> I don't know if there are better solutions but at least you can use an
> hashtable or a balanced tree or whatever (protected by a mutex) indexed on
> thread identifiers as reported by  "Thread.id (Thread.self ())" or
> something similar.

Yes, but that means that you need functions to lookup the values,
rather than having the value have process-dependent values globally.
Think like Sys.argv (etc) -- this'd require changes to the interfaces
(not such a big deal, since I have control over all interfaces).

But to go even further, having distinct descriptors for
stdin/stdout/stderr, then you could see where this would become
unstuck. Whilst I have code that can change the value transparently
for stdin/stdout/stderr, this'd make for a bigger process switch if I
had to do for all TLS values.

Perhaps what I need would require a change to the compiler and runtime
=/ What I'd also want to avoid, but I guess I'll have to face the
music....

Jonathan