Question

What is the result of std::wstring.length() function, the length in wchar_t(s) or the length in symbols? And why?

TCHAR r2[3];
r2[0] = 0xD834;  // D834, DD1E - musical G clef
r2[1] = 0xDD1E;  //
r2[2] = 0x0000;  // '/0'

std::wstring r = r2;

std::cout << "capacity: " << r.capacity() << std::endl;
std::cout << "length: "   << r.length()   << std::endl;
std::cout << "size: "     << r.size()     << std::endl;
std::cout << "max_size: " << r.max_size() << std::endl;

Output>

capacity: 351
length: 2
size: 2
max_size: 2147483646

Answer 1

std::wstring::size() returns the number of wide-char elements in the string. This is not the same as the number of characters (as you correctly noticed).

Unfortunately, the std::basic_string template (and thus its instantiations, such as std::string and std::wstring) is encoding-agnostic. In this sense, it is actually just a template for a string of bytes and not a string of characters.