Subject: Re: bug#61962: 30.0.50; New trouble with symbols with positions

From: Michael Heerdegen <[email-masked]>
Date: Tue, 07 Mar 2023 01:29:21 +0100

Alan Mackenzie <[email-masked]> writes:

> I think I now understand what's going on.  It's all to do with stripping
> symbol positions in eval-and-compile forms.  Before the patch of ~two
> weeks ago, the positions were stripped in e-and-c.  After the patch,
> they weren't stripped.
>
> I think the correct thing to do is to strip the symbol positions in the
> `eval' part of eval-and-compile, but leave them alone in the `compile'
> part.  This is actually quite tricky, since
> byte-run-strip-symbol-positions works destructively.  So I need to copy
> the code first, and there is no suitable function to do this.  copy-tree
> is close, but can't handle circular lists.  So I will have to write a
> safe version of copy tree.

Sounds all plausible.  I also don't have a better idea.

> In the mean time, could you try out the following patch which uses
> copy-tree as a first approximation.  I think it fixes the problem,
> apart from the above.

Yes, looks good.

I wonder now if other cases also suffer from the problem.  What happens
when I call `eval' in a macro expander (i.e. while generating the macro
expansion, not in the result of an expansion)?  And how does
`cl-eval-when' behave (this is actually a special case of the first
question) ?

Thanks so far,

Michael.