Re: [PATCH] (Updated) Run hook when variable is set

[Stefan Monnier]

>> But that's orthogonal to the "variable hook" functionality, right?
>> So I think we can keep this for some later changes.
> You originally objected to my patch slowing down Emacs.  So I looked for
> optimization opportunities to ensure that my patch paid for its performance
> costs.  I was successful, and not only did I offset the costs, I even
> produced a net improvement in speed, and provided benchmarks to prove it.

I'm sorry, but I consider this a form of lying.  It makes it sound like
"the new var-hook functionality actually speeds things up", even though
it's not this new functionality but some unrelated (tho bundled) change
which does it (and which could be applied independently).

> If I remove my optimizations, then my patch will slow down Emacs.
> And then you can once again object to the performance impact.

I'm quite willing to have Emacs be slightly slower for this new functionality.
I just want to reduce this speed impact to the minimum.

Offsetting this speed impact by adding unrelated optimization just hides
the speed impact.

> of the patch, so if you're so worried about the patch size, how about we

The issue is not patch size per se, but just keeping the patch focused
on its core purpose.

Those optimizations you found are good changes.  I'm just asking you to
put them in a separate patch.

>>> Because if you could, then as I explained in my previous message, you could
>>> convert a setq into a makunbound,
>> I don't think that's a serious problem.
> The tradeoff is providing a new capability (not previously present in Emacs)
> that's completely unnecessary (even for debugging) and pathological,

"unnecessary" and "pathological" are judgments which are actually hard
to make for such a generic hooking functionality where we don't (want
to) know what the applications will be.

As a general design principle Emacs doesn't really try to prevent you
from shooting yourself in the foot.

> Ok, I'll change it back.

Thanks,


        Stefan