[wip] BFD from an arbitrary object; Was: provide pass-through value in bfd_elf_bfd_from_remote_memory

[DJ Delorie]

> I agree in general, but I wouldn't do it at the cost of efficiency.

I'm trying to think ahead to the times we need to expand the list of
ops, and how many bad things can happen.  Worst case is, bfd expects a
field that gdb isn't providing, and calls into oblivion.  We need
something, either a length or an abi version (although length could
server that purpose too) so that such errors are caught cleanly.

> Note that multiple malloc calls aren't much of an issue, though, since
> BFD uses objalloc, which makes it pretty cheap to allocate memory.

Does gdb have access to that?  If gdb is creating the interface, gdb
needs to allocate the structures.

> > In that case, I'd prefer something less vague than "cookie".  How
> > about "data"?  I assume most backends will have this point to a
> > structure with various items in it, whereas "cookie" implies a single
> > value.  Or a dessert ;-)
> 
> Hmmm, you want something less vague than `cookie', so you suggest
> `data'?  I think I know what you're getting at, but the word is rather
> ambiguous.
> 
> How about `stream' or `storage'?

Well, it's a field in a structure called "stream" already, so we're
talking about stream.ops and stream.data.