[Development] Disabling exception support in QtCore?

[Olivier Goffart]

On Thursday 10 October 2013 08:22:44 BRM wrote:

> I have personnally maintained a 400k+ SLOC codebase based on QT.
> It made extensive use of Signals/Slots between objects. Even though I was
> pretty much the only developer working on it, I still had to quite often
> track through signals/slots to make sure I understood things. Not because
> the codebase was unclear, but because it was quite non-trivial. It would
> have been an extensive PITA to try to know which ones I could or could not
> use exceptions with.
> 
> I'm no compiler expert - but without help from the compiler to make sure
> that kind of things doesn't happen - e.g. marking signals/slots as
> Q_EXCEPTION_THROW and Q_EXCEPTION_SAFE and having some part of the compiler
> chain detect and at minimal warn of issues - it will not be feasible.


Programming is not easy.
Now, our goal is to make programming with Qt as easy as possible.

Tell me what makes programming easier:

1) We forbid any use of exception in any slot connected to any signal.
     - Programmers that don't use exceptions don't care because it does not 
impact them.
     - Programmers that uses exception in their application to forward errors 
cannot use signals and slots to propagate exceptions from one object of their 
application to another anymore.

2) We allow slots to forward the exception to the signal.
    - Programmers that don't use exceptions still don't care because it does 
not impact them.
    - Programmers that use exceptions can hapilly let exceptions go from the 
slot to where the signal is emitted.


If you are not using exception now as I understand from your text above, then 
nothing changes for you.

However, someone who is using currently exceptions, they will have to change 
their code for more complicated code because we decided to forbid it ("for 
their own good")

May I recall that exceptions through signals and slots always worked, and was 
used.    And now you need to give a good reason to forbid it.
Reducing the size of QtCore might be a good reason,  but just saying "it's for 
your own good" is not.


-- 
Olivier

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