[Python-Dev] Tagged integers

[Tim Peters]

[Christian Tismer]
> ...
> Boehm GC might become feasible.
> If we then can write C extensions without having to think
> of reference counts, code would be simplified quite
> much, and I would save 80 percent of debugging time.

There's no escape from gc debugging nightmares at the C level,
regardless of gc strategy.  With Boehm gc (Bgc) you have to ensure
that all live objects are reachable from what Bgc guesses is the
current root set, and screwing that up is just as deadly as screwing
up refcounts.  It's harder to debug, though, because refcounting is
very simple to picture, while Bgc is a relatively huge pile of
complicated code in its own right.  I'm sure Neil Schemenauer still
has fond memories of the pleasant days he spent trying to account for
Tk crashes last time he tried hooking Bgc to Python <heh>.  Bgc has a
special entry point to call, to register roots that Bgc can't find on
its own -- guess how *you* find out which roots those are?  One crash
at a time, and in the presence of threads you're damned lucky to get a
repeatable test case.