[D-runtime] DLL initialization in Druntime

[Brad Roberts]

On Mon, 17 Jan 2011, Sean Kelly wrote:

> Darnit, you're right.  So the ideal scenario would be if the GC proxy 
> could be set before the DLL load event was fired, which I think is 
> impossible.  I also think it's important that a D DLL be usable by both 
> a D and a non-D host app without a recompile, so we can't rely on 
> gc_setProxy() ever being called (which is why I'm not terribly fond of 
> gcstub to begin with).  This problem applies to any GC in the DLL 
> though, so it still needs a solution.
> 
> I can think of two solutions, though neither are terribly appealing.  
> The first would be to require that D DLLs not create threads in their 
> module ctors, and have gc_setProxy() call the module dtors, set the 
> proxy, then re-construct the modules.  The second would be for 
> gc_setProxy() to suspend all threads in the DLL, have the GC pass all of 
> its allocated blocks as roots/ranges to the proxy, and then restart 
> threads in the DLL.  The second seems far more robust, but imposes a 
> rather large functionality requirement on the GC (a pseudo-collection).
> 
> Thoughts?

#3) require that d dll's call the appropriate registration function first.  
Any user ctors must be 2-N.