Base classes of AUDACITY_DLL_API classes also need AUDACITY_DLL_API.

src/ClientData.h

@@ -22,7 +22,7 @@ Paul Licameli
 namespace ClientData {
 
 // A convenient default parameter for class template Site below
-struct Base
+struct AUDACITY_DLL_API Base
 {
    virtual ~Base() {}
 };

src/Prefs.h

@@ -165,7 +165,7 @@ private:
 wxDECLARE_EVENT(EVT_PREFS_UPDATE, wxCommandEvent);
 
 // Invoke UpdatePrefs() when Preference dialog commits changes.
-class PrefsListener
+class AUDACITY_DLL_API PrefsListener
 {
 public:
    PrefsListener();