Проблема с кодировкой

#include <string>
#include <codecvt>
#include <locale>
 
string utf8_to_string(const char *utf8str, const locale& loc)
{
    // UTF-8 to wstring
    wstring_convert<codecvt_utf8<wchar_t>> wconv;
    wstring wstr = wconv.from_bytes(utf8str);
    // wstring to string
    vector<char> buf(wstr.size());
    use_facet<ctype<wchar_t>>(loc).narrow(wstr.data(), wstr.data() + wstr.size(), '?', buf.data());
    return string(buf.data(), buf.size());
}
 
int main(int argc, char* argv[])
{
    string ansi;
    char utf8txt[] = {0xc3, 0xa1, 0};
 
    // I guess you want to use Windows-1252 encoding...
    ansi = utf8_to_string(utf8txt, locale(".1252"));
    // Now do something with the string
    return 0;
}

#include <string>
#include <locale>
#include <codecvt>
 
using namespace std::string_literals;
 
std::string to_utf8(const std::string& str, const std::locale& loc = std::locale{}) {
  using wcvt = std::wstring_convert<std::codecvt_utf8<int32_t>, int32_t>;
  std::u32string wstr(str.size(), U'\0');
  std::use_facet<std::ctype<char32_t>>(loc).widen(str.data(), str.data() + str.size(), &wstr[0]);
  return wcvt{}.to_bytes(
    reinterpret_cast<const int32_t*>(wstr.data()),
    reinterpret_cast<const int32_t*>(wstr.data() + wstr.size())
  );
}
 
std::string from_utf8(const std::string& str, const std::locale& loc = std::locale{}) {
  using wcvt = std::wstring_convert<std::codecvt_utf8<int32_t>, int32_t>;
  auto wstr = wcvt{}.from_bytes(str);
  std::string result(wstr.size(), '0');
  std::use_facet<std::ctype<char32_t>>(loc).narrow(
    reinterpret_cast<const char32_t*>(wstr.data()),
    reinterpret_cast<const char32_t*>(wstr.data() + wstr.size()),
    '?', &result[0]);
  return result;
}
 
int main() {
  auto s0 = u8"Blöde C++ Scheiße äöü!!1Elf"s;
  auto s1 = from_utf8(s0);
  auto s2 = to_utf8(s1);
 
  return 0;
}

string UTF8ToANSI(string s)
{
    BSTR    bstrWide;
    char*   pszAnsi;
    int     nLength;
    const char *pszCode = s.c_str();
 
    nLength = MultiByteToWideChar(CP_UTF8, 0, pszCode, strlen(pszCode) + 1, NULL, NULL);
    bstrWide = SysAllocStringLen(NULL, nLength);
 
    MultiByteToWideChar(CP_UTF8, 0, pszCode, strlen(pszCode) + 1, bstrWide, nLength);
 
    nLength = WideCharToMultiByte(CP_ACP, 0, bstrWide, -1, NULL, 0, NULL, NULL);
    pszAnsi = new char[nLength];
 
    WideCharToMultiByte(CP_ACP, 0, bstrWide, -1, pszAnsi, nLength, NULL, NULL);
    SysFreeString(bstrWide);
 
    string r(pszAnsi);
    delete[] pszAnsi;
    return r;
}