On 23-05-2012 15:46, deadalnix wrote:
Le 23/05/2012 14:32, Alex Rønne Petersen a écrit :
On 23-05-2012 14:21, deadalnix wrote:
Le 23/05/2012 05:22, Steven Schveighoffer a écrit :
I have come across a dilemma.
Alex Rønne Petersen has a pull request changing some things in the
GC to
pure. I think gc_collect() should be weak-pure, because it could
technically run on any memory allocation (which is already allowed in
pure functions), and it runs in a context that doesn't really affect
execution of the pure function.
So I think it should be able to be run inside a strong pure function.
But because it has no parameters and no return, marking it as pure
makes
it strong pure, and an optimizing compiler can effectively remove the
call completely!
So how do we force something to be weak-pure? What I want is:
1. it can be called from a pure function
2. it will not be optimized out in any way.
This solution looks crappy to me:
void gc_collect(void *unused = null);
any other ideas?
-Steve
Why a pure function can call a collection cycle ???? This is an impure
operation by essence.
I think what is need here is to break the type system to allow call of
impure function into a pure one.
I think you're missing an amusing point:
class C { this() pure {} }
C foo() pure
{
return new C(); // can trigger a collection!
}
Ok, but no direct call to GC collect will be done, so the function don't
need to be pure, it need to be somehow hacked into the allocation
mecanism, probably using compiler magic.
Sure there'll be a direct call to that. It's effectively what the GC
does when collecting.
So basically the allocation mecanism have to break the type system to
act like it is pure, even if it isn't.
--
Alex Rønne Petersen
a...@lycus.org
http://lycus.org
