fixed bug in stack
fixed bug in stack

hkuplg/fcore,bixuanzju/fcore,hkuplg/fcore,wxzh/fcore,wxzh/fcore,xnning/fcore,zhiyuanshi/fcore,zhiyuanshi/fcore,wxzh/fcore,xnning/fcore,hkuplg/fcore,bixuanzju/fcore,zhiyuanshi/fcore,bixuanzju/fcore,xnning/fcore