mysql_init 返回 NULL

问题是：在执行完命令./sqladvisor -f sql.cnf -v 1后，错误日志什么都没有。
以下是输出日志：
2017-03-31 15:50:01 15432 [Note] 第1步: 对SQL解析优化之后得到的SQL:select count(1) AS count(1) from im_server.message where (msgsender = '10006')
2017-03-31 15:50:01 15432 [Note] 第2步：开始解析where中的条件:(msgsender = '10006')
2017-03-31 15:50:01 15432 [Note] show index from message
2017-03-31 15:50:01 15432 [Note] 第3步：SQLAdvisor结束！错误日志:

后来在sqladvisor里面的main.cc添加一些日志，发现在mysql_sql_parse_field_cardinality_new的MYSQL *con = mysql_init(NULL);方法返回的con为NULL，后来单独写了个demo，验证mysql_init是否好使，确定返回非NULL,mysql环境是percona5.5，看官网推荐是5.6，会不会跟这个有问题，求助，先写了

Start in main.cc and inspect mysql_sql_parse_field_cardinality_new, focusing on the MYSQL *con = mysql_init(NULL) call and the surrounding error handling. Reproduce the command from the issue with the reported Percona 5.5 environment, then compare the behavior with the standalone mysql_init demo. Done means the cause of the NULL result is identified and the issue has a reproducible resolution.