Convert char[] to LPCWSTR

Question

Can anyone help me to correct this code:

    char szBuff[64];
    sprintf(szBuff, "%p", m_hWnd);
    MessageBox(NULL, szBuff, L"Test print handler", MB_OK);

The error is, it cant convert the 2nd parameter to LPCWSTR.

Answer 1

For this specific case, the fix is quite simple:

wchar_t szBuff[64];
swprintf(szBuff, L"%p", m_hWnd);
MessageBox(NULL, szBuff, L"Test print handler", MB_OK);

That is, use Unicode strings throughout. In general, when programming on Windows, using wchar_t and UTF-16 is probably the simplest. It depends on how much interaction with other systems you have to do, of course.

For the general case, if you've got an ASCII (or char *) string, use either WideCharToMultiByte for the general case, or mbstowcs as @Matthew points out for simpler cases (mbstowcs works if the string is in the current C locale).

Answer 2

You might want to look at mbstowcs, which will convert a conventional "one byte per character" string to a "multiple byte per character" string.

Alternatively, change your project settings to use Multibyte Strings - by default they are usually "Unicode" or "Wide Character" strings (I can't remember the exact option name off the top of my head).

Answer 3

Using MultiByteToWideChar() works for me:

void main(int argc, char* argv[])
{
 ...
 wchar_t filename[4096] = {0};
 MultiByteToWideChar(0, 0, argv[1], strlen(argv[1]), filename, strlen(argv[1]));

 // RenderFile() requires LPCWSTR (or wchar_t*, respectively)
 hr = pGraph->RenderFile(filename, NULL);
 ...
}

Answer 4

If you are compiling with UNICODE, make all the strings you work with double width - i.e. define them as wchar_t*.

If you really must convert ASCII to Unicode, use ATL conversion macros.

Answer 5

Since your tag suggests VC++, I am suggesting CString. If yes, then the following snippet will also work for your case:

CString szBuff;

szBuff.Format(_T("%p"), m_hWnd);
MessageBox(NULL, szBuff, L"Test print handler", MB_OK);