[Python-Dev] Why do we need Traceback Objects?

[Guido van Rossum]

> When I look into tracebacks, it turns out to be just a chain
> like the frame chain, but upward down. It holds references
> to the frames in a 1-to-1 manner, and it keeps copies of
> f->f_lasti and f->f_lineno. I don't see why this is needed.
> 
> I'm thinking to replace the tracebacks by a single pointer
> in the frames for this purpose. It appears further to be
> possible to do that without any extra memory, since all the
> frames have extra temporary fields for exception info, and
> that isn't used in this context. Traceback objects exist
> each for one and only one frame, and they could be embedded
> into their frame.
> 
> Does this make sense? Do I miss something?

Yes.  It is quite possible to have multiple stack traces lingering
around that all point to the same stack frames.

--Guido van Rossum (home page: http://www.python.org/~guido/)