Emit thread safety
@class MyServer: public QTcpServer
connect(this, SIGNAL(internalShutdown()), SLOT(doShutdown()), Qt::QueuedConnection);
MyServer instance created in main thread context and work with main thread events processing (app.exec()). And now, myServerInstance->shutdown() executed from other thread (not from main thread) -- executed from Control-C Handler (which is executed in temporary thread created by OS). Question is: is it safe that emit internalShutdown() inside MyServer::shutdown() executed in another thread context? (I mean emit keyword safety). Sorry for my English
The emit keyword itself doesn't do much. It is there for the looks of it. Essentially emitting a signal is calling a specific function. Signal/slot connections are by default made with the thread auto-detection enabled. The meta object will notice that different threads are being used and automatically a queued connection will be chosen. It is possible that a direct connection is enforced. In that case the called slot is executed in the emitting thread's context.
I believe there is an article on the wiki explaining this more in detail.
Bottom line is that signal/slot connections are locked, and therefore thread safe.