c.cpp

// list::sort
#include <iostream>
#include <list>
#include <string>
#include <cctype>

// comparison, not case sensitive.
bool compare_nocase (const std::string& first, const std::string& second)
{
  unsigned int i=0;
  while ( (i<first.length()) && (i<second.length()) )
  {
    if (tolower(first[i])<tolower(second[i])) return true;
    else if (tolower(first[i])>tolower(second[i])) return false;
    ++i;
  }
  return ( first.length() < second.length() );
}

int main ()
{
  std::list<std::string> mylist;
  std::list<std::string>::iterator it;
  mylist.push_back ("one");
  mylist.push_back ("two");
  mylist.push_back ("Three");

  mylist.sort();

  std::cout << "mylist contains:";
  for (it=mylist.begin(); it!=mylist.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  mylist.sort(compare_nocase);

  std::cout << "mylist contains:";
  for (it=mylist.begin(); it!=mylist.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

f.cpp

TCHAR * text;

#ifdef UNICODE
    /*/
    // Simple C
    const size_t size = ( wcslen(text) + 1 ) * sizeof(wchar_t);
    wcstombs(&buffer[0], text, size);
    std::vector<char> buffer(size);
    /*/
    // Windows API (I would use this)
    std::vector<char> buffer;
    int size = WideCharToMultiByte(CP_UTF8, 0, text, -1, NULL, 0, NULL, NULL);
    if (size > 0) {
        buffer.resize(size);
        WideCharToMultiByte(CP_UTF8, 0, text, -1, static_cast<BYTE*>(&buffer[0]), buffer.size(), NULL, NULL);
    }
    else {
        // Error handling
    }
    //*/
    std::string string(&buffer[0]);
#else
    std::string string(text);
#endif