Re: maphash

[Andrea Corallo <acorallo@gnu.org>]

Mattias Engdegård <mattias.engdegard@gmail.com> writes:

> 10 sep. 2024 kl. 17.52 skrev Helmut Eller <eller.helmut@gmail.com>:
>
>> The documentation states that puthash and remhash are only "allowed" to
>> use the current key while a maphash is in progress.  (Interestingly, it
>> says nothing about gethash.)
>
> That is correct. The purpose of these rules is to avoid us being shackled to a specific behaviour if a user breaks them; we don't want any more implementation restrictions than necessary.
>
> We still protect Lisp abstractions so the user shouldn't fear
> segfaults, but there are no promises when it comes to the iteration
> order, whether iteration will encounter added elements, the same
> element twice or some none at all, etc.
>
>> However, the code in comp.el uses puthash with other keys.  E.g
>> comp--add-cond-cstrs-simple iterates over a hashtable of basic blocks
>> and while the iteration is in progress, it calls
>> comp--add-cond-cstrs-target-block which puts new basic blocks into the
>> hashtable.
>
> This sounds like a bug in nativecomp then, even if it happens not to have any bad consequences right now.

Ops! Will look at thanks

  Andrea