bug#55676: [PATCH] non-recursive Lisp reader

[Lars Ingebrigtsen]

Mattias Engdegård <mattiase@acm.org> writes:

> You probably saw this one coming.

😀

> It's a restructuring of the Lisp reader so that it no longer uses
> recursion for reading nested data structures.

Wow, cool.

> The primary motivation is eliminating the limitation of the C stack
> (and potential overflow crash). As a happy side-effect, the change
> improves reader performance by a few percent, exact amount depending
> on what is being read. This translates into a small but measurable
> speed-up in loading packages (.el and .elc), and in
> byte-compilation. The performance increase is both from removal of
> recursion and closer attention to performance.

Sounds excellent.

> Care has been taken to not change the reader behaviour, although some
> error handling may differ in unimportant ways. Some obvious bugs found
> during the conversion have been fixed: for example, #_ followed by
> whitespace now represents the interned empty symbol; previously, it
> gave an unintended empty symbol. A non-breaking space after a single
> dot now results in the dot token instead of the dot as a symbol.

Hm...  sounds logical, I think.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no