c++ - Suppress warning "QApplication was not created in main() thread"

Question

I've created a Qt-based network library for use with applications that are not running a Qt event loop, and which are not necessarily otherwise Qt applications. This was made possible by creating a QCoreApplication instance in a thread per the answer from Is it possible to create local event loops without calling QApplication::exec()?

This works perfectly, but it makes Qt upset (I presume it's worried that I'll try to manipulate a GUI outside of the main thread which wouldn't work, but I'm not), and so it prints a warning: WARNING: QApplication was not created in main() thread.

I'd like to suppress that warning which will otherwise be printed to the X11 console and most likely cause my users to enter a bunch of needless deficiencies. However, I'd like to just supress THIS error, as I use qDebug for some legitimate purposes and want to see future warnings. Is there a way to do this, like some kind of Qt #pragma?

EDIT:

A similar question was asked before here: Qt console application "WARNING: QApplication was not created in the main() thread", but the answer was basically just a code review without any meaningful ideas to suppress the warning.

Answer 1

The problem arises because you're touching Qt APIs (in the main thread, or just in some thread) before creating QApplication. You can't do that. In particular, you're creating a QObject of some kind, which is setting somwhere in Qt what Qt itself should consider as the main thread.

The only Qt APIs you're allowed to use before creating a QApplication are the ones that are explicitely documented to be safe in that scenario.

So: don't do that. Build a QCoreApplication as the first thing, then you're free to go.