Crash while connecting to MySQL

I have a thread that opens a MySQL connection, executes a SELECT query, then closes the connection. Sometimes it crashes with a segmentation fault while trying to establish the connection. This is the backtrace I get:

Quote:

---

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1246762096 (LWP 5786)]
0xb51e232e in my_stat () from /usr/lib/libmysqlclient_r.so.15
(gdb) bt
#0 0xb51e232e in my_stat () from /usr/lib/libmysqlclient_r.so.15
#1 0xb51dad95 in escape_quotes_for_mysql () from /usr/lib/libmysqlclient_r.so.15
#2 0xb51db675 in get_charsets_dir () from /usr/lib/libmysqlclient_r.so.15
#3 0xb51db7a9 in get_charset_by_csname () from /usr/lib/libmysqlclient_r.so.15
#4 0xb51f80e9 in mysql_set_character_set () from /usr/lib/libmysqlclient_r.so.15
#5 0xb6e96652 in QMYSQLDriver::open (this=0x81308c0, db=@0x80e6638, user=@0x80e663c, password=@0x80e6640, host=@0x80e6644, port=3306, connOpts=@0x80e6650)
at ../../../sql/drivers/mysql/qsql_mysql.cpp:1091
#6 0xb7ebb28e in QSqlDatabase::open (this=0xb5afe2d0) at kernel/qsqldatabase.cpp:792
#7 0x0806278f in DbThread::run (this=0x80e0480) at dbthread.cpp:61
#8 0xb72b0c09 in QThreadPrivate::start (arg=0x80e0480) at thread/qthread_unix.cpp:146
#9 0xb724e112 in start_thread () from /lib/libpthread.so.0
#10 0xb70c32ee in clone () from /lib/libc.so.6

---

My code is like this:

Code:

---

void DbThread::run()
{
	QString connectionName = "DbThread-" + QDateTime::currentDateTime().toString("yyyyMMddhhmmsszzz");
 
	{
		// Connect to the database server
		QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL", connectionName);
		db.setHostName(m_host);
		db.setPort(m_port);
		db.setDatabaseName(m_database);
		db.setUserName(m_userName);
		db.setPassword(m_password);
		bool ok = db.open();
		if(!ok) {
			emit error(QString(tr("Error connecting to the database:\n\n%1")).arg(db.lastError().text()));
			return;
		}
 
		QSqlQuery query(db);
		query.exec("SELECT ...");
		if(query.next()) {
			...
			emit resultsOfMyQuery(...);
		}
		db.close();
	}
 
	QSqlDatabase::removeDatabase(connectionName);
}

---

It seems to be due to the MySQL client library but I wanted to ask here before going to the MySQL forums. Anyone had this problem and was able to solve it?

I'm using Qt 4.2.2 under openSUSE 10.2, although I also compiled it under Windows for other clients and it worked perfectly there.

Make sure that you keep all references to the QtSql module in one thread. It is very sensitive for this as the threading docs mention.