MySQL doesn't display errors in error log - mysql

Question

After having some trouble with installing a UDF in MySQL (Cannot install MySQL UDF) I'm facing another issue. When executing the function I get a "Lost connection to MySQL server during query" error (errno 2013). Error logging is enabled, but I can't see any error messages in the log file. The my.ini configuration file has the following log properties under mysqld:
log-output=FILE
general-log=0
general_log_file="mysql-general-log-file.log"
slow-query-log=1
slow_query_log_file="mysql-slow-query-log-file.log"
long_query_time=10
log="mysql.log"
# Error Logging.
log-error="mysql-error.log"
log-warnings=2
And here is the mysql-error.log output:
140314 21:29:25 [Note] Plugin 'FEDERATED' is disabled.
140314 21:29:25 InnoDB: The InnoDB memory heap is disabled
140314 21:29:25 InnoDB: Mutexes and rw_locks use Windows interlocked functions
140314 21:29:25 InnoDB: Compressed tables use zlib 1.2.3
140314 21:29:25 InnoDB: Initializing buffer pool, size = 307.0M
140314 21:29:25 InnoDB: Completed initialization of buffer pool
140314 21:29:25 InnoDB: highest supported file format is Barracuda.
140314 21:29:26 InnoDB: Waiting for the background threads to start
140314 21:29:27 InnoDB: 5.5.32 started; log sequence number 9975593
140314 21:29:27 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
140314 21:29:27 [Note] - '0.0.0.0' resolves to '0.0.0.0';
140314 21:29:27 [Note] Server socket created on IP: '0.0.0.0'.
140314 21:29:27 [Note] Event Scheduler: Loaded 0 events
140314 21:29:27 [Note] C:/Program Files/MySQL/MySQL Server 5.5/bin\mysqld: ready for connections.
Version: '5.5.32-log' socket: '' port: 3306 MySQL Community Server (GPL)
I've also tried to debug the UDF itself by adding a few print commands to the code, e.g.
fprintf(stderr, "%s", "Launching JVM\n");
fflush(stderr);
Unfortunately this didn't work either. Which other options do I have to track down the issue?