Reliably Checking Windows Bitness (32-bit or 64-bit) With C++

#include "stdafx.h"
#include <iostream>
#include "comutil.h"
 
#define RESPONSE_32_BIT "32"
#define RESPONSE_64_BIT "64"
 
using namespace std;
 
typedef BOOL (WINAPI *IW64PFP)(HANDLE, BOOL *);
 
int main(int argc, char **argv){
 
  BOOL res = FALSE;
 
  // When this application is compiled as a 32-bit app,
  // and run on a native 64-bit system, Windows will run
  // this application under WOW64.  WOW64 is the Windows-
  // on-Windows subsystem that lets native 32-bit applications
  // run in 64-bit land.  This calls the kernel32.dll
  // API to see if this process is running under WOW64.
  // If it is running under WOW64, then that clearly means
  // this 32-bit application is running on a 64-bit OS,
  // and IsWow64Process will return true.
  IW64PFP IW64P = (IW64PFP)GetProcAddress(
            GetModuleHandle(L"kernel32"), "IsWow64Process");
 
  if(IW64P != NULL){
    IW64P(GetCurrentProcess(), &res);
  }
 
  cout << ((res) ? RESPONSE_64_BIT : RESPONSE_32_BIT) << endl;
 
  return 0;
 
}