Passing references to slots in another thread - undocumented important behaviour

Qt's signals and slots mechanism allows sending signals with parameters to slots in other threads (with QueuedConnection for example).

There appears to be no official documentation to explain how sending a reference parameter over this sort of signal is thread safe. (it is, allegedly, but there are no official docs for it).

According to this https://stackoverflow.com/questions/8455887/stack-object-qt-signal-and-parameter-as-reference/18146433 there is a mechanism that creates copies of the objects for queued connections.

This is an important detail that should be documented otherwise users will end up jumping through hoops to protect themselves against concurrent access which is not happening.