/usr/share/cmake-2.8/Modules/TestForSSTREAM.cxx is in cmake-data 2.8.12.2-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | #include <sstream>
int main(int, char*[])
{
  std::ostringstream os;
  os << "12345";
  if(os.str().size() == 5)
    {
    return 0;
    }
  return -1;
}
 |