ios7.1 CommonCrypto库抱怨:隐式转换丢失整数精度:“NSUInteger”(无符号long)到CC_LONG (unsigned int)

I get the above error (in title) whilst doing a MD5 from file.. I can usually cope with these type of 32->64bit conversion issues..but in this case, I do not know what I should do as CC_MD5 is part of I get the above error (in title) whilst doing a