memory leak - where?

[wysota]

These are most likely false positives as you probably don't close the database connection gracefully when you exit your application, but that's ok. It could also be that the application crashes and that's why QCoreApplication's destructor doesn't have a chance to run. The rest of the leaks are unrelated to Qt and you can't do anything about them (apart from not using the offending libraries, such as fontconfig).

[Tomasz]

These are most likely false positives as you probably don't close the database connection gracefully when you exit your application, but that's ok. It could also be that the application crashes and that's why QCoreApplication's destructor doesn't have a chance to run. The rest of the leaks are unrelated to Qt and you can't do anything about them (apart from not using the offending libraries, such as fontconfig).

My application should work for a long time without problems, but more it's works valgrind shows more memory leaks. I'm always closing database after using it with MyDatabse.close(); Is there anything more I can do to make my application more reliable?

thanks in advance
best regards
Tomasz

[wysota]

My application should work for a long time without problems, but more it's works valgrind shows more memory leaks.

I don't think Valgrind will show you memory leaks while the program is running. A leak can only be detected with probability close to 100% when the application exits.

I'm always closing database after using it with MyDatabse.close();

There is also QSqlDatabase::removeDatabase() that frees all the resources.

Is there anything more I can do to make my application more reliable?

You need to interpret the memory leak report yourself and review your code to see if you are not leaking memory. Qt itself doesn't leak memory so if you really do have leaks (not that you think you do but that you are certain you do) then it's either in your code or in support libraries (such as db engines, font engines, etc.).

[Tomasz]

I don't think Valgrind will show you memory leaks while the program is running. A leak can only be detected with probability close to 100% when the application exits.

You're right. I meant that it shows leaks after closing application.
I'll try QSqlDatabase::removeDatabase() and let know how it works.

thanks
best regards
Tomasz

[wysota]

I'll try QSqlDatabase::removeDatabase() and let know how it works.

Don't expect miracles, it won't make your problems go away and from practical point of view the use of this method is meaningless as in your case you'd only use it when exiting the application anyway so it won't prevent the application from leaking memory.

[Tomasz]

I think I've found problem. Here we've got code:

ok = bdb.open();
 
    if (ok)
    {
        queryModel.clear();
        queryModel.setQuery("SELECT * FROM notifi WHERE complete='0'", bdb);
        queryModel.clear(); // <----- with this everything is OK
        bdb.close();
    }

ok = bdb.open();

    if (ok)
    {
        queryModel.clear();
        queryModel.setQuery("SELECT * FROM notifi WHERE complete='0'", bdb);
        queryModel.clear(); // <----- with this everything is OK
        bdb.close();
    }

To copy to clipboard, switch view to plain text mode 

And now my question - why if I close my database without clearing QSqlQueryModel strange things happens (data is still there but memory usage is still growing up each time function is executed)? I need to close database for other programs but i need to use data that I've just read from database to QSqlQueryModel.

thanks in advance
best regards
Tomasz

[wysota]

Destructor of the model will call clear() for you so this is not a memory leak situation. Of course you shouldn't be closing a connection with an active query and you will get a warning on the console when doing so. You should clear all the queries and only then close the database connection.

[Tomasz]

Of course you shouldn't be closing a connection with an active query and you will get a warning on the console when doing so. You should clear all the queries and only then close the database connection.

In this case I don't get any warning in my console. I'm only observing growing memory usage ('top' command), which disappears when I clean before closing. I'll think I need to learn more about using database in QT. I've got some questions about that problem but I'll search for answers in thread more connected with databases. Thanks!

best regards
Tomasz