/in/foo.cc: In function 'int main()':
/in/foo.cc:11:7: warning: statement has no effect [-Wunused-value]
  for(i<x/2;x1=x1+2;)
      ~^~~~
/in/foo.cc:11:18: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  for(i<x/2;x1=x1+2;)
                  ^
/in/foo.cc:11:14: warning: iteration 1073741822 invokes undefined behavior [-Waggressive-loop-optimizations]
  for(i<x/2;x1=x1+2;)
            ~~^~~~~
/in/foo.cc:11:2: note: within this loop
  for(i<x/2;x1=x1+2;)
  ^~~