Re: Redisplay hook error bactraces [Was: Fontification error backtrace]

[Stefan Monnier]

> What you suggest would imply a _lot_ of coding to make it happen.  Does
> there exist anywhere any support for copyging a specpdl, and somehow
> making a lisp object out of it?  Why do you think that copying the
> specpdl would be less work or less risky than directly generating a
> backtrace, as the current code does?

I don't think it needs to be much coding.

Stashing the full specpdl would be more work, admittedly, but turning
the specpdl into a list via something like `backtrace-frames` is trivial
(we could even easily move `backtrace-frames` to C if we wanted to be
paranoid about running ELisp at that point).

> The advantage of directly generating the backtrace is that all the
> infrastructure is already there.  We've got mapbacktrace which
> encapsulates the formats of the specpdl.  And debug-early.el, whose two
> functions total 60 lines (including doc strings and comments) and don't
> use any other Lisp whatsoever.

That potentially runs a crapload of code via various hooks, many of
which can be influenced by variables dynamically bound in the context of
the error.

Moving the bulk of the work to a normal context means we can be much
more relaxed about using "fully featured" code, so there'll be much less
resistance to over-engineering :-)


        Stefan