bug#36566: 27.0.50; debug is sometimes horribly slow

[Noam Postavsky]

Gemini Lasswell <gazally@runbox.com> writes:

> The third patch attached below fixes that by adding a macro to
> cl-print.el to wrap the printing of all the simple things with
> let-bindings of print-circle and print-gensym to nil.

> Patch #3 has the advantage of being straightforward logically and not
> breaking anything which doesn't use cl-prin1, but it undoubtedly also
> slows down cl-prin1 in the probably more common case that print-gensym
> and print-circle are both nil.  There are other ways to fix this, such
> as by adding a new entry point in print.c for printing simple strings,
> or by modifying the logic in print_preprocess to not create a hash table
> if the top-level object is a string with no properties.

This last idea sounds like a straightforward win to me, with no obvious
drawbacks.  I mean, no point in allocating a hash table if we can
cheaply detect it will never be used, right?