Never call mysql_real_connect more than once without calling mysql_init again

I spent a couple of hours digging into a problem that a program using MySQL C API sometimes used a wrong character set. The code was something like:

MYSQL mysql;
mysql_init(&mysql);
mysql_options(&mysql, MYSQL_READ_DEFAULT_GROUP, "test");
while (!mysql_real_connect(&mysql, host, user, password, dbname, port, NULL, 0)) {
    sleep(3);
}

The problem was that when mysql_real_connect failed, it called mysql_close inside that cleared all options set by mysql_options. Since we use default-character-set in my.cnf to set the character set to utf-8, it used latin-1 when it didn’t read my.cnf.

It almost always worked fine because mysql_real_connect succeeded, but it sometimes used a wrong character set when the first attempt to connect to the server failed.

When mysql_real_connect fails, you have to repeat from mysql_init.