Re: Runtime startup code for the GNAT Runtime...and a bit of humble pie.

[Shark8 <onewingedshark@gmail.com>]

On Tuesday, March 26, 2013 6:28:51 PM UTC-6, Diogenes wrote:
> 
> So I figure I might just be better off writing my own implementations of these things that have NO circular dependencies.

Circularity can certainly be a bad thing, the problem is likely that they (GNAT) didn't explain the circularity well. {And it's perfectly possible to have two package bodies dependent on the other's spec w/o a circularity in the spec structure.} There is, however, one spot that I've used it to a good degree to simplify things: in my LISP interpreter (made as an an intro to Ada 2012) I have two packages branching out from the base LISP which are mutually dependent: LISP.Lists and LISP.Elements -- each defining their respective objects and the operations on them. {List.Head returns an element and Element.As_List/To_List return lists.}

Though what I've found really useful in that project is private packages. {I use it to handle strings internally, keeping that from being exposed to the user.}

> One specific goal of my runtime is a clear hierarchy that progress directly from ada.ads out to the leaf packages(nodes). No circular deps. No package should depend on another package that depends on the first package.
> 
> This structure should take about %60 of the teeth gnashing out of the porting process.

I like that idea. One thing that might prove interesting is using generic packages: say for holding the definitions of those primitive/overridable functions you mentioned {clone(), futex(), etc} in its formal-parameters. That might also be an interesting way to handle different instruction-sets -- having the parameter link a lowish-level idea to the instruction [or several instructions]. It might be a way to achieve a compiler that's easier to retarget.