difference_type    97 gc/include/gc_allocator.h   typedef ptrdiff_t  difference_type;
difference_type   144 gc/include/gc_allocator.h   typedef ptrdiff_t   difference_type;
difference_type   178 gc/include/gc_allocator.h   typedef ptrdiff_t  difference_type;
difference_type   220 gc/include/gc_allocator.h   typedef ptrdiff_t   difference_type;