A bug nobody has pointed out yet is that star-star-t (sorry, can't figure out this site's markup for escaping stars) dereferences a null pointer. It appears to work because gcc decides to generate the same code for star-star-t as for star-t (which is correct behaviour if star-t is not NULL, and moot if t is NULL). The code should just be star-t there.
Also, sizeof(int star-star) in hnew should be sizeof( int (star)[2] ).
Also, sizeof(int star-star) in hnew should be sizeof( int (star)[2] ).