bug#70108: 29.1.90; `defalias' and `current-load-list'

[Eli Zaretskii]

> From: Mickey Petersen <mickey@masteringemacs.org>
> Date: Sun, 31 Mar 2024 16:34:37 +0100
> 
> Here's a curious one. This is not so much a bug, I think, as a gotcha
> and perhaps something that I wouldn't mind understanding a bit better.
> 
> My package creates a number of dynamic commands (think:
> tempo/skeletons) to expand text.
> 
> It does so using the common (defalias NAME (lambda () ...)) pattern.
> 
> This obviously goes into the C core where a bunch of stuff takes
> place. One of variables that gets updated (somehow) is
> `current-load-list'. Curiously, it ends up with duplicate entries. I'm
> presuming there is a good reason for this.
> 
> This variable can easily get overrun with identical entries if the
> inattentive programmer does not check if it is already bound.
> 
> Due to a screwup on my part, I did not `fboundp' check first, which had the
> odd effect of causing incredible slowdowns when I ran my 600+ ERT test
> suite.
> 
> I have not narrowed down exactly *why* my ERT suite, when beset by 600
> tests to run in one go, causes the slowdown. What I'm guessing from
> how each successive tests slows down, that there is some sort of
> non-linear searching going on here, and either `load' (and friends) or
> the mere fact that putting more defaliases into the system causes this
> slowdown to occur.

Adding Stefan.