foo.cc: In function 'int main()':
foo.cc:16:3: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
   else
   ^~~~
foo.cc:18:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'else'
    return 0;
    ^~~~~~
foo.cc:6:6: warning: unused variable 'x1' [-Wunused-variable]
  int x1;
      ^~