[Development] Q_OBJECT and "override"

[Christian Kandeler]

Hi,

as anyone who uses clang has probably already noticed, this compiler has 
recently added "-Winconsistent-missing-override" to the collection of 
flags enabled via "-Wall". As a result, you now get literally thousands 
of warnings when building any non-trivial Qt project. This is because 
the expansion of the Q_OBJECT macro contains virtual overrides that are 
not marked with the "override" keyword, so all QObject-derived classes 
using Q_OBJECT and making use of the "override" keyword will trigger 
this warning. Adding the keyword in the Q_OBJECT definition does not 
help in itself, as now all derived classes *not* using "override" would 
trigger the warning.
So how to deal with this?
1) Add "override" (or rather Q_DECL_OVERRIDE) to the definition of 
Q_OBJECT *and* all QObject-derived classes in Qt.
Pros: Is the correct solution.
Cons: Tedious work, will introduce some noise into the git history.
2) Remove "override" from all QObject-derived classes in Qt.
Pros: Less work than 1)
Cons: Entirely wrong. Discourages developers from using "override" in 
their code, for a start.
3) Explicitly disable the warning in the clang mkspecs.
Pros: Easy to do.
Cons: Users might want to enable the warning, but they can't, as they 
will then drown in warnings from our headers.
4) Let users deal with the problem by making them turn the warning off.
Pros: Even easier to do.
Cons: See 3). Also seems very lazy.

Opinions?


Christian