/in/foo.c: In function 'main':
/in/foo.c:14:6: error: 'x1' undeclared (first use in this function)
  for(x1=0; x1<n; x1++)
      ^~
/in/foo.c:14:6: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:15:7: error: 'x2' undeclared (first use in this function)
   for(x2=0; x2<n; x2++)
       ^~
/in/foo.c:14:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(x1=0; x1<n; x1++)
  ^~~
/in/foo.c:45:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   int max=b[0];
   ^~~