ptr);
+
+        m_ptr = NULL;
+        return ptr;
+    }
+
+private:
+    T* m_ptr;
+
+    wxDECLARE_NO_COPY_TEMPLATE_CLASS(wxCoTaskMemPtr, T);
+};
+
+#endif // _WX_MSW_PRIVATE_COTASKMEMPTR_H_