今天在CentOS5上安装Redis2.6时遇到如下问题：
/root/redis-2.6.4/src/zmalloc.c:223: undefined reference to `__sync_add_and_fetch_4' collect2: ld returned 1 exit status make[1]: *** [redis-server] Error 1 make[1]: Leaving directory `/root/redis-2.6.4/src' make: *** [all] Error 2
解决方法如下：
打开文件src/.make-settings，修改如下行：
OPT=-O2 # 修改为 OPT=-O2 -march=i686
