I want to convert std::string into a const wchar_t *

Is there any method? My computer is AMD64.

::std::string str;
BOOL loadU(const wchar_t* lpszPathName, int flag = 0);

When I used:

loadU(&str);

the VS2005 compiler says:

Error 7 error C2664:: cannot convert parameter 1 from 'std::string *__w64 ' to 'const wchar_t *'

How can I do it?

First convert it to std::wstring:

std::wstring widestr = std::wstring(str.begin(), str.end());

Then get the C string:

const wchar_t* widecstr = widestr.c_str();

This only works for ASCII strings, but it will not work if the underlying string is UTF-8 encoded. Using a conversion routine like MultiByteToWideChar() ensures that this scenario is handled properly.

If you have a std::wstring object, you can call c_str() on it to get a wchar_t*:

std::wstring name( L"Steve Nash" );
const wchar_t* szName = name.c_str();

Since you are operating on a narrow string, however, you would first need to widen it. There are various options here; one is to use Windows' built-in MultiByteToWideChar routine. That will give you an LPWSTR, which is equivalent to wchar_t*.

You can use the ATL text conversion macros to convert a narrow (char) string to a wide (wchar_t) one. For example, to convert a std::string:

#include <atlconv.h>
...
std::string str = "Hello, world!";
CA2W pszWide(str.c_str());
loadU(pszWide);

You can also specify a code page, so if your std::string contains UTF-8 chars you can use:

CA2W pszWide(str.c_str(), CP_UTF8);

Very useful but Windows only.

If you are on Linux/Unix have a look at mbstowcs() and wcstombs() defined in GNU C (from ISO C 90).

• mbs stand for "Multi Bytes String" and is basically the usual zero terminated C string.

• wcs stand for Wide Char String and is an array of wchar_t.

For more background details on wide chars have a look at glibc documentation here.