/in/foo.cc: In function 'void fibi()':
/in/foo.cc:5:67: warning: iteration 63 invokes undefined behavior [-Waggressive-loop-optimizations]
 void fibi () {fi[0]=1,fi[1]=1,fi[2]=2;for(int i=3;i<=66;i++) fi[i]=fi[i-1]+fi[i-2];return;}
                                                              ~~~~~^~~~~~~~~~~~~~~~
/in/foo.cc:5:52: note: within this loop
 void fibi () {fi[0]=1,fi[1]=1,fi[2]=2;for(int i=3;i<=66;i++) fi[i]=fi[i-1]+fi[i-2];return;}
                                                   ~^~~~