std::string str = “123”;
size_t nDestSize = mbstowcs(NULL, str.c_str(), 0) + 1;
//size_t nDestSize = strlen(str.c_str()) + 1;
wchar_t* wchDest = new wchar_t[nDestSize];
wmemset(wchDest, 0, nDestSize);
mbstowcs(wchDest, str.c_str(), nDestSize);
std::wstring wstrResult = wchDest;
delete[]wchDest;
wchDest = nullptr;