I have an interface which is used like the following:

if (SUCCEEDED(pInterface->GetSize(&size))
{
    wchar_t tmp = new wchar_t[size];
    if (SUCCEEDED(pInterface->GetValue(tmp, size)))
    {
        std::wstring str = tmp;
        // do some work which doesn't throw
    }
    delete[] tmp;
}

Is it safe and portable to do this instead?

if (SUCCEEDED(pInterface->GetSize(&size))
{
    std::wstring str;
    str.resize(size);
    if (SUCCEEDED(pInterface->GetValue(&str[0], size)))
    {
        // do some work
    }
}

Now, obviously this works (doesn't crash/corrupt memory) or I wouldn't have asked, but I'm mostly wanting to know if there's a compelling reason not to do this.