lost connection to mysql server during query

I am using MySQL for various personal projects and, because I have little experience with databases (except for very simple stuff), I recently decided to learn about stored procedures. The fact that all my queries were hardcoded made me feel uncomfortable. Since then, I started getting errors randomly:

Lost connection to MySQL server during query

followed by

MySQL server has gone away.

I looked at MySQL server has gone away in the documentation:

• [..] the server timed out and closed the connection. [..] By default, the server closes the connection after eight hours if nothing has happened. Not the case. The error happened after a few seconds or minutes of connecting to the server.
• You (or the db administrator) has killed the running thread with a KILL statement or a mysqladmin kill command. No, the server is still running. I can ping it, connect to it and issue commands without any problems. In fact, restarting my application works (only to fail again after a few queries).
• You tried to run a query after closing the connection to the server. No.
• A client application running on a different host does not have the necessary privileges to connect to the MySQL server from that host.No, privileges didn't change while my program was running.
• You got a timeout from the TCP/IP connection on the client side. Again, no. All suggestions about timeouts do not make sense. Actually, it looked like I was getting this error if I executed a bunch of stored procedure calls rapidly.
• Skipping more stuff about timeouts
• You can also get these errors if you send a query to the server that is incorrect or too large.This is getting interesting: a query [..] that is incorrect. Googling reveals posts such as this:

  Right! Solved it... [...] There are 2 queries which make up a navigation panel on this chat system, one shows public chatrooms, the other private. The query which made up the private chatrooms was: select distinct chatroom_label as label, chatroom_id as id from chatroom where chatroom_date_deleted_timestamp is null and chatroom_is_permanent_chatroom=1 order by chatroom_label desc, chatroom.chatroom_label asc which is obviously wrong since it's ordering by the same column twice. This didn't produce an error but instead crashed the MySQL connection.

  After double checking my queries, I found no problems. Indeed, very simple queries called in a loop would eventually fail.

Finally, after several hours of research, I stumbled upon this thread and especially this post:

Stored procedures always return one extra result set for the error status of the procedure so you need to set the CLIENT_MULTI_RESULTS option and need to iterate over the returned result sets using the mysql_more_results() and mysql_next_result() API functions.

Looking back at my code, I have a stored procedure that looks like:

create procedure get_something(sid int)
begin
  select * from somewhere where id=sid;
end

and I was calling it like this:

void f(MYSQL* handle)
{
  mysql_query(handle, "select get_something(0)");
  MYSQL_RES* r = mysql_store_result(handle);

  MYSQL_ROW row;
  for (;;)
  {
    row = mysql_fetch_row(r);
    if (!row)
       break;

    use(row);
  }

  mysql_free_result(r);
}

The problem is that the query returned more than one result set. After leaking these result sets for a few times (random), the connection was dropped. There are two bugs here: mine (leaking result sets) and mysql's (shitty error messages). The solution is to make sure all result sets are processed before issuing another query:

while(mysql_more_results(handle))
{
  mysql_next_result(handle);
  MYSQL_RES* r = mysql_store_result(handle);
  if (res)
      mysql_free_result(r);
}

In my case, since the actual call to mysql_query is wrapped inside another function, I added this bit before doing any query. It solved the problem nicely. For more informations and lots of "me too" posts, google is always helpful.