wchar_t crashes when return from a function

[bomberman]

I have a function like this:

const wchar_t* getId()
{
std::wstring id_w = L"12345678";
return id_w.c_str();
}

int _tmain(int argc, _TCHAR* argv[])
{
std::wcout.imbue(std::locale(""));
wprintf(L"This is wchar: %s", getId() );
}

It output "This is wchar: ?2345678", The first character is crashed.

But if I do it without function call, like this, it works fine.
int _tmain(int argc, _TCHAR* argv[])
{
std::wcout.imbue(std::locale(""));
std::wstring id_w = L"12345678";
wprintf(L"This is wchar: %s", id_w.c_str() );
}

Any ideas what is wrong?

Thanks

[newb16]

std::wstring id_w = L"12345678";
this is local variable, it's destroyed after function returns and the pointer to string obtained by c_str() is no longer valid.