Shared Delegates

[Andrew Wiley]

On Tue, Oct 18, 2011 at 12:53 AM, Benjamin Thaut <code at benjamin-thaut.de>wrote:

> 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<http://3d.benjamin-thaut.de/?p=18>
>
>
Ah, I was looking through the bug reports and didn't see this exact bug. Did
I just fail at searching, or should I file it?
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