C++ TCHAR array to wstring not working in VS2010

Question

I would like to convert a TCHAR array to a wstring.

    TCHAR szFileName[MAX_PATH+1];
#ifdef _DEBUG
    std::string str="m:\\compiled\\data.dat";
    TCHAR *param=new TCHAR[str.size()+1];
    szFileName[str.size()]=0;
    std::copy(str.begin(),str.end(),szFileName);
#else
    //Retrieve the path to the data.dat in the same dir as our data.dll is located
    GetModuleFileName(_Module.m_hInst, szFileName, MAX_PATH+1);
    StrCpy(PathFindFileName(szFileName), _T("data.dat"));
#endif  

wstring sPath(T2W(szFileName));

I need to pass szFileName to a function that expects

const WCHAR *

For completeness I am stating the void that I need to pass szFileName to:

HRESULT CEngObj::MapFile( const WCHAR * pszTokenVal,  // Value that contains file path
                        HANDLE * phMapping,          // Pointer to file mapping handle
                        void ** ppvData )            // Pointer to the data

However, T2W does not work for me. The compiler says that "_lpa" is not defined, and I don't know where to go on from here. I have tried other conversion methods that I found stated on the net, but they did not work either.

Answer 1

There are functions like

mbstowcs_s()

that convert from char* to wchar_t*.

#include <iostream>
#include <stdlib.h>
#include <string>

using namespace std;

char *orig = "Hello, World!";
cout << orig << " (char *)" << endl;

// Convert to a wchar_t*
size_t origsize = strlen(orig) + 1;
const size_t newsize = 100;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;

Look here for an article and here for MSDN.

Answer 2

The definition of TCHAR differs depending on if certain preprocessor macros are defined or not. See e.g. this article for the possible combinations.

This means that TCHAR may already be a wchar_t.

You can use the _UNICODE macro to check if you need to convert the string. If you do, then you can use mbstowcs to do the conversion:

std::wstring str;

#ifdef _UNICODE
    // No need to convert the string
    str = your_tchar_string;
#else
    // Need to convert the string
    // First get the length needed
    int length = mbstowcs(nullptr, your_tchar_string, 0);

    // Allocate a temporary string
    wchar_t* tmpstr = new wchar_t[length + 1];

    // Do the actual conversion
    mbstowcs(tmpstr, your_tchar_str, length + 1);

    str = tmpstr;

    // Free the temporary string
    delete[] tmpstr;
#endif