Canonical type nodes, or, comptypes considered harmful

[Doug Gregor]

On 11/7/06, Dale Johannesen <dalej@apple.com> wrote:
>
> On Nov 7, 2006, at 11:47 AM, Douglas Gregor wrote:
>
> > I just read Nathan's discussion [1] on changing GCC's type system
> > to use canonical type nodes, where the comparison between two types
> > requires only a pointer comparison. Right now, we use "comptypes",
> > which typically needs to do deep structural checks to determine if
> > two types are equivalent, because we often clone _TYPE nodes.
>
> One difficulty is that compatibility of types in C is not transitive,
> especially when you're compiling more than one translation unit at a
> time.
> See the thread "IMA vs tree-ssa" in Feb-Mar 2004.  Geoff Keating and
> Joseph Myers give good examples.

In that discussion, there was mention of submitting a defect report to
the C commit about this intransitivity. Has this defect report been
resolved?

  Cheers,
  Doug