valgrind reports uninitialised value

I wrote a C program to query mariadb in a infinite loop.during it was running under valgrind,I restarted mariadb,then valgrind show the following error(I have hidden my prog's call stack):

[root@localhost mariadb-connector-c-master]# ==11514== Conditional jump or move depends on uninitialised value(s)
==11514== at 0x5076D4E: my_real_read (net.c:654)
==11514== by 0x5077084: my_net_read (net.c:723)
==11514== by 0x507C42C: net_safe_read (libmariadb.c:391)
==11514== by 0x507D7B9: mthd_my_real_connect (libmariadb.c:1781)
.....

I build connect/C from github master and tried again,it still had this problem