[cfe-dev] Proposal: parsing Qt signals/slots with attributes

[Konstantin Tokarev]

20.09.2011, 12:10, "erikjv" <erikjv at me.com>:
> Hello,
> I would like to add support for recognising Qt's signal/slot mechanism to clang by using attributes. For that, I have a proposal for a few small changes to the clang parser. These changes use the attributes to mark AST nodes as signal/slot/invokable, and expose those attributes through libclang.
> A bit of background: if you are more familiar with Objective-C, then the signal/slot mechanism works nearly exactly the same as Cocoa's IBAction/IBOutlet: it uses a meta-type system to invoke the methods, or let slots connected to a signal know that the signal was emitted. Qt's meta-type system also allows for "invokable methods", which can be called/invoked without being tagged as slot.
> Example:
> class Test {
> public:
>     Q_INVOKABLE void invokableA();
> public slots:
>     void slotA();
>     void inlineSlotB() {}
> signals:
>     void signalC();
> private:
>     Q_SIGNAL void signalD(), signalE();
>     Q_SLOT void slotF(), slotG();
>     void not_a_slot_or_slot();
>     Q_SLOT void inlineSlotH() {}
> };
> (To be used properly with Qt, the class would also have to inherit from QObject, and have the Q_OBJECT macro right after the opening brace.)
> Taking a leaf from Cocoa's book, we can use the pre-processor to inject:
> #define signals protected __attribute__((q_signal))
> #define slots __attribute__((q_slot))
> #define Q_SIGNAL __attribute__((q_signal))
> #define Q_SLOT __attribute__((q_slot))
> #define Q_INVOKABLE __attribute__((q_invokable))
> Then the proposed change to clang is to handle it as follows:
> - for method declarations or inline method definitions, accept the q_signal/q_slot/q_invokable attributes, and add the attribute to the AST node
> - for C++ access specifiers, accept an additional (trailing) q_* attribute, and add the attribute to all AST nodes for methods until the next specifier
> This is equivalent to how moc (Qt's Meta-Object Compiler) generates the meta-object for a QObject.
> Attached is a proof-of-concept implementation/patch (with the above example as test-case). It also adds the attributes as cursor kinds to libclang, so a client application (like Qt Creator) can use it to find out which of the methods are "tagged" as a signal/slot/invokable


Could anybody review this patch? It's very important for Qt community.

-- 
Regards,
Konstantin