[Bug c/59850] Support sparse-style pointer address spaces (type attributes)

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59850

--- Comment #29 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Tom Tromey from comment #26)
> > 2. __force itself presents a problem as its semantics isn't well defined and
> > only sparse knows how to model it. in gcc it cannot be an attribute as
> > attributes apply to the outermost variable/etc, e.g., you can't use them on
> > a pointee in a pointer context.
> 
> Could you elaborate on this?
> I think I looked at all the sparse test cases here and I don't recall
> encountering any real issues (for address space I had to have a hack to
> deal with function return types, but this didn't seem to affect force).
> If you have extra tests not in sparse, that would be super.

If _Pragma can appear in the same places as __force, I think that would be a
superior approach. The trivial approach of using _Pragma("GCC diagnostic
ignore") does not seem to work in the middle of expressions, but that may be a
defect of the current implementation (PR60875 and PR52116).

Otherwise, a (type-generic?) __builtin_force_cast() perhaps would be even
better.

It seems strange and convoluted to use an attribute for this.