[Development] Module maintainers: QT_NO_CONTEXTLESS_CONNECT in your modules

[Hasselmann Mathias]

Hi Peppe,

thank you alot for this highly appreciated and super useful feature!
Give up counting how often I forgot the context argument.

Ciao
Mathias

Am 10.07.2023 um 18:02 schrieb Giuseppe D'Angelo via Development:
> Hi,
>
> https://codereview.qt-project.org/c/qt/qtbase/+/487560 introduces 
> QT_NO_CONTEXTLESS_CONNECT , a macro that disables the 3-arguments 
> connect -- in other words, it disables the
>
>>   QObject::connect(sender, signal, functor)
>
> overload, leaving only 4/5 argument(s) overloads
>
>> QObject::connect(sender, signal, receiver/context, functor/slot, (type))
>
>
> as well as the string-based connect().
>
>
> The reason for NOT using the 3-args overload is that it is error prone.
>
> For starters, it makes it hard to reason about the lifetime of such a 
> connection. It makes it very easy to connect to lambdas that capture 
> some local state in the receiver, but when the receiver is destroyed, 
> the connection isn't automatically disconnected (therefore, if the 
> signal is emitted, the program will crash). Fixing this may or may not 
> be straightforward, depending on how much state is captured.
>
> Second, it's also easy to forget that since there's no 
> receiver/context, the connection is always forced to be *direct*, 
> which complicates things if multiple threads are involved.
>
> -- 
>
> I'm about to enable the macro for (most) of QtBase:
>
> https://codereview.qt-project.org/c/qt/qtbase/+/489232
>
> I've also done the exercise of enabling it for qtdeclarative (patches 
> pending) and qttools (merged), but there's simply too much code out 
> there that *still* uses it. As I said above, fixes are not always 
> obvious (sometimes it's very unclear who the "receiver" is).
>
> -- 
>
> Since this is ultimately a code style issue, I'd like to leave the 
> decision with the module maintainers regarding whether or not enable 
> QT_NO_CONTEXTLESS_CONNECT for their own modules. Ideally, however, we 
> should enable it in headersclean, so please make at least those not 
> contain 3-args connect().
>
>
> Opinions? Objections?
>
>
> Thank you,
>