Crash while connecting to MySQL

[vfernandez]

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:

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:

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);
}

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);
}

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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.