fix for g++ 4.7
fix for g++ 4.7

KunYi/muduo,SourceInsight/muduo,mitliucak/muduo,shenhzou654321/muduo,KingLebron/muduo,guker/muduo,kidzyoung/muduo,lizj3624/muduo,zouzl/muduo-learning,jxd134/muduo,tsh185/muduo,zhuangshi23/muduo,westfly/muduo,shenhzou654321/muduo,zhanMingming/muduo,Cofyc/muduo,lizj3624/muduo,mitliucak/muduo,huan80s/muduo,jerk1991/muduo,ucfree/muduo,shenhzou654321/muduo,dhanzhang/muduo,flyfeifan/muduo,mitliucak/muduo,DongweiLee/muduo,lizhanhui/muduo,decimalbell/muduo,mitliucak/muduo,Cofyc/muduo,ucfree/muduo,devsoulwolf/muduo,penyatree/muduo,SuperMXC/muduo,SuperMXC/muduo,dhanzhang/muduo,SuperMXC/muduo,SourceInsight/muduo,Cofyc/muduo,devsoulwolf/muduo,huan80s/muduo,decimalbell/muduo,zouzl/muduo-learning,danny200309/muduo,wangweihao/muduo,ywy2090/muduo,tsh185/muduo,danny200309/muduo,KingLebron/muduo,june505/muduo,ucfree/muduo,zhanMingming/muduo,wangweihao/muduo,danny200309/muduo,jerk1991/muduo,flyfeifan/muduo,lizj3624/http-github.com-chenshuo-muduo-,KingLebron/muduo,decimalbell/muduo,SourceInsight/muduo,shuang-shuang/muduo,KingLebron/muduo,lizj3624/http-github.com-chenshuo-muduo-,pthreadself/muduo,ucfree/muduo,Cofyc/muduo,penyatree/muduo,huan80s/muduo,nestle1998/muduo,decimalbell/muduo,lizj3624/http-github.com-chenshuo-muduo-,guker/muduo,lvshiling/muduo,zxylvlp/muduo,lizhanhui/muduo,KublaikhanGeek/muduo,lvmaoxv/muduo,kidzyoung/muduo,Cofyc/muduo,youprofit/muduo,jxd134/muduo,yunhappy/muduo,ucfree/muduo,lizj3624/muduo,lizj3624/http-github.com-chenshuo-muduo-,ywy2090/muduo,wangweihao/muduo,SourceInsight/muduo,youprofit/muduo,danny200309/muduo,floristt/muduo,zhuangshi23/muduo,wangweihao/muduo,shuang-shuang/muduo,devsoulwolf/muduo,KingLebron/muduo,SuperMXC/muduo,dhanzhang/muduo,yunhappy/muduo,june505/muduo,lvmaoxv/muduo,zhuangshi23/muduo,DongweiLee/muduo,nestle1998/muduo,zxylvlp/muduo,devsoulwolf/muduo,SourceInsight/muduo,xzmagic/muduo,lvshiling/muduo,fc500110/muduo,decimalbell/muduo,KublaikhanGeek/muduo,dhanzhang/muduo,danny200309/muduo,xzmagic/muduo,devsoulwolf/muduo,shenhzou654321/muduo,mitliucak/muduo,floristt/muduo,floristt/muduo,shenhzou654321/muduo,huan80s/muduo,zxylvlp/muduo,daodaoliang/muduo,pthreadself/muduo,dhanzhang/muduo,fc500110/muduo,SuperMXC/muduo,lizj3624/muduo,wangweihao/muduo,lizj3624/http-github.com-chenshuo-muduo-,westfly/muduo,lizj3624/muduo,floristt/muduo,westfly/muduo,huan80s/muduo,zouzl/muduo-learning,floristt/muduo,KunYi/muduo,daodaoliang/muduo