/in/foo.cc: In function 'void chg(int, int, int)':
/in/foo.cc:22:20: warning: left operand of comma operator has no effect [-Wunused-value]
  #define l(x) d[x].l
               ~~~~~^
/in/foo.cc:44:11: note: in expansion of macro 'l'
  int mid=(l(u),r(u))/2;
           ^