I have encountered an interesting issue on Windows 8. I tested I can represent Unicode characters which are out of the BMP with wchar_t* strings. The following test code produced unexpected results for me:
const wchar_t* s1 = L"a";
const wchar_t* s2 = L"\U0002008A"; // The "Han" character
int i1 = sizeof(wchar_t); // i1 == 2, the size of wchar_t on Windows.
int i2 = sizeof(s1); // i2 == 4, because of the terminating '\0' (I guess).
int i3 = sizeof(s2); // i3 == 4, why?
The U+2008A is the Han character, which is out of the Binary Multilingual Pane, so it should be represented by a surrogate pair in UTF-16. Which means - if I understand it correctly - that it should be represented by two wchar_t characters. So I expected sizeof(s2) to be 6 (4 for the two wchar_t-s of the surrogate pair and 2 for the terminating \0).
So why is sizeof(s2) == 4? I tested that the s2 string has been constructed correctly, because I've rendered it with DirectWrite, and the Han character was displayed correctly.
UPDATE: As Naveen pointed out, I tried to determine the size of the arrays incorrectly. The following code produces correct result:
const wchar_t* s1 = L"a";
const wchar_t* s2 = L"\U0002008A"; // The "Han" character
int i1 = sizeof(wchar_t); // i1 == 2, the size of wchar_t on Windows.
std::wstring str1 (s1);
std::wstring str2 (s2);
int i2 = str1.size(); // i2 == 1.
int i3 = str2.size(); // i3 == 2, because two wchar_t characters needed for the surrogate pair.
sizeof(s2) returns the number of bytes required to store the pointer s2 or any other pointer, which is 4 bytes on your system. It has nothing to do with the character(s) stored in pointed to by s2.