[m-dev.] for review: bug fix for existentials and --trace all

[David Glen JEFFERY]

On 03-Oct-1998, Tyson Dowd <trd at cs.mu.OZ.AU> wrote:
> On 02-Oct-1998, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> > That change looks fine, but beware that it means that debugger (and
> > garbage collector) cannot assume that the type-infos and typeclass-infos
> > are always live.  I hope they are not assuming that.
> 
> I'm not sure what you mean by this.
> 
> The debugger and garbage collector use the concept of "type-info
> liveness" to control the lifespan of type-info variables.  This is
> done in liveness.m by extending the liveness of any type-info variable
> so that it is live whenever any variable whose type contains that type
> variable is live.

That seems like a safe approach. Even when the variable is existentially 
typed, the type-info will be live whenever the variable is live. I guess it
all "comes out in the wash".


dgj
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