Retrieving VolumeDetails of WINDOWS Drives - stuck with 'char []' to 'LPCWSTR' conversion

Question

I am trying to get the VolumeDetails of my WINDOWS system- Drive label plus its respective Volume Serial number. I've tried since an hour and built a code which gone wrong in syntax. At present I am getting the following error with it- error C2664: 'GetVolumeInformationW' : cannot convert parameter 1 from 'char []' to 'LPCWSTR' Here is my code:

    // getVolDrive.cpp : Defines the entry point for the console application.

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <direct.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>
#include <sstream>
#include <string>
#include <ctype.h>
#include <algorithm>

using namespace std;
//wchar_t mydrives[5];// = " A: ";
char mydrives[] = " A: ";

string retVolSno(char drives[]) //wchar_t drives[]
{
    DWORD dwSerial;
    stringstream ss;
    cout<<drives<<endl;
    if(!GetVolumeInformation(drives, NULL, 0, &dwSerial, NULL, NULL, NULL, 0))
    {
        ss<<"Error: "<<GetLastError();
    }
    else
    {
        ss<<hex<<dwSerial;
    }
    return ss.str();
}

int _tmain(int argc, _TCHAR* argv[])
{
    string cVolSno;
    ULONG DriveMask = _getdrives(); 
    if(DriveMask == 0)
        printf("_getdrives() failed with failure code: %d\n", GetLastError());
    else
    {
        printf("This machine has the following logical drives:\n");
        while (DriveMask)
            { 
                cout << "In While" << endl;
                if(DriveMask & 1)
                printf("%s", mydrives);
                wcout << mydrives << endl;
                cVolSno = retVolSno(mydrives);
                cout<<cVolSno<<endl;
                ++mydrives[1];
                DriveMask >>= 1;
            }
    }
    //std::transform(cVolSno.begin(), cVolSno.end(),cVolSno.begin(), ::toupper);
    //cout<<cVolSno<<endl;
    _getch();
    return 0;
}

I've also tried replacing char with wchar_t, I didn't got any build errors, but while executing the application, got Error Code 3- Path not found!.

CODE MODIFIED:

    // getVolDrive.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <direct.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>
#include <sstream>
#include <string>
#include <ctype.h>
#include <algorithm>

using namespace std;
//wchar_t mydrives[5];// = " A: ";
char mydrives[] = " A:\\\\ ";

string retVolSno(char drives[]) //wchar_t drives[]
{
    DWORD dwSerial;
    stringstream ss;
    wchar_t text[10];
    mbstowcs(text,drives,100); //strlen(drives)+1
    LPWSTR ptr = text;

    if(!GetVolumeInformation(ptr, NULL, 0, &dwSerial, NULL, NULL, NULL, 0))
    {
        ss<<"Error: "<<GetLastError();
    }
    else
    {
        ss<<hex<<dwSerial;
    }
    return ss.str();
}

int _tmain(int argc, _TCHAR* argv[])
{
    string cVolSno;
    ULONG DriveMask = _getdrives(); 
    if(DriveMask == 0)
        printf("_getdrives() failed with failure code: %d\n", GetLastError());
    else
    {
        printf("This machine has the following logical drives:\n");
        while (DriveMask)
            {
                if(DriveMask & 1)
                printf("%s \n", mydrives);
                cVolSno = retVolSno(mydrives);
                std::transform(cVolSno.begin(), cVolSno.end(),cVolSno.begin(), ::toupper);
                cout<<cVolSno<<endl;
                ++mydrives[1];
                DriveMask >>= 1;
            }
    }
    //std::transform(cVolSno.begin(), cVolSno.end(),cVolSno.begin(), ::toupper);
    //cout<<cVolSno<<endl;
    _getch();
    return 0;
}

OUTPUT:

This machine has the following logical drives:
ERROR: 123
ERROR: 123
 C:\\
ERROR: 123
 D:\\
ERROR: 123
 E:\\
ERROR: 123

Answer 1

I see at least these main issues:

1) wchar_t is the right type because you're compiling for UNICODE, you can write generic code using TCHAR macro or explicitly declare your buffer as wchar_t but that's what to do.

2) You have that error because you're passing wrong path to GetVolumeInformation() (trailing backslash is required so A: must become A:\).

Moreover please note that you have a little bit more easy way to achieve same result, you can use GetLogicalDriveStrings() to directly get a NULL delimited string list. Split it using, for example, this (don't forget UNICODE) and use c_str() with each entry.

EDIT about your modified code:
Why you drive path is A:\\ (escaped to A:\\\\)? Just one trailing backslash is needed so mydrives has to be declared as:

wchar_t mydrives[] = L"A:\\";

EDIT 2: there are more errors in your code so I'll post a reviewed version. There are more things I'd change but I'll point out just what doesn't actually work.

1. Function retVolSno to read volume serial number. Original version were almost right, in your modified version you perform useless character conversion. What you had to do was just to accept a wchar_t drive path.

2. Global variable mydrives. You actually don't need any global variable for that. It must be wchar_t and space before/after path are useless. One trailing backslash is needed. Line where you increment character value (++mydrives[0];) must be changed accordingly (index 0 instead of 1).

3. Check for drive availability. After if(DriveMask & 1) you did forget { then you won't print drive name but you'll perform GetVolumeInformation() even on unavailable drives (error 123). That's why indentation is important...

4. You're mixing UNICODE/NOT UNICODE and C/C++ stuff. I strongly suggest you pick one of them and you keep it (C or C++? UNICODE or NOT UNICODE?). For example you used C function printf() to print stuff and you have both std::string and wchar_t things.

Let's put everything together to have a working version. First the function to read serial number given drive path:

wstring getVolumeSerialNumber(const wchar_t* drivePath)
{
    DWORD dwSerial;
    wstringstream ss;

    if (!GetVolumeInformation(drivePath, NULL, 0, &dwSerial, NULL, NULL, NULL, 0))
        ss << L"Error: " << GetLastError();
    else
        ss << hex << dwSerial;

    return ss.str();
}

It's almost the same as your original version, just changed to work with UNICODE characters. Then main function that cycles through available drives and print out their serial number:

int _tmain(int argc, _TCHAR* argv[])
{
    wchar_t drive[] = L"A:\\";

    ULONG driveMask = _getdrives(); 
    if (driveMask == 0)
        wcout << L"_getdrives() failed with failure code: " << GetLastError() << endl;
    else
    {
        wcout << L"This machine has the following logical drives:" << endl;
        while (driveMask)
        {
            if (driveMask & 1) 
            {
                wcout << drive << endl;
                wcout << getVolumeSerialNumber(drive) << endl;
            }

            ++drive[0];
            driveMask >>= 1;
        }
    }

    wcin.ignore();

    return 0;
}

Answer 2

From the documentation , the first parameters should be with trailing slash if drive letter is passed.

lpRootPathName [in, optional]
A pointer to a string that contains the root directory of the volume to be described.
If this parameter is NULL, the root of the current directory is used. 
A trailing backslash is required. 
For example, you specify \\MyServer\MyShare as \\MyServer\MyShare\, or the C drive as C:\