On 2011-10-17 20:33:59 +0000, Andrew Wiley <wiley.andre...@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.
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
