On 08/05/2018 01:41 AM, xiewen wrote: > Hi Rob： > > Thank you and Elliott's help. > i have a doubt: > why is it removed if(options) ? Because free(NULL) is defined as a NOP in posix and C99, so there's no need to test: http://pubs.opengroup.org/onlinepubs/9699919799/functions/free.html Rob