Warning C4840:: non-portable use of class ATL::CStringT as an argument to a variadic function

I am testing Splitter Control and ran into the following errors after I corrected project path set up etc.

Warning C4840 non-portable use of class "ATL::CStringT>>" as an argument to a variadic function

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2. Problems

3. SplitterCtrl (Flexible Control with Custom Drawing)
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5. Compiler Warning (level 4) C4840
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7. static_cast Operator
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10. Static Cast in C++ – static_cast() Method
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13. std::to_string
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16. varargs and conversion operators in MFC CString
17. cannot convert argument 1 from 'ATL::CStringT>>' to 'const char *'
18. Variadic arguments
19. Variadic functions