C++ : Error while using TEXT() function windows.h

Question

I recently switched from Visual studio code to Visual studio 2019 because I wanted to download C++ package using VCPKG.

My code worked on Visual Studio Code but do not work on Visual Studio 2019, maybe because it's not the same compilator.

The code I found on a StackOverflow post ( Get Computer Name and logged user name ) retrieve the Computer name and the Username of a PC.

#define INFO_BUFFER_SIZE 32767
TCHAR  infoBuf[INFO_BUFFER_SIZE];
DWORD  bufCharCount = INFO_BUFFER_SIZE;
SID_IDENTIFIER_AUTHORITY pIdentStruct = SECURITY_NT_AUTHORITY;
PSID ptrSidStruct;
BOOL isMember;

Constructor::Contructor(): c_online(true), c_status("Alive"), c_master("Master IP"), c_port(80) 
{

  bufCharCount = INFO_BUFFER_SIZE;
  if (GetComputerName(infoBuf, &bufCharCount))
  { 
    c_pc = TEXT(infoBuf);
  }

  bufCharCount = INFO_BUFFER_SIZE;
  if (GetUserName(infoBuf, &bufCharCount))
  {
    c_user = TEXT(infoBuf);
  }
}

However while using the TEXT() function, I get the error "LinfoBuf not define". I don't understand this error, plus I declared infoBuf not LinfoBuf. I didn't find the GetUserName function using <windows.h> in MSND documentation but I found GetUserNameA using the header <winbase.h>

Answer 1

According to the Windows.h header file, TEXT() is not a function, its a macro. Its purpose is to convert string/character literals at compile-time to either wchar_t or char literals, depending on whether the UNICODE conditional is defined or not, respectively.

Basically the definition of TEXT is something like this,

#ifdef UNICODE
#define __TEXT(quote) L##quote

#else
#define __TEXT(quote) quote

#endif
#define TEXT(quote) __TEXT(quote)

In C++, narrow string literals are denoted as "some string" and wide string literals are denoted as L"some string" . A ## in a macro, like what we see above, concatenates tokens together. In this case, concatenating L in front of the macro argument when UNICODE is defined. So when we say TEXT("Hello") , the pre-processor output is L"Hello" when UNICODE is defined, otherwise the output is "Hello" .

Since infoBuf isn't a string literal, instead its a pointer, when you use TEXT(infoBuf) , the compiler resolves it to be LinfoBuf , where the L comes from the macro conversion.

GetComputerName and GetUserName are macro wrappers for the GetComputerNameA / GetComputerNameW and GetUserNameA / GetUserNameW functions, respectively. These functions output the names as char or wchar_t strings. When UNICODE is defined, the W functions are used, otherwise the A functions are used. So, if c_pc and c_user are containers of char s (like std::string ), your best option is to use GetComputerNameA and GetUserNameA directly, eg:

#define INFO_BUFFER_SIZE 32767
CHAR   infoBuf[INFO_BUFFER_SIZE];
DWORD  bufCharCount = INFO_BUFFER_SIZE;

Constructor::Contructor(): c_online(true), c_status("Alive"), c_master("Master IP"), c_port(80) 
{

  bufCharCount = INFO_BUFFER_SIZE;
  if (GetComputerNameA(infoBuf, &bufCharCount))
  { 
    c_pc = infoBuf;
  }

  bufCharCount = INFO_BUFFER_SIZE;
  if (GetUserNameA(infoBuf, &bufCharCount))
  {
    c_user = infoBuf;
  }
}