/in/foo.c: In function 'spfa':
/in/foo.c:34:5: warning: operation on 'op' may be undefined [-Wsequence-point]
   op=op>1+(n>>1) ? 1 : ++op;
   ~~^~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:45:8: warning: operation on 'ed' may be undefined [-Wsequence-point]
      ed=ed>1+(n>>1) ? 1 : ++ed;
      ~~^~~~~~~~~~~~~~~~~~~~~~~