/in/foo.c: In function 'main':
/in/foo.c:17:17: warning: iteration 2 invokes undefined behavior [-Waggressive-loop-optimizations]
     b[i][j]=a[i][j];
             ~~~~^~~
/in/foo.c:13:3: note: within this loop
   for(int i=0;i<3;i++)
   ^~~