+--- VTK-8.2.0/Rendering/FreeType/vtkFreeTypeTools.cxx.orig 2019-01-30 18:15:13.000000000 +0100
++++ VTK-8.2.0/Rendering/FreeType/vtkFreeTypeTools.cxx 2020-10-17 00:21:55.153442255 +0200
+@@ -387,7 +387,7 @@ FTC_CMapCache* vtkFreeTypeTools::GetCMap
+ }
+
+ //----------------------------------------------------------------------------
+-FT_CALLBACK_DEF(FT_Error)
++extern "C" FT_Error
+ vtkFreeTypeToolsFaceRequester(FTC_FaceID face_id,
+ FT_Library lib,
+ FT_Pointer request_data,
+--- VTK-8.2.0/Rendering/FreeTypeFontConfig/vtkFontConfigFreeTypeTools.cxx.orig 2019-01-30 18:15:13.000000000 +0100
++++ VTK-8.2.0/Rendering/FreeTypeFontConfig/vtkFontConfigFreeTypeTools.cxx 2020-10-17 00:38:23.457937944 +0200
+@@ -26,10 +26,8 @@
+
+ vtkStandardNewMacro(vtkFontConfigFreeTypeTools)
+
+-namespace
+-{
+ // The FreeType face requester callback:
+-FT_CALLBACK_DEF(FT_Error)
++extern "C" FT_Error
+ vtkFontConfigFreeTypeToolsFaceRequester(FTC_FaceID face_id,
+ FT_Library lib,
+ FT_Pointer request_data,
+@@ -75,7 +73,6 @@ vtkFontConfigFreeTypeToolsFaceRequester(
+
+ return static_cast<FT_Error>(0);
+ }
+-} // end anon namespace
+
+ void vtkFontConfigFreeTypeTools::PrintSelf(ostream &os, vtkIndent indent)
+ {