std::wstring AnsiToWstring(const std::string& input, DWORD locale = CP_UTF8 )
{
      std::wstring buf(input.size(),0);
      MultiByteToWideChar(locale, 0, input.c_str(), (int)input.length(), const_cast<wchar_t*>(buf.data()), input.size());
      return buf;
}
//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{
   std::wstring w_str2_substr = AnsiToWstring (Edit1->Text.c_str());
   std::wstring w_str1_srsstr = AnsiToWstring (Edit2->Text.c_str());
   ShowMessage(wcsstr( w_str1_srsstr.c_str(), w_str2_substr.c_str()) ? "true" : "false");
}

[Linker Error] Unresolved external 'std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(int, int, const std::allocator<wchar_t>&)'