/in/foo.cc: In function 'void block_delete(int, int)':
/in/foo.cc:101:9: warning: unused variable 'en' [-Wunused-variable]
     int en = idx, en_next = g[idx].next;
         ^~
/in/foo.cc: In function 'void block_rev(int, int)':
/in/foo.cc:117:9: warning: unused variable 'en' [-Wunused-variable]
     int en = idx, en_next = g[idx].next;
         ^~