Does the _T Macro effect std::string constructor?

Question

I inherited some old code which needs to stay multibyte/unicode compatible. It currently uses the _T() macro for this. I was wondering if std::strings are introduced, is _T() still needed?

e.g

std::string foo(_T("hello"));

Or is it now redundant?

Answer 1

It's not only unneeded. It's wrong. The _T macro expands to convert the string literal to a wide character (wchar_t) string literal if UNICODE is defined. However, the std::string constructor never expects a wide character string (const wchar_t*). It always expects const char*.

What you might do, if you were still concerned about this sort of thing (compiling for both Unicode and ANSI versions of the WinAPI), is define a new type based on std::basic_string

typedef std::basic_string<TCHAR> tstring;

And then this would be correct:

tstring foo(_T("hello"));