Program size, linking matter, and static this()

[deadalnix]

Le 17/12/2011 02:39, Andrei Alexandrescu a écrit :
> On 12/16/11 6:54 PM, Jonathan M Davis wrote:
>> By contrast, we could have a simple feature that was explained in the
>> documenation along with static constructors which made it easy to tell
>> the
>> compiler that the order doesn't matter - either by saying that it doesn't
>> matter at all or that it doesn't matter in regards to a specific
>> module. e.g.
>>
>> @nodepends(std.file)
>> static this()
>> {
>> }
>>
>> Now the code doesn't have to be redesigned to get around the fact that
>> the
>> compiler just isn't smart enough to figure it out on its own. Sure,
>> the feature
>> is potentially unsafe, but so are plenty of other features in D.
>
> That is hardly a good argument in favor of the feature :o).
>
> One issue that you might have not considered is that this is more
> brittle than it might seem. Even though the dependency pattern is
> "painfully obvious" to the human at a point in time, maintenance work
> can easily change that, and in very non-obvious ways (e.g. dependency
> cycles spanning multiple modules). I've seen it happening in C++, and
> when you realize it it's quite mind-boggling.
>
>> The best
>> situation would be if the compiler was smart enough to figure it out for
>> itself, but barring that this definitely seems like a far cleaner
>> solution than
>> having to try and figure out how to break up some of the
>> initialization code
>> for a module into a separate module, especially when features such as
>> immutable and pure tend to make such separation impossible without
>> some nasty
>> casts. It would just be way simpler to have a feature which allowed
>> you to
>> tell the compiler that there was no dependency.
>
> I think the only right approach to this must be principled - either by
> CTFEing the constructor or by guaranteeing it calls no functions that
> may close a dependency cycle. Even without that, I'd say we're in very
> good shape.
>
>
> Andrei

Very good point. CTFE is improving with each version of dmd, and is a 
real alternative to static this(); It should be considered when 
apropriate, it has many benefices.