[Development] Disabling exception support in QtCore?

[Julien Blanc]

Le 03/10/2013 10:36, Olivier Goffart a écrit :
> On Wednesday 02 October 2013 09:30:58 Thiago Macieira wrote:
>
>> That would mean any signal could throw ANY exception. It would also preempt
>> the execution of further slots, which might be important.
>>
>> Usually the person who connects a signal to a slot is a completely different
>> developer than who wrote the signal or the slot.
> I think your assumptions are false.
> When using signals and slot in an application one write both the signal and
> the slot at the same time, to wire two part of that same appliation.
This may be true in a (small) application, but definitely not if you are 
developping a library. Usually, you write signals but don’t have any 
clue about the slots that will be connected to.

>> That would mean people who do connections should have to pay attention to
>> what slots throw and know what signals can cope with exceptions being
>> thrown.
> Signals and slots are not different from normal functions in that respect
> (especially virtual functions)
> One need to take care who calls your function when you throw exceptions.
That would mean that both slots and signals needs to document which 
exception they can respectively throw/handle. With qt5 we gained static 
checking of signal/slot compatibility. Introducing exceptions here would 
ruin this gain, since it will introduce a new way for signal and slots 
to be incompatible.

And i don’t know how you can reasonably catch an exception in an 
asynchronous call.

IMHO, slots should be nothrow.

>> I would accept at most exceptions through the invokeMethod mechanism in a
>> DirectConnection, since that's a 1:1 relationship and there are no signals.
+1. Exceptions outside DirectConnection would be very strange animals.

Julien