QFile::atEnd() problem?

[wysota]

If I understand correctly, I should only use the approach I use now if I properly use mutexes, or pass the object by reference in a signal-slot setup?

Not really. You can't call directly methods from QObjects across threads unless they are explicitely mentioned as thread-safe. So yes, you can connect to them using signals and slots to transfer data across threads, but you can't pass QObjects themselves as arguments to signals or call the sending object's methods from within the slot living in another thread than the object.

To come back to the original problem: I have found that the problem may be caused my socket reading (where the data in the file comes from). Not yet sure how to fix it, but apparently, there's some \r and \n mess going on there, i.e.: \r\n from the network protocol, \n from writing to file, something like that.

Dump the data directly to a file without modifying anything and inspect it manually.