0                  Indicates success.
    -1                 Indicates failure, the named shared memory
                       object is not changed by the function call,
                       and errno is set to indicate the error:

                       o  EACCES - Permission is denied to unlink the
                          named shared memory object.

                       o  ENAMETOOLONG - The length of the name
                          argument exceeds PATH_MAX or a pathname
                          component is longer than NAME_MAX.

                       o  ENOENT - The named shared memory object
                          does not exist.