Question

I have a Visual Studio 2008 C++ application for Windows where I have wrapped some platform functions that take TCHAR-based parameters and therefore have both a wide-character and narrow version selected by an ifdef.

#ifdef UNICODE
    #define QueryValueW QueryValue
#else
    #define QueryValueA QueryValue
#endif

inline DWORD QueryValueW( HANDLE h, LPCWSTR str )
{
    return ::SomeFuncW( h, 0, true, str, 0, 0 );
}

inline DWORD QueryValueA( HANDLE h, LPCSTR str )
{
    return ::SomeFuncA( h, 0, true, str, 0, 0 );
}

I’d prefer to templatize this such that the compiler can automatically select the correct version of SomeFunc based on what type of string I pass in rather than an ifdef.

template< typename charT >
inline DWORD QueryValue( HANDLE h, const charT* str )
{
    // Call ::SomeFuncW or ::SomeFuncA depending on the type of `charT`.
}

Does anybody have a suggestion on how this can be accomplished? Preferably without resorting to RTTI.

Answer 1

This?

template<typename T>
inline DWORD QueryValue( HANDLE h, T str )
{
   //...
}

template<>
inline DWORD QueryValue<LPCSTR>( HANDLE h, LPCSTR str )
{
   //...
}

The first version will be called unless you explicitly call it with a LPCSTR parameter.