Shared Delegates

[Benjamin Thaut]

Am 17.10.2011 22:43, schrieb Michel Fortin:
> On 2011-10-17 20:33:59 +0000, Andrew Wiley <wiley.andrew.j at gmail.com> said:
>
>>
>> Okay, I realize there have been some discussions about this, but I have a
>> few questions about shared delegates because right now they are
>> definitely
>> broken, but I'm not sure how.
>> Take this code example:
>>
>> synchronized class Thing {
>> void doSomeWork(void delegate() work) {
>> work();
>> }
>> void work() {}
>> }
>>
>> void main() {
>> auto th = new Thing();
>> th.doSomeWork(&th.work);
>> }
>>
>> This doesn't compile because the type of "&th.work" is "void delegate()
>> shared", which cannot be cast implicitly to "void delegate()".
>> My first question would be whether that type is correct. It's true
>> that the
>> data pointer of the delegate points to a shared object, but given that
>> the
>> function locks it, does that really matter in this case? I guess I'm just
>> not clear on the exact meaning of "shared" in general, but it seems like
>> whether the data is shared or not is irrelevant when the delegate
>> points to
>> a public member of a synchronized class. If it was a delegate pointing
>> to a
>> private/protected member (which should be illegal in this case), that
>> would
>> not be true.
>> If that type is correct, the problem is that "void delegate() shared"
>> doesn't parse as a type (there is a workaround because you can create
>> variables of this type through alias and typeof).
>>
>> What, exactly, is wrong here?
>
> I think what's wrong is that a shared delegate should implicitly convert
> to a non-shared one. The delegate is shared since it can be called
> safely from any thread, and making it non-shared only prevent you from
> propagating it to more thread so it's not harmful in any way.
>

I reported this exact issue already a few months ago and simply didn't 
get any comment on it. If you really try to use shared to are going to 
hit more such problems.

See the shared section of my blogpost: http://3d.benjamin-thaut.de/?p=18
-- 
Kind Regards
Benjamin Thaut