Fixing cyclic import static construction problems

[Artur Skawina]

On 11/29/12 23:34, Jonathan M Davis wrote:
> On Thursday, November 29, 2012 23:28:07 Timon Gehr wrote:
>> On 11/29/2012 01:17 PM, Jonathan M Davis wrote:
>>> In the past when I've brought up similar solutions, he's been completely
>>> opposed to them. ...
>>
>> It is not a solution, it is a workaround.
> 
> What do you mean? The runtime sees circular dependencies between modules even 
> when there's no actual circular dependency between static constructors. We 
> need to fix that. One way is to just make the runtime not care, which wouldn't 
> be particularly safe. Another is to explicitly tell it that there are no such 
> dependencies. I don't see how that's not a solution. And unless someone can 
> come up with a way for the runtime to somehow determine on its own that 
> there's no actual, circular dependency, I don't see how anything better could 
> be done.

It's relatively easy for the /compiler/ to figure it out; it's just that
implementing a simple user-provided flag requires the least amount of work.
What Walter suggested can be tweaked to be sane (per-ctor flag) and will
still be useful if/when the compiler becomes smarter (think lazily initted
module fields).
For the compiler to check if the value of every imported symbol accessed
inside a mod-ctor can be evaluated at compile-time (if you encounter a case
where this is not true it means there (potentially) is a true dependency and
the ctors should be ordered) would require more work.

artur